Mobile object tracking systems

The invention relates to a mobile object tracking system for tracking mobile objects such as vehicles. An array of signpost stations is distributed around an area to be monitored, each signpost station being arranged to transmit a signpost identification signal. An object-based receiver is arranged to receive a signpost identification signal in the event of the object being located within a predetermined distance of a signpost station. An object-based beacon transmitter transmits an object identification signal and an object location signal derived from the signpost identification signal to a central control station via a network of receiver stations. The object is identified and the position of the object is located at the control station on the basis of the object identification and location signals transmitted from the beacon transmitter. The invention extends to a method of tracking mobile objects.