Road Network Operations
& Intelligent Transport Systems
A guide for practitioners!
Road Network Operations
& Intelligent Transport Systems
A guide for practitioners!
Various organisations engage in road network management. They include the town, city and regional authorities for road networks at every level. There are control centres dedicated to managing the traffic control systems for urban networks, motorways and other strategic roads, as well as for toll roads, tunnels and bridges. Each organisation will have a different perspective on the significance of ITS applications and services but most stand to gain some improvement in network efficiency, for example:
In these ways, the community’s requirements for mobility and commerce can be met more effectively and the need to construct new or expanded roadway facilities can be reduced:
The benefits of ITS for road network management can be considered under a number of headings:
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:
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:
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).
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.
A San Francisco system gives drivers real-time information on the occupancy and cost of over 19,000 city-owned parking spots. Drivers can use information on the parking charge, location and time to make their choice. Smartphone apps can help them find a space within an easy walk of their destination. A number of automotive manufacturers are also developing their own in-vehicle parking information systems.
US researcher Professor Donald Shoup has calculated that search for kerb parking in a 15-block city district can created about 1.52 million excess vehicle km of travel. This translates to 177,600 litres (47,000 US gallons) of wasted fuel and 73 tonnes of excess CO2.
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:
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.
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
Initial versions enabled the temporary use of the hard shoulder as an extra lane (“hard shoulder running”) when traffic built up, with Variable Speed Limits (VSLs) in force and VMS advising drivers accordingly. Emergency refuges were available at regular intervals.
The more recent design aims to deliver the same benefits for a lower whole life cost. The hard shoulder is available for use as a running traffic lane at all times, so permanently delivering extra capacity. On the London Orbital M25, enforced VSLs and a reduction in lane switching has successfully improved the capacity of the motorway without needing to increase the number of traffic lanes. Other countries are now adopting the idea.
Case Study (See Active Traffic 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.
The Bristol Freight Consolidation Scheme in the UK delivers to 115 businesses. It has reduced deliveries by 80% and achieved a 130 tonne reduction in CO2 emissions by use of two nine-tonne electric trucks which recharge at the centre at night. These return with recyclable waste. The reduced traffic congestion is predicted to deliver social benefit gains worth up to £2 million over five years.
(See Case Study: Broadmead Freight Consolidation Centre (UK))
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).
Concern for the impact on Australia’s road infrastructure (notably bridges) of increasingly heavy trucks has led to the regulatory Intelligent Access Programme (IAP) which restricts use by heavy trucks of the country’s road network.
It allows over-dimension vehicles access to normally restricted routes, in return for their carrying an on-board device that uses satellite-based tracking technology to monitor their compliance with IAP conditions and sends their locations to a control centre for analysis.
IAP enables qualifying road freight transport to increase its productivity by taking faster and more convenient routes, while controlling overall truck impacts on the road network and deterring non-qualifying vehicles.
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).
When the German Federal Agricultural Show organisers chose the medium-sized city of Koblenz as the location for 2011 the city had to plan for an additional 40,000 visitors a day over a six-month period. The city needed to expand it traveller information service and make it available on a regional basis.
The solution adopted, in coordination with the regional government, was to extend an existing regional, motorway-based intermodal traffic information system and expand the scope of its mobility web portal to cover urban as well as motorway traffic (See www.verkehr.rlp).
The city also needed to generate information for displays on VMS. The city could not afford to buy all the new traffic cameras that it would have needed, so it contracted a traffic information supplier to provide floating vehicle data (FVD)-based output to measure travel times and speeds. FVD involves anonymously monitoring moving vehicles that are equipped with, for example, Bluetooth-enabled mobile phones, turning them into mobile traffic sensors for notifying traffic conditions.
The project has raised interest in other German cities which have adopted elements of the approach. It has demonstrated the value to local governments of buying dynamic data from private traffic content providers. Bought-in traffic data proved to be a cost effective alternative to additional conventional traffic cameras.
At the 2012 London Olympic and Paralympic Games the successful operation depended heavily on effective traffic management on the critical Olympic Road Network (ORN) with traffic lanes reserved to give priority access to the 80,000-strong Olympic ‘family’ (so-called ‘games lanes’).
To monitor the network, Transport for London (TfL), the UK capital’s multimodal transportation agency, upgraded 1300 traffic signals and deployed 1400 CCTV cameras, some newly installed, others operating through data sharing arrangements with individual local authorities.
Case Study on Mobility Management for Major International Events
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.
The eCall system is an example of connected vehicle technology. A broken-down vehicle – or a vehicle involved in a collision – if vehicle fitted with eCall can send an automatic message about its location, description and the vehicle condition as the event occurs. This can aid prompt detection and rapid clearing of the affected road section to make the area safe for other traffic. The overall benefit is more efficient network operations. The automotive industry is now developing a range of services to lower the cost of dedicated unit installed for the purpose of archieving eCall.
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).
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