How does an enforcement gantry work?
The automatic enforcement gantries span the whole carriageway. As a vehicle drives through them, they identify whether it is required to pay toll and whether the toll has been paid correctly. Every vehicle that approaches an enforcement gantry is recorded by a detection and tracking device. The lane and exact time that the vehicle passes through the gantry are recorded so as to allow precise classification. In addition, a licence plate and overview picture is taken.
A three-dimensional scan is made when a vehicle passes through the gantry, which determines whether it is required to pay toll, i.e. whether it has a gross vehicle weight of at least 7.5 tonnes. If no toll payment is required, this data is deleted immediately.
Using DSRC (infrared short-range communication), the gantry checks if the vehicle uses the automatic system and if the customer has given the correct information, e.g. the number of axles. If this is the case, the image and sensor data is deleted. Other enforcement data from the communication between the gantry and the On-Board Unit is transmitted to Toll Collect so as to assure the quality of the units.
If the vehicle does not use the automatic system, the enforcement gantry uses the licence plate number to check whether there is a manual log-on or registered toll exemption in Toll Collect's records. This process only takes a few seconds. In order to be able to prove the possible multiple use of a manual log-on, booking data remains available for up to 24 hours so that it can be compared again. If a toll violation is suspected, the data is passed on to Toll Collect for further assessment.
The BAG toll inspectors can use the enforcement gantries as part of their stationary enforcement and investigate vehicles in the case of a suspected toll violation.