Intersection assistant systems make use of car-to-x communications
Accidents at intersections are among the most frequent causes for intra-urban traffic injuries and fatalities. For this reason, the participants of the Intersafe-2 project developed solutions to reduce the risk for vehicle occupants during a turn maneuver – in particular in situation with restricted visibility due to obstacles.
BMW’s intersection assistant is activated by an array of sensors. Based on highly precise location, a navigation system can determine that the vehicle is moving on a turning lane. In addition, a camera tracks the road markings; a downstream image processing software recognizes if the vehicle is on a moving lane. Once the intersection assistant has been activated, three front-side laser scanners monitor the road space ahead at distances of up to 100 meters. BMW points out that the laser sensors can identify also relatively small vehicles including motorbikes. Motorbike drivers are among the most frequent victims of carelessly conducted turns.
In case the system detects oncoming traffic but continues to move into the intersection, the assistant system at speeds of up to 10 km/h automatically conducts an emergency braking and brings the car to a full stop. At the same time, it issues acoustic and optic warning signals. In order to improve the safety situation, the driver however can override the system at any time.
In addition to the laser scanners and the camera, the vehicle is also equipped with a car-to-x communications unit. This does not only enhance the range of the vehicle detection to 250 meters, it also enables the drivers involved to recognize each other mutually even if they are obscured by an obstacle. However, both partners need to be equipped with the respective communications devices. In this case, an algorithm in the device computes the trajectory of all vehicles involved and identifies critical situations already before the driver(s) are able to recognize them visually. In this case, a car-to-car communications process takes place; both vehicles exchange data regarding vehicle type, position, speed and turn indicator status.
If one of these vehicles is a motorbike and the assistant has identified an imminent collision hazard, it increases the motorbike’s visibility by modulating and increasing the bike’s headlight illumination as well as by activating forward-looking position LEDs mounted at the rear-view mirror. If the driver continues to move into the intersection, the horn is additionally activated and, as a last measure, an emergency stop is conducted. All these measures are accompanied by indicators on the motorbike’s dashboard and the head-up display.
Volkswagen showed a similar approach. The company equipped a Passsat CC sedan with a number of assistant functions aiming at hazardous intersection situations such as left and right turn identification, traffic sign recognition and traffic light recognition. In order to identify traffic lights, the assistant prototype system made use of car-to-infrastructure communications. Of course, traffic lights also have to be equipped accordingly. Similar to BMWs design, the VW assistant system also implemented three escalation stages including emergency stop as the ultimate measure.
Other companies involved in the Intersafe-2 projects are Volvo Trucks, chipmaker NEC, tier ones VTT and TRW as well as sensor system manufacturer Sick AG.