It's not, but because rail is much stricter and the safety protocols semi-automated to fully automated, the self driving is much easier, and unexpected conditio

It's not, but because rail is much stricter and the safety protocols semi-automated to fully automated, the self driving is much easier, and unexpected conditions much easier to detect because expected conditions are very uniform. Self driving supervised trains can drive on non-ETS (not fully automated tracking and safety) rails too with additional precautions. Lines where trains are driven by humans, and where some safeties are manually operated, as long as the presence of those safeties and cars is programmed. These behave then more like driver assist and automated safety.