Travel Information Systems

Authors John Miles (Editor) Keith Keen (Assistant Editor) Charlie Wallace (Courage & Wallace, USA)

Uncertainty over journey and arrival times is a major problem for travellers and companies delivering goods. ‘Smart’ travellers and fleet managers increasingly expect reliable information to help them make well-informed decisions.

Accurate, integrated and comprehensive travel and traffic information helps all road users in their journey planning decisions and how to respond to disturbances that occur on the way. In this respect it supports the task of the road network operators as well.

Travel information – and by extension route advice – is considered to be a basic service. It constitutes the lowest level of traffic management. Road users are free to decide for themselves if and how to react to the information or advice.

Investment in travel information systems by the road operator is a way of improving customer service. Information systems can also promote intermodal travel, for example by encouraging drivers to leave their cars at a Park and Ride site (typically because of localised congestion or high pollution levels ahead) and continue by public transport. Parking information systems also contribute significantly to reducing city-centre congestion and pollution by alerting approaching drivers to available spaces.

Traffic information concerns the conditions of road network use and can include predictive and current (real-time) information on traffic conditions. Stronger forms of direction include hazard messages or incident warning, and eventually control measures such as notice of road obstructions, lane control, or speed control.

Traveller aid covers all measures to disseminate predictive or current information on traffic conditions and to improve general conditions of network use. Its general aim is safety and user comfort.

Travel aid tasks are not specifically aimed at modifying traffic flows. However, when used for information purposes they must be closely coordinated with traffic management measures as they may induce users to change their travel time, route or mode of transport. In this context, they may be integrated in broader strategies related to demand management.

Basic Principals

Generation of travel information by the network operator is a broad concept that cuts across the entire field of operations and entails several areas:

gathering regular information from operational partners
providing user information on predicted traffic conditions (before trip) or current traffic conditions (on trip)
the contribution user information can make to the operator’s communication policy and to the user relationship
road and traffic information as an important element for public transport, freight and fleet management operators

To be able to inform partners and drivers effectively, operators must first define information paths that should be coherent with the operation and management plans.

To fulfil the needs and expectations of everyone involved, the information should be timely and disseminated via all available channels and communication modes. They can be channels operated directly by the control centres (variable message signs, travel information website, RDS-TMC, traffic news broadcast etc.) or by added-value service providers who transform the information into the required data formats for smart phones and satellite navigation, and/or operate additional dissemination channels themselves. (See Traveller Services)

Provision of client-specific, personalised (enriched) information is often let to independent, value-added service providers, who extend and build on the information stream made available by the road operator. However, there should be an agreed framework for safety-related advice and direction in the absence of specific instructions from the traffic centre, in order to avoid confusion or the undermining of the set traffic policy.

RNO Information Systems

The purpose of this approach for the road operator is to achieve widespread, timely information dissemination to operating partners or road users, as required. This action involves listing all components of the information system, identifying blockage points and organising or reorganising the information chain to ensure the system functions effectively. (See Systems Approach)

Successful dissemination of information is the end result of a system in which each link is crucial to success, so the operator must ensure that each link functions effectively:

data gathering system must be adequate and reliable
during operations, information systems must be reliable and capable of forwarding data and information on time:
- substitute or back ups systems may be necessary for network security or emergency response
- data gathering and information dissemination paths may also differ depending on circumstances (crisis situation)
at staging points, information must not be unduly delayed – a person must be identified and available each time an action has to be performed (such as verification of information received or development of information for transmission)
at switching points, information must be forwarded as quickly as possible to the correct location

Computers can be used to automate all or part of the actions described above. (See ITS & Network Monitoring)

When information for users is relayed by an intermediary – especially the media – operators must listen to and/or read the messages actually sent by the intermediary, noting the date and time sent, to assess the quality of communication.

An information system is more effective when all players involved have a good overview and a clear understanding of their role. The quality of information received by users is very closely linked to the actual systems and can actually enhance the department’s image.

Objectives and Methods

The common objective of all traveller information services is to provide high quality, real-time, detailed information on transport operating conditions, including weather, so that individual travellers can make informed decisions regarding whether to make a trip, when to make it, what mode to take, and what route to take. Traveller information should be available both before a traveller begins a trip, as well as while the trips are under way, so that adjustments can be made to reflect changing operational conditions.

Traveller information can be provided in a number of ways. A summary is provided here. (See also Traveller Services and Driver Support)

In recent years the Internet has become ubiquitous as method of conveying pre-trip traveller information. Some systems offer subscribers the option of receiving alerts by mobile phone, e-mail, or other electronic methods regarding major incidents or conditions on specific routes. Telephone dial-up services remain a popular means of pre-trip and en-route information dissemination. Commercial broadcast media, including radio, cable television, commercial television, and teletext services are other commonly used methods of dissemination of travel information.

Telephone: In the United States, a nationwide three digit telephone number, 511, has been designated for traveller information services. The success of this initiative lies in issues such as the perceived accuracy, timeliness and permanent operation of the 511 service. Also, because of the variety of organisations involved (geographically, public/private, different travel modes), the issue of co-operation is the other challenge. The success of this initiative shows that appropriate institutional agreements, when designed early enough in the development process, can be a powerful lever to deploy effective ITS operations services. (See Journey Planning)

Driver information systems: by means of roadside VMS or in-vehicle units, contribute generally to a better performance of the traffic system by raising the level of awareness of drivers about the current status of the network and its likely evolution. Users of traveller information services generally agree that availability of high quality, real-time traveller information saves time, helps them to avoid congested locations and incidents, and reduces uncertainty and stress associated with travel. (See En-Route Information)

Variable Message Signs (VMS) are used to disseminate en-route traveller information in virtually all locations where electronic traffic monitoring also exists. These signs are typically placed in advance of key bottlenecks or decision points and can display fairly detailed information on location and extent of congestion, travel times, alternate routes, and downstream weather conditions (for example wind, precipitation, snow). (See Use of VMS) Highway Advisory Radio is also used, although its use appears to be declining with the growing popularity of traffic-responsive satellite navigation units and smart phone applications, which are now widespread. (See Radio)

In-vehicle navigation: En route information provided through in-vehicle navigation systems and smart phones is spreading. The VICS system in Japan, which enjoys a high market penetration of in-vehicle navigation systems, is one of the most extensive applications. Dissemination of detailed en-route information is accomplished through transmission from beacons or FM sub carrier broadcasts to the in-vehicle device. Other countries have followed Japan in deploying this kind of system. (See Advisory Systems)

Subscription services: Pre-trip and en-route information alerts provided through social media, messaging subscription services (Internet and Smartphone) is growing in popularity.

Information terminals and kiosks: Pre-trip traveller information in kiosks located in employment centres and other public places (e.g. freeway rest areas and shopping malls) are becoming commonplace, although the experience with kiosks this dissemination method has limited utility for real-time road information. Use of kiosks for public transportation information appears to be more successful. Real-time public transportation information is also successfully disseminated at transit stops in many locations using electronic signs. (see Kiosks)

Information Requirements

Information requirements are set by network operations stakeholders, transport operators, emergency services or assistance providers and road users themselves – the latter possibly clustered in Motoring Clubs and Road User Organisations. As might be expected, there can be some variety in the geographical extent and the level of detail of the information these players need in support of their activities, or to really fulfil their travel needs.

Predictive information: This information may be on a weekly, daily or even hourly basis and concerns general traffic condition forecasts and the main anticipated disturbances. Its implementation requires:

real-time centralisation of information on the network situation (traffic, weather) and on scheduled actions (roadwork, events)
transmission of regular information bulletins through national or local media (radios, newspapers, television), or specific road information facilities (kiosk, telephone enquiry service and Internet)

Real-time information: This information concerns the currently-experienced traffic conditions and disturbances affecting motorists on a given route. It requires:

a permanent system to detect and monitor traffic flow conditions
real-time information systems by variable message signs installed along the route, by specialised radios or by ITS servers. It may be necessary to have specific in-vehicle equipment to receive some of the information

Real-time information also includes information to operators of customised services or navigation and guidance systems.

Information Quality

High quality traveller information services must be driven by high quality data on transportation system conditions and performance. Effectively fusing data into useful information from various input sources is a significant challenge that is critical to overcome if traveller information services are to be effective.

For systems that automatically post or otherwise provide traveller information based on input from traffic monitoring systems, data reliability is a critical issue. Effective automatic means of checking or filtering raw data must be in place to ensure that erroneous or misleading information is not posted.

In order to be useful to travellers, traveller information needs to be multi-modal (road and transit), and regional (crossing jurisdictional boundaries) in scope and include information about motorways and urban streets, as well as location and availability of parking.

Travellers are interested in receiving end-to-end trip information in a single query. The objective for end-to-end travel planning involves links to intercity travel providers, such as rail and air lines, to provide complete travel and routing information, door-to-door. Future enhancements for end-to-end travel may include linking to intercity travel providers, such as rail and air lines, to provide complete travel and routing information.

Information provided by traveller information services must be immediately beneficial to the user in making travel decisions. Advising travellers through a variable message sign that there is “Congestion Ahead” on the network has little value if not supplemented by information on location, extent, and severity of the congestion and potential alternate actions.

It is important to maintain the accuracy of the information provided. For example, VMS which frequently show incorrect or no information will lose the trust of road users. This will defeat the whole purpose of the system. To ensure accuracy the issue of interconnections between the various centres must be addressed, if they are separate either in terms of the services that they provide or their locations. The seamless integration of information exchange between various centres becomes a major issue. This requires the adoption of a standard for data exchange and cooperation between the various players.

Commercial Services

Though there is significant private sector involvement in many examples of traveller information services, the commercialisation of traveller information for profit is variable. Traveller information services that have been financially successful have generally involved packaging traveller information along with other information. (See Location Based Services)

For traveller information services to be successful, they must be marketed to potential users on a continuous basis. This marketing should be tailored to various market segments (such as road users, transit users). Successful traveller information services also seek customer input on services offered and are responsive to feedback received. For example, VICS of Japan continually solicit user requests and demand through the Internet, in order to better accommodate their needs.

Though not widely provided at the moment, users are interested not only in real-time information on network conditions but also in predicted conditions (for example: “a key junction is currently uncongested, but if the current trend continues, what will conditions be when I reach the location in 30 minutes?”). This will be the next important development in traveller information services.

Information Exchange

Information transmitted must be adapted to the expectations of recipients so it can be used effectively. The information must be clear, understandable and useful to end users. Information that reaches its recipient is the end result of any initiative that answers the following questions:

Is the information accurate? The facts to be conveyed must be accurate or all credibility with partners/users will be lost.

Why provide information? Dissemination of information reflects intent by a operator that must be specifically defined – for example:

to provide the recipient with necessary or useful information
to elicit from the recipient an action that will be useful to the operator himself
to modify driver behaviour, promote safety, prevent or minimise operating problems and give drivers a sense that they are taken into consideration

Who should be informed? The targets for information may be police forces, other road operators, local or national media and the road users themselves. Who should be informaed will vary acording to:

the characteristics of the situation (circumstances such as the nature, gravity, location, context, anticipated length of current disruptions, and the timeline of planned events)
the network operator’s intention – in answer to the question "Why porvide the information?"

When should information be provided? Information about a current event is of interest to a recipient/users only if the users have it in real time. Choosing the time to send information about a planned event is not easy. This must be done early enough to allow for a response (especially if the operator expects cooperation from partners) but not so soon that it will be forgotten.

Where should information be provided? The destination of information (for example at a control centre, TV and radio stations, emergency servcies or a service provide) is defined by the network operations strategy and will be an integral part of operations planning. (See Planning and Reporting)

How should information be delivered? The information medium (social media, text message, Intenet, telephone, radio, e-mail, VMS’s, leaflets) is also determined by what is most cost-effective and the available resources. (See Traveller Services)

How should information be presented? Each recipient or group of recipients must receive the information in a personally tailored format. If there is a common language (event nomenclature, location, etc.), a message drafted in technical or even coded terms may be understood by a partner. To be legible by a partner, that message must not be buried in a lot of irrelevant details. For example:

traffic forecasts in the form of raw data on flows can be easily interpreted by a freeway operator
road users need information that is directly relevant to the route, timing, mode and location to their journeys
a message sent to a media outlet must be adapted to the practices of that outlet

Communicating Information

Messages to users must follow the guidelines below:

capture the recipients’ interest;
use their vocabulary, not operators’ jargon;
avoid giving them the impression they are being manipulated;
provide explanations wherever feasible;
indicate the source of information whenever possible.

It is usually very practical to use forms for exchanging information that has been defined in advance with the partners in question. Where they exist, standards for data exchange should be used.

Communicating is as much of an art as operating the road network. Network operators should:

identify staff responsible for presenting information and train them in media operating methods and drafting messages on VMS;
canvass at least a few users (not co-workers) to ensure that the planned wording will be clearly understood and will not raise additional questions (VMS message, radio announcement);
Make use of communication specialists to design a website or leaflet, for example.

Disseminating information to users entails drawbacks and constraints:

the operator needs to monitor the consistency of messages issued consecutively or simultaneously through various media;
operators have no control over the final form and timing of release when information is channelled through an intermediary;
foreign users may not understand the local language.

Advanced Traveller Information Systems (ATIS)

Road Network Operators and other transport or public safety professional have no direct control over road users (except, perhaps, at traffic signals). Each road user is an independent entity that observes situations from the perspective of his or her specific needs, does their own thinking and decision making and executes their decisions more or less independently. The only thing the transport profession can do is to inform the travellers in the best possible manner to enable them to make informed – and hopefully safe – decisions. (See Traveller Information Systems )

Use of VMS in Florida, USA

A survey by Florida DOT District 6 (Miami-Dade Co. and south) found that 92% of freeway/turnpike drivers read VMSs at least weekly, 97% said these signs provide accurate traffic alerts, and 78% reported a willingness to alter their route based on VMS postings. Use of 511 increased in the past year and 22% of respondents were more willing to change their departure time as a result of 511 information.

(Source: Rodriquez, J., “Miami Drivers Reported Travel Benefits from Using Dynamic Message Signs,” SunGuide® Disseminator, Florida DOT, January 2013.)

Advanced Traveller Information Systems, or ATIS are designed to support individual decision-making. The goal of ATIS is for travellers to have information at their disposal to help them make better-informed travel decisions about mode, route, departure time and activity choices. A side effect of these better decisions can often be supportive of efficient and safe traffic operations.

There is a full range of advanced traveller information provider systems and services. A summary is given in th table below along with advantages and disadvantages (in no particular order):

Characteristics of Traditional Traveller Information Techniques

Technology	Advantages	Disadvantages
Posting of messages on VMSs	Point and advanced information to the most-affected drivers Efficiently changed Modern full-matrix signs can use graphics and colour to enhance messages Ideal for child-kidnap alerts in a corridor	Doesn’t reach drivers off the roadway Fixed location Old signs difficult to read Not always widely trusted Not always read
Posting of messages on PDMSs	Point (and possibly advanced) information to most-affected drivers Can be deployed to unplanned situations/incidents	Takes time to deploy for unexpected events Not efficiently changed (unless remotely controlled) Sometimes difficult to read
511 (voice, automated)	Widely available Efficiently updated Widely accepted Can be accessed en route Can be (partially) financed by sponsorships or advertising	Must be proactively accessed Encourages phone use while driving Language issues, particularly in Interactive Voice Recognition (IVR)

Call taker	Highly responsive and effective Personalised	Less used today, but popular where they are Encourages phone use while driving More expensive than IVR
Website (TCC or 511)	Widely available Efficiently updated Can be automated (such as speed maps) User can view selected CCTV images Can be partially financed by sponsorships or advertising Widely accepted	Not universally accessible; must be proactively accessed via computer or mobile device Encourages mobile device use while driving Language issues
Media – radio traffic reports	Widely available Can be efficiently updated Widely accepted (many users say this is their primary mode) Can be accessed en route Financed by the media	Must be proactively accessed Always maintaining timely and accurate information

Media – TV traffic reports	Widely available Can be efficiently updated Can show station-selected CCTV images Widely accepted (many users say this is a primary mode) Can be accessed pre-trip Financed by the media	Must be proactively accessed Always maintaining timely and accurate information Not available en route
Airborne spotting and reporting	Widely available Agile relocation Efficiently updated Widely accepted Can be accessed en route Financed by the media in some regions	Must be proactively accessed Getting timely air time for incidents (unless it is a continuous traffic reporting station)
Kiosks and display signs	Popular with older, less tech-savvy and disabled users Provides peace of mind for transit riders Transfers/connection information for transit users	Limited availability (for example, transit terminals, rest stops and other fixed locations) Timely and accurate updates

In recent years, the proliferation of smartphones and other mobile devices (such as digital tablets and pads), the expanding use of social media and the increasingly wide-spread use of Floating Vehicle Data collection techniques have led to a number of truly advanced traveller information services. Some services collect data to be used by other traveller information providers.The Table below summarises these.

Characteristics of Advanced Traveller Information Techniques

Technology	Advantages	Disadvantages
Point (that is, fixed location) data collection systems	Passive, non-intrusive and non-threatening Reasonably accurate for journey times and inferred speeds	Requires additional infrastructure deployment Usually must funnel processed information through public or private entity at a cost
Floating (probe) vehicle tracking	Ubiquitous supply of probes More easily deployed in rural areas and areas not covered by ITS Useful for incident detection in such areas	Some concern for privacy issues Requires additional infrastructure deployment Must funnel processed information through public or private entity at a cost
Commercial traveller information services	Use a variety of data sources, including floating vehicles Feeds data to navigation maps in near real time Navigation maps show alternative routes Can direct information to subscriber via mobile phone (voice or text) or social media Well trusted	Sometimes paid by subscription Encourages mobile phone or mobile device use while driving

Social media – situation reporting	Expands number of eyes on the roadway Free for all users Increasingly used by traffic and emergency managers to inform travellers about incidents and emergencies	Encourages cell phone or other mobile device use while driving
E-mail alerts	Low cost Highly customizable	Paid by subscription Not as effective for en -route alerts
In-vehicle telematics (including personal navigation devices)	Expanding market Combines advantages of several techniques Great potential for growth beyond simple traveller information	Paid by subscription Demonstrated, but not widely deployed beyond Europe Marketing and software integration issues Standards among regions

Pre-trip information

Using radio and TV traffic reports, websites, navigation maps and Information Service Provider (ISP) feeds to enable travellers to change their travel mode, change the trip departure time or change the route of the trip, all to avoid an incident or just normal congestion, thus reducing traffic demand in the affected area. Further information on pre-trip information is provided here (See Pre-Trip Information).

En-route information

En-route information can be provided though VMS, radio traffic reports, (in Europe the RDS-TMC, Radio Data System – Traffic Message Channel), GPS (Global-Positioning System) or GALILEO navigation maps and Independent Service Provider feeds to a smartphone. The information can assist travellers, including drivers of passenger and freight vehicles, to change their trip plans whilst en route, for example by changing their route or even abandon the trip to avoid an incident or just normal congestion. This reduces traffic demand in the affected area. Even if a traveller does not change any trip plans, just knowing the nature of congestion, perhaps with some indication of journey time or incident location, can reduce driver frustration and anxiety, thus making them safer drivers that are less prone to take unnecessary chances, such as excessive lane changing.

VMS and Highway Advisory Radio (HAR) are used to alert rural travellers in mountainous areas about weather and other conditions on the roadway ahead.

En-route information during longer trips

On long-distance or international trips, applications like those mentioned above (as applicable) or kiosks at rest areas, can help these long-distance travellers either adjust their trip plans or at least have a more secure feeling about their trips. (See Kiosks)

Traveller information in the other modes can do such things as inform public transport passengers of the arrival of the next vehicle and provide transfer information. Whilst these do not directly impact traffic operations at that time, this type of traveller information makes travellers more comfortable and confident about using public transport, thereby encouraging them to continue to do so and not add to clogging the roadways with more cars. Some Integrated Corridor Management (ICM) concepts include public transport as well, particularly Bus Rapid Transit (BRT) systems.

Traveller information can also provide information that does not directly affect current travel, but serves other purposes, such as safety messages, smog alerts and for child-kidnapping alerts. Note that there is some debate about the use of VMSs and HAR for non-mission-critical purposes. (See En-route Information)

Managed lanes and Toll Roads

High-occupancy/toll (HOT) pricing is conveyed by VMSs, allowing Single-Occupancy Vehicle drivers to make a decision to use the HOT lanes, thus relieving demand in the general-use lanes. Similar information should be provided in the case of variable toll rates based on congestion so as to allow a driver to select an optional route.

Advice to Practitioners

There is a great deal of potential benefit that can be derived from using third-party data services (for example, real-time journey times on VMS, website traffic information, conducting historical analyses and so on). A number of commercial traffic Independent Service Providers (ISPs) provide services to both individual travellers and businesses as follows:

local radio provides traffic information in most metropolitan areas
navigation data to in-vehicle devices in a number of areas
probe vehicles are providing incident data
real-time, historical and predictive traffic information for many USA cities
traffic flow data, incident data and construction data in a number of areas

Further information: See Travel Information Systems and Traveller Services

Use of Variable Message Signs

Variable Message Signs (VMS) are capable of displaying pre-defined or freely programmable messages which can be changed remotely with individual pixel control. They consist of:

large general-purpose panels which allow the display of a variety of text messages and sometimes pictograms. Cost considerations mean these tend to be used on motorways
or smaller dedicated panels to display a dynamic speed limit or a specific message

DMS, VMS or CMS?

A Dynamic Message Sign (DMS) is any sign or graphics board that can change the message (text or pictogram) conveyed to the viewer. It may be either a Variable Message Sign (VMS) or a Changeable Message Sign (CMS) where:

VMS is a sign capable of displaying pre-defined or freely programmable messages which can be changed remotely with individual pixel control
CMS is a sign capable of displaying pre-defined fixed messages which cannot be changed remotely

See Roadside DMS

Roadside and overhead VMS are a basic traffic management tool for road owners and authorities – to provide information and advice to drivers and riders independent of any in-vehicle systems. In some cases VMS signs can replace fixed roadside signs to inform drivers of speed limits – if necessary with the flexibility of changing mandatory speed limits in response to traffic or road conditions where the legislation allows.

Research evidence shows that road user acceptance and compliance is substantially increased when the reason for a new, lower than normal, speed limit is displayed on the VMS in addition to the prevailing speed limit.

Hazards and Advisory Speed Limits

VMS can be used to convey maximum advisory (non-mandatory) speeds — to advise drivers and riders to slow down in fog, high winds and icy conditions or on the approach to an incident or slow-moving traffic ahead.

Icy Road Warning System in California

Evaluation of an icy road surface warning system installed on a mountain road in California indicated that, when the warnings of icy conditions were activated, mean speeds were more than 5 mph (8 km/h) lower than when no warnings were shown (Veneziano and Ye, 2011). In specific situations where ice was present but not likely to be expected by drivers (such as cold, clear and not-dry conditions), the reduction in speed was somewhat less — under 3 mph to around 3 mph (4.8 km/h). The speed data was collected at the VMS sign – rather than in the subsequent curve where the driver response may have been greater.

Fog Warning System in the Netherlands

A fog-warning system on the A16 in the Netherlands had two levels of lower speed limit available, depending on the level of visibility. It was found that when the system was activated, average speeds decreased by 9-10 km/h. When the very low visibility speed limit was displayed, average speeds were higher than appropriate for the road conditions indicating that the advisory speed limit of 60 km/h was not low enough to influence driver behaviour sufficiently.

Dynamic Speed Limits

Dynamic management of speed limits in response to traffic flows has been shown to reduce speed variability and smooth flows, reduce numbers of accidents and increase overall throughput. It also has environmental benefits through the reduction of emissions. It is mainly applied on motorways. When used in construction zones or for temporary narrow lanes, the safety impacts are considerable, particularly as regards the protection of roadside workers. Dynamic speed limits are often combined with camera-based speed enforcement. (See Work Zones)

Feedback to Drivers

Roadside VMS is commonly used, particularly on urban roads, to inform drivers that they are speeding in the hope of encouraging them to slow down. These VMS are linked to speed detectors. When triggered by a speeding vehicle they display the speed limit or a message such as “Slow down”. The devices can also be mounted on a trailer for portability – for use, for example, in work zones. Portable Dynamic Message Signs (PDMS) have been shown to have an effect on the proportion of drivers speeding and on average traffic speeds. Some of that impact may be a novelty effect — since few evaluations have looked at the persistence of changes.

Managed Motorways

“Smart” or “Managed” motorways are becoming more common as a means of managing high traffic flows on motorways. (See for example http://www.highways.gov.uk/our-road-network/managing-our-roads/improving-our-network/smart-motorways/).

Typically, as traffic builds up towards the critical 2,000 vehicle per lane per hour, speed limits are reduced. The aim is to reduce speed variance and shock waves caused by traffic slowing down and speeding up - which can lead to incidents and accidents. The overall objective is to maintain traffic throughput - but the schemes have also brought about reductions in accidents and secondary incidents. Speed limits are enforced with automatic camera-based technology (time over distance cameras in the more recent schemes). Another common feature is the use of the hard shoulder for traffic at times of high congestion (“hard shoulder running”) with appropriate VMS signing. (See Case Study: Active Traffic Management Pilot M42 (UK))

Advice to practitioners

National and regional standards are likely to apply to the design and installation of VMS. There are also applicable international standards for regulatory signs. Sixty three countries across the world have ratified the Vienna Convention on Road Signs and Signals. This states that road signs conveyed on VMS should generally conform to the text and symbols used on standard road signs. The Convention allows variations in colour in the interests of legibility. For example, it permits the use of dark text on a light background (the norm for speed signs) to be replaced by light text on dark background in the case of VMS - although the border must remain red.