An onboard unit for charging occupant number-dependent tolls for a vehicle inthe context ofa road toll system. The unit includes a Doppler radar or UWB impulse radarthat can bedirected onto the vehicle interior for measuring movements and generating atleast onemeasurement signal representing these； and an evaluation device, which isconfigured todetect signal patterns in the measurement signal that are typical for heart orrespiratoryactivity of an occupant, to count those signal patterns which occursimultaneously at anobservation time, and to calculate toll data as a function of that countvalue.
