The history of the three-point seat belt is often reduced to a simple narrative: in 1959, Volvo engineer Nils Bohlin invented the design, and the company freely shared the patent with other automakers to save as many lives as possible. There is truth in this story, but the wording about the invention requires clarification. The combined lap and shoulder belt was patented back in 1955, and Bohlin's merit was in developing a more effective design for a regular car.
The patent for the combined belt appeared in 1955
On June 14, 1955, US Patent No. 2,710,649 was issued for a combined shoulder and lap seat belt. Its authors were Roger Griswold and Hugh DeHaven. The application was filed on February 19, 1951.
The patent described a system that was supposed to hold the upper and lower parts of the body simultaneously. The belt combined shoulder and lap sections, and a common quick-release buckle was used to fasten them. Among the illustrations were aircraft seats, but the document provided for the use of the design in other types of seats — including automotive, dental, and medical.
One of the problems pointed out by the patent authors was that passengers could fasten the lap belt but leave the separate shoulder belt unfastened. Combining the two elements was intended to simplify the use of the system. Volvo later referred to this early design as Y-shaped.
How Bohlin changed the belt design
Nils Bohlin joined Volvo in 1958 from Saab, where he worked on pilot ejection systems. The engineer was tasked with creating a belt that would effectively restrain a person in an accident and be comfortable for everyday use.
Before the new design, cars used, in particular, diagonal two-point belts. Their fastenings and buckle placement could lead to dangerous load distribution in a collision. Bohlin proposed a different arrangement of attachment points: the upper part of the belt was fastened over the shoulder, and the lower points were located on both sides of the seat.
The lap and diagonal sections formed a V-shaped line with the apex pointing towards the floor. This geometry helped keep the belt on the body in a collision. An important condition was ease of use: the belt could be fastened with one hand, without the need to separately secure the shoulder part.
Bohlin's Swedish patent application is dated August 29, 1958. US Patent No. 3,043,625 was issued on July 10, 1962. The document mentions that the combination of shoulder and lap belts was already known. The main focus was on the placement of the fastenings and how the belt distributed the load on the body and the car's structure.
Volvo was the first to make the three-point belt standard
In 1959, Volvo began installing three-point seat belts on PV544 and Amazon models for Scandinavian markets. The company became the first automaker to offer such belts as standard equipment in the front seats of its cars. Subsequently, the design became widely adopted in the industry.
Volvo did not limit the use of the development to its own models. According to the company's historical materials, Bohlin's patent was immediately made available to other automakers without royalty payments. This helped spread the design beyond the brand.
However, buyers did not immediately accept the novelty: Volvo acknowledged that some motorists were skeptical of the three-point belt. Over time, it became one of the main elements of automotive passive safety.
In materials for the 50th anniversary of the design, Volvo reported that the belt saved over a million lives. In the Volvo Group historical reference, the company uses the wording that Bohlin improved the modern three-point belt, rather than creating the idea of combining the shoulder and lap parts itself.
What in Volvo's history is true, and what needs clarification
The assertion that Nils Bohlin was the first to combine shoulder and lap belts does not take into account the 1955 Griswold and DeHaven patent. However, this does not diminish the significance of the Volvo engineer's work: he developed a different geometry of fastenings, focused on effectively restraining a person in a car and convenient fastening.
The second part of the story — open access to the patent — is confirmed by Volvo's historical materials. The company indeed provided other automakers with the opportunity to use the development without paying royalties.
Therefore, it is more accurate to say not that Bohlin invented the three-point belt from scratch, but that he created a design that became a practical standard for cars. In this story, earlier patents, Volvo's engineering solution, and the subsequent spread of the technology are all important.