Road cables.

[Yambo]

the two tubes are there to be able to discriminate between the vehicles travelling in each direction, I am quite positive the speed would only be an indicative measure and not that accurate, also if it were to be used for enforcement it would have to be VCA approved which I am sure they are not

Whilst the speeds would not be used for actual enforcement the data produced may well be used to initiate enforcement. You're correct pp, the traffic numbers and speeds are measured for both directions.

Traffic speeds were grouped in speed categories, About 18 iirc (there's a lot of iirc coming from me - it was quite a long time ago! I thought I had a printout stored on my computer to illustrate but I can't find it. It may be on a disc somewhere . . . ) so it would indicate that x number of vehicles over the time period were travelling betwee 30 and 33 mph for example.

[Dodgy69]

Drove over these again today. There's 1set of 2 tubes on both carriageways just entering a roundabout. It used to be a straight road leading out of our village but they built a new estate with its entry road off this island.

When you're going straight across, say 99% of traffic , we don't slow down enough because if you cut the island it's straight. They did put one of those silly inner lane things on the island, but because they do nothing it's not slowing traffic.

Tbh, you can easily see if anything is coming out of the estate so it's not dangerous. So I'm thinking these are for monitoring speed on the island primarily.