Because railway lines, in the past, were not designed with autonomous operation in mind. It’s really only suitable for completely isolated systems (high speed b

Because railway lines, in the past, were not designed with autonomous operation in mind. It’s really only suitable for completely isolated systems (high speed bullet-train style lines walled off from their surroundings, or Western Australian iron ore trains miles away from anyone) or lightweight metro/subway style trains (e.g. DLR, airport “air trains”) that travel at low speeds or can stop quickly.