Don’t think we will be seeing 100 mph lanes British motorways are not designed for that speed. It is off course the bends that bring the problems.
I see fully autonomous cars on British roads within five years, sooner if we leave with a hard Brexit.
Roads, where all cars are autonomous, will be the safest we have ever had but the time when we have a mixture maybe 50/50 could be the least safe we’ve ever had.