The dynamic loads acting during a road accident on a child passenger of a bus depend not only on the vehicle construction but also on the properties of the personal protection system used. In motor coaches, the personal protection system basically consists of a seat with a seat belt. The positioning of the seat belt strap in relation to passenger’s body depends on the arrangement of the belt-to-seat anchorage points and passenger’s anthropometric characteristics. At this work, we explored the dynamic effects exerted on the body of a child occupying a bus seat during a road accident. For this issue to be tackled, a series of crash tests were prepared that constituted a physical model of a frontal impact of a bus against an obstacle. The tests were carried out with the use of seats where the position of a seat belt on a P10 test dummy (representing a child aged 9–12 years with a mass of 32 kg) could be adjusted. In this paper, results of the crash tests have been presented, which show the influence of changes in the positioning of the seat belt strap in relation to child passenger’s torso on the movements of, and on the values of the dynamic loads acting on, the child’s head and torso. Such changes have an impact on the longitudinal head and torso movements that take place in the limited space between bus seats. The analysis of the test results has shown the fact that the standard seat belt inadequately matches the anthropometric characteristics of children; the hazards that may arise from that have also been pointed out. Simultaneously, the analysis has offered a basis for improving the system of personal protection of bus passengers.