Quote Originally Posted by CrystalSkull View Post
How do they work? They ping you with a laser and get a measurement from that. How close, probably 50 metres, more info here - http://www.rta.nsw.gov.au/roadsafety...lespeedcameras

"Previously there was one warning sign 50 metres before a mobile speed camera vehicle. There will now be 2 warning sign on the approach to a mobile speed camera. The additional warning sign will be placed up to 250 metres before a mobile speed camera vehicle."
Laser.

Distance from car and time for laser to be fired and bounce back even though the time is nanoseconds it can be measured.