I’m not a fan of so- called Smart motorways- because as they are busy ( potentially) saving the environment - I’m getting killed because there is no hard shoulder to pull on to in an emergency.
The way that the 50/60 signs are randomly switched on/off on a clear afternoon with little traffic on the M5/M4- cannot have anything to do with traffic flow- more cash flow- into the local coffers.
It's a proven fact that fewer peeps are getting killed on Smart motorways, this is because most peeps are killed on the hard shoulders. When the speed limit changes you get 1 minute to slow down before the cameras operate. So providing you obey the limit you have nothing to worry about.
