Truvelo Speed Camera

The current model Truvelo Combi Smc was Home Office “type approved” in April 1999 for front or rear photography.

Speed measurement is carried out by means of two pair of piezo-electric sensors installed in the road surface. Their signals are processed by two totally separate circuits within the instrument. The two speeds are thus measured entirely independently from each other.

If the speeds differ very slightly, then the instrument uses the lower of the two speeds, which is then rounded down to the benefit of the motorist.

If the two measured speeds differ by more than 2 mph then the instrument gives a zero reading and no photograph can be taken.  A sensor based speed measurement system therefore can not produce an incorrect speed measurement.

The measured speed is compared to the threshold setting for the camera and a photograph will be taken if the measured speed is at or above the threshold setting.

For front photography operation the flash must always be covered by a magenta coloured filter.  The use of a magenta coloured filter gives rise to the popular misconception that infra-red illumination is used. It is not infra red.

When the camera is installed on site a number of “calibration” test shots are taken, and similarly when the camera is removed from site. If the camera was not within calibration then it would lock-out and would not function. This is an additional fail-safe system.

In addition a secondary check system exists whereby the front wheels of the vehicle must fall with the area of the three lines painted on the road at front photography sites.  The time taken for the vehicle to travel from the last sensor to the check lines is recorded on the negative to allow an arithmetic calculation to made.