But, Grunty, if a person is daft enough to do 60 down a narrow lane, towards a blind bend, is having a 40 limit on the road going to stop them doing that?! Is there going to be a speed camera on that road? No, because it wouldn't raise any cash. So everyone will just ignore the new limit.
Unenforceable or stupid laws just bring the whole law system into disrepute.
But if a 'normal', reasonable A-class road, where by-and-large it would be safe to do 60, were restricted to 40 or 50, loads of money could be raised by having a camera. Or what about the 'big' sc trunk roads EG A17, bits of the A52, A38. These are usually big, well-maintained roads, with proper junctions, no serious bends. Limited to 40-50, a veritable gold-mine.
So let me guess where the greatest impact of these proposals will be seen... It ain't going to be on country lanes.