M4 and roadwork cameras

[slaav]

I had a first good look at the average spee camera set up over the last few days due to an enforced 'commute' in and out of London. (Nr Reading from memory)
The signs clearly show average speed everywhere but I was amazed at the number of cars that were bombing along at 70+ and then slamming the brakes on at the cameras only to speed up afterwards. Do they work and are these people just simply idiots?

ALso, if in a 50 zone (same stretch with average speed checks) what would be the realistic 'trip' speed to get a ticket/FPN? Am slightly concerned as had cruise on at 53 all the way through but cant believe they are set that tight?

[Andrew D]

I'm not sure whether there's any legal requirement for a tolerance, but in my experience scameras are operated within the ACPO guideline equation:-

Speed Limit + 10% + 2mph = Bust

[puggit]

As discussed a few times on here - if you change lanes between cameras, you cannot be caught - they are not type approved across different lanes

[rs1952]

Another point, of course, is that regular users of the route will know where the cameras are, and more importantly, where the first one of the series is.

"Bombing along" at 70+ isn't going to get you a FPN from these cameras as long as you pass the first one at about 50 and keep going at that speed until the last one.

There are three each way on the section between junctions 10 and 11