http://www.chicagotribune.com/news/local/breaking/chi-galena-train-derailment-20150305-story.html
CN has had 3 tank car unit trains go on the ground within a month, in Norther Ontario. The latest one is just a few miles from the previous one. The latest burned a lot of oil, but put a lot into a major river too.
All three have interrupted Via Rail’s “Canadian” The latest shutting it down for almost a week.
Extreme cold does funny things to steel rails, and to the steel wheels also. Wheels are subjected to temperatures as low as -40C, then when braking, can get almost red hot. These conditions can cause the steel wheels to become brittle, and then crack easily.
Rails are subject to hot and cold also, and expand and contract longitudinally, with the changes, causing “Broken Rails”. These are rather hard to detect until they happen; often when the train is right on the spot. Other breaks can be detected by disruptions in the signal system that depends on the rails for electrical circuitry.
How many cars there are in a train, 100 or 10, matters little. If a wheel cracks, in one car; chances are it will go on the ground. If the rail breaks, under the train…
Others with more exact knowledge on the dynamics of rail/wheel engineering, please jump in, as I’m NOT an expert by any means…
Fred Mills