SAFETY STUDY
Adopted: March 1, 1988
PERFORMANCE OF LAP/SHOULDER BELTS
IN 167 MOTOR VEHICLE CRASHES 
NTSB Number: SS-88/02
NTIS Number: PB88-917002
SYNOPSIS
Lap/shoulder belts have been standard equipment in the front seats of cars sold in the United States for more than 20 years and have been recognized as providing superior crash protection, compared to other seatbelt types, since as early as the 1950s.Unfortunately, until the recent passage of State mandatory use laws, few people used their lap/shoulder belts. In 1982, only 10 percent of the drivers observed in a survey of 19 U.S. cities were buckled up, and in the first half of 1987, that figure had increased to 42 percent. While this increase is significant, still more than half of the drivers in this country are not making use of this lifesaving device.

In other words, although lap/shoulder belts have been around for years, they haven't, until recently, been "around" enough U.S. motorists to decrease substantially the number of highway casualties. Now with the increase in use associated with mandatory use laws, some experts estimate that as of the end of 1986 as many as 1,300 lives have been saved. Hopefully, the passage of more mandatory use laws, combined with effective enforcement and education campaigns, will increase use to a much higher level and save even more lives.

Lifestyle factors, that is, aspects of health that are under the individual's control (in contrast to heredity and environment), such as choosing to wear seatbelts, play a large role in the risk of death. Buckling up is a matter of intelligent risk management: by wearing a lap/shoulder belt, an occupant substantially reduces his or her chance of premature death. Motor vehicle accidents are the leading cause of death for Americans ages 1 to 35, and third leading cause of premature death for Americans of all ages.

That lap/shoulder belts are of value to reduce death and injury is undisputed, but just how valuable they are is a matter of debate. Manual seatbelt systems in motor vehicles (unlike passive restraints such as air bags and automatic seatbelts) have never been required to be tested for crash protection performance; complete and accurate data on their performance in real-world crashes have been extremely limited; and basic changes in vehicle design over the years could have affected belt performance. In addition, seatbelt performance is a timely topic since States are enacting mandatory seatbelt-use laws requiring front seat occupants (and rear seat occupants, in some cases) to wear their seatbelts.

With many of these factors in mind, the Safety Board conducted a study on the performance of seatbelts in real-world crashes during 1984-86. This case study emphasized the collection of accurate, complete data on a number of specific points relevant to the question of belt performance. Specifically, the Board wished to explore how well the belts protected occupants from injury during the crashes and what injuries, if any occurred despite (or perhaps because of) the belt.

This report is the second and final publication to come out of the Board's investigations; it presents the bulk of the cases investigated as part of the seatbelt performance study. It presents data on the performance of lap/shoulder belts in 167 accidents involving 180 case vehicles and 341 case vehicle occupants. Most of the occupants were seated in the front seat and most were restrained, so this report primarily addresses the crash performance of lap/shoulder belts for the driver and right front passenger. The accident selection criteria resulted in very few unrestrained case vehicle occupants, so few comparisons between restrained and unrestrained case occupants could be drawn.

RECOMMENDATIONS

As a result of this Safety Study, the National Transportation Safety Board made the following recommendations to the National Highway Traffic Safety Administration:

Revise publications on child passenger protection to eliminate the suggestion that parents, concerned about the relationship of the shoulder harness to the child's body, misroute the child's lap/shoulder belt, or that parents allow children to share a seatbelt. (Class II, Priority Action)(H-88-7)

Amend Federal Motor Vehicle Safety Standard 208 to require that windowshade-equipped lap/shoulder belts either be tested with the maximum amount of slack that can be introduced or that they be equipped with a pretensioner as part of the belt system to ensure, during a crash, the elimination of any slack Introduced Into the system prior to the accident. (Class II, Priority Action) (H-89-8)

Limit the angle of inclination allowable in reclining seats In passenger vehicles to no greater than the maximum angle that can safely be used with a lap/shoulder belt. (Class II, Priority Action) (H-88-9)

Evaluate the possibility of requiring an adjustable upper anchorage point for the shoulder portion of lap/shoulder belts In newly manufactured motor vehicles. (Class II, Priority Action) (H-88-10)