Project: Cooperative Road Traffic Signalling

Reference: STP 19/5/8

Last update: 03/09/2009 12:14:24


The objectives of the project are:
1. to conduct an initial feasibility study on the use of direct demand data communicated from individual vehicles to control traffic signals;
2. to determine whether cooperation between vehicles and the control system will enable more efficient operation;
3. to assess the potential benefits in terms of throughput, pollution, noise, energy efficiency, installation and maintenance costs and savings in existing vehicle detection;
4. to determine the pre-conditions for introduction of such systems in terms of the information required from the vehicle, the performance requirements of the communication and location systems and the market penetration level needed before a new traffic control system becomes viable;
5. to set out the policy issues which might arise and the next steps needed if the idea appears to offer potential benefits.


Use of intelligent traffic signals is well established within the UK. The existing SCOOT and MOVA systems are delivering proven benefits and continue to be rolled out to control more junctions.

Current developments are limited to making better use of information from existing detectors and bus information systems. However, the move towards Cooperative Vehicle Highway Systems (CVHS) introduces the potential to establish demand data from direct communications with vehicles. Modern in-vehicle electronic systems mean that information about the operation of car controls, accessories and navigation systems could be available for transmission to the infrastructure. With access to this data, traffic signal controllers would be able to run a very powerful model of real time demand to determine the correct strategy, monitor performance and forward information to adjacent junctions, as appropriate. This would introduce a radical step forward in functionality. Additionally, such a system would support communication directly back to specific vehicles and drivers, to give timely warning of signal status changes with potential safety benefits.

The project is a feasibility study to assess the potential benefits arising from such a system, and to assess the barriers, risks and costs in creating such a system. The outputs will be a report on the feasibility of the concept and guidance on the best approach and likely benefits. It is considered important to undertake a feasibility study at this stage so that future developments can be driven by policy requirements rather than be led by technology.


TRL Limited
Crowthorne House, Nine Mile Ride, Wokingham, Berkshire, RG40 3GA
+44 (0)1344 773131

Contract details

Cost to the Department: £35,519.00

Actual start date: 01 July 2004

Actual completion date: 13 May 2005


Cooperative road traffic signalling - potential costs, benefits and data exchange requirements
Author: K Wood (TRL Limited), N D C Wall (Shadow Creek Consulting) and P Sanger (TRL Limited)
Publication date: 31/05/2005
ISBN: ISBN 1-84608-900-X
Source: TRL Limited Published Project Report PPR041
More information:

Summary of results

  1. The idea behind the cooperative road traffic signalling project is that vehicle control and management systems are becoming increasingly sophisticated with a wealth of information passing between components on in-vehicle data busses. Communications with moving vehicles are also developing so that in the future it will be possible to exchange data between the infrastructure and vehicles at very low cost. The project has examined the potential benefits of the use and exchange of information between intelligent vehicles and intelligent traffic signal control systems. In particular, the aim is to look ahead and provide the DfT with information on which to base its future policy for traffic signal control. Without that information it is possible that technological developments and the commercial interests of others, such as traffic signal systems and car manufacturers, would dictate the future direction of signal control. Furthermore design decisions about in-vehicle telematics devices would be made without any awareness or consideration of the needs for new control protocols that might be supported on the same application platform. In this way an opportunity to include new protocols at very low marginal cost would be lost.

    The study has investigated a number of concepts that could form the parts of cooperative control systems. Benefits have been quantified as well as potential risks. Costs have also been assessed. However, the cost of implementing these new protocols will vary enormously according to whether or not they can be hosted on platforms that will be implemented primarily for other purposes. Investigation into other related development indicates that it is highly likely that cooperative traffic control could be implemented on the back of other developments, which makes the business case far more attractive.

    In summary, we have concluded that many of the ideas for cooperative traffic signal control identified in this study would appear to offer real benefits in improved efficiency of junction signalling and green waves. There are concerns about drivers abusing some use-cases that we have considered, such as advance notification of impending signal change, unless a strict enforcement scheme is provided. Introduction of these controls would require governmental policy decisions.

    One instance where large benefits would be obtained by preventing system abuse is in preventing red-running at traffic signals. The combination of cooperative traffic signal control and external vehicle control has been estimated to have the potential to reduce costs due to accidents by up to £125M per annum. Further benefits are predicted where different movements on an approach are signalled to start at different times, e.g. right-turning vehicles start before the straight-ahead movement. False starts would be reduced by providing customised information to drivers on which movements are about to start. Further benefits would be obtained by external control preventing vehicles starting to move that will not proceed in the permitted direction.

    Use of probe vehicle data is also predicted to have the potential for large benefits. It would be used to tune the parameters in existing dynamic traffic control systems, but the largest benefit is predicted to come from using the data to identify exit blocking due to problems downstream from a junction. Some of the benefit would come from allowing the signal control systems to respond better to partial exit blocking, but a larger benefit is expected from the ability to identify and quantify problems to justify action to reduce the basic problem. For example, to target parking enforcement teams to locations where illegal parking is having a particularly serious effect on traffic movements.

    Temporary traffic signals are often a cause of frustration to motorists when they can be clearly seen to be operating inefficiently. Probe vehicle data would allow signals to automatically adjust to the demands of the site where they are currently in use and control vehicles efficiently saving both delay and frustration.
    It is recommended that the requirements for cooperative traffic signal control are embedded into related developments of in-vehicle telematic platforms, floating-car data gathering systems etc, rather than invest in a dedicated capability. In this way it should be possible to phase-in enhancements as the penetration of suitably equipped vehicles reaches levels at which correct operation of these advanced control systems is possible. It is also noted that some of the benefits from cooperative traffic control can only be achieved by a step change to vehicle operations where all vehicles are required to operate in a new way at intersections. It is important that in-vehicle telematics units that will be installed in the intervening period will be able to support the cooperative control applications should a decision be taken to deploy them at some future date. In principle it would be possible to update the applications running on all these in-vehicle systems to provide a new set of capabilities that could then all be turned on at the same time, to allow a step change to be implemented.

    Current developments should take account of the requirements of cooperative traffic control so that the benefits from those systems will be delivered in a cost effective and timely way.