Currently HGV's are required to not exceed 40mph on single carriageway roads, which causes car drivers to attempt overtaking. As this occurs IN BOTH DIRECTIONS at the same time many head-on accidents occur, causing death, injury, and road closures.
If the speed was raised for HGV's and lowered for all other vehicles to 50mph, overtaking would not be necessary, and the overtaking would diminsh, thereby saving lives, and permitting the road to function more safely, with much less cost to the emergency services, and a reduction in road closure.
If this were implemented as a change to the 'National Speed Limit', it would be made at a very minimal cost.
Why is this idea important?
Casualty figures can be reduced, and road safety increased as a result of this change, plus it would have the benefit of being a very cheap method of implementation, whilst having no worse effect for the majority of law-abiding drivers; If the change was made, more people would be traversing single carriage ways in a safer, 'line' of momentum, rather than speeding-up, slowing down behind a lorry, making a judgement on overtaking safety, speeding-up again, on the erong side of the road etc..
As all traffic would be at the same speed, there would be no concertina effect, and probably, much less stress involved for car drivers, and certainly, much less for lorry drivers.