I understand that there are maniacs out there, but the technical skill required to do this combined with the cost and the level of insanity would make this scenario pretty unreasonable to consider a valid threat. Not saying it couldn't happen, but there are easier ways to cause a similar amount of damage.
How would I stop it?
- Box it in with dump-trucks, other semis, or armored vehicles.
- Use a tank or other armored vehicle from one of the many armories located everywhere.
- Use one of those MRAPs that the military has been giving law-enforcement recently.
- Shoot out tires.
- Armor piercing or 50 caliber rounds to the engine.
- Remote shutoff that is impossible to disengage without also disabling the GPS.
- I'm very close to a major air-force base, they have plenty of ways to stop a civilian semi-truck.
- Use one of the many armed drones, a military helicopter, or even an armed aircraft. I'd have no problem with the US military using an air-to-ground missile to take out a autonomous vehicle that was programmed to do harm, as long as they were sure that there would be zero civilian casualties.