A road with a NSL sign, as against a specific speed, will be made for a higher speed limit than we currently have. That's fact and I'm sure ALL the details are in the public domain.
Of course there are sections of road where they may have to impose a FIXED limit (that wouldn't change if tomorrow David Cameron said that a NSL sign meant 100mph on a single carriageway and 150mph on a dual-carriageway) and plenty of sections where it might not be actually safe to drive at speed.
Curves on motorways are much the same as railway lines - very gradual. Sometimes roads will even have the camber to aid tight turns. I've been on test tracks where you can happily take your hands off the wheel and accelerate and you stick to your lane perfectly. Takes a bit of confidence to do, I might add.
By the way, I am NOT suggesting we drive at 120mph here, or that the speed limit should be raised to 120mph. It's just that some people are convinced that 120mph is dangerous, which can't be the case given how safe German autobahns are (and usually just TWO lanes, so you're sharing lanes with caravans and lorries).
I do accept the point that we'd struggle to drop the speed limit completely given the amount of prats on the road, but sadly we've ended up having to cater for the lowest common denominator on the roads, on trains and life in general - as education standards fall and people expect to be able to do anything and everything without bothering to do a good job.
