Road Studs

[DavidUK]

Why are there pairs of metal studs (or painted blobs) that you drive over at frequent intervals on motorways and other roads?

[elpedro]

I think the things you mean are the bumps in the white lines (rumble strips) that make a loud noise when you drive over them to warn drivers who through a lapse in concentration are changing lanes without realising, normaly situated between the hard sholder and the main carageway or any other situation where a accidental change of lanes could well be fatal.

[PhilLew]

You also get metal studs or white painted squares in the middle of the carridgway, these are a measured distance apart and are used by the police to catch people speeding by measuring the time taken to travel between two known points, This can be done from a car following you or one parked on an overhead bridge so watch out!

[moonacre]

I think you may mean the marker studs that police use. They are set in the tarmac at specific distances and are used to calculate the speed of vehicles they are following (by measuring how many seconds between them).

[sddsddean]

They are called 'node points', and whilst the police do use them, they are also used to identify particular sections of road for highway maintainence works.

[Andy P.]

sddsddean is basically right about their name and use by highways departments. He has been misled about them being used by the Police for Speed Enforcement. I was a traffic cop for twenty years and I can assure him that they were neither big enough to be seen in order to be used for that purpose nor in convenient locations. They are called 'node points', and whilst the police do use them, they are also used to identify particular sections of road for highway maintainence works. sddsddean Fri 06/9/2002