I just returned from a couple of days at Disneyland. Midway through a ride on Space Mountain, it stopped and the lights came up. (For those unfamiliar with the ride, it's an indoor roller coaster that's entirely dark except for simulated star light.)
It took about 5-10 minutes to get going again, requiring a couple of ride technicians to literally push-start us and then gravity did the rest. It was really interesting to see the track layout since it's so difficult, if not impossible, to tell what's going on with the lights off. I counted five other coasters stuck on the track at the same time as us and was astounded at the number of stairs and ramps all over the place.