In the present study, sled analysis was conducted under the condition of 20g (20 times of gravitational acceleration) and 48 km/h of initial velocity, suggested by WC-19 to investigate the injuries of traffic minorities of tie-down type fixing inside a vehicle during crash. Also, four new parameters, which were related to angles between belts and wheelchair and their levels were limited by WC-19, were proposed and orthogonal array was prepared with different levels of each parameter. In the meantime, four parameters were optimised by minimising head injury criteria and chest acceleration of passengers in each case of the orthogonal array.