It was the increasing number of accidents, for one thing, that motivated investigations into methods of securing people inside vehicles. One of the earliest proposals on record, for example, dates from an 1840 issue of 'The Mechanics' Magazine'.
Talented English engineer Sir George Cayley, at the time, was seeking methods to improve railway safety. He had been present at the opening of the Liverpool and Manchester Railway, on September 15th 1830, and had witnessed the death of William Huskisson - a member of parliament who fell out of a train, landed on the tracks and was struck by George Stephenson's 'Rocket' locomotive.
As the number of routes, stations and locomotives continued to increase, incidents occurred more frequently. Cayley, frustrated by these 'sweeping and horrible catastrophes', promptly set about inventing ways of making rail travel safer. He published several articles detailing his creations, including the 'Means of Promoting Safety in Railway Carriages' in 1840.
In this article, a passing mention is made of 'a broad padded belt to be placed in front of each passenger, to retain him in his place in case of accident, and to prevent a collision with each other'. This wasn't Cayley's own concept, as he stated that it was a suggestion from 'some one', but the idea took hold - and, reputedly, Cayley later championed the concept of a lap belt alongside other safety concepts, and is even claimed to have used a lap belt in one of his early glider prototypes.
Edward Claghorn, from New York, is often cited as having the first patent for a 'safety belt' for use in vehicles. While he did indeed have a patent for safety belts approved in 1885, the patent makes no mention of vehicular use. Instead, it is cited solely as a device for aiding climbers and permitting them to carry tools at the same time. Not long after, however, Ella Cooley from Michigan patented a 'safety-belt' for securing children in 'a carriage or similar vehicle' in 1897.
During World War I, the benefits of safety belts became clear - with early aircraft often featuring lap belts and harnesses to keep pilots, gunners and observers securely in place. The focus wasn't entirely on safety, mind, but on keeping them in the desired position so they could better carry out their duties. These belts subsequently made their way into early passenger aircraft.
Little changed on the automotive safety front until after World War II, when the number of cars on the road increased exponentially. In America alone, the number of vehicles registered climbed from 31 million in 1939 to 71 million in 1959. Just ten years later, the number of registrations had risen to 105 million.
This surge in the number of cars, and the ever-increasing speed and capabilities of the cars in question, led to a dramatic rise in accidents. Many had been campaigning for safety improvements, including the obligatory use of belts, but little action had been taken - although manufacturer Nash had briefly offered optional lap belts in 1949, and the Sports Car Club of America had made lap belts obligatory for competition in 1954.
The American pilot and engineer Hugh DeHaven had been working since the 1940s on restraining passengers in vehicles, however, and was carrying out research at Cornell University for the Liberty Mutual Insurance Company and the seat belt-producing Hickok Manufacturing Company. The companies wanted to know how injuries occurred during crashes and, ultimately, the project concluded in the early 1950s that seat belts were key to improving safety.
Lap belts still left an occupant vulnerable to many head injuries, though. DeHaven, working with Air Force restraint specialist Roger Griswold, developed and applied for a patent on a safer three-point belt set-up in 1951 - a patent that was later granted in 1955. With its additional diagonal strap, the arrangement minimised the chance of 'shocking impacts of the head and upper torso on relatively stationary portions of the vehicle'. The idea of a diagonal belt wasn't new, that said, as a single diagonal belt solution had been proposed by American Harry Irwin in 1933. Alas, these designs remained concepts.
In 1955, the Society of Automotive Engineers appointed a 'Motor Vehicle Seat Belt Committee'. Colonel Don Wenger, a surgeon and former consultant to the Surgeon General of the United States, weighed in on the debate, too - publishing an article called 'Safer Cars' in the June 1955 issue of Popular Science. 'The U.S. Air Force is vitally interested,' he wrote, 'because 88 percent of all deaths occurring among Air Force personnel are due to crashes - and one-half of the crash victims are killed in cars.'
Wenger wasn't the only one with a critical safety message; Dr Charles Shelden was appalled by the scale and severity of accident-related injuries and came up with numerous ideas in 1955, including retractable seat belts, to reduce injury. Several bills and state legislations were introduced in December 1955, as a result of all these efforts, to require belts in cars or at least provide mountings for them.
Some manufacturers, such as General Motors, weren't keen on safety belts because of the purported lack of hard evidence about their benefit during accidents - and didn't want to hurt sales by making it look like driving could be dangerous, a move that harmed the development and deployment of seat belts. Fortunately, Ford and Chrysler felt otherwise and dealer-fitted optional lap belts were made available in 1955.
Saab stepped the game up, introducing standard-fit lap belts in 1958 - and it was again from Sweden that the next big step came. The Swedish government-owned power company Vattenfall had been carrying out safety investigations into accidents that affected its employees and found that crash-related injuries were most common. It contacted the companies that supplied its 15,000-strong fleet and, at the time, none showed any interest in supplying seat belts - indicating, like GM, that they might scare drivers.
Vattenfall assigned two of its engineers, Per-Olof Weman and Bengt Odelgard, the job of designing a seat belt for the company - aided by chief physician Stig Lindgren. The belt had to be better than the simple lap options on the market and, after taking some inspiration from American concepts, the result was the diagonal two-point 'Vattenfall type' belt.
Lindgren reputedly happened to know the recently appointed CEO of Volvo, Gunnar Engellau, and approached him with Vattenfall's new creation. As a result, to improve safety and potentially aid the company's export drive in America, some Volvos in 1958 were equipped with this two-point belt. 1958 was also the year in which Volvo appointed a new safety engineer - Nils Ivar Bohlin. He had worked at Saab, developing ejection seats, and was tasked with future safety developments at Volvo.
His key proposal was to develop an improved, safer three-point seat belt set-up; it referenced Griswold and DeHaven's earlier design but benefitted from key revisions that included making the strap a single piece and mounting the tongue and buckle low down - whereas the earlier American design had its diagonal strap and one part of the lap belt clipping into the other side of the lap belt, placing the buckle near the driver's inner thigh.
Bohlin's design resulted in much less belt movement and could also be easily buckled with one hand, making occupants more likely to use it. This revised layout was then made standard-fit in the 1959 Amazon and PV544 - although the patent wasn't granted until 1962. The benefits quickly made themselves clear and, as Volvo remarkably decided to make the design free for all to use, the fitting of three-point seat belts began to spread.
So, ultimately, we've Volvo and Bohlin to thank for introducing the three-point belt into a production car - a move that saved countless lives. Bohlin also went on to deliver numerous other safety solutions, including Volvo's side-impact protection system.