On city roads, if your car gets confused it can just stop, even without pulling over. This will annoy a lot of people but nobody will die. On a highway, you c

On city roads, if your car gets confused it can just stop, even without pulling over. This will annoy a lot of people but nobody will die. On a highway, you can't safely just stop. And there are still difficult driving situations. For example, construction zones often have poorly marked lanes (or multiple, contradictory lane markings), construction workers to watch out for, and nowhere to pull over. Exit and entry ramps may be clear, but merging at speed and in traffic is a difficult and unsafe problem. And any failure at highway speeds is far more dangerous than at 25mph.