Identification of the Best Possible Configuration of the Shoulder Strap of a Three-Point Restraint for Motor Coach Occupant Rollover Protection

The motor coach is an essential element of the mass transportation system in the United States and all around the globe. Rollover accidents associated with any motor coach without an adequate occupant protection system may result in serious or fatal occupant injuries. The seat belt is an essential safety device in protecting an occupant in a rollover accident. It has been observed that just a quarter roll of a bus results in fatal injuries to an unbelted occupant. This severe nature of occupant injury in a less severe bus roll is attributable to the large flying distance within the unpadded interior and the impact with other fellow occupants. In this situation the presence of a seat belt is mandatory to protect the occupants from serious injuries by preventing their ejection from their seats. The three-point restraint is the best possible solution for the motor coach seat belt requirement. The understanding of shoulder strap placement with respect to the occupant is important information. This information facilitates the best possible seat belt configuration for all occupants which will minimize the slippage of the shoulder strap during a rollover accident. The slipping of the shoulder strap is a function of rollover type, rollover direction, roll rate and the occupant location in a vehicle with respect to roll direction. A Finite Element bus model is used to conduct a trip rollover simulation at two different trip velocities. The motion file, as obtained from this simulation, is used to prescribe motion to a MADYMO facet bus model. The standard Hybrid III 50th percentile ATD (Anthropomorphic Test Device) is used to model all the belted occupants. The FE belt model is used to facilitate the simulation of slippage on the shoulder. This study demonstrates the best possible configuration of the three-point restraints for motor coach occupants in a rollover accident using the computational technique. Knowledge of this kind will help the industry to identify and implement seat belts with the best configuration for occupant rollover protection.Copyright © 2011 by ASME