Recent Advances Yield a Smarter, Safer Seat Belt

A seat belt is an automotive safety device designed to secure the occupants of an automobile and prevent any harmful movement that could result during a collision or a sudden stop. A seat belt functions to:

• Reduce the likelihood of death or serious injury in a motor vehicle accident by reducing the force of secondary impacts with interior strike hazards.
• Keep occupants positioned correctly for maximum effectiveness of frontal and side-impact airbags.
• Improve crash survivability by keeping occupants from being ejected from the vehicle during a crash or in an accident involving a vehicle rollover.

Origins of the Automotive Seat Belt

Seat belts were introduced in the World War I era in early aviation. They were used to secure airplane pilots during takeoff and landing. American automotive manufacturers Nash (1949) and Ford (1955) began to offer seat belts as factory options. Swedish carmaker Saab first introduced seat belts as standard equipment in 1958. The Saab GT 750 was unveiled at the New York Motor Show in 1958 with safety belts fitted as standard. Shortly thereafter, basic lap belts became standard equipment in US automobiles and have since been vastly improved and supplemented by computerized airbag systems.

The modern-day seat belt traces its roots back to Swedish inventor Nils Bohlin in 1959. In addition to designing an effective three-point belt, Bohlin demonstrated its effectiveness in a study of 28,000 traffic accidents in Sweden. Unrestrained occupants sustained fatal injuries at all speeds, yet none of the belted occupants were fatally injured at accident speeds below 60 mph. No belted occupants were fatally injured in any case where the passenger compartment remained intact – a basis for today’s passenger compartment core-cell and uni-body designs.

As airbags were introduced in the 1990s, occupants faced less risk of striking hard surfaces in the car during an accident. However, common injuries in high-impact collisions have been associated with the occupant’s body pressing into the seat belt itself. This is a particular problem for rear seat passengers who don’t have frontal impact airbags. Broken ribs, lacerated organs, and internal bleeding can result from this type of impact. However, the engineers at Mercedes have come up with a potential solution for this issue.

Daimler (Benz) Creates and Airbag for Seat Belts

The Beltbag, created by Daimler (Mercedes Benz) engineers, will enter production in a luxury-class model from Mercedes-Benz. The new seat belt design features an inflatable seat-belt strap that can reduce the risk of injury to rear seat passengers involved in a frontal collision by lessening the strain placed on the ribcage. Here’s how the new seat beat technology works:

• Should the crash sensors detect a severe frontal impact, the airbag control unit will trigger inflation of the Beltbag.
• A gas generator quickly inflates the multi-layered belt strap with Velcro seams to nearly three times its normal width.
• As a result, a larger surface area can better distribute the forces acting on the occupant, effectively reducing the risk of injury.

The Beltbag can be used in exactly the same way as a conventional seat belt. However, the design differs from that of the standard belt and received top marks in practical trials for being extremely comfortable to wear and for its extra-soft belt strap edge.

Currently, engineers do not plan to introduce the Beltbag for the front seat, as airbags are already included in the front on all models as a supplementary restraint system. The engineers at Daimler will continue working with virtual computer-generated human models that make it possible to obtain detailed findings on the biomechanical strain during a collision and to develop further seat belt improvements in future vehicles.