How slow do you need to go

[campbell]

Scamera vans provide a generally excellent photo of the driver.

I've seen one. It looked remarkably like me.

GATSOs are rear-facing so that the flash(es) won't blind the offender. So the story goes (and I think I believe that more than most other possible reasons, TBH). May also be to do with focusing the GATSO "beam" on a near enough area as to provide accuracy on the speed at which point pic1 is taken, then based on a fixed time delay, pic2 then fires. Doing it the other way around would need the beam to be focused further out and may well reduce the range of speeds which could be tracked.