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Nils Bohlin –
the man behind the three point seat belt

Three point seat belt

English translation of the story "Nils Bohlin - mannen bakom trepunktsbältet" on pages 22-24 in PV-Entusisten # 2 1999.



By Bengt Andersson

In August of 1959, Volvo was the first car manufacturer to introduce the three-point seat belt in their cars. More than 40 years have passed since Nils Bohlin made the invention. This was in a period when traffic safety issues were not on the agenda as much as they are today. But motoring in the 50's was not only a positive thing for the little man. It also took a lot of lives on our roads.
In the US, generally claimed to be the home of the automobile, the approach towards traffic safety was a bit strange. Ford refused to install seat belts in their cars in the middle of the fifties. The ironic reason for this was a notion that the consumers might think of the product as unsafe. This "Head-in-the-Sand" approach by many automobile corporations remained prevalent until a young lawyer by the name of Ralph Nader wrote a book named "Unsafe at any speed". The book made the whole of General Motors shake. Nader offered a scathing report detailing flaws in the design of the Chevrolet Corvair.
The Corvair, like the Volkswagen Beetle, featured a split rear axle. The driving shafts had cross joints in the inner end at the gearbox but not at the outer ends by the wheels. This meant that going through a curve at too high of a speed allowed the wheels to bend under the car, inducing a roll-over. Nader made research on a number of accidents involving the Corvair. The result was that GM altered the construction of the car.

Traffic safety with Volvo


Here in Sweden we were more awake when it came to interior safety in cars and Volvo was a pioneer. Already in the beginning of the fifties the technicians at Volvo performed crash tests. Unfortunately the test methods were not optimal so it was hard to evaluate the potential injuries to the persons inside the car. They built wooden test slopes with a barrier at the end of the slope. Then they sent the car downhill and the researchers tried to find out the results from the crash-test dummies.
One result was that as from PV 444 L, the cars were equipped with attachments for two point seat belts. As from PV544 A, two point seat belts were included as standard equipment on the Sports model. In August 1959, a PV 544 A with chassis number 240202 was the first car in the world to be equipped with a new type of seat belt – the three point seat belt. Now not only the Sports model had seatbelts – all cars had them as standard equipment.
The man behind the invention was Nils Bohlin, a young engineer who had been working with flight safety matters at SAAB. What was it that started the development of the three-point seat belt so quickly after the introduction of the two point belt? The two-point belt was attached diagonally across the body with the buckle right on the body. The belt was fitted to the propeller tunnel and the door pillar
When the belt had been on the market for some time, reports began to surface about people being severely injured despite wearing the seat belt. One reason for this was that the body could escape from the belt and exit car on impact. One of the Volvo's sales managers had such an experience and Gunnar Engellau, Volvo's President, did not like that. He contacted Nils Bohlin and asked what could be done to correct this major flaw. The idea occured to restrain the body at the hips. This was the start of the development of the three point seat belt. The work progressed rapidly and by August of 1959 it was introduced as standard equipment in the Volvo cars.

Problems in the USA


But all was not well. A debate ensuued as to whether it was dangerous to wear a seat belt. When Volvo started selling cars with the three point belts in the USA, the car industry claimed that according to their tests, the belt could be dangerous to wear. Bohlin had to go to USA to find out what had happened. What he found was that the Americans had been using a different kind of crash test dummy than he had. Bohlin went home, gathered crash test dummies and cars and went to Denmark. On a sand dune he built a testing slope. At the end of the slope he built a barrier of 120 tons. Towards that he aimed the cars for further crash tests. He was able to prove that the Volvo dummies had the same characteristics as a human body at impact. The threat was eliminated and Volvo could sell the three point belt in the US.
But the Americans did not give in. Reports from the Traffic safety authorities showed that the three point belt was torn apart in their tests. At Volvo in Sweden, similar tests were made and in all cases the belts survived.
Nils Bohlin once again had to go to the US to find out what was wrong. He found a fitting with a sharp edge. He had it filed down and then a new test was done. This time the belt survived and Nils Bohlin could return to Sweden.
In 1967 Volvo released research by Nils Bohlin involving 28000 accidents. It showed that the three point belt offered very good protection. This research turned out to become the basis for the legislation of seat belts in many countries.
Seat belt ad

Statistics


What has happened to the traffic safety in Sweden during the recent 40 years? The oldest and newest statistics with the National Swedish Traffic safety board is from 1960 and 1997. In 1960 1036 persons were killed in road accidents, 2983 had severe injuries and 18553 had minor injuries. At this time there were some 1 million cars in Sweden.
In 1997 541 persons were killed. 3917 had severe injuries and 17363 had minor injuries. This means that some 22000 persons were involved in car accidents both in 1960 and in 1997. But in 1997 there were some four times as many cars rolling on the Swedish roads as in 1960. Quite clearly you can see that the traffic safety has improved. The motoring public owes a great deal of gratitude for the automotive safety improvements implemented by Nils Bohlin and his three point seat belt.

Original text by Bengt Andersson,
translation by Dan Janson (thanks to Mark Hershoren for assitance)


Page updated November 22 1999.
© PV-Entusiasten, 1999