Cooperative traffic lights
A vehicle equipped with an onboard unit approaches a traffic light. While approaching, the vehicle receives messages via mobile communication and/or ITS G5 for intersection topology (MAP) as well as status and prediction information (SPAT).
The data provided on the intersection topology includes information on the number of lanes, stop positions, permitted turns, etc. Using the intersection topology, the vehicle can locate itself in relation to the fixed positions of lanes, stopping lines and traffic lights. In addition, the vehicle can identify the signal groups relevant for its intersection passage.
The status and prediction information includes the current status of all traffic lights of the intersection as well as a prediction of the remaining green and red time. The switching time prediction is determined either locally in the control unit of the traffic light controller or centrally in the traffic system management center. The messages are updated every second and received by the vehicle.
The information relevant to the driver is displayed in the vehicle. With the help of this information, the driver can adjust his/her speed accordingly to avoid unnecessary braking and acceleration. In the event of an unavoidable stop, the driver is shown the remaining red time relevant to him. All these data are the basis for an intersection assistant in the vehicle to implement a fuel efficient driving strategy.
There are two different options for data transmission to the vehicle:
- Mobile communication
- ITS G5 communication
In case of mobile communication, the above mentioned messages are transmitted into the vehicle by a service provider. In case of ITS G5 communication, the road-side-unit (RSU) transmits the data as soon as the vehicle enters its reception range.
- the traffic system management center of the city of Düsseldorf provides intersection topology information (MAP) as well as status and prediction information (SPAT – signal phase and timing) to a service provider
- vehicles request the above information from the HAV layer via mobile communication
- the RSUs at the traffic lights transmit intersection topology information (MAP) as well as status and prediction information (SPAT) to the vehicles via ITS G5
- in-car processing in intersection assistant functionality
- avoidance of stopping, braking and acceleration processes
- reduction of vehicle emissions
- increase of traffic safety
- reduction of accident risk
Contribution to connected and automated driving
- processing of prediction information into driving strategy (automated approach/passage)