Traffic management for tunnel upgrade scenario

In the course of the refurbishment of the German Engelberg tunnel, a new traffic management solution with congestion warning and travel time indication is being implemented.

The Engelberg Tunnel is part of German A 81 motorway and located north of the Leonberg motorway junction, linking the A 8 (E52) and A 81 (E41). The tunnel is of great importance as a link in the trans-European road network and serves several European regional corridors. Furthermore, the tunnel is part of the only efficient bypass of the capital of Baden-Württemberg, Stuttgart, with 110,000 vehicles passing through the two tubes every day.

Between 2019 and 2024, the tunnel undergoes an extensive structural and operational upgrading. This causes longer-term modifications in the course of the traffic, with re-routings to the opposite tunnel tube as well as closures of the tunnel at night. Traffic analyses have shown that congestion on the A 8 and A 81 motorways and on possible alternative routes is unavoidable, with traffic disruptions being very likely. Therefore, construction-related measures are planned in the form of an integrated congestion warning system and an integrated travel time display system. “The aim of both systems is to minimise traffic disruptions, related accidents and congestion, and to prevent the overloading of possible alternative routes“, explains Klaus Hahn, Head of Sales Interurban with SWARCO. “We have been entrusted with the implementation of the control centres for the two systems. The overall system will be provided with further services in a working partnership.“

Integrated congestion warning system

Network control systems are already in place on the A 8 from Munich in the direction of Karlsruhe and on the A 81 from Heilbronn towards Stuttgart. In the direction to Munich via the Leonberg junction, there are no traffic control measures in place so far. The congestion warning system intends to integrate this area into the whole traffic system, starting already at the Rutesheim junction. LED variable message signs (VMS) will automatically warn road users of traffic jams and display the current speed limits. Seven VMS will be installed on both sides of the roadway, plus two webcams for traffic observation purposes. By means of SWARCO’s tracking radar detectors of the type Caiman-PRO I mounted near the VMS, local traffic data are acquired, also when traffic comes to a standstill. An essential point of the system is the exchange of traffic data and VMS contents with the Road Traffic Centre of the state of Baden-Württemberg.

Integrated travel time indication

Traffic studies indicate that the measure will cause considerable congestion on the A 8 and A 81 motorways and possible alternative routes. For a targeted network control and to maintain the traffic quality on the alternative routes, the travel times on the two motorways and the alternative routes are displayed to the road users. The aim is to keep them as long as possible on the A 8 and A 81. All major access points to the Engelberg Tunnel are therefore equipped with travel time displays. Information is conveyed automatically at 10 sign gantries with a total of 15 freely programmable RGB LED displays from SWARCO with a B6 wide angle optic. The visualisation of the travel time displays as well as the pictures of the webcams are published on websites of the state of Baden-Württemberg.