This post has been migrated to http://www.thinkcode.se/blog/2011/12/30/how-many-train-wrecks-are-lurking-in-your-code
Train accidents are mostly considered to be bad things. People tend to get hurt when trains have accidents. Never the less, it is not so uncommon with train wrecks in software development.
Train wreck code is code that calls a method on the return value of another method call. This chain can be very long if a value is excavated deep down in a object graph.