Yes, Disney Parks (both Disneyland and Walt Disney World) have strict height requirements for many of their "thrill" attractions to ensure the safety of guests. These requirements are determined by the design of the ride's restraint system—such as lap bars, over-the-shoulder harnesses, or seat belts—which are engineered to secure bodies of a minimum size. For example, popular rides like "Space Mountain" usually require guests to be at least 44 inches tall, while "Rock 'n' Roller Coaster" or "TRON Lightcycle / Run" may require 48 inches. More family-friendly attractions like "Big Thunder Mountain Railroad" often have a lower limit of 40 inches. To accommodate families with children who don't meet these requirements, Disney offers a "Rider Switch" (or "child swap") service. This allows one adult to wait with the non-riding child while the rest of the group rides; then, the waiting adult can board the attraction without waiting in the full line again. Height is measured by cast members at the entrance of the attraction and often again right before boarding using a standardized measuring stick.