Speeds on roads should not be limited at all. I can see Jeremy Clarkson and Richard Hammond agreeing with this on The Grand Tour and even James May (no pun intended). Why, how, are you mad, you think.
I recently read an article stating that the partial introduction of autonomous vehicles (self-driving) would slow traffic down, which sounds daft. But it made me think about the time when all vehicles are autonomous, and programmed to learn about the road it’s driving on, weather conditions, other vehicles behaviour and how it’s functioning; tyre wear, load distribution, braking efficiency and all this data is linked to an almighty AI system, no doubt linked to IBM’s Watson computer. Now the car is better at determining how fast it can safely travel than arbitrary rules, so speed limits become irrelevant. The only determining factor now is programming the car’s probability of crashing, which should be set by the government and the absolute speed that the car could attain.