UN-ECE Regulation 66 [1] provides rollover safety for coach passengers by ensuring an adequate residual space remains during a standard rollover test. At present the energy requirement of the coach superstructure depends directly upon the unladen mass of the vehicle, with the passenger mass assumed to be self-arresting.

However, all modern coaches possess either 2 or 3- point seatbelts and if used by the passengers, the extra mass coupled to the coach structure increases the amount of energy to be absorbed during the rollover test.

Within the EC and DfT(UK) funded ECBOS (Enhanced Coach and Bus Occupant Safety) project, bay section rollover testing and validated computer simulations were performed in order to quantify the influence of the passenger mass on the structural deformation during rollover.

This work found that the percentage mass of the occupant that is effectively coupled to the coach structure during rollover was 71% for lap-belts, 93% for 3-point belts and 18% for unrestrained. These results will now be used for possible modernisation and updating of the Regulation.