I think that the UK cameras are triggered but magnetic coupling. Its the metal of the car that is detected between two points of known distance.The time between those two triggers gives you the speed.Older ones were based on pressure. As the tyre goes above the tarmac at the point that the pressure sensor is it gives two triggerings (front and rear axles) but this was totally inaccurate due to different vehicles size. Either way you could just try with your rc car. If you manage to trigger the camera you will see the flash!!!!!!!!!!!!!!!!!!!!