Following a pilot project, the Dutch Ministry of Infrastructure and the Environment’s Department of Waterways and Public Works (Rijkswaterstaat) has deployed a new truck-height warning system on the A22 motorway on routes to the Velsertunnel. The aim of the project is to reduce the number of excessively high loads being driven through the tunnel. Previously, the tunnel was frequently closed because over-height vehicles entered it, causing damage to the tunnel and truck, as well as creating long traffic jams in the area. It was estimated that closures to the tunnel during the rush hour, resulted in ‘social costs’ that amounted to EUR135,000 (US$152,700).
The new warning system comprises a vehicle-height measurement sensor, a camera, and roadside dynamic route information panels (DRIP) capable of displaying a photograph. If the height measurement sensor is triggered by a vehicle, it sends a signal to the camera, which then takes a picture of the vehicle. The photo is sent to the DRIP and is then displayed on the sign’s screen (pictured), together with a request to take the next exit. The agency says the great advantage of this system compared to other height warning systems, is that the driver immediately recognizes their own vehicle and knows that they must leave the highway. Netherlands-based speed camera manufacturer, Gatso, supplied the camera for the project, as it is the only camera system available that is able to portray the truck in full color, with the required detail for the image to be recognizable by the driver under both day and night conditions.
The height detection system provides a warning if a truck is greater than the statutory maximum of 13 feet (4m). The DRIP photo screens at the Velsertunnel are the first to be placed permanently in the Netherlands, and have proved to be an important addition to the existing warning system for over-height trucks. The signs have been installed are on the north and south side of the tunnel, a mile or two from the entrance, so that trucks still have enough time to exit the A22 highway and find an alternative route. A previous trial with similar signs, showed a significant reduction in the number of incidents caused by trucks that were too high to drive through the tunnel. With the new permanent system, the number of excessively high loads being driven on the A22 motorway to the tunnel has dropped by approximately 20%, and the number of over-height vehicles that are obliged to stop at the entrance has decreased by 40%. Traffic flow has also improved and the number of lost vehicle hours has decreased by 25% as a result of the deployment, with fewer tunnel repairs and closures required.