Note to self: If you happen to be running a train pulling 100 cars loaded with coal and happen to see smoke arising from the middle of the pack, stopping to examine the nature and cause of the smoke is a Good Thing.

It is, however, a Bad Thing if you stop over a wooden bridge made with creosoted ties, bents, and trusses; especially when the cause of the smoke is a vastly overheated wheel bearing that fails, dropping the truck support down onto the rail itself. The results, courtesy of heat conduction, are evident.

More info here.