I was wondering about this the other day........ presumably they'll need a fairly small aperture to ensure that both images captured are pin sharp and leaves no room for debate on the car licence plate. The car, when captured is also a good distance from the camera so the flash must be pretty good, although i know some flashes have a huge range. But the exposure must be really short to capture the motion of the car but freeze it to again leave no room for doubt when identifying it. so there's a fairly smally aperture (presumably) and a very fast exposure. I guess then the flash must be awesome to provide enough light for the whole thing to work. any one know for sure?