Just curious about how these work. Assuming you drive along a stretch of road with 5 average speed cameras are they tracking your speed only between each pair?

What if this happened (in a 50 zone):

Cam 1 (dont forget to wave)
Cam 2 Avg 48mph
Cam 3 Avg 80mph but for whatever reason it didnt pick you up
Cam 4 Avg 48 mph
Cam 5 Avg 45 mph

Is cam 4 going to give you a fine because it recognises your average speed between cameras 2 and 4 to be too high or do you get away with it on the basis cam 3 missed you? I guess what i am asking is if they work purely on the stretch of road between it and another or do they work the whole way along a row?

Also if its one of those overhead cameras can you not tailgate a lorry and they wont read your numberplate anyway?

I thought they worked in pairs, but if you've got 5 cams then they must work as a group so you would need to avg speed the whole way.

The bold works though.

Can either work in pairs or as part of a network (so even if a middle camera misses you the software can calculate average speed from the next one). The only way to avoid it is to not get your front plate snapped, as you say, but it's not worth the hassle. Changing lanes doesn't work (the original camera's and software had to work in pairs I think, so you could gamble on changing lanes, but according to a mate in traffic police the new system compares all lanes from all camera's so that doesn't work any more)

They are remarkably effective. There's loads in Nottingham, on the ring road and now on the M1 4 lane stretch. Particularly on the ring road where they've been up for years virtually no one speeds. It's quite relaxing knowing that you can trundle along at 40 (it's a 40 speed limit on the ring road) and not get tailgated for going 'too slow'.

I saw some on the Dartford bridge the other day - are they new and operational????