Deployment of Inter-urban Advanced Transport Telematics Test Scenarios

The project focused on automated detection of incidents, ramp metering (i.e. controlled access to motorways), the use of variable message signs and roadside warning lights, adaptive vehicle cruise control and automated driving systems. Assessments have been made of simulated traffic effects, road network operator interest, user responses, safety impacts, and legal and administrative issues. Significant findings include the following:

• The telematics applications most frequently deployed in Europe are automatic incident detection coupled with variable speed limits. Most operators wish to link this with variable message signs to encourage the re-routing of traffic.
• Roadside warning lights can improve safety, particularly in areas with poor visibility and prone to bad weather.
• Ramp metering has clear potential to reduce congestion on main carriageways, but more work is needed to optimise designs to reflect local traffic and road conditions.
• Adaptive cruise control is unlikely to have significant impacts on traffic efficiency in the near future. Technology penetration rates above 20% are required for this.
• The effects of adaptive cruise control on driver behaviour and their ability to respond in emergency situations need investigation.
  Cruise control may need to be set at a vehicle headway below 1.2 seconds to avoid reducing road capacity. However, this headway is below the level recommended by national administrations for safe driving.
• The legal considerations in developing automated driving systems are considerably more complex than with driver assistance systems.

Policy implications

DIATS has highlighted significant benefits of transport telematics applications:

• Automatic incident detection reduces unsafe situations and the duration of congestion for drivers approaching an incident.
• Ramp metering is extremely effective at reducing main carriageway congestion at peak levels of traffic flow. However, national guidelines are needed for the implementation of metering, for example, to minimise disruption on approach roads.
• Variable speed limits provide some safety benefits on motorway sections that are prone to prolonged heavy congestion.

There is a policy dilemma over the choice of vehicle headway for adaptive cruise control. Nationally recommended headways are somewhat greater than those observed on busy motorways. If drivers stick to national recommendations, motorway capacity will be reduced and congestion increased. If drivers select a smaller headway, the establishment of liability in case of an accident will be affected. Other policy issues include:

• whether the legal system should discourage the inappropriate use of cruise control on roads other than motorways (where the current technology may be inadequate to cope with demanding traffic conditions);
• the need for official standards for design and maintenance of cruise control systems;
• the liability of network operators that may provide advisory information or speed regulation signals to a cruise control system from a roadside infrastructure.