Safety Design | The Seven Different Types of Seat Belts

Photo: Steve Hathaway (Getty Images).

Watching classic movies is a great way to remind ourselves how open-minded our parents and grandparents were on the topic of working on their own deaths. They smoked like Victorian chimneys, ate like auditioning Hutts and tossed Jarts around with reckless abandon.

Take the classic Steve McQueen 1968 detective flick Bullitt as a prime example. Midway through the organized crime thriller, McQueen’s heroic titular character is on the trail of two hitmen. As Bullitt’s 1968 Ford Mustang GT prepares for one of cinema’s all-time great car chases through the streets of San Francisco against the bad guys’ 1968 Charger R/T, the murderer at the wheel of the Dodge puts on his driving gloves — and puts on his seatbelt. Even during a high speed chase against a tough, big city cop, the lap belt was optional.

During this wiser and more health-conscious 21st century, drivers put on their safety devices without thinking about it as they hop into any car or truck. The seat belt is so ever-present, there are seven, possibly eight, separate categories for the life-saving invention.

The Lap BeltThe oldest and simplest seat belt design, its name tells you its placement and purpose. Strapping across the midpoint of a driver or passenger’s physiognomy, the lap version looks to keep the body in the seat. However, it provides no support for the shoulders, neck or head — leaving a bounce off a dashboard on a collision’s menu.

The Shoulder Belt: Sometimes called a sash belt, but who do you know who wears sashes or ever refers to them as such? The shoulder belt wraps around the shoulder. While you’re unlikely to spot on in any car or truck, they do show up on older roller coasters or thrill rides. In many cases, the shoulder belt’s inability to stabilize anything but one quadrant of the upper body makes it too easy for the wearer to slip free in a collision or break/dislocate the shoulder bearing the belt.

The Three-Point Belt: This is the seat belt you find in the majority of modern vehicles. It offers a lap belt and cross belt that stretches from the shoulder diagonally across the chest to the lap belt fastener. That’s a fancy way of explaining what we all snap into place when he get into more or less everything we ride in these days.

The Belt-in-Seat: Sometimes installed in back seats where children are most likely to sit, the Belt-in-Seat (BIS) is the standard three-point design with the shoulder belt already connected to the backrest. Such belts are less adjustable and therefore might secure kids better.

The Automatic Seat Belts: The international automotive industry flirted with these for a while, but the three-point belt (with the added and now ever-present airbag) was deemed more effective, practical and acceptable. The automatic design offered shoulder belts that were supposed to move into place when the lap belt was connected.

The Five-Point Harness: You’ll only find five-point harnesses in some supercars or racing machines in which they’ve been specially installed aftermarket. However, most of the child seats we strap into back seats to keep babies safe offer the same design. The wearer is snugly secured at both shoulders, at two points across the waste and between the legs with a third belt.

The Six-Point Harness: Also used in auto racing, a six-point harness takes the design of a five-point and adds another belt between the legs to further secure and more tightly stabilize the entire body in case of a high-speed collision. Put simply. as race cars went faster, seatbelts needed to upgrade.

Finally, there’s potentially an eighth category — or perhaps it’ll be considered a subcategory of the above. Ford’s Inflatable Safety Belt takes the two primary pieces of in-car safety technology — the seat belt and the airbag — and combines them.

Ford engineers felt that the cross-chest strap of the traditional three-point harness could catch children near the throat. So, that strap across the body takes on a belt-long airbag that expands on sudden impact, cushioning the child against the belt’s strain.