Safety On Rails

New driver assistance system for light rail vehicles

Developed by Bosch Engineering, the new forward collision warning system for light rail vehicles combines a radar sensor with a video sensor to detect any cars, buses, nearby rail vehicles, and static obstacles on the tracks. If the system detects that an object is coming dangerously close, it gives the driver a warning and brakes independently to stop the tram.

Bosch developed a new driver assistance technology designed to actively prevent light rail vehicles from collisions.

The driver assistance system warns tram drivers of any impending collision. If the driver brakes too late, or not at all, the system engages the brakes independently to stop the tram and avoid an accident. The new driver assistance system is entering service in the city of Frankfurt, Germany.

“Our collision warning system significantly increases the safety of passengers and tram drivers,” said Bernhard Bihr, president of Bosch Engineering. The new system was developed at Bosch Engineering, a Bosch subsidiary, which adapted the company’s existing large-scale automotive production technology for the enhanced collision warning system for city rail transportation.

The technical supervisory authority of the German federal state of Hesse recently approved the electronic driver assistance system for use in public transportation. Once Frankfurt’s tram drivers have tested this technology, the first self-braking trams will go into regular service in the city, the company said.

Bosch launched the first version of its collision warning system in 2014. Besides giving the driver a warning, the new and enhanced system now is capable of braking the tram automatically and bringing it to a complete stop, in the event that the tram driver cannot react to the warning in time.  “We are taking the idea of automated mobility further—beyond the road—and developing solutions that offer increased safety and comfort for rail transportation,” Bihr said.

The new collision warning system combines a video sensor, a radar sensor and a high-performance rail control unit. With an aperture of up to 70°, the radar sensor monitors the area up to 160 m ahead of the tram and measures the speed and distance of any cars, buses or other trams. In addition to mobile obstacles, the radar sensor detects static objects such as buffer stops.

The video sensor is the ideal complement to the radar technology because it keeps an eye on the track ahead and detects anything crossing the rails more quickly and accurately, Bosch said. The central rail control unit processes information from both sensors, along with other factors, such as the speed of the tram, to provide a detailed image of the environment.

If the system detects that an object is coming dangerously close, it gives the driver a visual and an acoustic warning. Should the tram driver not react to the warning signals within two seconds, the automated system slows the tram to a complete stop. The braking action is very gentle so even passengers who are standing will not lose their balance. If necessary, drivers can also deactivate the braking operation or increase the braking power at any time, depending on how critical the situation is. This leaves drivers still in control of the situation, but means they can rely on the watchful eyes of their electronic assistant day or night and in almost any kind of weather.

“Our system is on all the time; it never gets tired, and cannot be distracted,” Bihr said.

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