Federal Highway Research Institute


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Testing area A4

In order to be able to control traffic on federal highways, the traffic volume must be detected and processed in real time. With the help of appropriate technology, congestions can be detected, the approaching traffic can be warned and the speed can be adapted to the situation at an early stage.

The picture shows the testing area A4

Among other things, the traffic control system checks how many vehicles travel at which speed on the respective road intersection. The number of vehicles can be distinguished into the classes of vehicles “passenger cars”, “trucks”, “buses” and “motorcycles”.

In addition to the traffic situation, weather events also play an important role in traffic control. Special sensors help to evaluate the current weather conditions. Slipperiness or increased precipitation can be detected at an early stage and appropriate measures can be initiated: for example, a reduction of the speed limit for the route affected or the use of gritting vehicles. The purpose of the testing area is the continuous evaluation and quality assurance of traffic data detection and the recording of the weather conditions on the basis of environmental data.

Location and layout

The picture shows measuring systems at the testing area A4

At the beginning of the 1990s, the Federal Highway Research Institute (BASt) set up a testing area for type approvals of traffic count equipment in cooperation with the Road Construction Administration of North-Rhine-Westphalia (straßen.NRW). Between 2010 and 2012, an additional testing area for research in and development of new sensor technologies was implemented to the area.

The testing area is located on the A4 federal motorway at kilometer 92.5 in the travel direction to Cologne between the Bergisch Gladbach-Bensberg (20) and Bergisch Gladbach-Frankenforst (19) junctions. In this area there are 2 directional lanes with a hard shoulder.

The area is divided into 2 sections. The area in front of the first gantry is used for the type approval of traffic count devices. The testing area for research and development is located in the area behind the first gantry.

There are 2 control houses for the technical equipment. These are equipped with appropriate data communication and power supply. The cabling, mostly for temporary installations, can be carried out quickly and easily using existing cable troughs. The use of infrared spotlights enables observations also in darkness. The measuring personnel are protected by reinforced safety barriers on the side strip.

 The picture shows a sketch of the structure of the testing area A4 Structure of the testing area A4

General conditions

The average daily traffic volume in the direction to Cologne is around 38,000 motor vehicles per 24 hours with a share of heavy traffic (motor vehicles >3.5t GVW) of 8.2 percent (as of 2019).

The speed limit of 100 km/h from 6 a.m. to 10 a.m. must be observed, as well as the overtaking ban for trucks on the left lane along the area. Despite these restrictions, the traffic reflects the entire spectrum from rush-hour to free-flow traffic in the evening hours and a sufficient proportion of motorcycles during the summer. Traffic and environmental data can be provided as reference values.

Testing and type approval

In this section of the testing area, approval tests of traffic count devices are carried out in accordance with the Technical Terms of Delivery for Road Stations (TLS). The test procedures for the approval of devices that count vehicles using inductive loops are described in TLS. In addition, alternative technologies - such as overhead mounted detectors - can also be approved.

The Federal Ministry of Transport has commissioned BASt to carry out approval tests of traffic count devices. The following partial tests are carried out according to the manufacturer‘s configuration:

  • vehicle classification
  • traffic volume
  • speed of vehicle

On the area for research and development, sensors are evaluated for the collection of environmental data. Various sensors record weather-related parameters such as road surface temperature, precipitation, water film thickness or wind. The sensors are installed in the roadway or mounted on a pole for non-contact measurements.

Further applications

The results and findings from the testing of and research in sensors for environmental data are incorporated into European standards and national regulations.

On the one hand the collected traffic and environmental data are used for the development of new acceptance and test procedures for the environmental sensors and on the other hand they can be used for further research projects. Furthermore, universities and manufacturers have the opportunity to examine new ideas and products for their practical suitability within the framework of development and research work.

Technical data

  • length: 150 m


  • 7 measuring points for traffic detection (inductive loop fields TLS type 1 and type 2)
  • 5 poles for environmental data (weather)
  • 2 gantries with data and power connection
  • 2 control houses

Reference systems

  • 1 speed reference system (no speed enforcement)
  • 1 video system with 5 cameras (no person-related data)
  • 5 pole cameras to monitor road conditions and precipitation
Special consultant: Sandra Eimermacher