Coach passenger injury risk during rollover: influence of the seat and the restraint system

In the last years the European Community funded several projects, whose general aim was to improve the safety of road users. Among them, the “Enhanced Coach and Bus Occupant Safety” (ECBOS) Project was set up in order to study improvements in current regulations and propose new standards for the development of safer buses and coaches. For what concerns the rollover protection (ECE66 Regulation), one of the main suggestions, proposed by the partners of the ECBOS project [1], is to take into account the presence of the passengers on board both in the numerical and in the experimental homologation tests. An additional mass in the vehicle increases the energy assumed to be absorbed by the structure in order to pass the test. That could lead the bus manufacturers to increase the strength of the vehicle super-structure in order to obtain a deformation level below the limits stated in the ECE66 regulation. A numerical study was performed to evaluate how an increment of the super-structure strength, that ensures the vehicle to pass the homologation test with the passengers onboard (i.e. to avoid intrusions into the residual space defined by the regulation), affects the injury risk for the passengers themselves. To perform such a kind of study, it is essential to model the interactions of the passengers with the coach inside environment accurately. One of the most important components that greatly influence the movement of the passengers inside the vehicle is the seat. For that reason, a detailed hybrid model (Mulibody – FE) of a seat was developed based of a real coach seat, whose data were provided by a seat manufacturer. Two configurations were analysed, changing the restraint system (two-point and three point belt). The injury risk for passengers was evaluated calculating the most significant injury parameters and criteria (HIC, TTI, VI, etc.).