The single rider line is a great secret for theme park visitors who want to pack as many rides into their day as possible. Parks use single rider lines to fill in the spaces when there's an extra, empty seat on a fast-moving ride, to ensure that every seat is filled before the ride starts. With relatively few people waiting in the single rider queue, you can save many minutes — and on some rides, more than an hour — by going with the single rider option.
You don't have to be visiting a park by yourself to use a single rider line. If you don't mind riding apart from the rest of your family, just have your whole group go through. (This makes single rider a solid option for families with teenagers, who'd just as soon not ride next to Mom and Dad.) The ride attendants will break up your group and assign you to seats separately at the loading point. But you'll likely all get on and get through within a few moments of each other.
Look for the single-rider lane at the attraction entrance, and if you do not see it, ask a ride attendant at the entrance for help. They will direct you. The following rides often offer single-rider lines:
Walt Disney World