The technology uses special cameras to track traffic flow through specific points on trunk roads, including roundabouts and traffic lights. The cameras 'tag' electronically certain vehicles and monitor their progress. This information is transmitted by radio link every four minutes to a computer at Trafficmaster's headquarters. This matches the cameras' sightings of the tagged vehicles to monitor the average speed or journey time for every four-mile link across the country.
PTFM will be introduced in the summer of 1998 as part of Trafficmaster's £10 million trunk road expansion programme.