Photo radars, or camera radars as they were first called, were in experimental stages of development as early as 1954 using S band radars. In 1983 the state of Texas tried a French-manufactured Ka band radar for a time but discontinued its use because the units were being stolen right off the road. Many communities continue to use photo radar because of the revenue it generates; some communities have outlawed photo radar, usually because of public pressure.

Photo radar (constantly transmitting) automatically detects a speeding violation (auto-lock) and photographs and/or video tapes the suspect vehicle, and records vehicle speed and typically the date, time and location. In states that have only one license plate (rear) two photographs (and cameras) are required to photograph the license plate and driver -- one photo (front of vehicle) to get the driver, another photo (rear of vehicle) to capture the license plate. Some units function at night by using a flash. Some units use an orange flash filter -- an orange flash is not as bright (as a white light flash) and should startle the driver less. Many photo radars connect to a computer or printer to retrieve stored data statistics such as number of violations, time and speed of each violation, etc.

A police officer does not have to see (or even be near) the alleged violation -- the process is automatic. The police officer is replaced by electronic circuits and a still and/or video camera. Many drivers do not even know they were recorded by photo radar (usually hidden in a van, pick-up truck, highway maintenance vehicle, etc.) until weeks later when a ticket and photograph (usually includes license plate and driver) arrives in the mail. Note that the registered vehicle owner may not be the driver, but the owner still gets the ticket.