Trams in Frankfurt have received approval for an electronic driver assist system that automatically applies the brakes to prevent an imminent collision.
Drawing on its extensive expertise in providing Advanced Driver Assist Systems (ADAS) for the automotive industry, Bosch is now ready to deploy automatic emergency braking systems to trams in the German city of Frankfurt.
Having already been equipped with collision warning systems since 2014, the new device takes the technology to automatic control in the case where the driver either doesn’t react to the warning or has no time to be able to react and avoid a collision.
Tram drivers are faced with the challenges of heavy city traffic in different weather conditions in mixed traffic environments. They’re unable to steer and have to rely on their own reactions or the ability of other road users to avoid collisions. With this in mind, the Bosch Engineering subsidiary looked to transfer successful collision avoidance technology from road vehicles to light rail transport.
Now, the technical supervisory authority of the state of Hesse, in which Frankfurt is a major city, has approved the use of this electronic driver assistance system for use in public transport applications. The first phase of its introduction is for local tram drivers to test it and the next phase is to deploy it across the city’s full fleet of trams.
Commenting on the introduction of this technology in Frankfurt, Bosch Engineering’s president, Bernhard Bihr said, “We are taking the idea of automated mobility further, beyond the road, and developing products that offer increased safety and comfort for rail transport as well.”
Sensors and control
The operation of the collision avoidance system fitted to Frankfurt trams is based on a combination of sensors and a high performance rail control unit.
The radar sensor has an aperture of up to 70 degrees and monitors the area ahead of the tram up to a distance of 160 metres, measuring the speed and distance of any vehicles within that path. It can also detect static objects within its path such as the buffer stops at a rail terminal. The radar sensor is coupled to a video sensor which monitors the track ahead and detects anything crossing the rails including pedestrians, cyclists and animals.
The output from both sensors are fed to the rail control unit which matches the input with tram speed and other parameters to assess the condition of the environment the tram’s operating within.
If the system detects that an object is coming dangerously close, it gives the driver a visual and 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 says.