most of what they are saying is rubbish about this. i used to deal with car accidents for a living.
Most accidents are not caused by speed. If you look at court cases over car accidents, one of the most common things you see is that it is that speeding is not the cause of injury or damage on its own. it is a contributing factor as to the severity of damage or injury, but not the cause.
in most cases accidents happen at low speeds, through people not paying attention to what is going on around them. And given cars stop quicker, have far greater protection for occupants and pedestrians, actually the amount of damage caused is less than it used to be, it is just litigation and repair costs that have gone up, and there are more cars and pedestrians that keep the figures ever increasing. Duel carriage ways and motorways are realy the only place where speed is a major factor as when you hit something, its generally pretty hard and at speed it can make a big difference, especially as cars do not leave sufficient space to stop for anything in front of them.
There will always be the argument of well if the vehicles were travelling slower, but you might as well say we should go back to driving with a man walking in front waving a red flag, then again he might end up being run over, so actually lets go back to just walking.
I think if the government lifted the motorway speed restictions people would be much happier to slow down in towns and villages where most of these accidents happen.