On Mon, 21 Jan 2008 20:02:01 -0000, "Kim Siddorn"
 wrote:

>Couple of things - can average speed cameras see in the dark

Almost certainly they will work well into the infra red so will pick
up the number plate. In about 1968 my father was in the home office
when they were testing materials for reflective plates, it was well
before digital cameras so they were considering film, and one of the
reasons for the bright yellow rear plate was for better contrast for
the cameras they were intending to use.

> and do they 
>REALLY only cover a lane apiece??

From what I've read it was more to do with how they presented the
system for some sort of legal compliance. The cameras cover multiple
lanes but are only compliant if they catch the same car in the same
lane, so shifting lanes between cameras made it impossible to
prosecute, I expect they've resubmitted the system for multiple lanes
by now.

Andrew Heggie