Unidentified cameras

During the last couple of weeks some new cameras have started appearing on London's roads. Each set is a gantry with five cameras pointing towards the oncoming traffic. So far I have seen three sites, the first is on the North Circular Road heading west at Neasden, it is this set that I have the most photos of and they apprear at the end of this entry. The second set have appeared on the North Circular Road heading east just before McDonalds, just before the IKEA in Neasden and I have one long shot of these cameras, I am convinced this second set has gone up this week. I also noticed a third set on the A40 westbound between the White City overpass and Savoy Circus. What are these cameras, there are five on each gantry for a three lane road. They don't look like average speed cameras. Are they perhaps the first signs of the system needed for road charging? Maybe they are just more surveillance cameras. It would be nice if we, the taxpaying public were told what was being put up to - in one way or asnother - monitor us.