About 100 years ago the British had a bad wreck after an engine change on an overnight train. A few years ago there was a write-up about it in The Railroad Magazine with thoughts as to had gone wrong.

Without finding the issue and rereading the article the basics is that the train left the engine change without the vacuum being taken on the train. The new locomotive's hose was never taken off of its dummy coupling; the engineer was oiling around while the inexperienced fireman (who was more of a "super cargo" than a real fireman) apparently did not notice that the vacuum was obtained much too quick. When they got to the next major station (which they were not scheduled to stop at) they could not slow down and overturned on a crossover.

Apparently the car inspectors, etc. at the engine change point were used to bottling the vacuum and manually releasing the brakes to enable a quicker reestablishing the vacuum and a quicker departure. The next day the company issued a bulletin making sure that this practice was not continued. This was never told during the investigation by a non-railroad army officer.

For Jim Boylan - everything ou could ever want to know about slip coaches.

http://mikes.railhistory.railfan.net/r134.html

in a nutshell; there were special shut-off cocks between the two hosepipes that were closed by the guard before the coupling was released.

Another short write-up with more photos:

http://www.eyewitnessnews.co.za/article ... x?id=37948