Valleying Explained – Theme Park Definition

Valleying occurs when a coaster train, having lost too much kinetic energy during the ride, fails to have sufficient momentum to crest the next hill or complete the next element and comes to a stop — or rolls back — in a valley between two high points on the track. Because the train is now sitting at a low point rather than at a brake run or station, it cannot be moved by the normal operating systems. Recovering a valleyed train typically requires maintenance personnel to physically push or winch the train over the next high point, or disembark riders and pull the train back.

Valleying is rare under normal operating conditions, since rides are designed with substantial speed margins. It is more likely to occur in unusually cold weather (when wheel bearings run sluggish and friction increases), on an underpowered train running with fewer passengers than designed for, after excessive trim braking, or on rides that were originally designed for different wheel and axle specifications than are currently installed. Valleying incidents occasionally occur on ageing wooden coasters whose track geometry has shifted over time. When a coaster is reported to have "valleyed," it typically takes the ride out of operation for hours while recovery work is completed.