Okay...Somebody Tell me How They Do it.

Leach Highway this morning. 70 kph zone, and the traffic slowed to 55 to skirt an accident. The usual angry impatient jerk in the junker Mitsubishi at the back  flashing his lights and tailgating - I mean this is Leach Highway after all...

Accident passed, the jerk pulls out into one of the passing lanes and floors it. Right past the white van with the black window parked in the bushes. Yellow flash from van. The jerk will be getting an expensive blue letter in the post and I, for one, am delighted for him. But I'm left puzzled by that flash.

You see, he was in a lane far from the kerb. It was not a terribly bright flash - and my own experience with photographic flash photography seems to need more light than that for objects that are moving far slower. and the light intensity falls off pretty dramatically with distance.

How does the traffic camera solve the exposure equation? What IS the traffic camera inside that white van? What is the lens? How does the shutter work?

It can't be super secret and after all it has the sanction of the WA police...so would some photographer please Facebook us or send in an explanation of the optics and physics involved?  I promise not to read it on my phone while I am driving.

Uncle Dick