Speed Enforcement in Tunnels

Since speed violations in tunnels lead to accidents with serious consequences, speed monitoring in these locations is particularly vital. However, the conditions present in a tunnel place special requirements on speed enforcement technology: Drivers who are digitally photographed following a speed violation cannot be irritated by a bright flash in the darkness of a tunnel, even though the flash must be bright enough to illuminate the interior of the vehicle. In order to fulfill these special requirements and to sustainably reduce the prevalence of tunnels as accident blackspots, JENOPTIK Robot has developed BlackFlash-Technology. Thanks to specially configured and adapted technology the flash of this black light flash system is nearly invisible to the human eye.

The pilot project for BlackFlash is the Rennsteig tunnel in Thuringia, where this technology was deployed for the first time in the context of fixed speed measurement, and where it quickly led to a change in driver behavior. In addition, traffic enforcement systems with BlackFlash flash technology have been installed in the Aubinger and Richard Strauss tunnels in Munich as well as many other motorway tunnels. The first inner-city tunnels to feature black light flash systems are the Rheinufer tunnel in Dusseldorf and the Britz tunnel in Berlin.

To ensure reliable speed enforcement using black light flash technology, a digital ROBOT SmartCamera and BlackFlash system are mounted on the tunnel wall for each lane. A measurement field consisting of three piezo sensors is also installed in the road surface for each lane. When a vehicle passes over this field it sends signals to the Intelligent Piezo Pre-amplifier (IPP). This digitizes the signal, and the speed is calculated without any doubt using the travel-time principle. If the established limit is exceeded, the invisible flash and ROBOT SmartCamera are triggered. The incident data (image, location, time, date, speed, etc.) are transmitted to a central penalty center and evaluated there.

It is also possible to connect the technology to a variable message sign (VMS) system. Such a connection was used in the tunnel in the Berlin district of Britz on the BAB (Federal Motorway) 100.