Road Works Speed Limit

[sigma]

Travelling through road works on the M1 yesterday got me thinking. The signs say 50mph limit but the cameras are 50mph average. Does it mean I can go no faster then 50mph or do the cameras imply I can exceed 50mph so long as I don't exceed the average speed of 50 mph.

[factor-fiction]

I am pretty sure that 50 mph is the speed limit but they use average speed cameras to get an accurate average. Maybe speeding wouldn't be picked up if you kept changing from 70 to 30 to 70... but I am sure they want you to aim for max of 50

[Baldric]

I'm assuming they use Number Plate Recognition (NPR) cameras that record your entry and exit times for the restricted section, if you average over 50mph, you're nicked!

[March-Hare]

There's a clue in the title - they take your average speed, so you can go 60mph between the first 2 cameras as long as you do 40mph until the next camera etcetera!

[ummmm]

I thought it was between each camera? I'm sure i read somewhere that someone got 3 tickets on a short stretch of the motorway...

[New Judge]

I don’t know whether you’re asking (a) if you’re allowed to go more than 50mph (so long as you average no more than 50) or (b) if the cameras will only detect you if you average more than 50 mph.

The answer to the first question is emphatically “No”. The limit is 50mph and you must not exceed that even for a short distance, or you risk prosecution.

The answer to (b) is “Yes”. The camera times your vehicle over the distance they are apart and calculates your average speed over that distance. So you could travel at five minutes at 100mph, pull over to the hard shoulder for five minutes (making sure you have a good excuse to be there) and you would only have averaged 50mph over that stretch.

Average speed cameras were introduced because people were simply slowing down to pass a conventional camera (which only measures your speed over a very short distance) and then speeding up afterwards. A good example of how they are sometimes abused can be seen on the M6 Toll road in the Midlands. I believe the entire stretch is policed by average speed cameras and it is not unusual to see drivers pull over into an area just before the Toll Plaza at the northern end to “wait for time” having tanked it at excessive speed. Quite why anybody should do this is completely beyond my understanding.

[mccfluff]

re new judge - the entire stretch is not policed by average speed cameras.

[New Judge]

I'm sure you're correct.mcfluff - I have no first hand knowledge. But I'd be surprised if some stretches were not covered as I've seen - and heard from - drivers who do precisely as I've described.