The Twilight Zone Tower of Terror at Disney’s Hollywood Studios features a total of eight elevator cabs (VVCs - Vertical Vehicle Conveyors) operating within the structure. However, the system is more complex than a standard elevator bank. The ride consists of four separate "Show Shafts" where the initial scenes (the 5th Dimension) take place, and two main "Drop Shafts" where the actual thrill sequence occurs. The elevator cabs are unique because they are self-propelled, allowing them to move horizontally out of the show shafts and into the drop shafts. This design allows Disney to run multiple cabs simultaneously to maximize "throughput" and keep the line moving. Behind the scenes, the ride is controlled by a sophisticated computer system that "randomizes" the drop sequence, ensuring that every ride is a slightly different experience. Maintenance teams regularly cycle these cabs out of service for inspections, which is why the ride may occasionally operate at a reduced capacity with only one of the two drop shafts active.