A couple of months ago, our local roads authority (UDOT, in Utah) decided that the speed limit on the motorways should be raised from 65mph to 70mph. At least up in the north of the state. The press and media were full of hysterical women screaming "won't somebody think of the children" and dire warnings from random people interviewed on the street about how it was going to be a bloodbath, a massacre, a dark day for road safety etc etc blah blah blah. The highway patrol were remarkably quiet about it - the one spokesman who did get interviewed said they would reserve judgement.
Well - as has happened pretty much everywhere this has been tried - guess what? Accident rates have fallen. The same happened in southern Utah when the limit was raised to 80mph. The same happened in Switzerland, the Netherlands, Spain, Greece, Sweden, Norway and all the other locations where enlightened authorities have realised that it's not the speed that is the problem, it is the DIFFERENCE in speed that is the problem, especially on motorways.
Now I know this isn't a popular view - the truth often isn't. But the facts speak for themselves and the theory behind it is simple and sound. It is this: A huge percentage of drivers are already breaking the speed limit and driving at 75. The law-abiding drivers are doing the posted limit - 65. This means the largest speed differential between the average driver and the law-abiding driver is 10mph. Raise the limit to 70 and the faster drivers don't suddenly all do 80 - they keep going at the speeds they're used to - 75. The difference is that the law-abiding drivers are now doing 70 and the differential has been cut in half to 5mph. That gives you a lot more time to react when everyone is travelling at speeds that are more closely matched. In areas where the limit was raised to 80, the speed differential has effectively become zero. In those areas, people were already doing 80, now the law-abiding drivers are doing the same speed.
Meanwhile back in England, they're crusading to lower the limit from 70mph to 50mph on the motorways. Although that's nothing to do with safety and everything to do with making money through automated speed cameras.