The 3-point safety belt has saved more than a million lives so far - it could be saving over a hundred thousand lives a year.
Wayne Gerdes – CleanMPG
– Jan. 8, 2009
Nils Bohlin, inventor of the single most important life saving technology in automobile history, the 3-Point safety belt.
Few people have saved as many lives as Nils Bohlin - the Volvo engineer who in 1959 invented the V-type three-point safety belt. To this very day, the safety belt still provides the most effective protection in the event of an accident.
It is impossible to put an exact figure on the number of lives the The Bohlin's three-point belt has saved since the 1960s but estimates put the figure at just over a million lives. Many times that number has avoided serious injuries thanks to the safety belt.
Within the US in 2004 (last reliable safety statistics), safety belt use is estimated to have saved 15,200 lives annually and resulted in society saving 50 billion dollars in costs.
The EU has similar statistics. In 2005 alone, an estimated 11,700 drivers survived road accidents specifically because they were wearing safety belts.
This makes the three-point safety belt the single most important safety device in the automobiles 120-year history.
As confirmation of the 3-Point belts effectiveness, Bohlin's invention has been identified by German patent registrars as one of the eight patents to have the greatest significance for humanity during the hundred years from 1885 to 1985. Bohlin shares this honor with patent-holders such as Benz, Edison and Diesel.
Nils Bohlin was born in 1920 in Härnösand, Sweden. He started his career in 1942 as an aircraft engineer. In 1955 he became responsible for the development of pilot ejection seats. Paradoxically, Bohlin was actually also interested in the exact opposite phenomenon - keeping the body as safe as possible during extreme retardation.
He soon got the opportunity to develop his ideas. In 1958 Nils Bohlin was recruited to Volvo as a safety engineer by the then-president of the company, Gunnar Engellau.
Simply put, the Two-point belt was not nearly safe enough. Volvo had already been equipping its cars with standard-two-point front safety belts back in 1957. Volvo president Engellau had a relative that died in a road accident owing among other things to shortcomings in the two-point belt. He therefore gave Bohlin the brief to develop a better alternative.
Bohlin realized that both the upper and lower body had to be properly secured in place, with one belt across the chest and another across the hips. His biggest challenge was to create a solution that was both simple to use and effective since the belt had to be able to be put on using just one hand.
In 1958 his work resulted in a patent application for Nils Bohlin's three-point belt. What Bohlin integrated into his design, and which he regarded as most important for a car safety belt, were four golden rules: the belt consisted of both a hip or lap belt and also a diagonal belt across the upper body, which was positioned correctly from the physiological viewpoint. That is to say across the pelvis and the ribcage, and attached at a low anchorage point beside the seat. The belt geometry formed a "V" with the peak pointing down towards the floor. In addition, the belt stayed in position and did not move when it was under load.
Bohlin's belt was in fact an effective demonstration of geometrical perfection rather than a cutting-edge innovation. The solution and the benefits of the three-point design soon spread throughout the world since Volvo immediately made Bohlin's patent available to all car makers.
Rear seat occupants needed protection too
Volvo soon realized the importance of ensuring that all the car's occupants were held securely in their seats, and work on equipping the rear seat with belts. People held the peculiar belief that sitting in the rear seat provided protection in a collision - after all, it was in the front that the occupants were in danger. The fact that the occupants of the rear seat are hurled forward and thus risk seriously injuring both themselves and the occupants of the front seats was suppressed. Today the wearing of seat belts in the rear is required by law and is quite simply a matter of course in many countries.
Practicality and statistics
If you are wearing a safety belt, your chances of surviving a collision improve by 50 percent. The three-point belt is and will remain the car's most vital safety detail. However, even more lives could be saved if belt usage increased. The largest problem in many car-intensive countries is that far too many people still choose not to use the safety belt. The belt represents by far the biggest lifesaving potential in modern traffic," adds Hans Nyth, head of the Volvo Cars Safety Center.
"What makes the three-point belt unique is that it improves safety for all types of occupants in the both the front and rear in all types of accidents. One often talks about the protective effect in head-on collisions, but the belt also helps prevent the car's occupants from being thrown out of the car in a rollover. 75 percent of people thrown out of cars in accidents die in the process."
Ways of increasing safety belt usage
Legislation requiring all cars to be equipped with safety belts began to be introduced way back in the 1960s. However, it was not until 1971 that the first laws requiring belt usage were enacted. That was in the state of Victoria in Australia, and traffic fatalities dropped by 18 percent that very first year.
Nonetheless, despite the excellent results it took another few years before the majority of European countries followed suit, with the USA only joining in during the past few years. There is still no legislation requiring rear safety belt use in many parts of the world, something that has a negative impact on both use of the belt and passenger protection in the rear.
Seat Belt Myths
- It could be dangerous to wear a belt if you get stuck upside-down in a car.
- It crushes your clothes.
- It is uncomfortable.
- The steering wheel or airbag will provide sufficient protection and so on.
The basic rule is that it is always better - for everyone and at all speeds - to wear a safety belt than to not do so (despite the little crease you might get in your shirt or blouse).
The safety belt is vital in collisions at low speeds in city traffic where most road accidents occur. The forces involved at low speeds are way higher than you might believe. Colliding at 30 mph corresponds to falling from the third floor of a building. A person who is forewarned can brace himself for an impact of up to about 4 mph.
Modern Day Safety Belts
Many people believe the three-point safety belt has not changed over the past fifty years. They are right. And wrong. The belt's ingeniously simple basic design is the same. The difference today is that the belt is part of a high-tech safety system under constant development.
The three-point belt has played a central role for occupant protection in all cars since its introduction in 1959. The inertia-reel mechanism, which made the belt more comfortable and flexible, became standard in 1969.
Controlling collisions and forces
One example is the belt pre-tensioner, which when it receives a signal from the crash sensor tensions the belt against the body of the seat occupant if a collision occurs. This reduces the gap between the belt and the body caused for instance by thick clothes such as a winter coat.
Seat occupants also benefit greatly from the force limiters that are integrated into the belts. Thanks to a sensor that monitors how quickly the belt is being reeled out, the force limiters can for instance detect the dynamic mass - the seat occupant's moving body - as it is thrown forward.
This in turn means that it is possible to tailor the force with which the seat occupant's body is restrained and to optimize the absorption of the resulting dynamic mass. If the body is restrained by the belt with excessive force, the body may suffer injury. If on the other hand the force limiter is set too low, the body will be thrown forward too quickly against the airbag or instrument panel.
Sensors determine how the systems interact
The size of the seat occupant and the type of collision are the main parameters that determine when and how the belt pre-tensioners, airbags and force limiters will be deployed. In order to make the right decision in each case, the car's on-board computer uses data obtained from thousands of pre-programmed collision scenarios and real-life accidents.
Scenarios spanning the entire range from high-impact head-on collisions to under run crashes into trucks and difficult to interpret side impacts have been used in the system's development. The type of accident determines how quickly and at what level the various systems are activated.
The information comes from sensors located all over the car. A main processor in the middle of the car collates the data and accordingly decides how the systems, including the safety belt, should interact.
The motorized belt is an exciting new technology that tightens the belt and places the driver in the right position in potentially hazardous situations. For instance, the system could register if the car is being driven with more steering wheel movement. In such a situation, there may be a benefit from having the support of the belt. The belt may also receive a signal from the car's collision warning system that an obstacle is approaching. Or that the car has noted that the driver is beginning to be drowsy or inattentive.
If so, the belt can provide a warning and alert the driver to the situation by pulling tight and positioning him or her in the seat. One benefit of this system is that it can be activated an unlimited number of times without being used up, unlike for instance pyrotechnical belt pre-tensioners.
The four-point safety belt has also been discussed as a possible alternative and several solutions have been presented over the years. Today however, there is no good technical solution that offers a suitable balance across the entire requirement specification.
The four-point belt has obvious advantages. For instance, it restrains the occupant more effectively if the car rolls over (one reason why rally cars are fitted with four-point safety harnesses or belts with even more attachment points). It also reduces the small risk of the seat occupant sliding out from under the three-point belt.
However, the four-point belt also has disadvantages. It should preferably be designed as a cross, forming an X pattern across the body. It is across the ribcage that the human body is strongest and has the best chance of absorbing incoming collision force. The challenge therefore is how best to effectively attach the upper point of the belt to the car where there is no natural attachment point in the bodywork.
Historical and base documents courtesy of the Volvo Motor Corporation.