White squares on motorway - why?

[jeeves]

Something that has perplexed me for some time, when you drive along the motorway, what are the white painted squares that you see every now and again?

Are they something to do with distance markers for the police to measure speeding by?

 

[gcol]

http://www.karacare.co.uk/law.html
Visually Assisted Speed Computer And Recorder (VASCAR) is THE way that the police use to record your speed this way. Ever wondered what the white squares in the center of a lane were for? They are speed reference marks that allow VASCAR to be used. VASCAR can be used for 'pre-determined distance' or 'following' speed checks.

If a police car fitted with VASCAR is following you, when you pass over one of these reference points (reference points can also be STOP lines at a Pelican Crossing or a SLOW sign in the road) the time switch is turned on. When the police car passes over the same reference point the distance switch is turned on. Then they watch for you passing another reference point whereupon the time switch is turned off and the same with the distance switch when the police car passes that point. As both the time and distance is now known to the computer, the target vehicle's speed is instantly displayed and is a very accurate figure.

The pre-determined distance check is even easier - both reference points need to be in clear view and all he does is operate the one switch. The reference points then need to be referred to in court.

VASCAR is most often used in following checks where you don't even have to maintain an equal distance, you merely have to say you used the same fixed points on the road for both the target and yourself. Not widely known is this fact: It can be used for 'opposing' checks although it is not easy to do and is not commonly used. You trip the time switch for an opposing vehicle as it crosses a fixed point, you then turn off the time and turn on the distance as it passes you then turn off the distance when you pass the fixed point. Then you have the necessary for the time taken to travel a set distance and the computer does the rest. All that remains to be done then is turn and catch up to the offender!

 

[jeeves]

Excellent! Thank you very much, I did have a little search on t'internet but had no luck.

 

[Steve]

Theres some here:

http://www.wikimapia.org/#y=53538693&x=-1177659&z=19&l=0&m=a&v=2

Not a motorway either.

Always wondered what they were for!