with an average travel speed of a vehicle from one beacon to the next one the validity time frame of the most recent toll fee level has not yet expired when the onboard unit reaches the next beacon thus an expiration of the validity time frame i e an interruption of the chain and therefore transmission of the toll fee level to the central station occurs only in exceptional cases for example stopping during the trip turning onto a different street etc consequently only data records containing a toll fee level accumulated over several beacon locations normally arrive in the central station and thus do not allow any precise inferences of the individual beacon locations as a result a high data security or confidentiality for the sensitive movement data of the onboard units is achieved while simultaneously maintaining the post pay billing functionality in the central station fig1 schematically shows an exemplary road toll system 1 that comprises a central station u201c central system u201d cs 2 and a plurality of geographically distributed beacons u201c roadside equipment u201d rse 3 that interact with vehicle devices or onboard units obus 4 the onboard units 4 are carried in vehicles not shown that are moving on a road network 5 a location related time dependent and or travel path dependent toll fee for the vehicles is determined with the aid of the beacons 3 and the onboard units 4 and is charged in the central station 2 for this purpose each beacon 3 can localize a passing onboard unit 4 to its beacon location p specifically by setting up a radio connection 6 with the onboard unit.