Federal Motor Carrier Safety Requirement (FMCSR) 393.76(h) states that “a motor vehicle manufactured on or after July 1, 1971 and equipped with a sleeper berth must be equipped with a means of preventing ejection of the occupant of the sleeper berth during deceleration of the vehicle.” [1] Furthermore, this standard requires that “the restraint system must be designed, installed and maintained to withstand a minimum total force of 6,000 pounds applied toward the front of the vehicle and parallel to the longitudinal axis of the vehicle.” [1] Today, sleeper berths are equipped with sleeper restraint systems that function to contain the sleeper occupant inside the sleeper berth during reasonably foreseeable crashes. To assess the effectiveness of sleeper restraint systems, computer simulation models of the sleeper cab environment and these restraint systems were developed, with a simulated supine occupant in the sleeper.
The model was evaluated using two different rollover crash scenarios. The first rollover scenario used measurements from a previously reported tractor-trailer, driver side leading, and quarter-turn rollover crash test. [2] The second rollover scenario was based on reconstruction of a very severe crash that occurred on a mountain road, where a tractor-trailer rolled, passenger side leading. When the tractor was in approximately the 90 degree roll position, the trailer landed and pivoted on a guardrail. As the trailer was crushing the guardrail, the top passenger side of the tractor's cab struck the guardrail. The inertia of the truck, combined with the guardrail impacts, continued the roll and the truck became airborne as it entered a 25 ft. deep ravine. The truck impacted the bottom of the ravine and came to rest with the tractor completing approximately 360 degrees of roll and the trailer completing approximately 315 degrees of roll. This simulation effort demonstrated that tenting style and blanket style sleeper cab restraints contain a supine sleeper occupant in the sleeper berth, preventing ejection, in two rollover crash scenarios when the sleeper compartment itself remains intact.