Bumper (car)
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A bumper is a structure attached to or integrated with the front and rear ends of a motor vehicle, to absorb impact in a minor collision, ideally minimizing repair costs.<ref>Template:Cite book</ref> Stiff metal bumpers appeared on automobiles as early as 1904 that had a mainly ornamental function.<ref name="ATJ-1924">Template:Cite journal</ref> Numerous developments, improvements in materials and technologies, as well as greater focus on functionality for protecting vehicle components and improving safety have changed bumpers over the years. Bumpers ideally minimize height mismatches between vehicles and protect pedestrians from injury. Regulatory measures have been enacted to reduce vehicle repair costs and, more recently, impact on pedestrians.
History
Bumpers were, at first, just rigid metal bars.<ref>Template:Cite web</ref> George Albert Lyon invented the earliest car bumper. The first bumper appeared on a vehicle in 1897, and Nesselsdorfer Wagenbau-Fabriksgesellschaft, an Austrian carmaker, installed it. The construction of these bumpers was unreliable as they featured only a cosmetic function. Early car owners had the front spring hanger bolt replaced with ones long enough to attach a metal bar.<ref name="ATJ-1924"/> G.D. Fisher patented a bumper bracket to simplify the attachment of the accessory.<ref name="ATJ-1924"/> The first bumper designed to absorb impacts appeared in 1901. It was made of rubber, and Frederick Simms gained a patent in 1905.<ref name="Hodges">Template:Cite book</ref>
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Automakers added bumpers in the mid-1910s, but consisted of a strip of steel across the front and back.<ref name="Davis">Template:Cite web</ref> Often treated as an optional accessory, bumpers became more and more common in the 1920s as automobile designers made them more complex and substantial.<ref name="Davis"/> Over the next decades, chrome-plated bumpers became heavy, elaborative, and increasingly decorative until the late 1950s when U.S. automakers began establishing new bumper trends and brand-specific designs.<ref name="Davis"/> The 1960s saw the use of lighter chrome-plated blade-like bumpers with a painted metal valance filling the space below it.<ref name="Davis"/> Multi-piece construction became the norm as automakers incorporated grilles, lighting, and even rear exhaust into the bumpers.
On the 1968 Pontiac GTO, General Motors incorporated an "Endura" body-colored plastic front bumper designed to absorb low-speed impact without permanent deformation. It was featured in a TV advertisement with John DeLorean hitting the bumper with a sledgehammer and no damage resulted.<ref>Template:Cite web</ref> Similar elastomeric bumpers were available on the front and rear of the 1970-71 Plymouth Barracuda.<ref>Template:Cite book</ref> In 1971, Renault introduced a plastic bumper (sheet moulding compound) on the Renault 5.<ref>Template:Cite book</ref>
Current design practice is for the bumper structure on modern automobiles to consist of a plastic cover over a reinforcement bar made of steel, aluminum, fiberglass composite, or plastic.<ref>Template:Cite web</ref> Bumpers of most modern automobiles have been made of a combination of polycarbonate (PC) and acrylonitrile butadiene styrene (ABS) called PC/ABS.Template:Citation needed
Physics
Bumpers offer protection to other vehicle components by dissipating the kinetic energy generated by an impact. This energy is a function of vehicle mass and velocity squared.<ref>Template:Cite journal</ref> The kinetic energy is equal to 1/2 the product of the mass and the square of the speed. In formula form:
- <math>E_\text{k} =\tfrac{1}{2} mv^2 </math>
A bumper that protects vehicle components from damage at 5 miles per hour must be four times as tough as a bumper that protects at 2.5 miles per hour, with the collision energy dissipation concentrated at the extreme front and rear of the vehicle. Small increases in bumper protection can lead to weight gain and loss of fuel efficiency.
Until 1959, rigidity was seen as beneficial to occupant safety among automotive engineers.<ref name="Automotive Plastics">Template:Cite web</ref> Modern theories of vehicle crashworthiness point in the opposite direction, towards vehicles that crumple progressively.<ref>Template:Cite web</ref> A completely rigid vehicle might have excellent bumper protection for vehicle components, but would offer poor occupant safety.<ref>Template:Cite web</ref>
Pedestrian safety
Bumpers are increasingly being designed to mitigate injury to pedestrians struck by cars, such as through the use of bumper covers made of flexible materials. Front bumpers, especially, have been lowered and made of softer materials, such as foams and crushable plastics, to reduce the severity of impact on legs.<ref name="autonews1">Template:Cite web</ref>
Height mismatches
For passenger cars, the height and placement of bumpers are legally specified under both U.S. and EU regulations. Bumpers do not protect against moderate-speed collisions, because during emergency braking, suspension changes the pitch of each vehicle, so bumpers can bypass each other when the vehicles collide. Preventing override and underride can be accomplished by extremely tall bumper surfaces.<ref>Template:Cite web</ref> Active suspension is another solution to keeping the vehicle level.
Bumper height from the roadway surface is essential in engaging other protective systems. Airbag deployment sensors typically do not trigger until contact with an obstruction, and it is crucial that front bumpers be the first parts of a vehicle to make contact in the event of a frontal collision, to leave sufficient time to inflate the protective cushions.<ref name="Underride" />
Energy-absorbing crush zones are completely ineffective if they are physically bypassed; an extreme example of this occurs when the elevated platform of a tractor-trailer completely misses the front bumper of a passenger car, and the first contact is with the glass windshield of the passenger compartment.
Truck vs. car
Underride collisions, in which a smaller vehicle such as a passenger sedan slides under a larger vehicle such as a tractor-trailer often result in severe injuries or fatalities. The platform bed of a typical tractor-trailer is at the head height of seated adults in a typical passenger car and thus can cause severe head trauma in even a moderate-speed collision. Around 500 people are killed this way in the United States annually.<ref name="autosafetyexpert1">Template:Cite web</ref>
Following the June 1967 death of actress Jayne Mansfield in an auto/truck accident, the U.S. National Highway Traffic Safety Administration recommended requiring a rear underride guard, also known as a "Mansfield bar", an "ICC bar", or a "DOT (Department of Transportation) bumper".<ref name=URG>Template:Cite web</ref><ref>Template:Cite book</ref> These may not be more than Template:Convert from the road. The U.S. trucking industry has been slow to upgrade this safety feature,<ref name="Underride">Template:Cite web</ref> and there are no requirements to repair ICC bars damaged in service.<ref>Template:Cite web</ref> However, in 1996 NHTSA upgraded the requirements for the rear underride prevention structure on truck trailers, and Transport Canada went further with an even more stringent requirement for energy-absorbing rear underride guards.<ref>Template:Cite web</ref> In July 2015, NHTSA issued a proposal to upgrade the U.S. performance requirements for underride guards.<ref>Template:Cite web</ref>
Many European nations have also required side underride guards to mitigate lethal collisions where the car impacts the truck from the side.<ref name="autosafetyexpert1"/> A variety of different types of side underride guards of this nature are in use in Japan, the US, and Canada.<ref>Template:Cite web</ref> However, they are not required in the United States.<ref name="autosafetyexpert1"/>
UN Regulation 58 sets forth requirements for rear underrun protective devices (RUPDs) and their installation, among which is that trucks and trailers of various types must have such devices with height above the ground not more than Template:Convert, Template:Convert, or Template:Convert.<ref>Template:Cite web</ref>
SUV vs. car
Mismatches between SUV bumper heights and passenger car side impact beams have allowed serious injuries at relatively low speeds.<ref name="Underride"/><ref>Template:Cite web</ref> In the United States, NHTSA is studying how to address this issue Template:Asof.<ref name="nhtsa1">Template:Cite web</ref>
Beyond lethal interactions, repair costs of passenger car/SUV collisions can also be significant due to the height mismatch.<ref>Template:Cite news</ref> This mismatch can result in vehicles being so severely damaged that they are inoperable after low-speed collisions.<ref>Template:Cite web</ref>
Regulation
In most jurisdictions, bumpers are legally required on all vehicles. Regulations for automobile bumpers have been implemented for two reasons – to allow the car to sustain a low-speed impact without damage to the vehicle's safety systems, and to protect pedestrians from injury. These requirements conflict: bumpers that withstand impact well and minimize repair costs tend to injure pedestrians more, while pedestrian-friendly bumpers tend to have higher repair costs.<ref>Template:Cite book</ref>
Although a vehicle's bumper systems are designed to absorb the energy of low-speed collisions and help protect the car's safety and other expensive nearby components, most bumpers are designed to meet only the minimum regulatory standards.<ref>Template:Cite book</ref>
International standards
International safety regulations, devised initially as European standards under the auspices of the United Nations, have now been adopted by most countries outside North America. These specify that a car's safety systems must still function normally after a straight-on pendulum or moving-barrier impact of Template:Convert to the front and the rear, and to the front and rear corners of Template:Convert at Template:Convert above the ground with the vehicle loaded or unloaded.<ref name="nhtsa1"/><ref>Template:Cite web</ref>
Pedestrian safety
European countries have implemented regulations to address the issue of 270,000 deaths annually in worldwide pedestrian/auto accidents.<ref name="autonews1"/>
Bull bars
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Specialized bumpers, known as "bull bars" or "roo bars", protect vehicles in rural environments from collisions with large animals. However, studies have shown that such bars increase the threat of death and serious injury to pedestrians in urban environments,<ref>Template:Cite web</ref> because the bull bar is rigid and transmits all force of a collision to the pedestrian, unlike a bumper, which absorbs some force and crumples.<ref>Template:Cite report</ref><ref>Template:Cite journal</ref> In the European Union, the sale of rigid metal bull bars that do not comply with the relevant pedestrian-protection safety standards has been banned.<ref>Template:Cite web</ref>
Off-road bumpers
Off-road vehicles often utilize aftermarket off-road bumpers made of heavy gauge metal to improve clearance (height above terrain), maximize departure angles, clear larger tires, and ensure additional protection. Similar or identical to bull bars, off-road bumpers feature a rigid construction and do not absorb (by plastic deformation) any energy in a collision, which is more dangerous for pedestrians than factory plastic bumpers. The legality of the aftermarket off-road bumpers varies by jurisdiction.
United States
Bumper regulations in the United States focus on preventing low-speed accidents from impairing safe vehicle operation, limiting damage to safety-related vehicle components, and containing the costs of repair after a crash.<ref>Template:Cite journal</ref><ref>Template:Citation</ref>
First standards 1971
| File:71 Dart Front Bumper L.jpg | File:74 Valiant Front Bumper.jpg |
| File:71 Dart Rear Bumper.jpg | File:74 Valiant Rear Bumper.jpg |
| Front and rear bumpers on Chrysler A platform cars before (left, 1971) and after (right, 1974) the U.S. 5-mph bumper standard took effect. The 1974 bumpers protrude farther from the body and the rear one no longer contains the taillamps. | |
In 1971, the U.S. National Highway Traffic Safety Administration (NHTSA) issued the country's first regulation applicable to passenger car bumpers. Federal Motor Vehicle Safety Standard No. 215 (FMVSS 215), "Exterior Protection," took effect on 1 September 1972—when most automakers would begin producing their model year 1973 vehicles.<ref name=Billion>Template:Cite magazine</ref> The standard prohibited functional damage to specified safety-related components such as headlamps and fuel system components when the vehicle is subjected to barrier crash tests at Template:Convert for front and Template:Convert for rear bumper systems.<ref>Template:Cite web</ref> The requirements effectively eliminated automobile bumper designs that featured integral automotive lighting components such as tail lamps.
In October 1972, the U.S. Congress enacted the Motor Vehicle Information and Cost Saving Act (MVICS), which required NHTSA to issue a bumper standard that yields the "maximum feasible reduction of cost to the public and to the consumer".<ref name=Congressional>Template:Cite web</ref> Factors considered included the costs and benefits of implementation, the standard's effect on insurance costs and legal fees, savings in consumer time and inconvenience, as well as health and safety considerations.<ref name=Billion/>
The 1973 model year passenger cars sold in the U.S. used a variety of designs. They ranged from non-dynamic versions with solid rubber guards, to "recoverable" designs with oil and nitrogen filled telescoping shock-absorbers.<ref>Template:Cite journal</ref>
The standards were further tightened for the 1974 model year passenger cars, with standardized height front and rear bumpers that could take angle impacts at Template:Convert with no damage to the car's lights, safety equipment, and engine. There was no provision in the law for consumers to 'opt out' of this protection.<ref name=Billion/>
Regulatory effect on design
The regulations specified bumper performance; they did not prescribe any particular bumper design. Nevertheless, many cars for the U.S. market were equipped with bulky, massive, protruding bumpers to comply with the 5-mile-per-hour bumper standard in effect from 1973 to 1982.<ref name=Billion/><ref>Template:Cite book</ref> This often meant additional overall vehicle length, as well as new front and rear designs to incorporate the stronger energy-absorbing bumpers, adding weight to the extremities of the vehicle.<ref name=Billion/><ref>Template:Cite journal</ref> Passenger cars featured gap-concealing flexible filler panels between the bumpers and the car's bodywork causing them to have a "massive, blockish look".<ref name="cranswick">Template:Cite book</ref> However, other bumper designs also met the requirements. The 1973 AMC Matador coupe had free-standing bumpers with rubber gaiters alone to conceal the retractable shock absorbers.<ref name="cranswick"/> "Endura" bumpers, compliant with the regulations yet tightly integrated into the front bodywork, were used on models such as the Pontiac Grand Am starting in 1973 and the Chevrolet Monte Carlo starting in 1978, with significantly lower mass than heavy chromed-steel bumpers with separate impact energy absorbers.<ref>Template:Cite web</ref><ref>Template:Cite magazine</ref>
| United States (left) and rest-of-world (right) | |
| File:1979 Mercedes 300SD 116.120.jpg | File:Mercedes Benz W116 aka 280SE in Belgium.jpg |
| File:BMW-535is.jpg | File:BMW 525i E28 01.jpg |
| File:Lamborghini Countach US spec 5000QV.jpg | File:Lamborghini Countach (8014529631).jpg |
| Front bumpers on Mercedes-Benz W116 (top), BMW E28 5 Series (middle), Lamborghini Countach (bottom). The U.S. bumpers are larger and protrude farther from the bodywork. | |
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The bumper regulations applied to all passenger cars, both American-made and imported. With exceptions including the Volvo 240, Porsche 911, and Rolls-Royce Silver Shadow, European and Asian automakers tended to put compliant bumpers only on cars destined for the U.S. and Canadian markets where the regulations applied. This meant their North American-spec cars tended to look different than versions of the same model sold elsewhere.
U.S. bumper-height requirements effectively made some models, such as the Citroën SM, ineligible for importation to the United States. Unlike international safety regulations, U.S. regulations were written without provision for hydropneumatic suspension.<ref>Template:Cite web</ref>
Zero-damage standards 1976
The requirements promulgated under MVICS were consolidated with the requirements of Federal Motor Vehicle Safety Standard Number 215 (FMVSS 215, "Exterior Protection of Vehicles") and promulgated in March 1976. This new bumper standard was placed in the United States Code of Federal Regulations at 49 CFR 581, separate from the Federal Motor Vehicle Safety Standards at 49CFR571. The new requirements, applicable to 1979-model year passenger cars, were called the "Phase I" standard. At the same time, a zero-damage requirement, "Phase II", was enacted for bumper systems on 1980 and newer cars. The most rigorous requirements applied to 1980 through 1982 model vehicles; Template:Convert front and rear barrier and pendulum crash tests were required, and no damage was allowed to the bumper beyond a Template:Convert dent and Template:Convert displacement from the bumper's original position.<ref name=NHTSA_87>Template:Cite web</ref>
All-wheel-drive "cross-over" cars such as the AMC Eagle were classified as multi-purpose vehicles or trucks, and thus exempt from the passenger car bumper standards.<ref>Template:Cite book</ref>
Stringency reduced in 1982
The recently elected Reagan administration had pledged to use cost–benefit analysis to reduce regulatory burdens on industry, which impacted this standard.<ref>Template:Cite news</ref>
As discussed in detail under Physics, before 1959, people believed the stronger the structure, including the bumpers, the safer the car. A later analysis led to the understanding of crumple zones, rather than rigid construction that proved deadly to passengers because the force from impact went straight inside the vehicle and onto the passenger.<ref name="Automotive Plastics"/>
NHTSA amended the bumper standard in May 1982, halving the front and rear crash test speeds for 1983 and newer car bumpers from Template:Convert to Template:Convert, and the corner crash test speeds from Template:Convert to Template:Convert.<ref>Template:Cite web</ref> In addition, the zero-damage Phase II requirement was rolled back to the damage allowances of Phase I. At the same time, a passenger car bumper height requirement of Template:Convert was established for passenger cars.<ref name=NHTSA_87/>
NHTSA evaluated the results of its change in 1987, noting it resulted in lower weight and manufacturing costs, offset by higher repair costs.<ref>Template:Cite web</ref>
Despite these findings, consumer and insurance groups decried the weakened bumper standard. They argued that the 1982 standard increased overall consumer costs without any attendant benefits except for automakers.<ref name=Congressional/><ref name=IIHS_1615>Template:Cite magazine</ref><ref name=IIHS_177>Template:Cite web Template:Small</ref><ref>Template:Cite news</ref> In 1986, Consumers Union petitioned NHTSA to return to the Phase II standard and disclose bumper strength information to consumers. In 1990, NHTSA rejected that petition.<ref name="smartmotorist">Template:Cite web</ref>
Consumer information
In the United States, the Insurance Institute for Highway Safety (IIHS) subjects vehicles to low-speed barrier tests (Template:Cvt) and publishes the results, including repair costs.<ref>Template:Cite web</ref> Car makers that do well in these tests tend to publicize the results.<ref>Template:Cite news</ref>
In 1990, the IIHS conducted four crash tests on three different-year examples of the Plymouth Horizon. The results illustrate the effect of the changes to the U.S. bumper regulations (repair costs are quoted in 1990 United States dollars):<ref name="smartmotorist"/>
- 1983 Horizon with Phase-II 5-mph bumpers: $287
- 1983 Horizon with Phase-I 2.5-mph bumpers: $918
- 1990 Horizon: $1,476
Bumpers today
Today's bumpers are designed to mitigate injuries to pedestrians and minimize weight at the ends of the vehicle, thereby increasing occupant protection from progressive crumpling in a serious accident.<ref name="MV"/> They are no longer made of steel and rubber,<ref name="MV"/> but of a plastic outer fascia over a lightweight, impact-absorbing polystyrene foam core.<ref name="MV">Template:Cite web</ref>
Canada
Automobile bumper standards in Canada were first enacted simultaneously as those in the United States. These were closely similar to the Template:Convert U.S. regulation, and the Canadian requirements were not lowered to Template:Convert in 1982 as was done in the United States.<ref>Template:Cite web</ref>
Some automakers provided stronger Canadian-specification bumpers throughout the North American market, while others chose weaker bumpers in the U.S. market. This limited grey import vehicles between the U.S. and Canada.<ref>Template:Cite web</ref>
In early 2009, Canada's regulation shifted to harmonize with U.S. Federal standards and international UN Regulations.<ref>Template:Cite web</ref> As in the U.S., consumer protection groups opposed the change, while Canadian regulators maintained that the Template:Convert test speed is used worldwide and is more compatible with improved pedestrian protection in vehicle-pedestrian crashes.<ref>Template:Cite web</ref>
See also
- Automobile safety
- Buffer (rail transport)
- Bumper sticker
- Cost–benefit analysis
- Crashworthiness
- Government failure
- Headstock
- List of auto parts