Comment by Fargren

> Has there ever been a case where two self driving cars collide with each other?

I don't think that's relevant to trains. Cars can avoid a collision much more easily than trains can. Cars can swerve, and if they are at a distance at which line of sight tells them they will hit an obstacle, they are moving slow enough to stop before hitting that obstacle. Trains have to stay on tracks, and they need up to 4 kilometers to stop moving.

The constraints are very different, so the solutions and tradeoffs will be different too.