Bit late to the party, but the cameras are switched off for loads of reasons. I check the M1 Southbound cameras between 27 and 25 every day just before I set off on my journey home and at least one of those cameras are 'In Operational Use' at least once a week. I presume it could be for any reason the operator feels fit, but often it's just because there's a build up of traffic near one of the junctions.
