How Photo Radar Works

Photo radar combines a camera, radar, and a computer that records the date, time, speed and location of the violation.  The system is mounted in an unmarked van that may move to any school zone or neighborhood having trouble with speeding. 

Although photo radar uses the same Doppler principle as traditional radar, its unique feature is that it transmits a very narrow beam across the road, thereby eliminating the risk of tracking two vehicles at once. Also with photo radar, the offending vehicle is tracked much closer to the photo radar unit.

In Boulder, the photo radar vans are positioned at the side of the road.  A radar beam is transmitted from the unit in the van across the roadway immediately preceding the photo radar van. When a vehicle enters the radar beam at a speed higher than the threshold speed established for the program (currently 10 mph or more over the posted speed limit), the camera is activated and takes a photograph of the vehicle, which includes an image of the driver.  A second camera takes a picture of the license plate of the vehicle.  The computer system captures the speed of the vehicle and then transmits information regarding the speed, date, time and location of the violation to a data box.  This data box is then superimposed on the photograph of the vehicle.

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Why are speeders allowed a 9 mph buffer?

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This provides a reasonable margin of error for inaccurate vehicle speedometers and short term lapses of attention by otherwise law-abiding and generally cautious drivers.  Boulder's focus is primarily on intentional, aggressive, and negligent speeders.  Statistics tell us that at 10 mph over the posted speed limit, the probability of being involved in a crash doubles.  At 20 mph over, the probability increases to 11 times greater.  We are trying to change the driving behavior of those who are most likely to cause crashes.

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Is this technology really reliable and accurate?

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The Boulder Municipal Court has conducted extensive evidentiary hearings and determined that camera radar technology is scientifically reliable and legally admissible in Boulder Municipal Court cases.  Click here for a copy of the Court's ruling(s) on the admissibility of photo radar evidence.  

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What if the equipment malfunctions, could I mistakenly receive a citation?

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No.  If the equipment malfunctions, then it automatically turns off, no photographs are taken, and no citations are generated. 

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Last Updated on Wednesday, 08 April 2009 02:44