This paper describes the method of incorporating a three point seat belt for the rear centre seat passenger in an Estate car. The necessary analyses were carried out to determine the load path through the belt, seat structure and the floor, highlighting the area to be redesigned. It was assumed that the 2/3 folding seat back would be supported in its upright position by the floor and the vehicle inner wall only. The support from the 1/3 seat back was ignored. The specifications are based on a very severe front crash and therefore represent the worst case.The design, which is in both steel and composite material versions, complies with forward and rearward accelerations (16000N belt load) concerning the passenger, as well as 100kg of luggage. It also complies with a severe forward deceleration (21500N) related to the centre seat passenger. In the case of the 16000N, the deformation was limited to 100mm, whilst for the 21500N the requirement was ‘no material separation’. Occupant simulation was also carried out to study the effect of the strengthened seat and seat assembly on the occupant safety.