Apparatus for measuring the speed of land vehicles.

摘要

An apparatus for measuring the speed of land vehicles has two magnetic field sensors (14 or 15), arranged at a distance (d) from one another in the direction of travel, for detecting changes in the terrestrial magnetic field, and has an evaluation unit (21) which determines the shift in phase or time of the electric output signals of the magnetic field sensors (14, 15) and calculates the vehicle speed (v) therefrom and from the distance (d) of the magnetic field sensors (14, 15). In order to ensure a satisfactorily accurate and reliably reproducible speed measurement in road traffic, the two magnetic field sensors (14 or 15) are arranged along and immediately adjacent to a route (10). The spatial distance (d) between the magnetic field sensors (14 or 15) is kept smaller than the minimum distance (a) between successive vehicles (10). It is preferred for the distance (d) between the sensors to be selected only half as large or smaller than this minimum distance (a) between vehicles.