Stacking

Stacking occurs when a roller coaster's loading and unloading process is slower than the ride cycle time, causing trains to accumulate in the brake run waiting for the station to clear. Instead of dispatching one train as the previous one returns from its circuit, the operator must hold multiple trains in the brake run — bringing the ride to a brief stop between each dispatch. Every second a train stacks directly reduces hourly capacity and extends the standby queue wait time.

Common causes include slow guest loading (often because of complex restraint systems such as over-the-shoulder harnesses that require individual adjustment), bag check requirements, understaffing, or slow guests in specific seats. Experienced park visitors can observe stacking from the queue: watching whether a train is waiting in the brake run when the station dispatches is a reliable indicator of operational efficiency. Notably, some rides with excellent ride experiences are undermined by consistent stacking — a coaster's theoretical capacity and its actual operated capacity can differ substantially.