white squares on the roads

[greendon]

what the the white painted squares 30cm x 30cm on our road surfaces for

[sddsddean]

Almost certainly 'node points'. They are used by the local council/highways agency to identify sections of road for maintenance. Although these sound a bit larger than usual (though I have seen them that big), they are normally a pair of squares or circles about 4" across, or sometimes road studs are used. Some will say they are also used by the cops to set their speed cameras, but after working on highways in one way or another for over 20 years, I have never had anyone (police or public) confirm this.

[redbreast]

I always thought that the metal 4" squares were for Ordinance survey information, when driven over by their vehicles a distance was measured. I could by wrong as usual. You seem to know what you are talking about

[chrisrob]

A few years ago, when they were painted on a stretch of motorway nearby, the local paper said it was to enable police helicopters to accurately measure road distances when watching speeding traffic!

[Electrochem]

The previous answer is correct. They are a set distance apart and can be used by the police to calculate speed.