The trouble with automated trains as with many things of technology is that when one little thing goes wrong the whole system comes to a halt until that thing is resolved which can take hours. As of right now every time PTC fails to work on a train, crews are just being told to override the system and take the train anyways. But just like pilots who increasingly rely on automated systems, their skills are degrading such that they may not be able to handle a bad situation when the automatic system itself fails. As automation allows train lengths and tonnages to grow, engineers who rely on automation may not be able to run such trains if the automation fails.