Rail creep is defined as the longitudinal movement of rails with respect to sleepers in a railway track. The most serious effect of rail creep is buckling of the track laterally, which can result in derailment if not addressed. There are several causes of rail creep, including wave action as wheels load and unload the rails, percussion from rail joints, dragging forces as trains start and stop, and thermal expansion/contraction from temperature changes. To remedy rail creep, tracks are adjusted through manual means such as grinding rails, replacing worn fastenings, or using mechanical correctors that push rails back into position.