Photos of cars on freeway, speeding sign

Freeway Management and Operations Handbook

Description of Figure 15-3: Microwave Radar Operation

The left side of this schematic shows a cross section of a microwave radar sensor, mounted high above the road surface. A controller cabinet is level with the road surface, with power and data cables connecting it to the microwave radar and antenna, mounted on a horizontal surface. A note states that the radar assembly should have "sign bridge, overpass, pole, or mast arm mounting".

The right side of the drawing shows a vehicle facing the microwave antenna, with a double-headed arrow going between them as the "path of transmitted and received energy". A note states: "Reflected signal from vehicle can be used to determine presence (occupancy), passage (count), and speed, depending on the waveform that is transmitted by the radar sensor".