Fog warning system
A fog warning system ( NWA for short ) is a technical device on the road that is used to automatically warn road users in good time of sudden fog or similar visual impairments. In the area of motorways in particular , the danger from swift clouds of fog in connection with high driving speeds is particularly high. It is therefore not uncommon for serious accidents to occur .
Development and application
The idea of warning traffic about visual obstructions has been around for a long time. Warning devices have been used on many routes in Europe for many years to reduce the dangers. Until now, endangered stretches had to be continuously monitored by employees of the motorway maintenance department in order to recognize the need for a warning. Video surveillance or on-site surveillance was necessary for this.
Fog warning systems with simpler technology have been in use since the 1990s. For example, a system on the A 8 between the Hohenstadt junction and the Ulm / Elchingen motorway junction has been in operation since 1993.
In order to improve the reliability and speed of the fog warning, a test project was carried out in Austria in 2003 on the A1 West Autobahn , in which the use of a fully automatic warning system was tested on the ten-kilometer section in the Upper Austrian lake region. The system was built by Siemens and warns of obstruction of view due to fog and heavy snowfall. Regular operation has been running since 2004. The reason for the Austrian ASFINAG motorway administration to build the facility was a serious accident on the A 1 west motorway on September 30, 2003, in which 8 people were killed.
In the meantime, many traffic control systems (VBA) have an environment data sensor system that records and evaluates both visibility and other environment data. It is thus possible to inform the driver of potential dangers (fog, snow, rain, etc.) with the help of variable message signs and to warn him accordingly.
functionality
The visibility sensors are the central element of a fog warning system . Visibility sensors work according to different methods. Usually the reflection value of a measuring beam (mostly infrared light) on water molecules (fog droplets) is measured with an optical sensor and the visibility is extrapolated from this.
Along the area of the road that is to be monitored for fog, visibility measuring devices are set up in a few hundred meters at the roadside. If one of the visibility measuring devices falls below a predefined visibility range, the system generates a corresponding message. This message is transmitted to the driver of the vehicle with the help of variable message signs above the lane in order to make road users aware of the danger by means of appropriate warning notices. It is very important that the traffic is cleared in advance, i. H. without any visual obstruction, warning and reducing speed.
literature
- Research Society for Roads and Transport (Ed.): Notes on the collection and use of environmental data in route control systems . FGSV Verlag, Cologne 2010, ISBN 978-3-941790-54-4 .