The manufacturer Truvelo is best known for the introduction of front facing speed cameras in the UK.
How do they work?
The Truvelo camera is a forward facing camera taking pictures using an infrared flash gun (the driver will not be able to see the flash so as not to distract or cause temporary blinding). The camera film is sensitive to infrared: the reflected light provides the film with the correct exposure resulting in a crystal clear picture of the driver committing the offence (incriminsting evidence).
The piezo road strips (inductive loops) are a known distance apart, and the time between compressions is measured to give the resulting speed of the vehicle. The system takes a single photograph along with four readings on a two axle vehicle and uses the average time for compressions to calculate the resulting speed.
How do they help road safety?
They act as a deterrent, as they photograph the front of the car, you do not have time to slow down as you pass them – they may have already got you!