>> In 2001 the BVG’s Underground Department were running about 1,400 underground vehicles. Outside peak traffic periods, and during the nightly breaks in operation, trains are accommodated on loop lines and sidings. These are mostly in underground tunnels and can be reached by simply crossing the tracks. To prevent the vehicles in the tunnel areas being left at the mercy of vandals the BVG has installed, among other things, LMS laser measurement systems developed for building protection purposes – a tamper-proof system that reliably detects persons and signals, and raises the alarm via the existing emergency call and information system.

Infrared carpet of light “rolled out” for unwanted visitors

The LMS building protection sensor is based on actively scanning laser measurement technology. The sensor is a laser scanner with potential-free relay outputs, e.g. for triggering a camera. The scanner detects persons – independent of the brightness of the building and surroundings – by emitting a fan-shaped laser impulse up to 180° wide and evaluating the time-of-flight of the individual reflected impulses. Its high immunity to interfering light ensures that the LMS retains its full detection capabilities even when deliberately dazzled. Ranges of up to 80 can be reliably monitored with this “infrared light carpet”. The geometries the monitored fields can be divided up and assigned to specific stations, tunnels or platforms, as required. Its protective armoury against tampering includes a security code to protect device access.

Sprayers caught

This security technology has already had its first successes. Graffiti sprayers have been caught red-handed, and the vehicles did not need to be taken out of operation to clean up the graffiti. This saves the BVG millions every year.