Over-the-shoulder harness
Over-the-shoulder restraints (often abbreviated to OTSRs) are "U"-shaped restraints which swing down from behind the rider's head to secure the torso. Some also have a belt, which secures the bottom of the restraint to the seat, passing between the rider's legs.
Many roller coasters with inversions have over-the-shoulder restraints. Over-the-shoulder restraints keep riders seated upright and secure, but can cause discomfort if they are hard or unpadded, or if the rider's ears and head hit the restraint. This problem is often aggravated by a rough ride. As a result, many prefer lap bars to over-the-shoulder harnesses.
History
They are thought to have been introduced by Arrow Dynamics in 1975 on Corkscrew at Knott's Berry Farm, which is the first modern roller coaster with inversions.
Since 2011, Bolliger & Mabillard have used vest harnesses instead of over-the-shoulder restraints on some of their roller coasters. Vest harnesses are thinner and more flexible than over-the-shoulder restraints, and reduce headbanging, but they can eliminate some airtime, as they may tighten throughout the ride.
Mechanism
Over-the-shoulder restraints on Arrow roller coasters used a hydraulic cylinder and various valves to secure riders. They were controlled by a foot pedal at the side of each car which is operated by the ride attendant. When the pedal is in the lock position, a one-way valve allows the restraint to be tightened but not opened, while the restraint can move freely when unlocked.[1]