A derailment occurs when the wheels of a locomotive or car leave the rails, dropping into the gauge or onto the ties. It ranges from a minor yard incident where a single axle drops at low speed, to a catastrophic main line pileup. Derailments require heavy equipment to rerail the cars and often cause severe damage to the track structure, ties, and switches.
Heard on the job
We had a minor derailment on track four when the switch points gapped under the rear truck.