Motorway lane marking question?

Question

Pure idle curiosity, but when I'm on the motorway, occasionally there's a set of marks going across the carriageway. Large squares, or sometimes they're circles or diamonds, one painted in each lane. I don't mean speed camera tracks, they almost look like crossings, which would be insane. Someone told me they were to do with taking a traffic census, but I'm not sure.

Does anyone know what they are?

Thanks.

Answer 1

police speed traps they put camera up on bridge and when you pass the 1st square they time you to the next square and then workout your average speed.but they arent used anymore as modern technology has taken over with digital cameras etc.