The vehicle receives the following protocols standardised according to ETSI from a roadside unit on the respective control unit of the traffic signal system:
SPaTEM (Signal, Phase and Timing Extended Message).
MAPEM (Map Extended Message).
This ensures that the vehicle always receives information on the position of the relevant signalling device, its current signal status and the duration of the signal phase.
Furthermore, the vehicle sends out the protocol CAM (Cooperative Awareness Messages), which is also standardised according to ETSI, or CAM-R09 for public transport vehicles. With the help of this message, the vehicle is registered and deregistered at the traffic light system.