An investigation was conducted into the sources of slack caused by comfort and convenience devices, which can affect the safety performance of the basic three-point belt design. Limited field observations were made to correlate sources of slack identified from the literature and personal experience to the wearing configurations of shoulder straps on the typical American highway. From this background, a research program was carried out to investigate with sled tests in the laboratory the dynamic restraint performance of three-point belts with previously observed and documented amounts of slack. The tension relief (eliminator) "windowshade" device (TRD) was chosen as the item for laboratory scrutiny because it is the single most frequent cause of slack in American belts and because it produces a pattern of slack which mimics that from many other sources. The results of these sled tests define the expected envelope of performance of a typical TRD. From these results, design improvements to three-point belt comfort and convenience devices are suggested which will improve, in an immediate and cost effective manner, the safety performance and reliability of belts containing these devices. (A) For the covering abstract of the conference see IRRD 837684.
Abstract