Today’s safety technologies do not stand alone, and were not created in a vacuum. They arose from building blocks that made them possible. These are some of the major steps along the way that made automotive safety systems what they are today.
History does not remember Arthur W. Savage of San Diego, California, as the inventor of the radial tire, despite receiving U.S. patent 1,203,910 on May 21, 1915. More costly, harder to construct, and less forgiving than its bias-ply cousin, the radial tire nearly disappeared from sight until Michelin stepped in and developed and commercialized it. From its headquarters in Clermont-Ferrand, France, the tire maker took Savage’s idea—wrapping the cord from side-to-side at 90° to the rim and placing circumferential belts between the cords and tread—used steel for the belts, and called the resulting tire the “Michelin X.” In an instant, tire life nearly doubled, fuel economy increased, and vehicle ride and handling (once suspension systems were modified for the radial’s unique characteristics) markedly improved.
The spot-type disc brake is another American invention. Elmer Ambrose Sperry of Cleveland, Ohio, designed an electric vehicle in 1898 that featured a large disc integral with each front hub. Electromagnets pressed pads fitted with friction material against the discs when the brake was engaged, while springs caused the pads to retract. However, it was Englishman William Lanchester who first patented disc brakes four years later, and put them on his cars. With only copper at hand to act as the friction material, Lanchester’s disc brakes had a short service life. Once perfected in the late 1940s, however, disc brakes proved to be much less prone to heat-induced fade, performed better in the wet, and produced shorter stopping distances than drum brakes. As costs fell and demand for better braking performance increased, disc brakes moved from racing cars to sports cars to every new car and truck on the road today.
Mercedes engineer Béla Barényi was the first to patent (in 1951) the rigid passenger cell/crumple zone combination still used today, as well as the safety steering wheel. In an accident, the vehicle’s front and rear structures are designed to deform and progressively absorb collision energy, helping to leave the passenger structure (or “safety cage”) intact. Mercedes-Benz’s 1959 W 11 series was the first series production automobile to feature this design, and the first to include a collapsible steering wheel. It featured a large impact absorber connected to the steering column via a plastically deformable element. A few years later, the collapsible steering column was added to Mercedes’ safety repertoire. In 1966, Barényi and Mercedes-Benz development manager Hans Scherenberg devised the definitions of “active” and “passive” safety still used today.
Seatbelts & Airbags
Though Edward Claghorn of New York was issued a U.S. patent for a safety belt on February 10, 1885, it was California doctor C Hunter Shelden who first proposed retractable seatbelts in a November 5, 1955 article in the Journal of the American Medical Association. However, it was Volvo’s Nihls Bohlin who developed the 1955 patent of Americans Roger Griswold and Hugh DeHaven into the modern three-point seatbelt. Only recently has it been supplemented by an inflatable belt design that reduces rear seat injuries.
Airbags were first patented in 1951 by German Walter Linderer, though it was former U.S. Navy man John Hedrick whose 1953 patent built on Linderer’s idea and coined the term “airbag.” In 1968, Allen Breed patented the electromechanical crash sensor, and sodium azide (since abandoned) became the first fast-acting propellant. This combination made it possible to detect a crash and deploy an airbag within the 30 milliseconds needed for it to be effective. Now vehicles have multiple airbags designed for frontal, side and rollover events.
French aviator Gabriel Voisin created an anti-lock brake (ABS) system for airplanes in 1929 that used a flywheel attached to a drum that ran at the same speed as the plane’s wheel. If the wheel slowed below the speed of the flywheel (i.e., it was skidding), a valve attached to the flywheel opened and released pressure on the brakes. Twenty-nine years later, Britain’s Road Research Laboratories created the first practical ABS system (“Maxaret”), testing it on a Royal Enfield motorcycle. It was first applied to Britain’s Jensen Interceptor in 1966, but was withdrawn due to cost, complexity and a lack of reliability. Lincoln’s 1968 Continental Mark III featured a rear brake-only system design by Kelsey-Hayes that used wheel-speed sensors on the rear wheels to transmit information to a rudimentary electronic controller. It modulated pressure to the rear brakes via an in-line vacuum-operated valve, but it also proved too costly and unreliable. Nowadays, ABS is standard on most new cars.
Microprocessors & Sensors
The transistor moved electronics forward, but it was the invention of the low-cost microprocessor that sparked the electronics revolution. Without it, automotive safety systems would not be what they are today.
Integrating an entire central processing unit (CPU) on a chip or chips decreased the cost of processing power. Advances in miniaturization doubled that power approximately every 18 months. Ignition modules were the first major application of automotive microprocessors, and this gradually spread to the fuel system with the advent of electronically controlled carburetors. That was followed by electronic fuel injection. As automotive sensors came of age, the CPU’s ability to more finely control systems within the vehicle also improved. However, what once were discrete systems in the 1970s, 1980s and most of the 1990s were quickly integrated into larger-scale controllers that shared information across the vehicle platform. Suddenly, ABS became affordable, traction control moved from brake-intervention units to powertrain-intervention designs, electronic stability control was born, and a whole host of other features arrived on the scene. Today, automakers and suppliers are fusing the data from the sensors around the vehicle to add depth and functionality.
As electronics continue to spread through the vehicle, even greater safety will be achievable. It may eventually be possible to create a car that never crashes as processor power grows and vehicles communicate with each other and the infrastructure. However, that day is still somewhere in the future. In the near-term, fusing advanced electronic stability control, electric steering and radar/lidar will make accident avoidance systems commonplace. From there, it is a short road to the fully autonomous vehicle.
Though legal and other hurdles—especially the wariness of the driving public and the initial cost of these systems—may delay the advent of driverless cars, as with all of the safety technologies featured, this technology will begin at the top of the food chain and trickle down as costs diminish. We may never get to the day when cars don’t crash, but—even 40 years ago—could anyone have foreseen what is now considered commonplace?