We need speed limits, but sensible ones.
The big problem is that many people feel the need to travel at the speed limit whatever the road conditions and traffic density are. I have witnessed many accidents where people have driven at speeds beyond their field of vision eg going round a bend as if nothing could be watining to turn right at a junction.
Over the years cars have become more refined and the standard of driving has dropped dramatically. There is no courtesy on the road and indicators are rarely used.
I would not like to see cars fitted with speed limiters. What is needed is better driver education and a system which fines speeders according to their income, eg 30% of their weekly income. I also believe that this percentage should be increased to 50% after two convictions.
The time saved on most journeys by doing an extra 5 - 10 mph is negligible.
Lastly, there is no fast lane on a motorway. Unless you are overtaking slower moving traffic you should keep to the inside lane. I have to admit that I travel at about 75/80 on the motorway when and where conditions allow it and I find myself struggling to overtake because some moron is doing 90+ and driving like a suicide pilot. I see the outside lane on the M6 full of fools every day driving about twenty feet apart.
It is better to 5 minutes late in this world than dead early in the next.