How the Three-Point Seat Belt Was Invented
Nils Bohlin, an engineer at Volvo, designed the three-point belt still used in cars today, and Volvo let other makers use it freely. Here is how it came about.
In this article
The seat belt in nearly every modern car, one strap crossing the chest and another across the lap, was designed by a Volvo engineer named Nils Bohlin in the late 1950s. Volvo chose to let other car makers use the design without paying for it. This article follows the story from the first belts of the early 1900s to the three-point belt and the rules that made wearing one normal.
Belts before Bohlin
According to the German Patent and Trade Mark Office (DPMA), a safety belt was presumably used in a car for the first time on 31 May 1902, during a record attempt by a car called the Baker Torpedo on Staten Island, New York. The car crashed and two spectators died, but the two people in the car survived, and the belts were credited. In 1903 a Frenchman, Gustave-Désiré Leveau, received what the DPMA calls the first safety belt patent, for a four-point belt.
For decades after that, belts came in several forms. The simplest was the two-point lap belt, a single strap across the hips. Racing cars used more complex belts with up to six attachment points. The DPMA says none of these had become established in ordinary car construction before Bohlin's invention.
A lap belt has a weakness that engineers of the time knew about: it holds the hips but lets the upper body fold forward in a sudden stop. Volvo's own history page says earlier designs such as the lap-only belt protected passengers but could be improved.
Who Nils Bohlin was
Nils Ivar Bohlin worked at the Swedish aircraft maker Saab, where, the DPMA notes, he had developed belts for pilots' ejection seats. He then joined Volvo as an engineer. That background mattered, because aircraft restraints are designed to hold a person's body in a crash or an ejection.
The design
Bohlin's belt joins three anchor points: one low on each side of the seat and one above the shoulder. A single continuous strap runs from the upper anchor across the chest, then across the lap to the buckle. Because the two parts form one strap, the belt holds both the upper body and the pelvis.
The patent text, quoted on Volvo's heritage page, says the belt "effectively, and in a physiologically favorable manner" prevents the strapped person's body from being thrown forward. The DPMA describes the design as holding the upper and lower body in a physiologically favourable way and as easy to fasten and release.
Giving the patent away
The most unusual part of the story is what Volvo did next. Volvo's heritage page says the company gave the design to the rest of the industry without payment or claims, so other manufacturers could use it freely. A safety feature that only one maker could fit would protect only that maker's customers; sharing it let the belt spread across the industry.
Volvo says its three-point belt is now found in most vehicles and that its use is written into law in many countries. The company also says the invention has been credited with saving at least one million lives worldwide. That figure is Volvo's own statement of a credited estimate, not a measured count, and other organisations publish different estimates.
From fitted to required
Having a belt in the car is one thing, and wearing it is another. The DPMA gives Germany as an example of how slowly this changed:
- 1974: all new cars had to be fitted with safety belts.
- 1976: wearing a belt became compulsory, but was poorly accepted at first.
- 1984: a fine of 40 Deutschmarks for not wearing a belt took effect on 1 August. According to the DPMA, wearing rates rose from about 60% to over 90%.
- 2004: three-point belts became mandatory on all seats, ending the tolerance of lap belts on rear seats.
- 2014: seat belt reminders became mandatory in all new vehicles in the European Union.
The DPMA also says that by 1961 more than three-quarters of new cars in Sweden had safety belts, which shows how quickly the idea was taken up in the country where the three-point design began.
What came after
The belt did not stop developing. The DPMA lists airbags, crumple zones, belt tensioners and belt force limiters as later additions that work together with the belt. A tensioner pulls the belt tight in the first instant of a crash, and a force limiter lets a little strap out afterwards so the belt does not press too hard on the chest. Recent patents the office mentions include an adjustable anchor position for the shoulder strap and improved pre-tensioners.
The basic shape, though, is still the one Bohlin drew: three anchor points and one strap. Few car parts from the 1950s remain in use with so little change to their core design.
This article is general historical information. For how to wear a belt correctly, follow the car maker's manual and local law.
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