CTA Tattler

Anatomy of a train derailment

There have been a couple train derailments in the news this year. That made me wonder: Just how does a train derail? So I asked the CTA Insider, and here's his response:

"There are a couple of ways a train could derail. There was a situation where a train was past a switch point (the train was not in service - there being passengers on board) and for whatever reason the motor man backed the train up (which is never supposed to be done - they are to walk to the other end of the train and move the train as if it where headed in that direction) and because the switch was already activated the train wheels went up past the rails.

  "This is considered a derailment but not in the dangerous sense. Any time the wheels come above the rails it is a derailment and if the shoe (the part that touches the third rail) comes off the power, the lights go out and the car loses power but it is mostly seen as a situation where the train leaves the tracks altogether.

"If a train where to hit something or roll over something there is the possibility of a derailment. That Brown/Purple collision awhile back is a perfect example -- the rear train does not stop but the front train has its brakes applied. The rear train pushes against the front and somewhere along the cars the knuckles buckle and the forward momentum pushes the car sideways enough for the wheels to clear the rails.

"The motor man is supposed to stop before they get to anything lying on the tracks because it could cause the train to raise up enough to push it off the rails. Even snow has been a problem some winters. Sometimes the motor man is moving too fast through a crossover or around a corner and the train will ride up the side of the rail and leave the track.

"It's always a rough ride through a derailment for the passengers and the motor man, who sometimes can be thrown around pretty harshly. The derailment that happened a couple of years ago on the O'Hare line was ruled as human error as there was track work going on at the time and this motor man didn't respond correctly and ran into the train sitting ahead while going at least 25 mph. That caused 3 or 4 cars to accordion across both sets of tracks. I had a friend on the rear train and he said people were flying around like rag dolls in a dryer. Speed is a factor in most situations but a lot of times it is inattention to duty.

"Normally there's not much damage done to the trains undercarriage or to the tracks but there is the possibility of the train knocking the third rail off the chairs it sits on which will cause a shut down of service along that section of track until track men get there to lift it back onto the chairs. The trains themselves are lifted by a crane and placed back on the tracks, and then pulled to the shop to be inspected and fixed if possible.

"With the derailment that happened in 1977 I'm not sure how it worked for that situation but I believe it was the same premise. I have a picture of that accident on my wall at home as a reminder of how bad it could be if people don't pay attention. There's also some ghost stories of that particular four car train that went around for years after it was put back in service, how the train would make screeching sounds and ghostly passengers would be seen by car cleaners passing through the cars at night during their shifts."

Photo by Alex Garcia, Chicago Tribune, via chicago-el.org