There is no doubt that we are living in an age of technological marvels. Automotive safety technology is no exception as we rapidly approach the point at which vehicles drive themselves. The development of vehicle safety systems from seat belts to Advanced Driver Assistance Systems (ADAS) has been an, unfortunately, costly process. In early automobiles, safety was not a consideration at all. As automobiles became more popular, so did visits to the hospital from automobile accidents. Not surprisingly, the patent offices are filled with patents by doctors, nurses, and engineers seeking ways to save lives and reduce injuries in car accidents. Eventually, under pressure from doctors and the public, vehicle safety systems would be developed and implemented by manufacturers on a large scale.
We, at Full Blown Advanced Automotive Center, have taken it upon ourselves to become experts in the technology of vehicle safety and have decided to share a small piece of our knowledge. Over the next few weeks we will be releasing a series of blog posts to discuss vehicle safety systems; their origins, development, how they work, and how they are fast becoming staples of the automotive industry.
When we hear some mention of automotive safety, certain technologies stand out in our mind as absolute standards of automobile production. Seat belts are among the oldest developments in automotive technology, and it has become difficult to even imagine a vehicle without them. Safety glass is almost as old as the invention of the automobile as well. Airbags, or SRS (supplemental restraint systems,) have become so common in passenger vehicles that we take the technology for granted. Continue reading below for Part I. of Vehicle Safety Systems: Seat Belts, Safety Glass, and Supplemental Restraint Systems.
The lap seat belt was originally developed for use in gliders in the mid 19th century to keep the pilots from falling out of their aircraft. The first wide scale use in automobiles was in 1885 as lap belts installed aftermarket to keep New York City taxi passengers in their seat during the fare. Seat belts were only an aftermarket afterthought for early automobile owners, and if a car did have them, it was more about keeping passengers (children) in their seats. In the 1930's many doctors were conducting studies on vehicle safety, specifically, seat belts. Under recommendations by the medical community auto manufacturers began offering seat belts as optional equipment namely Nash Motors in 1949 and Ford in 1955, and the first car to have lap seat belts as standard equipment was the 1958 Saab GT 750.
The modern three-point seat belt was patented in 1955 by American inventors Roger Griswold and Hugh DeHaven. Later in 1959 Volvo engineer Nils Bohlin perfected the design with all three points anchored to the vehicle body and buckled at the inside anchor. He made it standard in all 1959 onward Volvo models. Furthermore, Bohlin demonstrated in a major study of vehicle accidents in Sweden that the seat belt prevented any fatalities, at time of crash, below 60mph. Bohlin's seat belt design revolutionized the industry, and essentially every auto manufacturer worldwide would eventually use his design, in large part because Volvo decided to share their design publicly and freely to other manufacturers. After Bohlin passed away in 2002, Volvo estimated that Bohlin's seat belts had saved over a million lives. In large part due to Bohlin's success at Volvo, legislatures around the globe began requiring that all vehicles have seat belts installed at time of manufacture. In 1966 the U.S. National Traffic and Motor Vehicle Safety Act made seat belts mandatory standard equipment in the U.S.
Seat belt technology continued to improve with the development of pre-tensioners by Mercedes-Benz in 1981 S-class sedans. The pre-tensioners were developed as part of the airbag supplemental restraint system to pre-tension the seat belts in a collision and reduce the movement of passenger bodies from excessive contact with the airbag. Pre-tensioners improved passenger safety in an accident significantly, which in turn alleviated concerns about the safety of airbags. Pre-tensioning seat belts are now standard equipment on all production vehicles. Seat belts have also now become an integral part of the supplemental restraint airbag systems using sensors in the seat belt buckle, weight sensors in the seats, and even infrared cameras do determine passenger size and sitting position (on select models). The data from the array of sensors is processes by the SRS module and, in the event of a collision, engages the pre-tensioner in the seat belt assembly to maximize safety and prevent injury and/or death to the vehicle occupants.
Vehicle safety legislation required LATCH (Lower Anchors and Tethers for Children) to be installed standard on all vehicles model year 2002 and up. LATCH is a set of anchor points on the body of the vehicle usually hidden behind the rear seats and often identified by a small plastic button or flag attached to the seat. The child seat is equipped with tethers with similar nylon construction to seat belts which attach to the anchors and prevent movement of the child seat in the event of a collision. LATCH is an active restraint used in conjunction with the regular seat belt to better secure the child seat and prevent injury to small children from impact as well as rear airbags if equipped.
Glass was first used in horse-drawn carriages in the 19th century as a way to protect drivers and passengers from dust and weather, and was carried over to the earliest automobiles. Early automotive glass was simply standard glass which, as you know, breaks easily into large, sharp shards that could actually endanger the vehicle occupants. In 1903 French scientist Edouard Benedictus accidentally discovered a way to produce shatter-resistant glass when a flask with a dried colloidion film cooked on to it was dropped and cracked but did not break. By the 1920s auto manufacturers had recognized the benefit of this laminated glass with film applied to each side. In the event of debris striking the windshield, or in an accident, the glass would not shatter and break into sharp shards; but, would resist punctures, break into small pieces that otherwise remained intact between lamination, and ultimately prevent injury to drivers and passengers in an accident.
Laminated safety glass production methods have improved over the decades to reduce weight, shatter resistance, puncture resistance, and reduced manufacturing cost. Modern laminated safety glass is designed somewhat differently now than in the 20th century. The glass is now made by pressing a piece of PVB (polyvinyl butyral) plastic between two layers of glass and then the outsides are laminated with a colloidiol solution. Modern layered and laminated safety glass is so strong that it can even prevent the roof from being crushed in a rollover crash. The glass is more likely to break away from the vehicle as a whole windscreen rather than break into small pieces that could injure occupants. Modern safety glass also reflects most ultraviolet light and is designed to be repaired in many cases rather than requiring replacement.
In the late 1930s, auto manufacturers began introducing tempered glass for side and rear windows, known as sidelites and backlites. Tempered glass is made through a process of heating, cooling, stretching, and compressing the glass. Tempered glass can still be shattered unlike laminated glass, but breaks into small, dull pieces. Most modern vehicles still use tempered glass for the side and rear windows today. Most manufacturers do not install laminated glass for side and rear applications so that if the vehicle occupants need to escape the vehicle the tempered glass windows can be broken allowing passengers to escape. However, some manufacturers do install laminated glass in the side or rear as a security feature as laminated glass makes it extremely difficult to break into the vehicle.
SRS (Supplemental Restraint System)
The supplemental restraint system, more commonly known as airbags, can trace it's origins all the way back to 1919, when a patent was submitted by two dentists in England for airbags to inflate to protect airplane and vehicle parts in the event of a crash. Little development of the idea was seen in either aerospace or automotive industries until 1953 when industrial engineer and U.S. Navy sailor John Hetrick was awarded a patent for a compressed air inflated airbag. Hetrick used his knowledge of compressed air from working with torpedoes to develop the idea. The airbag would deploy by compressed air when a spring loaded switch detected impact on the bumper of the car. Hetrick's design would only be used in testing of experimental Ford cars in 1971. Testing by Ford found that the compressed air system was not capable of deploying the airbag quickly enough to prevent injury to occupants and was abandoned by Ford. In 1964 Japanese automotive engineer Yasuzaburou Kobori designed and patented a new airbag system that used an explosive to inflate the airbag and solved the problem with Hetrick's compressed air system inflating the airbag fast enough. Kobori's design illuminated another problem in the development of SRS systems. The spring loaded trigger in the bumper of early designs was found, also, not able to activate the airbag for deployment quickly enough. In, 1967 inventor Allen K. Breed developed a crash detection device consisting of a steel ball attached to a tube with a magnet. At the point of impact the steel ball is forced away from the magnet instantaneously and, when combined with Kobori's explosive airbag, was able to deploy the airbag in less than 30 milliseconds, fast enough to prevent injury to vehicle occupants.
While Ford had tested and abandoned airbags in 1971, General Motors began limited production in 1973 Chevy Impalas with driver airbags. Chevy continued with driver and passenger airbags in the 1974 Oldsmobile Tornado. Customer demand for the technology was limited and at the time was marketed as an alternative to seat belts rather than as a supplement to seat belts. The technology was also prohibitively expensive in the 1970s and there was debate about the safety of airbags at the time, mainly because they were marketed to be used without seat belts. GM stopped offering optional airbags for the 1977 model year. Ford and GM both extensively lobbied against mandatory requirements for airbags throughout the 70s and 80s.
In 1981 Mercedes-Benz began installing optional driver airbags in their W126 S-Class sedan, and it was the first automobile to feature pre-tensioning seat belts. Mercedes' airbag system was installed as a supplement to seat belts wherein the seat belt and pre-tensioner were active restraints, while the airbag deployment was a passive restraint system. This is now a common feature in all SRS systems today. Mercedes continued to offer airbags as an option until 1998 when U.S. regulations mandated supplemental restraints on all passenger vehicles.
Modern automobiles are not just equipped with a driver side airbag but with additional airbags for passengers, side impact airbags, curtain airbags to protect the head from impacting glass, knee airbags, and even rear airbags. The 1987 Porsche 944 introduced the passenger standard airbag. The 1995 Volvo 850 introduced side impact airbags which deploy from the seat. The 1995 Kia Sportage had knee airbags installed in the lower dash. The 1997 BMW 5 and 7 series were the first vehicles to offer curtain airbags deployed from the forward A-pillar. The 2008 Toyota iQ was the first car with seat cushion deployed airbags to prevent the occupant from sliding forward under the seat belt, and the iQ was also manufactured with rear curtain airbags to protect rear passengers' heads in an impact. The 2009 Toyota Crown Majesta introduced rear center airbags to protect rear passengers. In 2013 General Motors began installing center front airbags to offer greater protection to the driver and front center passenger in the Traverse, Acadia, and Enclave models. Toyota developed seat belt installed airbags in the 2010 Lexus LFA. And, in 2014 Volvo introduced, on the V40 model, pedestrian impact airbags that deploy on the outside of the car from the A-pillar to protect pedestrians from injuries when being struck by the car.
In 1991, the United States passed legislation for automotive safety requiring that all passenger vehicles sold in the U.S. after 1997 be equipped with a supplemental restraint system. Airbag technology has continued to improve since becoming standard in 1997. Occupant sensing SRS systems detect whether or not a vehicle seat is occupied, and became standard following legislation on 2006 and up models. At first this technology was available to front passengers only, but now many late model vehicles are being produced with rear passenger seat sensors as well. In the early 2000s several manufacturers developed multi-stage, or smart, airbags. The multi-stage SRS system combines data from seat weight sensors, seat angle sensors, vehicle speed/angle sensors, lasers or infrared passenger sitting position sensors, and collision sensors which allow the vehicle computer to make split second decisions whether to deploy the airbags at partial force, full force, or not at all. Per legislation mentioned previously, all passenger vehicles built during or after 2006 must have multi-stage airbags.
Airbags have had their safety and effectiveness challenged, especially early in their development. Early airbags often did not deploy quickly enough, deployed with not enough/too much force, and when used without seat belts often resulted in worse injuries. From 2002 to 2015 airbags made by Japanese parts manufacturer Takata and installed by 19 different automobile manufacturers, were subject to immediate recall following dozens of deaths and hundreds of injuries caused by the airbag. An explosive cylinder in the airbag inflator could fragment during airbag deployment causing metal shards to strike the vehicle occupants. 41.6 million vehicles in the U.S. are affected by this recall. The defective parts can be replaced by the vehicle dealer at no cost to the owner.
The three safety features discussed above merely scratch the surface of modern safety technologies, but are, nonetheless, three of the most important and highly developed automotive safety technology. Seat belts, safety glass, and SRS systems have saved countless lives. No doubt auto manufacturers will continue to compete to produce the safest vehicles. Stay tuned for part 2 of our series on vehicle safety systems, and remember to call, click, or stop by if any of your vehicle safety systems are not working, in disrepair, or if you have an indicator light on. At Full Blown Advanced Automotive Repair we are dedicated to ensuring that your vehicle and your family are safe and secure in your vehicle.