Well, all trains in Denmark are equally exposed to the elements and deal with leaves, snow, ice, bugs (we don't really have crickets though). Even our Metro is

Well, all trains in Denmark are equally exposed to the elements and deal with leaves, snow, ice, bugs (we don't really have crickets though). Even our Metro is only partially underground. Emergency braking does not become more sufficient with a driver on board, so I do not understand that logic. The signal system is not less able to track occupancy on country-side, and it is much better suited to react early than a driver with their limited sight and fallibility. The signal systems have come a long way since the days of just monitoring simple track segment occupancy. I am not suggesting you just slam self-driving trains on a random track without setup - it takes a signal system overhaul if not already prepared - just that self-driving trains has been a solved problem in regular commercial operation for well over two decades.