What happens when a runaway train is careering down the track into the path of an oncoming engine?
Derailers are devices which can be carried to a place on a track and installed so as to protect eg people working in the vicinity. If a train approaches without warning it is automatically derailed (usually onto a fairly safe, flat patch of ground).
Today’s invention is a derailer which is carried by trains themselves and which, in the event of an impending crash, is rapidly lowered into place to allow the train to leave the track.
It takes the form of a pair of curved rail sections normally carried above an engine and hinged so as to be able to drop down in front of the engine’s front wheels rapidly and detach from the vehicle.
These could be made of some comparatively expensive but lightweight material and be long enough to direct the engine off the track, whilst leaving the rear section still on the rails.