Given how many cars there are on the world's roads – around 600 million – and given how many of those driving them are stupid, drunk or just careless, we should perhaps be surprised that the seat belt has "only" saved a million lives in its half-century-long career.

It remains the most successful contribution to safety in the history of motoring, though it ranks some way behind penicillin or antiseptic surgery in the league table of life-savers. Put at its most basic, your belt prevents you being slammed against the steering wheel or in the case of rear passengers, careering with the force of a charging elephant into the people in the front of the car, and it stops you being thrown from a car in an accident. It reduces your chances death or injury by at least 50 per cent.

Found in almost every modern car, the conventional "three point" seat belt (where the chest as well as the lap is restrained by an additional strap) was invented by Volvo 50 years ago, the company is keen to remind us. I won't begrudge them an opportunity to gain some corporate glory from such the anniversary because they never stopped anyone else using their convenient and effective device. So thanks, Volvo, for being so magnanimous, and thanks to an engineer named Nils Bohlin who came up with the idea.

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But this 50th birthday is a particular one, for Volvo did not invent the safety belt, nor did they put them in their cars first, and their three-point design was not entirely novel. A crude belt had been developed as far back as the early 19th century by an Englishman, Sir George Cayley, for his pioneering glider (it worked; he died of old age). An American car company, Nash, offered them in 1949, while Ford fitted them as an option to some models from 1955 under an initiative by a rising executive, Robert McNamara. The Swedish firm Saab fitted a two-point seat belt as standard in 1958. An early three-point safety belt was patented by two Americans, Roger Griswold and Hugh De Haven in 1951, the CIR-Griswold Restraint. But they left the buckle in the middle.

It was Volvo, and in particular Ohlin, who successfully stood on the shoulders of these giants and pulled the essential features together in his patent for the "Basics of Proper Restraint Systems for Car Occupants". He moved the buckle to the side. Ohlin's essential insight was not into engineering but human nature; he recognised that we are too lazy to put effort into saving our own lives. He'd worked as an aircraft designer at Saab and as he explained later, "The pilots I worked with were willing to put on almost anything to keep them safe in case of a crash, but regular people in cars don't want to be uncomfortable even for a minute."

The key was to find a system that could be fitted fast: "I realised both the upper and lower body must be held securely in place with one strap across the chest and one across the hips. The belt also needed an immovable anchorage point for the buckle by the occupant's hip, so it could hold the body properly during a collision. It was a matter of finding a solution that was simple, effective and could be put on conveniently with one hand."

Celebrating 50 years of the seatbelt



Even so, there was consumer resistance, at least outside Scandinavia. Few poeple wanted to pay for them. Folk myths about seat belts decapitating or trapping people spread unhelpfully. Initially Volvo's wonderful new system was only fitted as standard to cars for the Swedish market; the first came off the production line on 13 August 1959.

Worldwide standard fitting came in 1963 and with Saab's parallel efforts, helped build the Swedish auto industry's formidable reputation for safety. Americans remain more reluctant to belt up to this day, and this, albeit minimal, incursion onto traditional notions of freedom of event is why the air bag was developed, fitted as standard to Cadillacs in 1974 and now commonplace. Some 5,000 lives a year are still lost as a result of Americans not wearing seat belts, though more than 80 per cent do belt up now.

Wearing front seat belts in Britain was not made compulsory until 1983, and since then has saved between 35,000 and 50,000 lives. The famous "Clunk-Click Every Trip" campaign fronted by Jimmy Savile in the 1970s did much to gain public acceptance for compulsion. Compulsory seat belts for rear passengers arrived in 1989 for children and in 1991 for adults. Some 94 per cent of drivers and front seat passengers wear belts, and 96 per cent of children on the back are strapped in, but only 69 per cent of us wear our rear seat belts. Perhaps that's because the fine for defying the law is usually only £30, with no points on your licence. We could save another 400 lives a year by everyone in the car wearing seat belts.

In its race against human complacency, the seat belt is still making good progress. The "inertia reel" system that locks the belt when you're thrown forward arrived in the 1960s, and those annoying bleeps for when you're not strapped in appeared in the 1970s. Cars are being fitted with "seat belt pre-tensioners", where the car "senses" an accident is imminent and tenses the seat belt moments before the collision. That first appeared on a Mercedes-Benz S-Class limo in 1981, and is trickling down to more modest transport.

In the future we may well see the four or five point seat belt (better in rollovers), more electronic control and perhaps even inflatable belts. One way or another, though, the seat belt is here to stay. As one Volvo boss is reported to have said a few years ago: "There is a little bit of Nils Bohlin in every car."

Vital devices: Other lifesavers

Catseyes

Motorists near Bradford in the early 20th century used reflections from the steel tramlines to navigate at night. One driver, Percy Shaw, missed them so much once they were removed that he invented Catseyes in 1933. Whether inspiration truly struck in the shape of a feline on a dark night remains a mystery, but the name became the company trademark. Growing car ownership and the blackouts of Second World War saw it go in to mass production. Today, Catseyes are used around the world and are considered responsible for revolutionising traffic safety.

The Pacemaker

The 1920s saw many experiments using electricity to stimulate the heart. The term 'pacemaker' was coined in 1932 by American physiologist Albert Hyman, to describe his invention: a machine to pump electricity into the heart via a needle through the chest wall, powered by a hand crank and spring motor. The idea was condemned by the medical community for interfering with 'natural events'. The first fully implantable pacemaker went to Arne Larsson, in Sweden, 1958. It failed after three hours. Over the course of his life, Larsson had 26 pacemakers. He died, aged 86, of non-heart related illness in 2001. The 500,000th pacemaker fitted in the UK was implanted in April 2009.

Smoke alarm

Voted Britain's favourite invention on a number of occasions, the smoke alarm is a real lifesaver. According to the UK Fire Service, people who live without one double their chances of dying if a fire was to start in their home. Originally patented in 1969 by Americans Randolph Smith and Kenneth House, three kinds are available today; 'ionisation' devices are the cheapest and detect small smoke particles from flaming fires like chip pan blazes, optical smoke detectors detect bigger particles from burning fabric and overheated wires, and the third variety combines both technologies. Many modern smoke detectors also use some of the cheapest nuclear technology available. Radioactive particles in americium-241 produce a small electric current which is tripped by smoke entering the device and triggers an alarm. For more information on keeping you and your family safe from fire, visit www.direct.gov.uk/firekills.

In video: Celebrating 50 years of the seat belt at independent.co.uk/motoring

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