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Seat belt

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A seat belt is a primary restraint system (PRS) used in vehicles.

Female driver buckling seatbelt
Female driver buckling seatbelt

Its main goal is to secure drivers and passengers against harmful movement. This movement happens during a collision or a sudden stop. When a vehicle is in motion, the people inside travel at the same speed as the car. If the car hits an object and stops instantly, the people inside continue moving at the previous speed.

Female driver buckling seatbelt
Female driver buckling seatbelt

The seat belt applies an opposing force to prevent occupants from hitting the car's interior. It can also prevent people from being ejected during a crash or a rollover. Additionally, it keeps passengers positioned correctly so that airbags work with maximum effectiveness.

Seat belt BX
Seat belt BX

The material used for the belt is called webbing.

Female driver buckling seatbelt
Female driver buckling seatbelt

This webbing must have high tensile strength to resist tearing under heavy loads. Early seat belts often used nylon, but modern belts use 100% polyester. Polyester is preferred because it has better UV resistance and lower extensibility, meaning it stretches less. Nylon was prone to stretching and could lose strength due to tiny abrasions.

Seatbelt testing apparatus
Seatbelt testing apparatus

Most webbing is 46 or 48 mm wide. It uses a 2/2 herringbone twill weaving pattern to maximize thread density. This pattern includes about 300 warp threads for every 46mm of width. This high density ensures the belt remains a reliable safety measure during high-speed impacts.

There are several different types of seat belt configurations. A two-point seat belt, often called a lap belt, is a strap that goes over the waist.

These are the standard in commercial airliners to protect against up and down movement during turbulence. In cars, lap belts were common before modern laws required more protection. A three-point seat belt includes both a lap belt and a shoulder harness.

Passenger Experience Week 2018, Hamburg (1X7A3813)
Passenger Experience Week 2018, Hamburg (1X7A3813)

The shoulder harness, or sash, is a strap that goes diagonally over the outboard shoulder. This design is much safer for land vehicles because it restrains the upper body as well. Using only a lap belt can lead to "seat belt syndrome," which involves the separation of lumbar vertebrae.

Seat belt BX
Seat belt BX

The history of the seat belt involves many different inventors and eras. English engineer George Cayley invented early versions for his glider in the mid-19th century. By 1928, all aircraft were required to use them. In 1949, Nash became the first American car manufacturer to offer them as an option. However, customers did not want them, and only 1,000 were used after the first year. In 1955, Roger W. Griswold and Hugh DeHaven patented the first modern three-point restraint.

Seat belt BX
Seat belt BX

Later, Nils Bohlin developed the modern three-point belt for Volvo in 1959. Bohlin proved its effectiveness by studying 28,000 accidents in Sweden. His research showed that belted occupants were not fatally injured in accidents below 60 mph if the passenger compartment stayed intact.

Safety regulations have changed significantly due to these discoveries. In 1966, the United States passed the National Traffic and Motor Vehicle Safety Act. The first compulsory seat belt law began in 1970 in Victoria, Australia. This happened after testing Hemco seat belts in police vehicles reduced officer injuries. In the U.S., mandatory laws began appearing in the 1980s. Some people even resisted these laws by cutting seat belts out of their cars. Today, all new cars sold in the U.S. must have a lap and shoulder belt in the center rear seat.

Lives Saved by Safety Belts and Air Bags, NHTSA, DOT
Lives Saved by Safety Belts and Air Bags, NHTSA, DOT

The effectiveness of these devices is supported by significant data. An analysis in 1984 showed that front-seat passengers saw fatality reductions between 20% and 55%. Major injury reductions ranged from 25% to 60%. The Centers for Disease Control and Prevention states that seat belts reduce serious crash-related injuries and deaths by about half.

Lives Saved by Safety Belts and Air Bags, NHTSA, DOT
Lives Saved by Safety Belts and Air Bags, NHTSA, DOT

In the case of vehicle rollovers in U.S. cars and SUVs between 1994 and 2004, wearing a belt significantly reduced the risk of death. These numbers highlight why the seat belt is considered a vital component of vehicle safety.

Seat belts connect to many different fields of study and safety systems. Accident investigators use the webbing to determine if someone was wearing a belt. They look for traces of clothing or melted nylon fibers caused by friction heat. The development of the seat belt is also linked to the development of the airbag. Because the belt holds a person in place, the airbag can deploy against the body at the correct moment. This combination of the belt and the airbag creates a comprehensive system for protecting human life during high-speed travel.

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🖼️ Images & Media (16)
File:Female driver buckling seatbelt.jpg
Female driver buckling seatbelt.jpg
File:Lives Saved by Safety Belts and Air Bags, NHTSA, DOT.svg
Lives Saved by Safety Belts and Air Bags,...
File:Aircraft Safety Belt.png
Aircraft Safety Belt.png
File:Airplane seat belt 2.jpg
Airplane seat belt 2.jpg
File:Passenger Experience Week 2018, Hamburg (1X7A3812).jpg
Passenger Experience Week 2018, Hamburg...
File:Passenger Experience Week 2018, Hamburg (1X7A3813).jpg
Passenger Experience Week 2018, Hamburg...
File:Seat belt BX.jpg
Seat belt BX.jpg
File:Seatbelt.jpg
Seatbelt.jpg
File:Bucket seat with Schroth six-point harness in a 2010 Porsche 997 GT3 RS 3.8.jpg
Bucket seat with Schroth six-point...
File:Intertial-reel.jpg
Intertial-reel.jpg
File:Gurtstraffer.gif
Gurtstraffer.gif
File:1990 Honda Civic DX interior.JPG
1990 Honda Civic DX interior.JPG

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