The RTMS is a miniature radar operating in either of two microwave bands, employing the FMCW (Frequency Modulated Continuous Wave) principle. It transmits a low-power microwave signal of constantly varying frequency in a fixed fan-shaped beam.

The beam "paints" a long elliptical footprint on the road surface. Any non-background targets will reflect the signal back to the RTMS where the targets are detected and their range measured.

The RTMS range measurement resolution of 2 metres (7 ft.) allows the "slicing" of the footprint ellipse into 32 range-slices. The user can define a number (1 - 8) of detection zones, each consisting of one or more range slices.

The RTMS internal microcomputer controls in realtime 8 opto-isolator relays corresponding to the detection zones. Relay contacts are closed when a target is present within the respective detection zone. The contact-pairs can be connected directly to traffic controllers. In addition, short-term statistical data on each zone are accumulated and transmitted by the RTMS via its serial port. Typically, every 30 to 300 seconds a message containing the Volume, Occupancy, Average Speed and Classification by length data in each detection zone is transmitted.

The long microwave wavelength and the range-measurement capability make the RTMS immune to all weather effects and to most occlusion situations allowing vehicles hidden behind other vehicles to be detected, as shown in the diagram