Planes can be automated because their routes are segregated and scheduled (for commercial flights). There is no chance of a pedestrian walking through an air co

Planes can be automated because their routes are segregated and scheduled (for commercial flights). There is no chance of a pedestrian walking through an air corridor and very little chance of a bicycle being left on a runway. While not perfect, their activities are surveilled by third parties which greatly contributes to system safety. Monorails, which operate on the ground but not at grade level, can also be automated for the same reasons and have an even better safety profile than airplanes. I'm not suggesting monorails vs cars, but rather pointing out that the environment in which the transit operates is paramount. Self-driving is trying to automate around the chaos created by human-driven cars on unpredictable routes, while planes and trains have neither of these issues. And that's why it's currently an unsolved problem.