The idea that average speed cameras work only if the vehicle remains in the same lane is a popular myth. When they were first developed this had an element of truth. However, now all the cameras (which work by ANPR) at a single location simply feed all the registration numbers that they detect into a single system and all the data from each end of the stretch is analysed.
Also keep your eyes open for the road side speed indication discs, Locally we've got quite a few roads covered by AVS cameras limited to 50mph and some of the are stretches of dual carriage way.
"Surely as a Driver you should be aware of Speed Limits?"
Surprisingly, we humans are fallible. This is one of the reasons we devised question and answer sites with motoring sections, subdivided into categories including road rules.
In the unlikely event that one as all-knowing as yourself ever needs to refresh their memory or, and I'm reaching here, ask a question on a subject you've no knowledge of at all, feel free to rattle your keyboard.
On the A127 they have been in operation for a few years, they did have teething troubles but only for a little while. Some drivers still seem to think they can drive like hell between the cameras and drop to the speed limit when passing, many have been caught as average speed means just that.
Thanks (nearly) everybody...I just wanted to make sure of the difference between dual and non-dual carriage ways.
By the way, they have now installed some average speed cameras along a particularly dangerous part of the M4 and loads of people have been caught since they went live earlier this week !
Of course they caught loads. One has only to travel on any motorway to see the vast majority going faster than the limit, because hardly anyone thinks the limit is right. So motorway drivers are low hanging fruit.
I was always under the impression that a dual carriageway was a 2 lane highway in the same direction and the limit was 60. However if there is a barrier on the central reservation the speed limit is 70.
Not sure if I am correct.
We too have these average speed cameras approaching our city.
Sycamore3House...I think you will find that a dual-carriage way is what our America friends call a Divided Highway. That is, with some kind of barrier between the two directions.
When I went to school ( if my memory is correct) you add up the total (90) and divide by the journey's (2) so the average would be 45 mph, but then I may be wrong.