Abstract: A route guidance system for vehicles comprises central computing apparatus (6), transmitting apparatus (1) by way of which the central computing apparatus (6) is informed of the positions of respective vehicles on a road network and by way of which the vehicles are supplied with route guidance data calculated by the central computing apparatus as to the best routes for the respective vehicles to take to respective desired destinations, the transmitting apparatus (1) including transmitting devices (4) for carrying by the respective vehicles and by way of which the central computing apparatus (6) is informed as to the desired destinations, computing apparatus (8) serving to inform the central computing apparatus (6) as to traffic congestion on the network, and speech synthesisers (4) for carrying by the respective vehicles and arranged to speak instructions to the drivers of respective vehicles as to the routes to be taken to their respective desired destinations.

Abstract: A method of monitoring traffic flow comprises reading registration plates of the vehicles of a multiplicity of series of vehicles passing respective locations on a road network, if necessary selecting samples of readings from the readings relating to the vehicles of the series, and determining whether readings of the samples are deemed to contain matching readings. The samples are used as probes or targets to measure average journey times which are compared with reference journey times. The selecting of the samples at the respective reading locations is performed according to an algorithm common to all of the locations.