Speed limits need to be set to what the police are really going to enforce. What is legal and what you can get away with should be the same thing, especially as self driving vehicles become more common. One of the main issues with using Tesla self driving is that it won't let me keep up with traffic in many places. I can't blame manufacturers for not allowing people to use their programs to break the law since they could be held liable. Tesla does allow 5mph over the speed limit on non-divided roads and 10mph on divided roads but that generally isn't enough to keep up with traffic. If the cars were programmed to strictly follow the law there would be chaos on the roads. Limits should be limits, not political devices. They should also be reasonable.