This is where we disagree. I do a fair mileage each year and try to avoid motorways because a) I'm never in a hurry, and b) I don't particularly enjoy motorway driving. Where conditions allow I tend to cruise along at around 63 - 64 mph. I am very very rarely overtaken these days - in fact, I would say, at those speeds I do far more overtaking myself, than the other way around. So my experience is that on today's NSL roads the vast majority of motorists are driving at between 60 and 70 mph (faster on dual carriageways I grant you). Now if the NSL limit was removed, a number of things would happen. Many drivers would undoubtedly begin to drive faster. On some previously NSL roads they would be up to 90 or even 100 and this increases risk in a number of ways. There would be far more overtaking - and that increases risk. There would be far more misjudgement of correct speed for bends - and that increases risk. There would be far more 'road-rage' as faster drivers feel themselves being 'thwarted' by slower motorists (and you see this on the motorways all the time!). Overall I have no doubt that removing the NSL would be a disaster.
Kev