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Three-Point Car Seat Belt: Yesterday's Innovation Continues to be a Perfect Safety Solution

The three-point car seat belt was introduced in 1959 by Volvo engineer Nils Bohlin and was first used in the PV544 and Amazon 120s sold in Nordic countries in Northern Europe. Since then, it has saved millions of life as a passenger buckled up with a seat belt has 50% better chances of surviving during a car accident.

The three-point safety belt is a seatbelt with three mountings, two at either side of the occupant's lap and one behind the shoulder. The mounting behind the shoulder is either attached to the seat or a car’s body. Today, the yesterday’s innovation has completed 50 years of its life in the industry and has played a significant role in protecting car passenger. It effectively catches and restrains passengers in the seat. Though these days an ample of safety devices has been introduced, seat belt still holds its dominance in the car industry.

It is believed that in the past 50 years the three-pointed seat belts have seen many modifications with the introduction of high-end technologies. However, the basic design of the belt is the same but there are many features added to make this age-old innovation a significant part of the modern high-tech car technology.

Principle of Working

Three pointed seat belts work on the principle of inertia and keep the driver from flying through the windshield and the dashboard in case of an accident or an abrupt stop. A seat belt has the ability to extend and retract so when the driver desires to lean down he or she can do so even when the seat belt is buckled. Whereas, in case of an accident the belt secures the driver tightly in his or her position.

Take for example, if a car is running at a speed of 100 km/h then in case of an emergency stop or an accident the driver will be thrown out of the windshield with the same speed at which the car is running if the driver is not wearing a seat belt. If the driver is thrown out at a speed of 100 km/h then it’s obvious that he or she will be badly injured or even killed.

Chronology of Three-Pointed Seat Belt

Below is the chronology of seat belts that unveils its journey from birth to present day modified seal belts:

The three-pointed safety belt was introduced by a Volvo engineer in 1959.
In 1969 the inertia-reel safety belts were introduced that were equipped with locking mechanism. These were used to tighten only when the belt was fast pulled by the driver and do not tighten when pulled slowly.
In the year 1971, safety belt reminders were installed to alert the driver if he or she forgets to tighten the seat belt before starting a journey.
In 1972 three-pointed safety belts also became standard in the rear seats.
In 1986 three-pointed safety belts became standard in the rear middle seats also in case of an SUV or MPV.
In the year 1987 mechanical pre-tensioners were added to the belts.
In 1991 automatic height adjustment feature was introduced in the front seat safety belt.
In 1992 pyrotechnical belt pre-tensioners triggered by crash sensors were fitted in the front seat belts.
In the year 1996 force limiters were introduced in front seat belts.
In 2003 adaptive force limiters were introduced in front seat belts.
Adaptive force limiters for low-speed impacts were introduced in front seat belt in 2008.

Innovations in Three-Pointed Seat Belt

The two most important innovations in three-pointed seat belts are as follows:

Pre-Tensioners: Pre-tensioners work in conjunction with the conventional locking mechanism of the three-pointed seat belt. These are triggered by crash sensors that are used to determine the need to deploy the airbag in case of an accident. When the pre-tensioners receive any such signal from the sensors they tension the belt against the driver’s body to reduce the gap between the belt and the body. The main function of pre-tensioners is to tighten any slack in the three-pointed seat belt. This makes it easier for the belt to restrain the body at the earliest and reduce the chances of injury.
Force Limiters: Most of the modern cars are fitted with force limiters or load limiters integrated into the belts to minimize the belt-inflicted injuries. In some cases when there is a severe accident occurred at extremely high speed then the seat belt can also cause an injury. This is because when the initial speed of the passenger increases, the belt takes a greater force to restrain the driver and if the body is restrained by the belt with excessive force the driver’s body may get injured. In such cases, force limiters help to release excess of belt webbing so that less force is applied to the belt and the driver can be protected from the belt-inflicted injury.

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