Traffic control aims to manage and control the movement of traffic on roads to optimise the use of existing road capacity. ITS applications include:

• urban traffic control that is demand-responsive and may incorporate transport policy elements – such as public transport prioritisation or queue management
• adaptive signal control systems along arterial roads that adjust signal timings to current traffic conditions – such as those caused by special events or incidents
• freeway control systems that use ramp metering and lane control techniques to smooth traffic flow
• integration of highways and network signal systems for the purpose of corridor or “area-wide” optimisation of traffic flow

The implementation of effective traffic control strategies requires timely and accurate traffic information. The better the data, the more effective the control strategies that can be implemented. Information is gathered from various sources – such as detector loops in the road pavement, roadside and overhead sensors and analysis of digital camera images. The data can be combined and used to decide upon the best (or optimal) course of action for managing traffic on the network. (See Traffic Control)

Traffic control is one of the most basic building blocks of an intelligent road transport system, since it requires detection, control, communications and support systems – that are fundamental to the operation of several other ITS services. Traffic control and traffic operations centres (TCCs and TOCs), responsible for these functions, now exist all over the world. (See Traffic Control Centres)

ITS plays a significant role in improving incident management, particularly on highways, motorways and other high speed roads. This is because it uses vehicle sensors (such as inductive, buried, loops, radar and CCTV cameras), data processing and communications technologies to quickly detect and verify an incident. Sophisticated decision support systems then help traffic managers to decide how to best respond to any given incident. Using ITS in this way can improve safety and network efficiency, saving lives and money. (See Traffic Incidents)

One of the application areas where ITS has achieved great success is in the area of electronic payment. Among the prime examples of electronic payment are Electronic Toll Collection (ETC) systems such as the EZPass System in the USA or the European Electronic Toll Service. These systems allow drivers to pay road tolls without stopping or slowing down their travel speed – minimising delays and improving air quality in the vicinity of toll plazas.

ETC systems can take various forms such as:

• a mainline toll plaza with payment at the barrier;
• an open highway collection system where tolls are collected at main-line speeds;
• a closed system where tolls are charged based on entry and exit locations.

These systems can impose different tolls for different classes of vehicles, and can provide for the automatic enforcement of violations. Other examples include integrated payment systems – designed to allow a traveller to pay for different services (for example driving on a toll road, paying for parking, paying for transit) using the same medium or device (See Electronic Payment).

ITS can be applied to implement strategies aimed at increasing the frequency of Multiple-Occupancy Vehicles (MOVs) and promoting the use of High-Occupancy Vehicle lanes (HOVs). ITS can help make the operation of HOV lanes more effective and adaptive to changing traffic conditions – by adjusting vehicle occupancy requirements at different times of day, based upon current traffic and congestion levels. ITS also can help implement congestion pricing strategies – where toll charges are adjusted to influence demand. For example, tolls can be increased during peak hours in urban areas or in the vicinity of environmentally sensitive tourist attractions in rural areas. (See Demand Management)

ITS can be applied to better manage the allocation and price of parking spaces. This helps improve the travel experience of drivers by providing real-time information on spaces in parking lots. ITS-based parking information systems can be integrated with city-wide traffic management and control – to minimise parking search times and optimise traffic management overall. Electronic toll tags can also be used as a means of controlling access to a controlled parking area. (See Access Control)

ITS can help improve the environmental sustainability of road transport. Some ITS applications use environmental sensors to collect information about exhaust emissions from vehicles at a certain location, or over a wide area. The information can then be used to intelligently divert traffic away from areas where air quality has fallen below an acceptable threshold – or by not letting vehicles access these environmentally sensitive areas. The information can also provide valuable input to the development of air quality improvement strategies – and to alert vehicles’ operators if their vehicles are not compliant with adopted emissions standards. ITS can also be used to manage congestion and reduce delay – which has beneficial impacts on emissions and air quality. (See Driver Support)

The purpose of a highway-rail intersection ITS application, is to provide improved warning and safety control devices where a railway (railroad) crosses a road or highway at a level crossing (an “at-grade” crossing). On the approach roads to the crossing, any signalised intersections can be connected to the control and warning devices at the highway-rail intersection (HRI), so that signals can be coordinated to manage queuing and divert traffic. The technology can also monitor the “health” of HRI equipment – and report any detected malfunctioning. (See Enforcement)

ITS system and service applications have an important role to play in emergency situations:

• emergency notification and personal security applications;
• emergency vehicle management;

Emergency notification and personal security applications include systems that:

• allow a driver to initiate a distress call in the event of an incident (emergency and a non-emergency such as mechanical breakdown);
• enable the vehicle itself to automatically notify emergency management services (EMS) personnel in the case of a collision.

The European eCall and American OnStar systems are good examples:

• eCall: http://ec.europa.eu/digital-agenda/en/news/ecall-all-new-cars-april-2018;
• OnStar: https://www.onstar.com/web/portal/home?g=1).

Emergency vehicle management focuses on applications intended to reduce the time from the receipt of an emergency notification to the arrival of the emergency vehicle at the scene of the incident. This is accomplished through:

• optimal emergency fleet management – to identify the locations of emergency vehicles in real-time and dispatch the vehicles that can reach the scene of the incident most quickly;
• dynamic route guidance – to guide the emergency vehicle to the fastest route to the incident scene or a suitable hospital;
• signal priority or pre-emption – to give priority to trams and buses. (See Emergency Response)

The goal of pre-trip travel information is to provide travellers with information about the status of the transport network before they begin their trip. The information provided can be limited to road or multimodal transport – and can include:

• real-time flow conditions (average traffic speeds or point-to-point travel times)
• road incidents and suggested alternative routes
• scheduled road construction and special events
• transit routes, schedules, fares and transfers
• park-and-ride facilities, locations and availability

In the early years of ITS, travellers were able to access this information at home or work (via a computer or a telephone system) and at places generating traffic (for example, a shopping mall – via a touch-screen kiosk). Nowadays, with the proliferation of smart phones and mobile devices connected to the internet, travellers can access travel information anytime, anywhere. More advanced versions of these systems can provide users with predictive travel conditions, as well as help with trip planning. (See Pre-trip Information)

En-Route driver information is aimed at providing drivers with travel-related information after they start their trip – during the journey. Traditionally, this has been achieved by means of Variable Message Signs (VMS), radio broadcasts and Highway Advisory Radio (HAR). More recently with the widespread introduction of smart phones and mobile devices – and with the interest in developing Connected Vehicles – more effective means are available to provide travel information and to personalise it for the traveller specific to the journey and locations.

The development of Connected Vehicles that will be able to communicate with the infrastructure as well as with other vehicles, will allow greater opportunity for the delivery of advisory and warning messages to drivers (for example, warning motorists of unsafe conditions such as sharp curves, wet pavements, icy conditions – and alerting motorists if they exceed the safe speed limit and alerting drivers to unsafe weather conditions.) (See En-route Information and Driver Support)

The widespread use of GPS navigation devices provides drivers with detailed turn-by-turn instructions on how to get to their destinations. These directions traditionally relied on static information – for example historic travel times for different road segments, held in a navigation database. More sophisticated guidance systems are dynamic – with directions responding to changing traffic conditions based on real-time information about traffic speeds and incident locations. The digital maps that support these device need to be kept up-to-date – for example, by downloading updates on new road links and traffic restrictions.

Route guidance is now widely available through in-vehicle systems, portable devices and smartphone handsets. The benefits include reduced travel delays arising from navigational errors and lower stress levels for drivers, especially when driving in an unfamiliar area. Problems can arise for local communities when a product – intended for the general motorist – is used by drivers of large or heavy vehicles and the recommended route is a road unsuitable for those vehicles. (See Navigation and Positioning)

Ride-matching and reservation is aimed at encouraging carpooling by providing real-time matching of the preferences and demands of users with providers – and by serving as a clearinghouse for financial transactions. A traveller can call a service centre and provide it with information about the desired trip origin, destination, and time. In return, the traveller will receive feedback on a number of ridesharing options from which to choose. (See Ride Sharing / Matching)

Traveller service information is intended to provide travellers with “yellow-pages” information. This may include information on the location of services such as food, lodging, gas stations, hospitals, police stations – as well as information on the location of points of tourist attractions. Examples of these applications are already included in many GPS navigation devices and smart phone apps. (See Location Based Services)

Public transport management applications use advanced communications and information systems to collect data to improve the:

• operation of the vehicles and facilities
• planning and scheduling of services
• management of personnel

Real-time data collected from vehicle tracking and location systems can be used to ensure schedule adherence – and to implement corrective actions when a particular vehicle is running behind schedule. Real-time information applications can also help facilitate passengers’ transfers at connecting stations. Off-line, the data collected can be analysed and used to revise schedules, to better plan routes, to satisfy contract reporting requirements, and to improve customer information systems. (See Operations & Fleet Management)

En-route information applications are intended to provide public transport travellers with information after their trips have started. Among the key pieces of information which are typically provided are:

• information on expected arrival times of transit vehicles
• transfers and connections
• ride-share opportunities

Various information dissemination devices could be used including signs and kiosks at bus stops, internet websites that can be accessed via smart phones and mobile devices, and various types of smart phone apps. (See Information Dissemination)

Personalised Public Transport (PPT) is based on the idea of using flexibly-routed vehicles to offer more convenient services to travellers – in some cases door-to-door. There are two main types of PPT:

• flexibly-routed operations – in which fixed-route buses are allowed to deviate from their main route to pick-up or drop-off passengers
• random route operations – which operate with variable-routing based upon the pattern of service requests received

Ideally, this type of application will offer journey reservations – and vehicle assignment and scheduling to be developed in real-time. (See Dynamic Routing / Scheduling)

Video: Good News tests: Kutsuplus service – personalised public transport

Public transport security ITS applications are aimed at improving the security of public transport users, operators and support staff. This can be achieved by integrating vehicle location technologies and monitoring systems to provide a warning and response system to deal with security-related incidents. For example, transport stations and terminals, parking lots, bus stops and the inside of transport vehicles can be monitored with CCTV with image processing for surveillance – so that an alarm is triggered, either manually or automatically, by an “at-risk” event. Critical infrastructure, such as bridges, tunnels, rail track, can also monitored in this way as part of a public transport security strategy. (See Network Security)

Electronic clearance is designed to allow compliant commercial vehicles to continue past checkpoints at mainline speeds. As a vehicle approaches a checkpoint, communications between the vehicle and the inspection station take place – often by means of a dedicated short-range wireless link – allowing the authorities to check relevant information, such as the vehicle’s credentials, weight, safety status and cargo. This system allows enforcement personnel to select potentially unsafe vehicles for inspection, while permitting safe vehicles to bypass the commercial vehicle checkpoint. (See Credential Checking)

As a complement to commercial vehicle electronic clearance, automated roadside safety inspection ITS applications use automated inspection capabilities to facilitate safety checks with greater speed and accuracy during a safety inspection at a vehicle inspection site. This helps reduce the amount of time spent by the vehicle examiners inspecting vehicles, whilst also providing more reliable data on the safety status of the vehicle. (See Safety Information Exchange)

Among the many ITS automotive engineering applications are systems that monitor the safety condition of a vehicle and cargo as well as the driver – without the need for the vehicle to slow down. The monitoring capabilities may include:

• sensing the condition of critical vehicle components, including brakes, tyres and lights
• sensing shifts in the cargo while the vehicle is in motion
• monitoring the time-on-task of drivers
• monitoring the drivers’ alertness level

Safety warnings are provided to drivers and can be made available to vehicle fleet managers or controllers and to roadside enforcement personnel. (See Safety)

ITS applications can smooth the administrative processes required of commercial fleet operators by government or regulatory bodies. They may allow the automatic purchase of credentials (such as a port permit or other selective access toll) and include automated reporting of mileage and fuel use. This saves the operator time and money. (See Enforcement)

ITS has a part to play in the response to incidents involving hazardous materials (HAZMAT). Law enforcement and HAZMAT response personnel can be provided with timely, accurate information on cargo contents at the scene of an accident – so they know exactly how to handle the materials involved in an appropriate way. Emergency responders can be provided with access to this information – either through remote access to the relevant databases, or, in real-time, through the use of readers that communicate with the HAZMAT vehicle’s on-board transponder. (See Emergency Response)

ITS applications provide real-time communications between drivers, dispatchers and intermodal transport providers for the purposes of vehicle location identification, dispatching, and tracking – to help optimise freight operations and vehicle utilisation. (See Operations & Fleet Management)

The automotive industry has been working on a variety of collision avoidance systems that are either already in production or close to market. (See Warning and Control) These systems include:

Rear-End Collision Avoidance

These systems monitor the separation distance between vehicles and warn drivers when sensors detect another vehicle that may be dangerously close. If the driver does not react appropriately, automatic vehicle control actions may be initiated. Examples of these systems are already installed in the vehicles of some automotive manufacturers, such as Mercedes and Volvo.

Advanced Emergency Braking

Advanced Emergency Braking Systems (AEBS) detect the possibility of a collision with the vehicle ahead and warn the driver – using visual, audio or tactile feedback. If the driver takes no action, the system automatically applies the vehicle's brakes. At lower speeds AEBS acts to prevent a crash – at higher speeds it will reduce the severity.

Adaptive Cruise Control

Adaptive Cruise Control (ACC) tracks the vehicle in front, and automatically maintains a desired minimum distance (or time headway) from that vehicle. So long as this minimum distance is maintained, the vehicle will travel at the set speed. If the separation distance falls below this minimum value, the ACC system adjusts the vehicle’s speed to regain the minimum headway (in time or distance).

Reversing Collision Warning and Control

These systems detect slow moving or stationary objects and pedestrians that are in the path of a vehicle that is reversing – and warn the driver accordingly. Detecting these objects requires the use of relatively short-range sensors on-board the vehicles, such as a rear-view camera. Examples of these systems can be found fitted to many of today’s vehicle models.

Lane Departure Avoidance

Lane departure systems aim to help drivers avoid accidents that could result when a vehicle leaves its own travel lane and strays into the path of a vehicle in another lane. This is achieved by warning drivers and/or assuming temporary control of an at-risk vehicle. Among the most well-known of these systems are:

• Lane Change/Blind Spot Situation – Display, Collision Warning and Control, which provide drivers with information about the presence of vehicles in their blind spots, warns them of potentially dangerous lane change manoeuvres, and may assume temporary control of the vehicle’s steering and braking to avoid collisions;
• Lane/Road Departure Warning and Control, which assist in keeping a vehicle in its proper lane – typically using vehicle-based technologies (such as video image processing and optical/infrared scanning).

Intersection Collision Avoidance

ITS technology has been tested in applications that will avoid, or to decrease the severity of, collisions at intersections. These systems track the position and status of vehicles within a defined area on approach to an intersection through the use of vehicle-to-vehicle communications and/or vehicle-to-infrastructure communications. If a potentially dangerous situation is detected that is likely to lead to a collision warning messages are delivered to the driver – for example, in cases where a vehicle fails to stop at a red light or attempts to make a turning manoeuvre in the absence of an adequate gap.

Vision Enhancement for Collision Avoidance

ITS applications have been developed to help eliminate and/or reduce the severity of accidents that result from poor visibility – such as night driving, heavy rain or foggy conditions. These systems include in-vehicle sensors that can capture images of the driving environment and display them graphically to the driver, for example through a head-up display. One example that illustrates the concept is the Driver Assistance System for Snowploughs developed by the University of Minnesota http://www.lrrb.org/media/reports/200313.pdf).

The goal of safety readiness ITS applications is to eliminate and/or reduce the number of collisions caused by impaired drivers (though tiredness, alcohol or drugs), a failure of vehicles’ components, or any degraded infrastructure conditions that could affect the safety of the vehicle. Systems are available that monitor the performance of the driver – and either warn or assume temporary control of the vehicle if a driver’s performance is impaired. Other systems monitor the performance of critical components of a vehicle (such as the braking system), and warn drivers of their imminent failure. There are also systems that can monitor the roadway and provide warnings to the driver of unsafe conditions – such as loss of tire traction on wet or icy road surfaces. (See Policing/Enforcement and Warning Systems)

Pre-crash restraint ITS applications anticipate an imminent collision and activate the appropriate passenger safety systems prior to the actual impact. For example, sensors are available to detect the rapid closing of distance between the vehicle and an obstacle. On detection, the system attempts to reduce the danger of the impact of the collision by settings restraints to absorb or dissipate the force of the impact – such as triggering an airbag. (See Partially Automated Driving)

A long-term goal of vehicle safety systems is a fully automated highway-vehicle system (AHVS) – where specially equipped vehicles travel, under fully automated control, along dedicated highway lanes – or where a self-driving vehicle pilots itself through mixed traffic. The AHVS concept has the potential to significantly improve the safety, as well as the efficiency, of highway travel by reducing the number and severity of crashes, decreasing congestion, and reducing vehicle emissions and fuel consumption. (See Automated Highways and New Applications)

The safety risks associated with AHVS operations need to be analysed carefully so that the risk of mal-function is minimised. Many automotive manufacturers are currently involved in significant research and demonstration projects aimed at making autonomous (or self-driving) cars, a reality. A number of countries are preparing to test the readiness of driverless cars. Nissan, for example, has promised the production of autonomous cars by 2020 – and Google has sponsored the development of a self-driving car. Initiatives from public and private enterprises may help accelerate the deployment of self-driving cars. An example is here: http://www.autoblog.com/2013/08/27/nissan-promising-autonomous-car-production-by-2020/ (See Warning & Control)

Video: A Ride in the Google Self Driving Car

ITS technologies can be used to keep track of maintenance and construction vehicles such as snow ploughs – so that operators can monitor whether required tasks are being carried out as planned. ITS can also be used to monitor the condition of maintenance and construction vehicles – using on-board sensors to alert users of any required maintenance or repair activities. (See On-board Monitoring and Telematics)

Using Road Weather Information Stations (RWIS) and other similar environmental sensors (whether fixed location or on-board maintenance vehicles), ITS can help collect accurate, localised information about the weather – including road surface conditions. ITS can also help in the processing of the data and in disseminating information to the public. Information from RWIS can help detect hazardous conditions – such as icy roads, high winds, dense fog – and to plan, more effectively, winter maintenance operations and optimise resource allocations. (See Weather Monitoring)

Winter maintenance operations can be supported by systems that monitor and track routes for snow ploughs and grit spreaders – to determine the correct roadway treatment needed. This will be based on current and predicted weather information and information collected from environmental sensors. (See Weatther Management)

ITS can play a key role in helping improve the safety of work zones and construction sites on highways – as well as better manage the flow of traffic through the work zone. Information collected from permanent and temporary ITS monitoring facilities can be used to better control traffic and to provide advisory and warning messages to drivers – for example through dynamic message signs (DMS). The traffic information collected from the work zone can also be shared with traffic operations centres and to support traveller information systems. (See Work Zones)

ITS technologies can be used to monitor the condition of critical infrastructure such as bridges and road tunnels. Information from fixed sensors as well as vehicle-based sensors play a part. One recent idea is to use information from probe vehicles – about their vertical acceleration – to determine the pavement surface condition and detect different types of distress, such as potholes or surface roughness. (See Probe Vehicle Measurements)

Stakeholders can be categorised into primary and secondary stakeholders. Primary stakeholders are distinguished by the level and nature of their involvement:

• level of involvement – those with direct responsibilities in managing, operating and maintaining the system will be primary stakeholder. Others – with a lesser impact on the business practices and usage of a system – will be secondary stakeholders
• nature of involvement - service providers, service users and customers are always primary stakeholders:
  • private sector service providers include automobile manufacturers and their suppliers, commercial vehicle operators, private transport companies and value-added service providers
  • public sector service providers include government departments of transport, regional planning organisations, public transport planning agencies, local government and enforcement agencies
  • users or customer groups include drivers, passengers, pedestrians and customers receiving shipments

For example, in deliveries and commercial vehicle operations, the vehicle owners and delivery services providers and their customers are the primary stakeholders for ITS services to customers. Enforcement bodies such as the police and vehicle examiners are primary stakeholders in relation to weights and permits regulations and enforcement. From the public policy perspective local communities will also have an interest, albeit a secondary one unless there is public concern about the potential impact of operations.

Both primary and secondary stakeholders have roles in the planning, development, operations and maintenance of ITS projects. All stakeholders with a potential interest in the project must be identified and engaged – from planning to operations and maintenance stage of a project. Their input and participation is necessary for the successful realisation of an ITS project.

It is important to be aware of, and sensitive to, possible issues at all times – in what may be an evolving situation, as an ITS project develops. Secondary stakeholders can introduce issues which must be recognised and dealt with. Generally it is better to uncover interests and issues early on in the planning stages – so that proper adjustments can be made. An effective communication strategy with stakeholders provides the opportunity to develop contingency options.

ITS investments usually need political and public support. Public agencies must communicate the anticipated benefits of the ITS deployment in terms that policy makers and the public can understand. In the early stages of ITS deployment, a careful assessment of risk is essential covering the technology, market perspective, political and public acceptability. Some aspects may require a regulatory framework to ensure public safety, interoperability and rules for procurement – and where necessary an enforcement policy (such as speed control.) (See Contracts)

A priority for ITS is to consult the widest possible range of interests and to build local partnerships to achieve consensus on objectives and scope of investments in ITS – and joint problem-solving. Stakeholders are impacted by any failure or success of an ITS project. This means there is a need to develop an all-inclusive process to identify and engage all stakeholders from the start of the planning phase of ITS projects. This may lead to the involvement of new stakeholders, such as financial institutions, retailers, broadcasters, telecommunications providers and value-added service providers. Each stakeholder will have their own distinct business practices and goals – and should take ownership of their roles and responsibilities in any ITS project at each stage of the project.

There is often a role for an ‘ITS champion’ to take the initiative, drive forward consultation and keep all partners and stakeholders on board.

A total system approach to ITS deployment means paying attention to both technical concepts and institutional measures needed to integrate key technologies to deliver effective user services.

Successful ITS operations are enabled by a regulatory and institutional framework that is fit for purpose – with cooperative agreements between stakeholders that define clearly each party’s role and responsibilities. An equitable cooperative agreement between stakeholders – guided by suitable risk distribution, cost sharing and revenue or benefit sharing – may solve some of the regulatory and institutional challenges. (See Interagency Working)

A self-contained ‘silo’ mentality within an organisation may frustrate the development of ITS services. A lack of attention to end-user needs and requirements and poor management and project control in a primary stakeholder organisation – may also undermine the planned ITS deployment and incur excessive cost. Deficiencies such as these, may make the ITS service economically unfeasible.

A cooperative agreement can take the form of a ‘Concept of Operations’ – where each stakeholder’s roles and responsibilities are described and each party agrees on the allocation of operational roles and responsibilities.

The agreement should be based on appropriate risk distribution, cost sharing and revenue or benefit sharing – according to the role and level of involvement of each stakeholder. This must be developed at the planning stage of an ITS project and may have an important place in defining any ITS architecture. (See How to Create and ITS Architecture?)

By way of example, the table below summarises a Concept of Operations that was developed for Bloomington/Monroe County in Indiana USA, as a part of the county’s regional ITS architecture. Stakeholders are mapped to different transport services and each stakeholder’s roles and responsibilities are specified.

Concept of Operations for ITS Services (Based on Bloomington City/Monroe County, Indiana State, USA)

Transport Service	Stakeholder	Role/Responsibility
Emergency Management	Public Safety Agencies	Provide emergency call taking Dispatch appropriate agency(s) to incidents Coordinate various systems and agencies during emergencies
Freeway (Motorway) Management	Highway Operator	Operate traffic information devices (DMS, HAR) Monitor traffic conditions
Incident Management	Highway Operator	Operate Freeway Service Vehicles Provide information to travellers using traffic information devices (DMS, HAR) Provide assistance to Public Safety Agencies responding to incidents on roads under INDOT’s jurisdiction
Public Safety Agencies	Receive emergency calls for incidents Dispatch appropriate agency(s) to incidents
Maintenance and Construction Management	Highway Operator	Provide maintenance of national and regional (Interstate Routes) Coordinate with other agencies that provide maintenance and construction
City/County Authority	Provide maintenance of urban streets and rural roads Coordinate with other agencies that provide maintenance and construction
Highway Pavement Management	Highway Operator	Collect data using roadside devices
Surface Street Management	City/County Authority	Collect data using roadside devices
Public Transport Management	Bus/ Coach Operators	Provide fixed route bus service Provide demand response (Paratransit) bus service Monitor Public Transport assets (vehicle locations, video surveillance)
Traveller Information	Highway Operator	Provide information to drivers (Dynamic message Signs, Highway Advisory Radio)

 

The leading stakeholders in an ITS deployment may parallel those involved in a construction project: the client, professional consultants, products and service suppliers, contractors and specialist subcontractors:

• the client can be a public authority or private operator – or, often, a multi-agency grouping under a lead agency
• ITS professionals who advise on, and manage, an ITS deployment – are typically drawn from the disciplines of civil, electrical or transport engineering and transport planning. Their specifications define project needs and anticipated costs, and guide the developers and suppliers – including computer software and hardware, detectors and sensors, communications networks, cameras and infrastructure equipment, fixed and portable devices
• system integrators may be needed for complex ITS projects – especially when the component systems must operate together reliably

Transport professionals who are responsible for launching ITS at project or programme level, may be unfamiliar with certain aspects of a deployment – either technical or institutional. (See ITS Technologies and Strategic Planning)

Private sector involvement is generally motivated by the opportunity to generate revenue and/or make a profit. Commercial businesses must be able to generate a profit through their activities to survive in a competitive market place. The continuing development of technology and advances in user needs and expectations means that the potential for new products and services is always there. The private sector can provide these new products and services, as and when time demands. Increasingly, the public sector is looking to the private sector, for the investment in ITS infrastructure and the delivery of certain ITS services – such as providing travel data. The private sector business case will largely depend on risk assessment of several factors. (See Formulating a Programme)

It is likely that the private sector will wish to develop market opportunities for new service needs arising from public sector investments in ITS. For example, a company might make use of traffic data (advisory and predictive) collected by public agencies to develop customised, real time travel information as a value added service for its customers. Arrangements of this kind – if they are exclusive to one provider – can become problematic unless they have been awarded on the basis of fair and open competition.

Private investment in road infrastructure and traffic services is growing as many public agencies struggle to meet increased travel demand within limited budgets. For example, toll roads and traffic control centres are often implemented through a partnership contract or franchise (See Contracts and Toll Collection). Private sector participation offers new opportunities and challenges to the transport industry.

The challenge in a public private partnership lies in how to achieve a balance between the policies and objectives of public agencies – while satisfying the business goals of private companies. To achieve a successful public private partnership, various issues need to be addressed:

• defining and agreeing the roles and responsibilities of the public and private sector in each phase of the life cycle of the project
• sharing the development and operational risks
• ensuring that both benefit from the partnership
• cost sharing
• private sector interest in the transport service
• public sector support for the private sector’s business case

In preparation for negotiations with private industry, public agencies need to determine their requirements – which may be encapsulated in an ITS regional architecture. By defining requirements before entering into a resource sharing agreement the stakeholders will be in a stronger position to conduct the negotiations.

Motivating factors for public private partnerships in ITS include:

• the opportunities that ITS offers as a market for the development of new products and services by the private sector – based on access to publicly owned data (open data) and permission to install equipment on the road network (See Open Data)
• mobilising private sector investment in ITS deployments – which would otherwise be a challenge for public sector budgets to meet.

Examples of viable partnerships which benefit both sectors include:

• a cellular phone company that provides telecommunications support to public agencies for their ITS infrastructure connections – in the expectation of business growth from road users (such as travellers) accessing traveller information services through their wireless mobile devices
• a public agency that gives permission to telecommunications companies to construct cellular communication towers or install fibre optic cables on publicly-owned land alongside a highway – in return for in-kind ITS programme-related hardware, software and services up to an agreed value

ITS Architecture plays an important part in Road Network Operations. The ITS architecture is a primary element in ITS planning. Two types of ITS architecture are typically defined:

• a high level architecture (which can be either a Framework or Model Architecture), often for publicly funded ITS deployments in a national, regional or local area
• a low level architecture (project-level) for specific ITS deployments, such as a Regional Traffic Control Centre

A high level ITS architecture provides the framework for the deployment of ITS across a wide geographical area with multiple jurisdictions and different stakeholders participating in common or inter-dependant operations. The architecture specifies how the various ITS components interact with each other to address the transport problems. It provides the basis for planning, designing, deploying, maintaining and integrating systems to realise transport objectives.

An ITS architecture does not specify the ITS scheme design in detail. Nor does it require a particular design approach. Instead it does the important job of specifying the performance criteria that the system components must satisfy – and defines a general framework from which several alternative designs or design options may be developed. These distinct designs will conform to the common ITS architecture. (See What is ITS Architecture?)

An ITS architecture should define the following:

• functions: that describe what the ITS system has to do to meet the user requirements – such as “collecting traffic data” or “providing incident information”
• physical entities: the locations where ITS functions are to be performed – such as a traffic management centre or traffic signal controllers
• interfaces and information flows: the interfaces showing data exchange connectivity (existing or proposed) and the information flows between physical entities. For example, an interface between a traffic management system and roadway traffic detectors might be two-way:
  • in one direction, speed data flows from the traffic detectors to the traffic management system
  • in the opposite direction, a sensor control command flows from the traffic management centre to the traffic detectors

Maximum benefit from ITS requires interoperability and interchangeability of systems between regions and within a region. Interoperability refers to the condition where different types of systems can interface with each other to meet the system’s functional requirements. Multiple brands of a device on the same communications channel is an example of interchangeability. One of the primary goals of ITS is to integrate a variety of previously independent systems to minimize redundancy and maximize efficiency – so adhering to ITS and other industry standards will satisfy the interoperability and interchangeability requirements and support future efficient system expansion. Legislative requirements to comply with industry and ITS standards in any ITS project will support interoperability, interchangeability and future cost-effective expandability of the system. (See ITS Standards)

Technology is changing at a rapid pace and this trend is expected to continue indefinitely. ITS builds on technology-based services – and the pace of technological change is an important consideration in planning and deployment. Three issues must be addressed when considering changes in technology for any ITS applications. These are: upgrade, legacy systems and systems integration.

Upgrade

With technology changing rapidly, even during the course of an ITS project, it is important to anticipate the possibility of system upgrades. Newer technologies can improve the performance of an already deployed system – and may require a decision on whether to upgrade the system or replace it. Where it is possible to look ahead, work planning and design should allow for the possibility of upgrades so they can be accommodated efficiently and without technical complexity. A possible disadvantage is that system upgrades may require highly skilled professionals to operate and manage the new systems in the future.

Legacy Systems

As new systems and upgrades come on line, they must be integrated with earlier “legacy” systems. The challenge lies in making the new systems interoperable. ITS architecture can show where and how established legacy systems will need to interface with new systems to deliver the desired (integrated) system functionalities and performance. A field evaluation plan for testing the interoperability between a legacy system and new systems will provide the basis for testing the integrated system after deployment.

Systems Integration

Systems integration is about how different systems are connected together so that they can perform the desired tasks in an optimal way. ITS requires different types of hardware and software (which may come from different manufacturers and be implemented at different times) to be integrated to satisfy user requirements.

Problems – that can pose a significant challenge to systems integration – technically and because of the cost, are:

• using hardware and software that are unique to one supplier
• system interfaces that do not follow industry and ITS standards

Adhering to established industry and ITS standards and the use of open architecture will support future cost-effective systems integration.

A system-wide outlook at the inception of a project will help develop a deployment plan that supports a cost-effective implementation strategy:

• an ITS architecture that takes account of user needs regionally and nationally will support cost-effective project development locally, even when the projects take place at different points in the timeline. This is because the entire system, with its subcomponents and interdependencies, are considered at the outset of each project

If the design provides for interchangeability of components it will encourage competition and allow scope for future improvements in cost, design, functionality and safety (See ITS Architecture):

• ITS technologies provide multiple options to address particular user needs or requirements. Availability of many options for the same set of requirements (for example electronic tolling equipment) may promote different products in different regions that are not compatible or interoperable with each other. A common architecture and a set of standards that have evolved from a common architecture can solve the problem of interoperability

ITS architecture can show where standard interfaces will bring significant benefits:

• it does not assume the use of specific ITS technologies or components. It should instead, be generic, to allow freedom for system developers to design what they see as optimum solutions – meeting appropriate standards and accommodating the interfaces needed for interoperability and likely future extensions

ITS architecture shows how different stakeholders are connected with one another through data exchange:

• ITS architecture helps to identify institutional interdependence that can assist in reaching regional goals. It can serve as a guide on how different agencies can share the same ITS infrastructure to achieve their own institutional objectives

The existence of an ITS architecture can assist in integrating systems coming on-line in different phases:

• it is not possible to meet all user requirements at any one time, with one project. ITS projects are usually completed in phases

ITS architecture can support security services related to disaster response and evacuation, freight and commercial vehicles, hazardous materials, rail, transit and transport infrastructure:

• in addition to supporting transport services, ITS architecture can contribute to regional and national security

The ability effectively to enforce basic traffic rules against offending drivers is a key tool in increasing road safety, as is the awareness among the motoring public that enforcement is in operation (See Policing and Enforcement).

Enforcement – Red Light

Red-light running is a major traffic safety issue. In the USA, it is accounts for some 800 deaths and an estimated 165,000 injuries a year. Automated camera enforcement provides the evidence necessary for prosecution.

Enforcement - Speed

Speed enforcement is becoming more sophisticated and driver-friendly. Conventionally the main technique has been the use of single-point “spot” speed cameras, which record the driver exceeding the limit as they pass by. In the UK, speed cameras of this kind have often drawn hostility from motorists who perceive it as an unfair means of raising money from enforcement fines.

Speed over distance (SOD) or average speed enforcement (ASE) are seen as fairer methods.

Average speed enforcement is demonstrating higher levels of compliance than spot-speed in a number of European countries where it has been deployed.

“Soft” speed enforcement aims to influence driver behaviour – it does not impose legal or financial penalties. A European example involves detecting a vehicle as it approaches from a measured point ahead, which allows the time needed to cover the distance to be calculated to determine whether the vehicle is speeding. This can trigger a dynamic message sign to display a warning message. (See Vulnerable Road Users)

Beneficial ITS vehicle technologies include:

• anti-lock braking
• electronic stability control
• collision warning
• adaptive cruise control
• parking management
• driver drowsiness detection

The basis of all these systems, and the safety benefits that they bring, is the development of on-board sensors linked to the vehicle’s engine management and braking systems. (See Driver Support)

Anti-lock braking systems (ABS) intervene to help stop loss of vehicle traction (skidding – for example, in icy weather or wet conditions). ABS works closely with electronic stability control (ESC), which detects the loss of steering control and applies the brakes individually to the wheels to correct the steering. The US Insurance Institute for Highway Safety and the US National Highway Traffic Safety Administration estimate that comprehensive use of the technology could avoid one-third of fatal road traffic accidents.

Crash avoidance systems use autonomous braking, which comes into effect if a driver fails to brake in time. The technology is an advance on the (widely-used) autonomous cruise control, which automatically adjusts a vehicle’s speed to keep it a safe distance behind traffic ahead. Both the US and the EU are moving towards making mandatory, the fitting of frontal collision warning systems. Automotive manufacturers have started to include these systems into their production lines. The EU estimates that these will save 5,000 deaths and 50,000 serious injuries a year.

Automatic parking uses sensors to detect the presence of objects around a vehicle to guide the vehicle safely into a clear space.

Driver drowsiness detection is a response to studies that suggest that up to 20% of road traffic accidents are due to fatigue. It works by monitoring a vehicle’s movements and assessing the likelihood of these being controlled or uncontrolled.

ISA systems are based on satellite navigation equipment that will determine a vehicle’s position. The digital map used for navigation can be expanded to include precise details of the start and end locations for speed limits as well as other information – such as road geometry and route numbers and place names. The vehicle speed is automatically adjusted to take account of the speed limit (See Intelligent Speed Adaptation).

The main ISA options are:

• advisory: to provide the speed limit and warn the driver when this is exceeded
• mandatory: when the speed limit is set and the system makes it difficult or impossible to exceed – some systems allow the driver to accelerate out of an emergency situation by overriding the system.

Trials indicate the potential for safety, efficiency and improvements – including 42% reductions in fatal crashes, fuel efficiency gains of 5%, and smoother traffic flows resulting in less congestion (See: http://www-nrd.nhtsa.dot.gov/pdf/esv/esv20/07-0247-W.pdf).

Widespread adoption of ISA could bring the additional benefit of reduced insurance costs. In Europe, ISA systems that meet European New Car Assessment Programme (Euro NCAP) requirements gain an advantage in relation to the car’s overall ‘Safety Assist’ rating.

Fast detection of a traffic accident – particularly in a tunnel or on a bridge where there are physical and geographical restrictions – is essential to trigger a rapid response. Resources need to be deployed to deal with casualties, remove obstructions, provide driver alerts and – if necessary – divert oncoming traffic, and restore normal running conditions as soon as possible (See Traffic Incidents).

Automatic Incident Detection (AID) systems use cameras and traffic monitoring technology to record and analyse traffic data and quickly detect incidents using motorway incident detection systems. A sudden build-up of congestion, for example, can indicate that there is an incident ahead.

Response times to road traffic accidents and medical emergencies are critical, with the ‘golden 15 minutes’ typically cited as the optimum window for early and effective treatment. The key needs are fast response and accurate direction to accident scenes. Automatic traffic signal priority for emergency vehicles is increasingly common.

ITS technologies introduced to speed up the process include automatic crash notification systems, which many automotive manufacturers are building into their vehicles. These work by sensing an impact and sending out an automatic alert via mobile phone networks to a call centre. In Europe, the EU’s eCall (emergency Call) initiative aims to mandate, from 2018, European automotive manufactures to install these systems.

Emergency service providers can make use of real-time dynamic route guidance systems to dispatch and route vehicles around known congestion and roadworks to minimise response and return times. Speeding ambulances, themselves, risk causing, or being involved in, road traffic accidents. The US General Services Administration records over 6,000 ambulance crashes a year. In-vehicle ‘black boxes’ can monitor and record driver behaviour and highlight training needs.

Road construction workzones are vulnerable locations for road users and site workers – especially at night when it is less disturbing to traffic than in the daytime. It is important for traffic to be managed through the work zone at safe speeds. Construction workers are close to moving traffic and need to be protected – as many vehicles exceed recommended speeds (See Work Zones).

Workzone traffic management schemes can draw on ITS technologies such as Bluetooth detection, which anonymously registers the passing of vehicles carrying Bluetooth devices (See Wireless Telecommunications). This provided the US state of Texas with a cost-effective alternative for monitoring the speed of vehicles over a lengthy section of road reconstruction on the I-35 highway.

There are examples of basic roadworks equipment being equipped with ITS features to provide a safety role. For example:

• detection sensors fitted in the flashing lanterns installed on US traffic barriers will collect real-time speeds from passing vehicles for processing to set speed warning signs – benefits in terms of accident rate reductions are estimated variously between 15% – 66%
• traffic cones can be upgraded and converted into wireless sensor perimeters to detect and report an impact at any point around a workzone for fast detection to initiate rapid response.

In rural areas, intersection crashes typically occur less often than in urban ones. They are often more severe because of the higher vehicle speeds and the consequences can be more serious because of longer emergency response times. New intersection decision support systems use traffic sensors and advanced computing to monitor vehicles moving along rural divided highways (dual carriageways). They process the data generated to alert drivers waiting to merge with, or cross, the traffic – when the gaps are too short for them to be able to do so safely.

Wild Animals

Collisions with wild animals on rural roads are increasing wherever human development spreads. This is an issue of growing relevance to developing and emerging economies. A crash involving a large animal can cause death, serious injury, severe vehicle damage and disruption to other road users. Physical defences such as fencing and over/underpasses are not always possible or cost-effective, given access and maintenance issues. In-vehicle and roadside systems are being developed to detect large animals. The sensors can distinguish between moving vehicles (with warm engines) and animals, alerting drivers to their presence (See Information and Warning).

People want healthy, attractive and comfortable living environments. Tough air quality standards are being imposed in many countries. One way of enforcing these standards is by creating low emissions zones (LEZs) – such as those introduced in Sweden in 1996. Vehicles which do not comply with the emission standards are required to pay a penalty charge. Automated enforcement is typically by camera supported by ITS-enabled back-office enforcement operations.

The enforcement of vehicle emissions legislation – such as the Euro standards introduced in Europe in 1993 and subsequently adopted in other parts of the world – encourages the use of cleaner road vehicles. It does so by putting pressure on operators to accelerate vehicle replacement or to fit their existing vehicles with pollution reducing equipment. In Berlin, the share of compliant diesel-engine vehicles rose by 38% between 2006 and 2011 – largely because fleet operators installed diesel particle filters.

The cost of setting up the London (UK) LEZ was comparatively low because it made large-scale use of the city’s existing congestion charging infrastructure. Creating an LEZ using existing enforcement infrastructure – as in the London case – makes economic sense.

Noise pollution tends to attract less public concern than air pollution but it is a growing nuisance and poses a health hazard to people living on or near sites experiencing high levels of traffic noise. Traffic models for forecasting traffic noise impacts are emerging which take advantage of readily-available data on road geometry and the built environment.

CO2 and noise emissions often respond to similar solutions:

• promoting the use of electric/hybrid rather than petrol or diesel engine vehicles
• Low Emission Zones (LEZ) can contribute to reducing noise pollution – since vehicles complying with higher emissions standards are generally quieter than older ones
• encouraging modal shift from road vehicles to public transport
• enforcing existing speed limits and introducing lower limits in specific situations –for example, 32km/h zones in residential areas

Cities can become cluttered with street furniture installed for traffic management and the safety of road users and pedestrians. The additional infrastructure (gantries, roadside cabinets and mounting posts) for ITS deployments – such as cameras for congestion charging enforcement, and on-street sensors for air quality monitoring – add to the clutter. This can be a serious issue in unspoilt rural areas and historic town centres – where tourism brings economic benefits.

There are ways to mitigate the visual impact of ITS equipment. For example:

• a reduction in the number and size of gantries for tolling equipment is possible by rationalising the equipment required
• satellite-based charging systems are now proven technology and will reduce the scale of physical tolling infrastructure
• air quality information – needed for traffic management that can reduce pollution levels – is possible to collect using very small sensors or ‘motes’ that can be attached unobtrusively to buildings, existing street furniture, vehicles – and even on people

In time, it is possible (with good design and appropriate technology) that cooperative vehicle systems may reduce the need for invasive ITS installations on roads – since they will automatically collect, process and transfer data and traffic information between vehicles, the roadside and drivers.

Transport links, the availability and quality of public transport, journey times and reliability are important factors for local communities and in deciding where to locate businesses.

When people and businesses relocate the more well-informed they are about transport options, the more likely they are to opt for well-connected locations. In North America, Australia and New Zealand, neighbourhood rating systems and journey planning which makes use of data from public transport operators, cyclists and pedestrians to highlight areas with good facilities.

ITS can also be used to manage and monitor environmental zones. For example, DMS and VMS can be used for signing the zone, especially if different access regimes apply to drivers at different times. ITS can also be used in air quality monitoring and in communicating the results to stakeholders. Example of these are:

• Queensland, Australia – where the South East Queensland Air Quality model uses GIS to map current air quality and for forecasting in connection with land use and transport planning decisions. The GIS maps are also used as a communications tool, to inform about air quality and promote the need to improve it
• Turin, Italy – where ITS is deployed for traffic management and public transport operations in response to pollution forecasts to reduce the severity of poor air quality.

ITS has been used as part of a coordinated approach to promote travel choices that will help reduce congestion and pollution in cities. It provides:

• the tools to implement road pricing and congestion charging, in order to discourage or modify traffic demands
• facilities to improve the attractiveness of alternatives such as public transport, car-sharing, carpooling, and cycling

Car pooling 

Car pooling (also known as ride-sharing) and car clubs are enjoying a boom, thanks to ITS technologies. ITS applications such as a car pool database (of drivers offering spare seats and potential passengers looking for a ride) – together with a user forum – can enable planned sharing of car journeys. Car pooling reduces individuals’ fuel, parking and toll costs – and in the USA, allows them use of dedicated high-occupancy vehicle (HOV) lanes. It helps to reduce traffic demand, cut emissions and relieve the pressure on parking. Employers can offer and promote schemes as an incentive to their workforces.

Car clubs provide members with the use of a car on an as-needed basis for specific journeys – delivering them savings on insurance, depreciation and road taxes. Local governments around the world are promoting schemes on their travel websites as making useful contributions to modal shift. Booking is by phone or internet. For some schemes, a member’s smartcard opens the vehicle and is used to process payment for use and fuel from the member’s account. Transport for London calculates that those driving fewer than 9,600km a year can save up to £3,500 as compared with owning a car.

Cycling

Cycling is gaining popularity worldwide as an alternative travel mode, one that is attractive on personal and public health grounds. On busy urban roads, cyclists are vulnerable – particularly prone to collisions with heavy goods vehicles (HGVs) overtaking or making turning movements at road junctions. ITS-enabled protective systems being investigated include:

• controlling access by HGVs in city centres – with electronic charging or access control and automated enforcement
• fitting HGVs with video cameras that pick up images of cyclists at risk in the danger zone around the vehicles – and flash an audible or visual alert to their drivers
• an identification system, with cyclists wearing a transponder (similar to an in-vehicle toll tag) that is read by an HGV’s on-board unit and again warns the driver

Town and city authorities want road networks that run smoothly and efficiently, for the benefit of residents, businesses and visitors. The quality of transport in a city is a central factor for business investment and location decisions, maintaining and increasing income from tourism, and building electoral support for local politicians. ITS systems such as urban traffic control (UTC) are valuable tools for those responsible for management of the infrastructure (See Urban Operations).

Urban Traffic Control

Urban traffic Control (UTS – also known as Area Traffic Control) is one of the world’s longest-established ITS applications, with its origins in the 1970s in response to growing car ownership that led to congestion on city streets. UTC provides the means to monitor road traffic flows in built-up areas, and modify these in response to congestion and other conflicts (for example, the balance between public transport and private cars). One way is by automatically adjusting traffic signal phases at intersections in response to flows and the needs of public transport vehicles (See Urban Traffic Control).

Widely used UTC systems around the world include:

• SCOOT, developed in the UK and increasingly being taken up in other countries across the world
• SCATS, developed in Australia and now in use in much of Asia
• the Open Traffic Systems (OTS)/Open Communication Interface for Road Traffic Control Systems (OCIT) specifications used in German-speaking areas of Europe
• comtrol systems based on standards contained within the US National Transportation Communications for ITS Protocol (NTCIP)

Integrated Systems

UTC installations form the core of more developed and sophisticated arrays of urban ITS applications that expand their functions by linking in additional capabilities. They do this by introducing common databases and data dictionary, allowing the mechanisms (such as cameras and sensors) used for traffic management, parking management, traffic signal control for priority for buses, air quality management in response to pollution, and weather monitoring to communicate and share information with each other via a single, integrated control centre (See Urban Networks).

Major benefits include:

• improved journey times
• improved air quality from reducing air pollution generated by slow-moving traffic
• reduced delays to public transport
• traffic speed control
• protection of historic and environmentally-sensitive areas

Central to integrated operations is the adoption of agreed open standards and specifications for products across the ITS industry, to ensure their interoperability. Open specifications make it possible easily to add fresh functions when needed, and free local governments from dependence on individual suppliers when it comes to needing replacement parts or system upgrades. Agencies can then shop around for the most competitive prices and service offers, which in turn stimulates innovative commercial development (See ITS Standards).

Drivers searching for parking space can add significantly to urban congestion. Parking guidance systems monitor space availability on-street or in car parks via in-bay sensors that detect vehicle presence and give drivers the resulting information through VMS or via smartphone apps. When a car overstays its paid-for time, the system can alert enforcement officials, who then need to spend less time patrolling and can be deployed more efficiently.

Smart parking deployments give car park operators and city governments useful data on levels of demand. They can use this information to adjust charges, levying higher rates to increase turnover on their busiest sites, and lower ones to attract drivers to underused spaces.

Interurban highways need to run smoothly and efficiently, avoiding congestion and delays. These can also impact on connecting local roads and spread disruption further. The operator need to ensure they are making the best possible use of their existing road assets, to avoid or delay the cost and environmental disruption of adding new lanes – for which ramp metering and monitoring of usage at different points of the network is helpful (See Highway Operations).

Highway management systems

Highway management systems include automatic incident detection, CCTV for the benefit of control centre operators, automation of traffic flow monitoring and software to control speed limits before queues occur. Case studies have shown the delay-savings benefits achievable from the strategic use of variable message signs (VMS) give a positive cost-benefit which justifies the initial capital investment. For example, queue protection systems deliver significant socio-economic benefits from reducing numbers of killed and seriously injured road-users. They also produced significant secondary benefits through incident-delay savings (See Highway Traffic).

Savings from cost reductions in journey times are important to all road users, but the benefits are most relevant to the operators of vehicle fleets and highway infrastructures. The quantifiable benefits come in one of two ways:

• delay-savings through diverting traffic away from the incident along a less congested route since, while the journey time may be greater, delays on the approaches to an incident and lengthy carriageway closures can be considerably greater and extend the journey time even more
• less congestion on the approach to the incident, aiding a quicker recovery of normal traffic flows once the incident is cleared.

HOV and HOT

In the USA highway management techniques commonly include high occupancy vehicle (HOV) and high occupancy toll (HOT) lanes on motorways and expressways.

HOV lanes, introduced in the US in the 1970s and later adopted in Australia and New Zealand – though rare in Europe - are open to cars carrying at least two passengers (for example, in car sharing schemes), and buses and, sometimes, green (low emission) vehicles. The aim is to increase higher average vehicle occupancy and person throughput with the goal of reducing traffic congestion and air pollution. Some HOV lanes are reversible, to accommodate differing peak flows.

HOT lanes give drivers of single-occupancy vehicles access to HOV lanes on payment of a charge levied by, for example, by automatic number plate recognition, or electronic fee collection (EFC). Tolls can increase in line with traffic density as this increases within the lanes, to reduce the risk of their becoming congested.

In the Los Angeles HOT system, drivers use specially-developed "switchable" transponders to indicate the number of occupants. The EFC reader that picks up the setting uses it to decide automatically on chargeability. For enforcement, a beacon near the EFC reader lights up in response to the scanning and alerts highway patrol officers to check the stated occupancy setting.

Managed Motorways

So-called “Smart” or managed motorway sections use ITS technologies for active traffic management to control flow and speeds and give users relevant information on overhead variable message signs (VMS), to help them make the best use of heavily congested segments. They can impose variable speed limits (VSLs) where the speed limit is altered to reflect current traffic conditions.

Traffic sensors detect slow-moving and stationary traffic and alert HA regional control centres to the changing conditions. These set relevant VMS messages and variable speed limit signs (VSL) to correspond with traffic movements. The “Dynamic Roadspace Utilization Manager (DRUM) is another good example of ITS software application that has been applied to great advantage during contruction works on an active motorway. The principle is based on first cone-on and last cone-off approach to road work closures.

See: http://trl.co.uk/software/software_products/drum.htm

Freight movements have an essential part to play in the local economy, but delivery vans, articulated trucks and other heavy vehicles can also be a source of nuisance – because of increased accidents, congestion, noise nuisance and environmental pollution. Many city streets are not suitable for large vehicles; moreover loading and unloading activities can be a major source of obstruction to moving traffic. Some cities impose restrictions at different times of day (night-time lorry bans in residential areas, daytime restrictions on deliveries in shopping streets and touristic localities). ITS technologies are useful in these circumstance as a means for vehicle identification and controlling access (See Operations & Fleet Management).

Freight consolidation centres (FCCs), located at points close to town centres or shopping malls and major road junctions, help to avoid or reduce the impact of Heavy Goods Vehicles (HGVs) on urban roads. They can help mitigate traffic congestion and may have a positive impact on local air pollution. Using logistics tracking and tracing systems, they take in large incoming consignments destined for numbers of in-town retailers, for breaking up into individual loads. These then travel on by smaller and less polluting vehicles at convenient times over the final leg. There are currently over 114 FCCs worldwide, mostly in the EU – specifically France, Germany, Italy, the Netherlands and the UK.

A system deployed in the Netherlands and elsewhere in Europe rewards truck drivers whose driving is environmentally-friendly with green lights at intersections. It interfaces with the city’s signal control network and incorporates data on cities’ speed limits, encouraging compliance with these by integrating with trucks’ own engine management system for speed limiting and acceleration monitoring. A dashboard display keeps drivers informed on their performance and fuel consumption and driving performance, with low scores generating warnings.

Commercial drivers and their vehicles can be a reliable source of information on current traffic conditions the network. Increasing use of just-in-time deliveries means that vehicle fleet operations managers and drivers are increasingly interested in the real-time status of urban road networks.

Overweight and over-height vehicles pose real threats to road safety and transport infrastructure. Systematic enforcement against overloading of trucks is a cost-effective way of reducing damage to the road pavement. Weigh-in-motion systems save trucks time by checking their safety status as they drive over measurement plates at highway speeds. In the US, a developed version also checks trucking company and driver credentials by automatically accessing electronic data banks, enabling officials to focus on trucks that are likely to be suspect and achieve higher success rates. The US DOT estimates that manual checks can save around 0.7% of road traffic accidents involving trucks (approximately 440,000 each year). Automated screening can improve this to above 3.5% (See Weight Screening).

Major events place abnormal pressures on road and public transport networks because people come in large numbers. In addition, travel demand is often concentrated into comparatively short periods of time as people arrive and leave the event. The events can be regular or exceptional – and last for a day (as with sports fixtures), weeks (Olympics/Paralympics) or may continue for months (festivals).

Successful management of a major event requires close coordination between all parties: the event promoters, the authorities for roads and highways that are affected, the police, emergency services and transport operators. There may be heavy reliance on ITS – for example VMS to keep travellers informed about current options and CCTV to assist the network controllers in their tasks. At the same time, costs of additional equipment that may be needed for only a short period for non-recurrent events demand careful scrutiny (See Planned Events).

The connected vehicle concept is the subject of major ITS research programmes in a number countries including Europe, the USA and Australia. Techniques for two-way wireless communication of data, vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I), are being developed to increase road safety and mobility. Related telematics services such as Automatic Crash Notification and breakdown call button are direct results of the connected vehicles concept. (See The Connected Vehicle - PIARC Report)

Over and above its main aim of safety, V2I can help to reduce the delays and congestion resulting from road traffic accidents. V2I keeps vehicles in electronic contact with the roadside infrastructure, not only to help avoid crashes but also decrease the environmental impacts of traffic by smoothing traffic flow and minimising rapid accelerations and decelerations. One specific benefit being piloted is the ability to transmit traffic signal phase and timing information directly into the vehicle at upcoming intersections.

With V2V, vehicles ‘sense’ potential dangers by means of detectors that determine the presence of other vehicles, their positions and speeds. The on-board systems will then warn drivers and/or intervene automatically in engine management or braking systems, to avoid an accident.

Eventually, the hope is that V2V and V2I will reduce both the quantity and size of roadside infrastructure, by sending important safety- and mobility-related information directly into vehicles (See Warning & Control System).

A European project is working on methods of mining the data gathered by ITS installations to measure levels of road usage and so be able to predict more accurately when maintenance is likely to be needed. The approach could also allow consideration of more environmentally-friendly options in road maintenance programmes, for example to give priority to noise reduction.

For monitoring individual ITS installations in operation, the concept of an ‘online filing cabinet’ for storing information can help road maintenance engineers progressively improve overall performance rather than simply reacting to faults being notified. There is even the prospect of locating wireless sensors into road surfaces, to gather and relay information on condition and maintenance needs.

In the event of an incident or spill of hazardous materials (HazMat) the emergency services personnel need timely and accurate information about the vehicle location and nature and contents of consignments, so they can respond appropriately and maintain safety for the public and other road users (See Safety Information Exchange).

In the USA freight carriers move an estimated 700,000 shipments of hazardous materials every day. Electronic access to carriers’ databases for early identification of the vehicle and cargo enables responders to:

• save community resources by reducing routine HazMat team response times, unnecessary evacuations, and unjustified highway closures
• minimise resources expended in typically assuming a worst-case scenario and committing unnecessary levels of equipment and personnel
• minimise environmental and public health impacts by restricting the quantity of hazardous material that escapes, reducing the area affected and the extent of clean-up needed, and initiating mitigation measures more quickly

Natural disasters play havoc with the transportation infrastructure which is, at the same time, vital to keep operating as well as possible as a means of rescue and evacuation and bringing in supplies and equipment (See Emergency Response).

In humanitarian relief supply chains, ITS plays a key role in the last 1km-2km delivery from a local distribution centre (LDC) to affected populations. Computerised management of available vehicles and planning of delivery schedules can optimise resource allocation and routing decisions with the aim of minimising transportation costs and maximising benefits for those in need. This can be particularly important for disasters in developing countries with inadequate road networks.

Existing traffic management systems can play vital supporting roles. Bluetooth-based traffic monitoring proved effective when a factory in Texas caught fire and later exploded. Residents needed immediate evacuation, with school buses and ambulances coming in to rescue them and needing priority access.

Terrorist attacks – and the threat of them – are now facts of life in many parts of the world. Transport infrastructure is a natural target because of the large numbers of potential victims and the effects of the resulting disruption on much larger numbers of people and on regional and local economies.

Particularly vulnerable are large numbers of passengers moving through confined spaces, for example, transport termini and interchanges – and metro stations. Passenger evacuation systems depend for their effectiveness on the amount and quality of information made available. Simulations can model individual passenger movements to provide for the needs of the elderly and disabled, and integrate planned lifts and escalators for the capacity calculations needed to estimate realistic evacuation times.

Prevention of terrorist acts can be strengthened by systems for the early detection of would-be perpetrators. Analysis of CCTV footage of rail and bus stations can detect people making unusual movements.

Almost all ADMS now include a web-based graphical interface to support users’ queries. The interface is commonly based on Geographic Information Systems (GIS) technology. GIS comprise a set of computer software, hardware, data, and personnel – that store, manipulate, analyse, and present geographically referenced (or spatial) data. GIS can link spatial information on maps (such as roadway alignment) with attribute or tabular data. For example, a GIS-digital map of a road network would be linked to an attribute table that stores information about each road section on the network. This information could include items such as the section ID number, length of section, number of lanes, condition of the pavement surface, or average daily traffic volume. By accessing a specific road segment, a complete array of relevant attribute data becomes available.

The Graphical User Interface (GUI) shown in the ADMS architecture diagram above shows that the data archived in the ADMS can be accessed by different stakeholders over the Internet. Custom applications and reporting functions may be designed including performance measurement, predictive traveller information, traffic simulation model development support, and many other applications.

Digital maps are a pre-requisite for satellite navigation and many other ITS applications, such as automated driving and traveller information systems. Many technologies are currently available for creating and updating digital maps. For example, digital maps can be created by collecting raw network data, digitising paper maps, from aerial photographs and other sources. An initiative called OpenStreetMap (http://www.openstreetmap.org) intends to develop digital mapping for the whole world. The maps are developed from GPS traces collected by ordinary people and uploaded to the website. Aerial imagery and low-tech field maps are often used to verify that the resulting maps are accurate and up to date.

A navigation database is a commercially developed database used in satellite navigation systems. It is often based on a Network Gazetteer (See Basic Info-structure) and will contain all the elements needed to construct a travel plan or a route from a specific origin to a specific destination. Additional criteria may be added such as the route passes through a specific point, that it avoids tolls, that it is the fastest or shortest available, or that it minimises fuel consumption or emissions.

A navigation database is multi-layered and requires more than the basic coordinates for the road network links and nodes, although that is an important starting point.

Additional features necessary for navigation include:

• the complete road network geometry, which must be regularly updated
• a full and complete functional classification of the roads
• toll roads
• freeways/ expressways
• major urban arterial roads
• main streets
• residential streets
• low access streets (private roads, unpaved roads)
• accurate information on street and highway interconnections
• details of all motorway overpasses and underpasses
• road characteristics, including one-way information, turn restrictions, divided lanes, number of lanes and lane-use restrictions, stop lights, stop signs and construction status
• street, village, town and city names and alternative (alias) names where appropriate
• address ranges for both sides of the street
• postal location codes (postcodes, ZIP codes)
• "vanity" names for buildings and locations as well as the postal address

Navigation databases also contain information on points of interest and landmarks, such as public transport facilities, major office buildings by name, hotels, restaurants and tourist attractions, post offices, government buildings, military bases, hospitals, schools, petrol stations, convenience stores, shopping centres and malls, toll-booths – and in some countries, the location of speed cameras.

Crowd-sourcing and social networking has enabled the creation of navigation databases that are adapted to the needs of specific groups of road-users, such as truck drivers and cyclists. There are also important developments taking place in pedestrian navigation.

Further information

Infromation on pedestrian navigation: http://www.insidegnss.com/node/513 and http://www.navipedia.net/index.php/Pedestrian_Navigation

Location-based services are computer applications that use location data to control features or the information displayed to the user. They have several applications in health, entertainment, mobile commerce, and transport. In road transport, for instance, location-based services can be used to provide point of interest information (using data held in a navigation database – such as the closest fuel station or restaurant. Location-based services can also be used to display congestion or weather information according to the location of the user (See Location-Based Services).

In co-operative systems, vehicles share data with each other and with the road infrastructure using vehicle to vehicle (V2V) and vehicle to infrastructure (V2I) communications. Vehicles that are connected in this way can make use of real-time information on moving objects (such as other vehicles nearby), and on stationary objects that might be transitory (traffic cones, parked vehicles and warning signs). This highly detailed, constantly changing information is held in a data store known as a Local Dynamic Map (LDM). The LDM supports various ITS applications by maintaining information on objects that influence, or are part of, the traffic. Data can be received from a range of different sources such as vehicles, infrastructure units, traffic centres and on-board sensors. The LDM offers mechanisms to grant safe and secure access to this data by means of V2V and V2I communications.

The data structure for the LDM is made of four layers:

• the first layer stores the static map information. This is data about the road network, provided by a map data supplier, that is permanent
• the second layer extends the static map with information that is important for co-operative systems – for example road signs, intersection features and landmarks for referencing and positioning
• the third layer contains information that is dynamic and transient, such as weather, traffic attributes and road conditions
• the top layer contains highly dynamic information about the position of vehicles and road users – detected by in-vehicle and other sensors. It also keeps track of the available communication nodes. This fourth layer is particularly important for Connected Vehicle applications

Location referencing and object positioning for the upper layers of the LDM is complex and requires adequate location referencing methods. Since not all ITS applications need location referenced information, the use of this data is not mandatory.

These technologies allow the location of vehicles to be ascertained in real-time as they travel across the network. AVL has many useful applications for vehicle fleet management, such as improving emergency management services by helping to locate and dispatch emergency vehicles. AVL can be used for probe vehicle detection and on buses to locate vehicles in real-time and determine their expected arrival time at bus stops.

A number of technologies are available for AVL systems including dead reckoning, ground-based radio, signpost and odometer, and Global Positioning Systems. GPS is currently the most commonly used technology.

Fixed point transponder-based systems

Another system for tracking and locating vehicles uses fixed point transponders which can read and communicate with other equipment – for example, toll tags on-board vehicles. These systems can determine when a vehicle passes by a certain point, and provide useful information on travel times and speeds.

Mobile phone triangulation

A third method for locating vehicles is through mobile phone triangulation. The location of a mobile phone user is identified by measuring the distance to several cell phone towers within whose range the user is located. Using this technology, the location of the vehicle can be identified within an accuracy of about 120 meters. In rural areas, where few cell towers are located, the tower can measure the angle of transmission, which – along with the distance – can be used to locate the phone user even though the user might only be within the range of single cell phone tower. The estimated location in this case is not very accurate (within about 1.6 km).

Traffic detectors (or vehicle presence detectors) are used in many ITS applications for – network monitoring, traffic control, speed measurement and automatic incident detection. Many different types of detection technologies are available. The following are typical technologies that have been developed to measure traffic data in specific locations and zones. (See Vehicle Detection)

Inductive Loop Detectors (ILD)

Inductive loop detectors are currently the most widely used devices for vehicle detection, although microwave radar detection is also common. Their main uses are at intersections in conjunction with advanced signal traffic control systems, and on freeways for traffic monitoring and incident detection purposes. ILDs typically take the form of one or more turns of insulted wire embedded in the pavement. The loop is connected via lead-in cable to the detector unit, which detects changes in the loop inductance (changes in the in the magnetic field of the sensor) when a vehicle passes over it. ILDs can be used to detect a vehicle’s presence or passage. They can also be used to measure speed (by using two loops a short distance apart) and for classification of vehicle types. The main problem with using ILDs, however, is their reliability. Because ILDs are subject to the stress of traffic, they tend to fail quite frequently. Moreover, their installation and maintenance require lane closure and modifications to the pavement.

Microwave Radar Detectors

Microwave radar detectors are examples of non-intrusive detection devices whose installation and maintenance does NOT require lane closure and pavement modifications. Unlike inductive loops, non-intrusive detection devices are not embedded in the pavement. Instead, they are typically mounted on a structure over, or to the side of, the road such as the radar detection system in the photograph below.  Depending on the type of electromagnetic wave used, microwave radar detectors can measure either vehicle presence, or vehicle presence as well as speed. They are also widely used to detect pedestrians waiting at pedestrian crossings.

One of the major advantages of microwave sensors is their ability to function under all weather conditions. Exceptions can be extreme weather such as sand-storms. Given that these sensors are installed above the pavement surface, they are not typically subject to the effects of ice and ploughing activities. Experience shows that microwave sensors function adequately under rain, fog, snow, windy conditions. Their main problem is that they can be obscured by tall sided vehicles – reducing their accuracy when they are installed at the side of the carriageway.

Infrared Sensors

Infrared (IR) sensors are also non-intrusive detection devices. There are two types: passive and active detectors.

Passive IR detectors do not transmit energy – instead, they detect the energy that is emitted or reflected from vehicles, road surfaces and other objects. Passive infrared detectors can measure speed, vehicle length, vehicle counts and occupancy but their accuracy is affected by adverse weather conditions.

Active IR detectors emit a beam of Infrared energy which is reflected back to an IR receiver. They function in a similar way to microwave radar detectors – by directing a narrow beam of energy towards the road surface. The beam is then reflected back to the sensors – and vehicles are detected through changes in the “round-trip” transmission time of the infrared beam. Active infrared detectors supply vehicle passage, presence, speed, and vehicles classification information. They work well in controlled environments such as tunnels – and infrared can be used for safety purposes to detect over-heating vehicles or fire. Their accuracy is affected by weather conditions such as fog and precipitation.

Ultrasonic Detectors

Ultrasonic vehicle detectors function in a similar way to microwave detectors by actively transmitting pressure waves, at frequencies above the human audible range. These detectors can measure volume, occupancy, speed, and classification. Ultrasonic sensors are sensitive to environmental conditions. They require a high level of skill for their maintenance.

Acoustic Detectors

Vehicle traffic produces acoustic energy or audible sound from a variety of sources within the vehicle and from the interaction of the vehicle’s tyres with the road surface. Using a system of microphones, acoustic detectors are designed to pick-up these sounds from a specific area within a lane on a roadway. When a vehicle passes through the detection zone, a signal-processing algorithm detects an increase in sound energy and a vehicle presence signal is generated. When the vehicle leaves the detection zone, the sound energy decreases below the detection threshold and the vehicle presence signal ends. Acoustic sensors can be used to measure speed, volume, carriageway occupancy and presence. The advantage of acoustic sensors is that they can function under all lighting conditions and during adverse weather.

Magnetometers

Similar to inductive loop detectors (ILD), magnetometers provide for point detection, but they differ from ILD in that they measure changes in the earth’s magnetic field resulting from the presence of vehicles. They can provide information on traffic volume, lane occupancy, speed as well as vehicle length. In general, there are two types of magnetometers:

• micro loops which are installed in the pavement in a similar way as ILDs
• wireless magnetometers

Micro loops, (like inductive loops), require lane closure and pavement modification, with consequent delays to traffic. In recent years, the use of wireless magnetometers has received increased interest because of advances in battery technology which allow a unit to operate wirelessly for a period of 10 years before needing to be replaced.

Videos:

Traffic Detector Video Training Course - Part 1 - Detector Theory

Traffic Detector Video Training Course - Part 2 - Detector Design

Traffic Detector Video Training Course - Part 3 - Detector Installation

Traffic Detector Video Training Course - Part 4 - Detector Maintenance

AVI can be used to identify vehicles as they pass through a detection zone. Typically, a transponder (or a tag) mounted on the vehicle can be read by a roadside reader as the vehicle passes by. This information can then be transmitted to a central computer. Currently, the most common road transport application of AVI technologies is in combination with Automatic Toll Collection systems (such as EZPass). With these systems, the value of the toll is automatically deducted from a driver’s account each time the driver goes through the toll plaza.

Automatic Number Plate Recognition (ANPR) Systems

An important method of AVI, in common use, are ANPR (also known as Automatic Licence Plate Recognition - ALPR) systems which use optical character recognition technologies to identify and recognise vehicle registration plates. They typically consist of a specially adapted video camera linked to character recognition software. As a vehicle passes an ANPR/ALPR camera its registration number is read and can be checked against a database of vehicle records. There are two broad types of ANPR/ALPR systems:

• those that perform all the optical character recognition (OCR) processes in the field in real-time
• those that transmit the images to a remote computer for OCR processing

With recent advances in computer hardware and software – processing in the field in real-time has become quite feasible (it typically takes less than 250 milliseconds). This avoids the cost associated with the need for large bandwidth to transfer images to a remote server.

Weigh-in-motion sensors are designed to measure and record axle weights and gross vehicle weights while the vehicle is in motion (driving – not stopped). WIM systems are attractive because they avoid the need to stop and weigh every vehicle. They have not eliminated the need for weighbridge sites for accurate weighing of trucks, but WIM acts as a filter and only vehicles which register an excess axle load need to be stopped and checked. The key component of any WIM system is the force sensor – for example quartz crystals produce electric charge when a force is applied along the vertical axis (the weight of the vehicle). WIM systems have several applications in ITS, especially as a part of an electronic pre-clearance system for commercial vehicles, as well as for enforcement applications. (See Enforcement and See Video)

Further Information

http://www.worldhighways.com/categories/traffic-focus-highway-management/features/weigh-in-motion-and-anpr-techology-aid-highway-protection/

Speed detection is an integral part of speed camera enforcement systems used to detect speed-related violations of traffic rules especially at accident hot spots. (See Speed Management) Regulation of speed is important at work zones where personnel are at increased risk of an accident. It is also a feature of active traffic management schemes on motorways. Some speed enforcement systems automatically link speed cameras to vehicle number-plate (Licence-plate) recognition for issuing enforcement notices. (See Traffic Management and Integrated Strategies) Speed detection can also be used as a safety measure at signalised intersections on fast arterial roads by using microprocessors to extend the green time at traffic signals when a vehicle is approaching at speed.

For measuring speed, the most common device is a radar meter or sensor which uses the Doppler principle. Specifically, the device measures the difference in the emitted and reflected frequency of a radar wave – which is proportional to the speed of the moving object. Other types of vehicle sensors can be adapted in pairs to measure speeds – such as ultrasonic sensors and magnetometers.

Journey time monitoring is related to speed monitoring. Vehicle journey times are significant sources of information for network performance monitoring and advising road users about travel delays in real-time. They are a measure of the level of service on offer. Some road authorities display point-to-point journey times on roadside VMS as a form of real-time information. Journey time data (historic and in real-time) is also a useful resource for journey planning and logistics support. (See Journey Time Monitoring)

Travel Times and Speed over Distance

Various methods are available to anonymously track vehicles on the network and enable network operators to determine average travel times, point-to-point demand and traffic flow conditions. For example, Automatic Toll Collection (ATC) systems can be used to determine the average travel time on highways between toll collection plazas or specially installed roadside readers. Infra-red (IR) tag-equipped vehicles are used as probes for monitoring traffic flow conditions – which are detected by transponder readers, installed along roadways. Aggregate data on average speeds and travel times can be compiled and this helps support incident and traffic management. To protect travellers’ privacy, these systems scramble the toll tag identifiers and only keep records of trips made by anonymous vehicles.

A number of other techniques are used to provide continuous, non-invasive, point-to-point tracking of individual vehicles to determine travel times and calculate average speeds. They include automatic number-plate recognition cameras (ANPR cameras) to identify vehicle licence plates. A new development is point-to-point monitoring of Bluetooth signatures emitted by equipment present in the vehicle. Bluetooth sensors have been used successfully for point-to-point average speed monitoring as a cheaper alternative to ANPR. Some road authorities use aggregated data (made anonymous) to display on VMS to provide drivers with expected journey times between key points on the network.

Environmental sensors are used in road network monitoring to detect adverse weather conditions such as icy or slippery conditions, high winds or precipitation (snow or rain) or the presence of fog/mist. This information can then be used by operators to alert drivers via variable message signs (VMS). It can also be used by highway maintenance personnel to optimise winter maintenance operations. (See Weather Monitoring)

Environmental sensors can be divided into six types:

• road condition sensors that measure surface temperature, surface moisture, and presence of snow accumulations
• visibility sensors that detect fog, smog, dust clouds, heavy rain, and snow storms
• thermal mapping sensors that can be used to detect the presence of ice
• anemometers to detect wind speed
• air quality sensors to monitor pollution levels
• noise sensors to measure traffic noise levels

Many manufacturers provide complete weather station systems that are capable of monitoring a wide range of environmental and surface conditions. The figure below shows one example of these weather stations.

(Figure 4.7 to be located here – to be supplied by the author)

Weather stations typically include the following types of sensors and capabilities:

Road condition sensors: A critical component of any road weather information system (or RWIS) is a set of road condition sensors that measure surface temperature and moisture, and detect the presence and thickness of snow and ice. Road condition sensors can be embedded in the pavements. They can also be non-intrusive – mounted to side or above the road surface. Non-intrusive road condition sensors typically measure the emitted infrared radiation from the road surface.

Visibility sensors: These sensors are designed to measure visibility along a road section. They typically use the principle of “forward scattering” or diffraction of light to detect changes in visibility resulting from inclement weather conditions such as fog, haze, and smoke. The sensors need to be carefully sited because they can only provide spot measures at a specific location. For example, fog detectors need to be sited as near as possible to the source where mist or fog forms first.

Thermal mapping: Given that temperatures can vary significantly along a roadway segment, thermal (temperature) mapping sensors are typically a critical component of an effective ice detection system. Thermal mapping provides road operators with information on road-surface temperatures to inform decision making on the need to set-up warning messages on VMS or to deploy snow clearance, road salting and gritting services. Examples of thermal imaging sensors include thermal imaging cameras/ video and infrared thermography.

Wind speed sensors: These are an essential component of an environmental sensing station and are installed at high and exposed bridges and windy locations on the road network. They typically measure surface wind speed and direction and can be used to provide warnings to vehicles towing trailers and high-sided vehicles. For safety reasons it is sometimes necessary to close the road in high winds.

Cell phones are a very effective tool for incident detection. Many regions have established an incident reporting hotline to encourage citizens to report traffic incidents. This has the advantage of low start-up costs.

Anonymous Mobile Call Sampling

The widespread use of cell phones can provide useful traffic information. Triangulation techniques can determine a vehicle’s position by measuring signals from an on-board cellular phone within the vehicle. To enable this, the cell phone needs to be communicating with more than one cell-phone cell – preferably three or more for accuracy – so that triangulation can take place. Each phone is typically identified by its electronic serial number. This concept was first tested in the Washington D.C. area in the mid 1990s. This concept is different from GPS-based AVI systems in which the GPS unit on the phone determines the location, which is then communicated from the phone to a central processing system.

Emergency Roadside Telephones (ERTs) were regularly provided prior to mobile telephones becoming widely available. ERTs still provide a valuable service where there is a low ownership of mobile telephones or a mobile-phone black spot. They provide an accurate location to the operator of where a caller is located and enable stranded motorists to call for help. More generally, they allow travellers to report incidents such as accidents or stray animals on the carriageway.

To use a call box, the motorist just needs to lift the receiver or press a key to request the services of the police or emergency services. The caller is automatically connected to a control room operator.

Advanced types of ERTs provide background noise cancellation against traffic noise, and a simple question and answer facility based around «yes» and «no» keys for the profoundly deaf and foreign travellers. The Operator has a formal list of questions that they can ask in sequence by typing in the questions. The questions appear on a small screen at the ERT and the user answers using the yes and no keys. The option to select different languages is a great advantage near ports and border crossings where there is a high percentage of foreign visitors. They also have a call-back facility that enables the operator to call the stranded motorist, with a beacon and ring tone to attract attention.

Typically, the phones are located on the side of the freeway, and are spaced at distances ranging from 0.25 miles to 0.50 miles apart. On all-purpose dual carriageway arterial roads, freeways and motorways they need to be located in pairs on either side of the road to avoid travellers being tempted to cross the road to use one.

(Figure 4.5 Call Box – Image to be provided by Barry Moore)

These are teams of trained officers who are responsible for covering a given segment of the freeway. Mobile patrols have a central part to play in road network operations, spotting debris on the road, dealing with incidents and the general public. A freeway service patrol vehicle [Figure 4.6] is typically equipped to be able to help stranded motorists and, where possible, to clear an incident site. Mobile patrols are capable not only of responding to incidents, but in some cases to perform the entire incident management process (from detection to clear-up).

Technology, in the form of secure mobile communications and hand-held tablets, provides support. TETRA mobile radio communications offer digital transmission capability whilst maintaining the advantages of a Private Mobile Radio (PMR) system. In future service patrols may have command and control capability to direct and manage the deployment of on-road resources – and the potential to set VMS and signals on location, remotely from the road side.

Figure 4.6 A Freeway Service Patrol Vehicle

A relatively new technique for collecting traffic-related information based on mobile reports is crowdsourcing – using social networks such as Facebook and Twitter. Crowdsourcing is the process of obtaining information online that is provided by a crowd of people. This method has become feasible in recent years because of the significant developments in positioning and communications technologies that are linked to mobile phones which have internet connectivity. In road transport, crowdsourcing concept can be used to collect vital travel-related information in collaboration with members of a community. One of the most famous and successful of these crowd-sourcing applications is WAZE (https://www.waze.com/) – one of the world's largest community-based traffic and navigation apps. Users of WAZE share real-time traffic information, allowing members of the on-line community to save time and fuel while travelling.

Vehicles are used to report journey times and detect traffic incidents – monitoring their progress in time and space. This can be done by either using automatic vehicle location systems or by tracking the progress of identified vehicles between known fixed points on the network. The location of the vehicle in time and space is communicated to a central computer where data from different sources is fused to determine the status of traffic flow over the transport system.

Vehicle probes can provide very useful information that other detection techniques cannot – including information on link travel times, average speeds, and origin-destination information.

Different technologies are available. These include:

• Automatic Vehicle Identification (AVI);
• Automatic Vehicle Location (AVL);
• Anonymous Mobile Call Sampling;
• Bluetooth and Wi-Fi Networks.

Vehicle probe methods give more reliable but less dense data than crowd-sourcing, which may provide better geographical coverage. Vehicle probes are often deployed by road network operators in collaboration with the owners of vehicle fleets that regularly travel the network.

Video image processing (VIP) identifies vehicles and their associated traffic flow parameters by analysing imagery supplied from CCTV cameras which normally have a fixed field of view. The addition of VIP significantly improves the usefulness of CCTV, particularly where there are a large number of cameras installed, which an operator cannot view at the same time. VIP also provides the means for alerting operators to a traffic incident.

Analogue CCTV images are digitised and then passed through a series of algorithms that identify changes in the image background. In modern digital cameras the video image is already in a digital form – ready for processing. A VIP system consists of a video camera (a digitiser in the case of analogue cameras) and a microprocessor for processing the digital-image – and software to interpret the image content and extract detection information from it.

VIP for Traffic Detection

With digital processing CCTV provides an above-ground alternative to inductive loops or other means of vehicle detection. One big advantage of VIP systems is their ability to provide detection over a number of lanes and in multiple zones within the lane – providing wide area detection. The user can easily modify the detection zones, within seconds, through the graphical interface – without the need to close traffic lanes and dig-up the pavement. Poor lighting, shadows, and bad weather can negatively affect the performance of VIP systems. Evaluation studies in Oakland County, Michigan indicate that modern VIP systems yield excellent performance with a detection accuracy of over 96% under all weather conditions.

VIP for Incident Detection

VIP systems can be combined with CCTV systems to provide an excellent detection tool, particularly for incident detection and verification purposes. When an incident occurs, the user can switch from the VIP mode to the standard CCTV mode, and then verify the occurrence of the incident via pan/tilt/zoom controls.

 

Dynamic Message Signs are also referred to as Variable Message Signs and Changeable Message Signs. In this website the following terminology is used:

• Dynamic Message Sign (DMS) refers to any sign or graphics board where the message (text or pictogram) conveyed to the viewer can change.

A DMS may be either a Variable Message Sign (VMS) or Changeable Message Signs (CMS) where:

• VMS is a sign capable of displaying pre-defined or freely programmable messages which can be changed remotely, namely with individual pixel control;
• CMS is a sign capable of displaying pre-defined fixed messages which cannot be changed remotely;
• A Portable Dynamic Message Sign is referred to as a PDMS.

DMS are among the most common types of devices for information provision. They can either be fixed  or portable as shown below. They can be text-based, graphics based or a combination of the two (See Traffic Management)

DMS can be used to provide travellers with instructions such as closed lanes or recommended speeds and information on traffic and weather conditions, incident locations and expected delays, construction work, alternative routes and speed advisories. Different types of DMS can be light-reflecting, light-emitting, and hybrid according to the technology used. Light emitting diodes (LEDs) are generally the preferred option where there is a power supply (including solar options).

Light-reflecting signs

As the name suggests, these rely on an external source of light, such as the sun, headlights, or overhead lighting, to make them visible – by reflecting the light source. Different types of light-reflecting signs include rotating drum and reflective disk matrix signs. Rotating plank/drum signs are made of one to four multi-faced drums, each containing two to six fixed text messages or graphics. The main application of rotating plank/drum technology when it is incorporated into a fixed direction sign – is to provide variable instructions, that are identical in appearance to the fixed sign face, to show an alternative direction to a destination.

Reflective disk matrix signs comprise an array of permanently magnetised, pivoted indicators that are black on one side, and reflective white or yellow on the other. When a specific pixel is activated, an electric current flips the indicator from the black finish to the reflective yellow finish.

Reflective disk matrix signs were popular in 1970s for freeway management systems because they were less costly than light-emitting signs. Mechanical failure of some or the entire message is common (disk failure). As LED signs become less costly the older technology is falling out of use.

Light-emitting signs

These generate their own light on or behind the viewing surface – either in monochrome or full colour. Light emitting diode (LED) and fibre-optic DMS are two examples:

• where LED are used to create display pixels they are typically amber in colour – although full-colour and white LED display panels are now coming into use;
• fibre-optic DMS funnel light energy from a light source through fibre bundles to the sign face.

LED has become the preferred technology. New versions of LED DMS provide a display known as a full matrix that can display graphics and images.

Hybrid DMS combine the characteristics of both light-reflecting and light-emitting DMSs. One of the best examples of hybrid DMSs is the reflective disks/fibre-optic or LED DMS. During weather conditions when light-reflecting DMS are not clearly visible, these hybrid systems can use light-emitting technologies such as fibre-optics or LED. When the sun is shining, the light sources are turned off. Solid state LEDs are more reliable than reflective disks since there is no risk of mechanical failure.

In-road markers or lane lights (also known as intelligent road studs) can be used to convey important messages to drivers, in addition to their most direct function of lighting the way at night. For example, in-road markers can be used to communicate the usage of a lane. Intelligent road studs have been used for signing the use of the hard shoulder during periods of heavy congestion, hazard warnings and operation of part-time bus lanes

These devices are typically located inside the vehicle and, similar to DMS, are designed to provide information to drivers while en-route. In-vehicle information devices can provide information by either audio or visual means. Examples of auditory in-vehicle information devices include highway advisory radio (HAR), cellular phone hotlines and commercial radio. Examples of visual in-vehicle devices include video display devices and head-up displays (which drivers can read without altering their normal viewing position

Highway Advisory Radio

Highway advisory radio (HAR) provides another means for disseminating information to drivers while en-route. Typically, information is provided through an AM receiver. Drivers are informed about the existence of an HAR signal by signs which are typically installed upstream of the signal, advising drivers to tune in to a specific frequency (typically either 530 kHz or 1610 kHz) (See Radio).

HAR can be used to provide travellers with information similar to that provided by VMS. One advantage of HAR compared to VMS is that it is less distracting – since information is provided through a different sensory channel (audio) which reduces visual information overload. More complex messages are also possible with HAR compared to DMS. The disadvantage is that users have to tune to the frequency themselves.

Cellular Telephone Hotlines

Another way of providing information to drivers en-route, – which has increased in popularity with the widespread use of cellular phones – involves establishing a “hotline” phone system for traffic information that drivers can call from their cell phones while en-route (such as the 511 system in the US). The phone systems typically include a touch-tone menu that allows callers to receive route-specific traffic information – this gives the driver control over the type of information received.

AUDIO: Local radio

Commercial radio is another means of providing en-route traveller information. The primary disadvantage of commercial radio is the accuracy and timeliness of the information. Typically, information is broadcast only when normal scheduling permits – and in many cases, this may be inappropriate since an incident might have been cleared by the time normal scheduling permits broadcasting.

Video and Head-up Display Terminals

A recent approach to disseminating traffic information en-route involves the use of dashboard displays, video and head-up display terminals. Close attention to the design of the Human-Machine Interface is needed to minimise driver distraction (See Human Factors).

These technologies are widely used for pre-trip and off-roadway information dissemination. They include cable TV, phone systems, the internet, pagers, smart phones and tablet computers. Many metropolitan areas around the globe now have websites dedicated to traveller information. These systems provide travellers with a wealth of travel-related information, including current travel conditions, alerts, and other timely information. A traffic map showing current speeds, locations of any incidents or construction zones typically form a central part of these websites. Among the technologies used for off-road roadway information dissemination are dynamic public information displays and kiosks – and mobile devices.

Dynamic Public Information Displays and Kiosks

Large shopping malls and motorways often have dynamic information displays and kiosks where real-time travel conditions may be provided. This is also true of many motorway rest areas. These displays and kiosks were very helpful before widespread public take-up of mobile computing devices and smart phones. With the advent of these technologies, public information displays and kiosks have played a secondary role in information dissemination. They are still available at many sites and are useful for those sectors of the population who do not have access to mobile computing and smart phones.

Mobile Devices

The high market penetration of smart phones, tablet computers and personal navigation devices has provided the transport industry with an invaluable tool for disseminating travel information. The unique advantage of these nomadic and mobile devices is that they make travel information available to travellers on a continuous and uninterrupted basis.

Many navigational devices and services include real-time information about the transport network conditions. This is demonstrated by services such as Google maps and navigation – as well as by GPS navigation devices that can receive real-time traffic condition information. Crowd-sourcing is also being used to collect and disseminate travel information.

Point-to-point microwave communication uses ground-based transmitters and receivers resembling satellite dishes to provided dedicated backhaul links where landlines would impractical or prohibitively expenses to connect roadside networks to a control center. They are usually in the low-gigahertz range and limited to line of sight. Repeater stations can be spaced at approximately 48 km intervals to cover greater distances.

Wi-Fi has become a very popular technology for the exchange of data wirelessly using radio waves over a computer network. Wi-Fi can support non-critical ITS applications because it avoids delay – but does not have bandwidth guarantees. Wi-Fi operates using unlicensed frequencies – so are more susceptible to interference. The technology has potential for use in ITS as a means for connecting field devices to a Traffic Control Centre – for example, where a wired communications solution would be too expensive. In this case, a secure Wi-Fi connection, such as the wifi-mesh network shown in the figure below would need to be provided. This shows a multipoint to multipoint WiFi Mesh network suitable for VMS, car park counters, traffic signals, remote monitoring and non-enforcement CCTV.

Wi-Fi is based on the Institute of Electrical and Electronics Engineers’ (IEEE) (IEEE) Standard 802.11. It is designed to provide local network access over relatively short distances (between 50 – 100 meters) with speeds of up to 54 Mbits/second.

(Figure courtesy of Barry Moore)

Bluetooth

Bluetooth technology also supports data exchange over short distances. It uses short-wavelength ultra-high frequency (UHF) radio waves. Bluetooth technologies are used in many different applications such as smart phones, headsets, tablets and laptop computers. Recently, there has been increased interest in building on the presence, on-board vehicles, of Bluetooth devices in “discoverable” modes, to track and monitor traffic. These applications use roadside Bluetooth detectors to discover Bluetooth devices on-board the vehicles and detect their unique identifier. By tracking the same identifier through different location points, important traffic parameters can be determined such as travel time, speed, vehicle origin and destination.

Another group of communications technologies widely used in ITS is dedicated short-range communications (DSRC). DSRC was developed specifically for vehicular communications and is likely to witness a dramatic increase in use with the introduction of Connected Vehicle technologies. The technologies are used in a number of ITS applications including:

• electronic payment for parking and tolls;
• commercial vehicle pre clearance;
• bus and emergency vehicle signal priority;
• in-vehicle signage;
• probe vehicle data collection;
• highway-rail intersection warning;
• intersection collision avoidance;
• vehicle-to-vehicle cooperative systems such as Adaptive Cruise Control (ACC) and Forward Collision Warning (FCW).

In the USA, DSRC generally refers to communications on a dedicated 5.9GHz frequency band reserved specifically for Wireless Access in Vehicular Environment (WAVE) protocols – defined in the IEEE 1609 standard and its subsidiary parts. These protocols are based on the widely-used IEEE 802.11 standard for Wi-Fi wireless networking.

Several DSRC technologies are used in transportation. These include:

Passive microwave (tag & beacon)

Passive tags do not have an internal power supply. Instead, they use the very small electrical current induced in the antenna by the incoming radio frequency signal, to transmit a response. For this reason, the antenna has to be designed not only to collect power from the incoming signal, but also to transmit the outbound backscatter signal. The main advantage of passive microwave tags is that they can be quite small and have an unlimited life. Passive microwave was used in ITS for early types of electronic toll collection systems. Innovations in their use continue.

Active microwave (IEEE 802.11/WAVE)

Active tags have their own internal power source which can generate the outgoing signal. Compared to passive tags, they may have a longer range and can store additional information sent by the transceiver. Active microwave is employed in many electronic toll collection systems. More expensive on-board units have batteries which need replacing.

Infra-red (DSRC)

Infra-red DSRC uses infra-red technology, as opposed to radio spectrum or microwave, for short-range communications. Infra-red DSRC can be used in ITS where it is difficult to secure a frequency spectrum license. The technology is also appropriate when the weather is generally rainy – but not foggy. Infra-red DSRC is less susceptible to security intercepts.

Bluetooth is a wireless technology designed to allow data exchange over short distances (a maximum of about 10 meters). Most cell phones on the market today have Bluetooth technology. They also have Wi-Fi wireless technology, which uses radio waves for connections for distances to a Wi-Fi base station of up to 90 meters. In recent years, several automotive manufacturers have been embedding Bluetooth technology into their vehicles to allow drivers to connect their phones or music devices to in-vehicle audio systems.

When activated, Bluetooth and Wi-Fi transceivers continuously broadcast “discovery” messages to allow other devices to find and connect with them. The discovery messages include a unique identifier that can be used for vehicle detection and tracking. Essentially, all that is needed is a Bluetooth or Wi-Fi sensor installed close to the roadway. These sensors record the time at which a a vehicle equipped with an on-board Bluetooth or Wi-Fi device drives past them. By utilising the unique identifiers recorded at successive monitoring points, information on travel times along a road segment – or the pattern of Origin-Destination flows through a network – can be derived.

The use of Bluetooth or Wi-Fi is ideal for crowd sourcing but the results have to be calibrated as:

not all vehicles report an identifier – since some will not be equipped with the technology or the equipment may be turned off – leading, in both cases, to no count being registered

or a single vehicle may have several active devices – leading to multiple counts.

When using this vehicle sampling technique a key challenge is to ensure that a sufficiently high proportion of vehicles are equipped with Bluetooth and Wi-Fi devices. In urban areas, this may not be a major concern, but in other regions low market penetration may limit the application of these detection technologies.

Communications over a wide area are often required in Network Operations – particularly in rural areas where the options for voice and data communications and the transmission of CCTV images are more limited.

WiMax

WiMax stands for Worldwide Interoperability for Microwave Access. WiMax is designed to provide much higher bandwidth, compared to Wi-Fi, and at a much extended range. Recent years have seen increased interest from the ITS industry in integrating WiMax and Wi-Fi as an alternative communications medium to wired communications.

Under ideal conditions, WiMax could have a range of more than 40 kilometres, and offer speeds of up to 70 Mbits/seconds. It implements the IEEE 802.16 Standard, with newer standards designed for speeds of up to 1 Gbits/second. A typical WiMax network would consist of a base station connected to several client radios (Customer Premise Equipment or CPE).

Cellular Data

Cellular networks were established primarily for voice communications, but there is steadily growing increased interest in their use for data communications as well. Two voice communication cellular technologies have evolved in this way:

Global System for Mobiles (GSM)

Code Division Multiple Access (CDMA)

They differ in the way they transfer data. GSM divides the frequency band into multiple channels for use by different users. CDMA digitises calls and unpacks them at the back end. Both GSM and CDMA have been refined and enhanced over the years to allow for increased speed. For example GPRS (for packet data communications) uses the GSM cellular network at speeds suitable for transmitting commands to VMS and car park counters.

The latest cellular data technology is Long Term Evolution (LTE) (also known as 4G LTE). Unlike GSM and CDMA, LTE is designed primarily for data communications, with voice as an override. It offers high bandwidth, low latency, and supports full data rates while travelling at high speeds (a feature which is important in the ITS environment with fast-moving vehicles). Cellular data communications can be used in ITS where wireline communications are not available or are cost-prohibitive.

Digital Radio Data

Digital Radio Data (DRT) refers to the practice of transmitting digitised and compressed data over FM radio. This allows small amounts of digital information to be embedded in conventional FM radio broadcasts. A good example of a DRT application in ITS is the Radio Data System-Traffic Message Channel (RDS-TMC), where digitally encoded traffic information is made available for in-vehicle navigation devices. RDS-TMC is an early form of digital data transmission. It was developed in Europe to exploit the Radio Data System used by some broadcasting authorities. Travel information is transmitted digitally over FM radio frequencies – and a decoder, built into the car radio or navigation device, interprets the digital code for text or graphic display.

Spread Spectrum Radio

Spread spectrum radio is a radio network that has a “line-of-sight” requirement (unobstructed line of path between a subject and an object). In this network, one radio serves as the master and the other as slave. An example of the use of spread spectrum radio in ITS is the connection between a set of traffic controllers at signalised intersections and the Traffic Management Centre (TMC) needed for monitoring and signal timing purposes.

In some cases, it might not be possible to directly link the two radios because of distance or interference – in which case another radio (called a repeater) would need to be installed in-between the two radios. These networks are most commonly used to allow a number of traffic controllers to communicate with one another, or to communicate with a traffic operations centre. They can broadcast over the unlicensed frequencies of 900MHz, 2.4 GHz and 5.8 GHz. The 5.8 GHz frequency provides the highest bandwidth at about 54 Mbits/second, but is very susceptible to line-of-sight problems.

Whilst theoretically, spread spectrum radio can provide a communication range of up to 60 miles, in practice the range is much shorter because of line of sight attenuation or obstructions.

Computer signal control systems first appeared in the 1960s when computers were first used to coordinate the traffic signal controllers for a group of intersections – but without the benefit of today’s “feedback” of information from the field detectors to the computers. In this type of system (known as open-loop control) the traffic plans that are implemented are not responsive to actual traffic demand. Instead, plans are developed “off-line” using data from historical traffic counts – and implemented according to time-of-the-day and the day of the week.

This system is quite basic, but it still offers several advantages including:

• the ability to update signal plans from a central location – greatly facilitating implementation of new signal timing plans as the need arises;
• the ability to store a large number of signal plans – that can be implemented depending on prevailing traffic conditions;
• automatic detection of any malfunction in the operation of the controllers or the signal heads.

The next level of sophistication is signal control systems where information from field traffic detectors is fed-back to the central computer. The computer uses the information on current traffic conditions to select the signal plan to be implemented (closed loop control). Plan selection is made according to one of the following methods.

Select a Plan from a Library of Pre-developed Plans

Here, the system has access to a database (library) that stores a large number of different traffic patterns along with the “optimal” signal plans (developed off-line) for each traffic pattern. Based upon information received from the traffic detectors, the computer matches the observed traffic pattern to patterns stored in the library, to identify the most similar pattern. The “optimal” plan associated with the identified pattern is then implemented. This type of adaptive traffic control system is often referred to as a First Generation system. Its distinguishing feature is that the plans, while responsive to traffic conditions, are still developed off-line. First Generation systems work on the basis of current traffic data and do not generally have traffic prediction capabilities.

Develop Plan On-line

In this method, the “optimal” signal plan is computed and implemented in real-time. The optimal signal timings are computed in real-time using current data on traffic conditions obtained from detector information. This requires sufficient computational power to make the necessary computations on-line. It also needs enough data from the vehicle detectors to make the calculations. The systems that develop plans on-line are classified as either Second-Generation or Third-Generation systems. They typically have a much shorter plan update frequency compared to First-Generation systems, typically every 5 minutes for Second-Generation systems, and from 3 to 5 minutes for Third-Generation systems. In addition, some Third-Generation systems use forecasts of traffic conditions obtained from feeding the detector information into a short-term traffic-forecasting algorithm.

There are a number of examples of adaptive traffic control systems in use around the world. Amongst the most widely accepted algorithms are SCOOT, SCATS and RHODES.

SCOOT

SCOOT (Split, Cycle, Offset Optimisation Technique) is an adaptive traffic control system developed by the United Kingdom’s Transport Research Laboratory (TRL) in the early 1980s. SCOOT operates by attempting to minimise a performance index (PI) – typically, the sum of the average queue length and the number of stops across the controlled network. In order to do this, SCOOT modifies the length of the cycle, the amount of green time given to each signal phase (known as the time “splits”), and the offset time for each set of signals (the time difference between the cycle start times at adjacent signals). SCOOT computes these calculations in real-time in response to the information provided by vehicle detectors.

The operation of SCOOT is based upon Cyclic Flow Profiles (CFP). These are presented as histograms (graphical representations of user-specified ranges) that show the variation in traffic-flow over a cycle – which is measured by loops and detectors that are placed midblock on every significant link in the network. Using the CFPs, the offset optimiser calculates the queues at the stop-line. The optimal splits and cycle length are then computed.

Several additional features have been added to SCOOT to improve its effectiveness and flexibility, including the ability to:

• provide signal priority for public transport (transit) vehicles;
• automatically detect the occurrence of incidents;
• add-on an automatic traffic information database to feed historical data into SCOOT – enabling the model to run even if there are faulty detectors.

SCATS

The Sydney Co-ordinated Adaptive Traffic System (SCATS) was developed in the late 1970s by the Roads and Traffic Authority of New South Wales in Australia. For operation, SCATS only requires stop-line traffic detection, not the midblock traffic detection that is necessary for SCOOT. This simplifies installation since the majority of existing signal systems are equipped with sensors only at stop-lines. SCATS is a distributed intelligence, hierarchical system that optimises cycle length, phase intervals (splits), and offsets in response to detected volumes. For control, the network of signals is divided into a large number of smaller subsystems, each ranging from one to ten intersections. The subsystems run individually unless traffic conditions require the “marriage” – or the integration – of the individual subsystems.

RHODES

Since 1991, the University of Arizona has been developing a real-time adaptive control system called RHODES, which stands for Real-time Hierarchical Distributed Effective System. RHODES is designed to take advantage of the natural stochastic (random) variations in traffic flow, to improve performance – a feature which is missing from systems such as SCOOT and SCATS.

The RHODES system consists of a three-level hierarchy that decomposes the traffic control problem into three components: network loading, network flow control and intersection control:

• at the highest level, a stochastic traffic equilibrium model is used to predict expected traffic loads on the links of the network;
• the second level, Level 2, represents the high-level decision-making process for setting signal timing to optimise traffic flow. This recognises the unpredictable (stochastic) nature of traffic and attempts to take into account future expected traffic loads over the next few minutes. Level 2 is concerned with setting approximate phase sequences and splits for a given corridor (target timings).

Level 3 is concerned with intersection control – determining the optimal time to change traffic signals for the next phase sequence and whether the current phase should be shortened or extended. The time frame for control level 3 is typically in the order of seconds and minutes.

Where there alternative routes available the problem of optimising traffic on the network can be tackled mathematically. For dynamic route guidance (DRG) the “objective function” (an equation expressing the operational function that needs to be maximised or minimised) – is the measure of the highway network’s performance that needs to be optimised. For example the objective might be to minimise the total travel time for all vehicles. The decision variables are the proportions of traffic that splits at each diversion point – to optimise network performance. The traffic-splits define how traffic should be distributed. The aim is to model traffic flow in the region and ensure that it is maintained at the nodes and along the links of the network, without congestion setting in. ITS software can then be used to solve the problem of optimising the objective function and recommending a routing strategy that will vary in real-time according to traffic conditions. Routing advice will be given in traffic broadcasts and on VMS, or with in-vehicle route guidance for those vehicles that are equipped.

Public transport priority (known as Transit Signal Priority or TSP in the USA) is a measure aimed at reducing delay for public transport vehicles (buses, trams, taxis) at signalised intersections by giving their movements preferential treatment. The methods for doing this can be divided into passive and active strategies. The basic difference is whether specialised sensors and detectors are used to detect approaching public transport vehicles. Without supporting technologies to specifically identify these type of vehicles, passive TSP technology simply improves conditions for all vehicles along a public transport corridor.

Active technologies detect an approaching bus or tram (this is typically accomplished by having a transmitter on the vehicle that communicates with a receiver or detector on the roadside signal controller). Different algorithms or strategies are available for active bus priority. Amongst the most common are:

Green Extension: this extends the green time if a bus or tram is detected, to allow the priority vehicle to pass – up to a certain pre-determined limit. This strategy only benefits a small portion of vehicles, but the reduction in delay for beneficiaries is significant (equal to the length of the whole red interval)

Early Green: shortens the green time for conflicting phases, by a pre-defined amount of time – for example when the bus arrives whilst the traffic light is in its red phase. Early green benefits a large percentage of buses, but the saving per vehicle is not as large as for Green Extension

Phase Rotation: under this strategy, the sequence of green time for different manoeuvres at the intersection is changed so that the priority vehicle is not held up. One common modification – that allows the vehicle to cross the opposing traffic stream – involves swapping a dedicated turn signal at the start of the cycle (the “leading” phase) to the end of the cycle (the “lagging” phase).

Actuated Transit Phase(s): involves establishing transit phases, which are only active when a bus/tram is present. In this case, a special transit signal face would display, for example, a letter “B” for Bus or “T” for Tram.

Phase Insertion: this allows the same phase to appear more than once during the same cycle in order to serve the transit vehicle.

The OBE are:

• the equipment inside the vehicle with which the drivers will interact;
• and the technologies needed to provide vehicle-based information for use within CV applications.

Some of the vehicle-based information can be obtained from GPS or other similar sensors (for example location, speed, and direction), whereas other information (for example acceleration, instantaneous fuel consumption, anti-lock brakes activation, wiper status) may be obtained from vehicle engine scanning tools and other systems monitoring the vehicle’s different subsystems.

Connected vehicles are instrumented with a wide range of sensor technologies to enable applications aimed at improving safety and efficiency – including:

• position sensors such as GPS or Inertial Navigation Systems (INS)
• speed and braking sensors;
• vehicle proximity sensors that can also measure the distance or headway between the subject vehicle and the car in front or behind;
• sensors able to detect sleepy or incapacitated drivers (these typically use video cameras and sophisticated video image processing/pattern recognition algorithms);
• near-and far-distance obstacle detection sensors based on either LIDAR (LIght Detection And Ranging) or radar technologies to identify hazardous situations or imminent collisions – to warn the driver and take evasive actions to prevent the collision.

Roadside units and equipment are infrastructure systems that communicate with vehicles and collect data from the vehicle. Roadside equipment can support infrastructure-based applications – or applications involving co-operation between vehicles and the infrastructure (such as intersection collision avoidance systems, and eco-signals which inform approaching vehicles about the remaining green-light time to enable drivers to adjust their speed). Roadside equipment also supports remote applications by communicating information collected from the vehicles to a central location for processing. They also may help support the security and integrity of cooperative vehicle systems.

The communications network is the infrastructure needed to provide connectivity between vehicles (V2V), between vehicles and the infrastructure (V2I), and between roadside equipment and other parts of the system (V2X). Wireless communications are required for V2V and V2I communications, whereas roadside equipment may use wireless or wired networks.