I saw the Lac-Mégantic derailment disaster on youtube and wikipedia, I thought why are couldn't they have a simple heavy wheel chuck that it capable of totally stopping a train from moving down a slight incline- I don't think any sane engineer would stop a train on a serious incline. Something they bolt together in a few pieces and digs under the rails- sure put on a lots of brakes but this would make it impossible. Something made of steel that you could carry with you. Less risky than relying on many complicated subsystems that could have faults and fail. A quick search only found light weight wheel chucks that can't be relied upon for even one carriage. So why not a simple solution rather than needing 20 brakes to all work and the engineer to apply all of them ?