According to KTLA-TV, a ride car leaving the boarding station “rolled back,” slamming a second car car inside the station that was boarding other guests.
The crash happened during Knott’s “Halloween Haunt” event about 8:15 p.m. on Thursday. Authorities said the injuries were minor.
The Pony Express was built at Knott’s Berry Farm in 2008. It launches from zero to 38 miles per hour in 3 seconds and reaches a top speed of 40 miles per hour, relatively tame by today’s roller coaster standards.
Rollbacks, while not common, are a regular occurrence on roller coasters. They happen when a ride car is not launched fast enough to make it to the top of the first lift. This can be caused by a number of factors, including wind gusts, cold weather and ride cars that don’t have enough passengers and therefore they don’t have enough momentum.
Most coasters have a chain lift or other device to prevent rollbacks, as well as a braking system to stop a car if it does roll back.
There’s no word yet as to the cause of the Pony Express roller coaster rollback.
Another roller coaster at Knott’s Berry Farm, the hydraulically launched Xcelerator, is known for having rollbacks. On the Xcelerator, a car that rolls back is stopped by magnetic fins before it re-enters the boarding station.
Two other U.S. roller coasters based on the Xcelerator’s design – Kingda Ka at Six Flags Great Adventure and Top Thrill Dragster at Cedar Point – are also known to have more frequent rollbacks.
Here’s footage of a Kingda Ka rollback:
[Image credit: Flickr user Magic Madzik]