Yes, a better idea would be to enforce decent lane discipline.

Indeed.

The argument I heard on the radio this morning that people aren't capable of controlling vehicles at 80 but are at 70 is of course, utter nonsense.

I don't know about this, but I think we should also consider the consequence of accidents at 80 as opposed to 70.

I would imagine the difference between crashing and being pulverised at 70mph are not significantly different to crashing and being pulverised at 80mph.

I guess there's more energy to transfer at 80 than 70. Someone should work that out.

Kinetic energy increases as the square of the velocity, 0.5 x mass x velocity squared.

80 squared is 6400; 70 squared is 4900 so the impact energy is 130% at 80 mph what it would be at 70 mph. Stopping distances are also longer at higher speeds, as is the distance travelled while you are processing the fact that some wally has just cut you up horribly and you need to slam on the anchors.

At 70 mph on dry roads, the stopping distance is 315ft; at 80 it is 360 ft. Both double on wet roads.