One of the most common types of
restraints on
roller coasters today, OTSRs are typically made of
plastic and fold down over the rider's shoulders, pinning them to the seat at their
lap. This allows for very little movement and almost no
airtime, yet OTSRs are generally fairly
comfortable and theoretically they minimize
headbanging, a common and unpopular aspect of many coasters. OTSRs are common on rides made by
Bolliger & Mabillard and
Intamin but have been used by many manufacturers of
inverted rides. A stand-up OTSR attaches directly to the
saddle while a sit-down OTSR attaches to the seat with a standard
seat belt.
Source: http://www.coasterforce.com/restraints.htm