The Big yellow boxes are Gatsos, with analogue (35mm film), they get your from behind. The smaller yellow ones are digital and have an internet connection - they never run out of film!
The blue ones that have a yellow plate that faces you are Tru-velo. They use induction loops rather than radar to detect your speed. They use an infra-red flash so as not to blind you, and were introduced so that you couldn't use the "Ferguson defence" where you claim you were not the driver. They are digital, too.
SPECS (average speed cameras) tend to be on gantries which are painted yellow.
The Cobalt-blue cameras are traffic master - they don't detect speed, just read your plate for traffic flow information.
arent these traffic cameras so they can see flow of the traffic etc?