In frontal crashes, rear-seat occupants are protected by belt systems. Force transfer to the chest can be limited with retractor load limiters to reduce the risk of thoracic injuries, but this comes at the expense of larger forward excursion of the occupant, increasing the risk of injuries from interior contact. The objective of this study was to investigate whether an additional load limiter at the lower diagonal belt portion (B4LL) would influence the belt force distribution and, consequently, reduce chest loading without substantially affecting the forward excursion. A frontal crash at 56 kph was simulated with the mid-sized male version of the SAFER Human Body Model and THOR on a generic rear seat. The reference belt system consisted of a retractor model, including a pretensioner and a load limiter (at 5 kN), and a locking tongue. The added B4LL was modeled using a spring with a constant force level that varied from 3 kN to 5 kN. The B4LL effectively reduced forces in the lower area of the diagonal belt – in contrast to the retractor load limiter, which did not substantially affect these forces. The B4LL reduced the chest injury measures in both the occupant models without substantially increasing the forward displacement.