If 49% of drivers speed on the motorway then it's time to put speed cameras on the bridges.
keep up joe the M25 has had speed cameras for 15 years at least (got a ticket for 71 when restricted to 60 at heathrow just after i passed my test!! )and several others also have them M2 and M42 are 2 that i can think of, they aren't always on only when traffic volume neccessitates.
the average speed on the M3 and M27 which i use regularly is around 80 during the early morning and evening but during the day that drops to 65-70 because of the sheer volume of traffic!
as for the stupid 60mph rule for vans that should be abolished, has anyone ever been done for 65 - 70 on a motorway as a result? I certainly haven't! 98.3 mph on the other hand 4 points £325!!