Anybody every wondered what those flashing signs on gantries over motorways mean? They certainly can’t have anything to do with speed limits.
A case in point. Last Thursday I was beetling down the M4 on my way home. The signs overhead started flashing “50”. So I slowed down a bit to around 65. All the other traffic was whizzing past. “Still, there must be a reason for this”, I thought to myself. The next lot of signs were flashing “40”. Not wanting to be rear-ended by approaching traffic, I stayed at 65. All the other traffic was still whizzing past. A few miles down the road the signs were once again flashing “50”. Still nobody took any notice. I sped up a bit. That was the end of the flashing speed limits (if that’s what they are – I think the Highway Code must have it wrong).
I think the controller in charge of the M4 traffic regulation switched them on the night before and went home.
The other fun thing that the traffic controllers do is set the signs flashing to, say, “50”. Everybody still drives at 70. A few miles down the road the signs will flash “40”. Everybody still drives at 70. Then you’ll see the sign flashing “END”. Everybody screeches to a halt.