Bumper (automobile)

Chromed plated front bumper on a 1958 Ford Taunus

Detail of a rear bumper with integrated tail lamps and a rubber faced bumper guard

In automobiles, a bumper is usually a metal bar or beam, attached the vehicle's front-most and rear-most ends, designed to absorb impact in a collision. Regulations for automobile bumpers have been implemented to allow the car to sustain a low-speed impact without damage to the vehicle's safety systems.

Description

The main function of a bumper is to protect the car's body in a slight collision, typically at parking speed.^[1] The bumper structure on modern automobiles generally consists of a plastic cover over a reinforcement bar made of steel, aluminum, fiberglass composite, or plastic.^[2]

In most jurisdictions, bumpers are legally required on all vehicles. The height and placement of bumpers may be legally specified as well, to ensure that when vehicles of different heights are in an accident, the smaller vehicle will not slide under the larger vehicle. Although a vehicle's bumper systems should be designed to absorb the energy of low-speed collisions and help protect the car's safety and other expensive components located nearby, most bumpers are designed to meet only the minimum regulatory standards.^[3]

Bumpers are not capable of reducing injury to vehicle occupants in high-speed impacts, but are increasingly being designed to mitigate injury to pedestrians struck by cars, such as through the use of bumper covers made of flexible materials.

Height mismatches

Even when bumpers cannot protect against moderate or high speed collisions, their height from the roadway surface is important in engaging other protective systems such as energy-absorbing crush zones and airbags. Major height mismatches can cause highly lethal underride collisions, in which a smaller vehicle, such as a passenger sedan, slides under a larger vehicle, such as a tractor-trailer. The platform bed of a typical tractor trailer is at the head height of seated adults in a typical passenger car, and can cause severe head trauma in even a moderate speed collision. In addition, modest mismatches between SUV bumper heights and passenger car side door protection have allowed serious injuries at relatively low speeds.^[4]

North America

United States

First standards

Front and rear bumpers on Chrysler A platform cars before (left, 1971) and after (right, 1974) the US 5-mph bumper standard took effect. The 1974 bumpers are larger, heavier, and mounted farther away from the body, and they no longer contain the taillamps.

Freestanding 5-mph shock-absorbing zero-damage bumper, AMC Matador coupe

In 1971, the US 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. 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 5 miles per hour (8 km/h) for front and 2.5 mph (4 km/h) for rear bumper systems.^[5] The requirements effectively eliminated automobile bumpers designs that featured integral automotive lighting components such as tail lamps.

In October 1972, the US 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".^[6] 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.

The 1973 model year passenger cars sold in the US used a variety designs. They ranged from non-dynamic versions with solid rubber guards, to "recoverable" designs with oil and nitrogen filled telescoping shock-absorbers.^[7]

The standards were further increased for the 1974 model year passenger cars with standardized height front and rear bumpers that could take angle impacts at 5-mile-per-hour (8 km/h) with no damage to the car's lights, safety equipment, and engine. This often meant additional overall vehicle length, as well as new front and rear designs to incorporate the stronger energy absorbing bumpers.^[8] Passenger cars featured gap-concealing flexible filler panels between the bumpers and the car's bodywork causing them to have a "massive, blockish look."^[9] A notable exception that year was the new AMC Matador coupe that featured "free standing" bumpers with rubber gaiters alone to conceal the retractable shock absorbers.^[9]

Strengthening standards

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 49CFR581, 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; 5 miles per hour (8 km/h) front and rear barrier and pendulum crash tests were required, and no damage was allowed to the bumper beyond a ³⁄₈ in (10 mm) dent and ³⁄₄ in (19 mm) displacement from the bumper's original position.^[10]

All-wheel-drive "cross-over" cars such as the AMC Eagle were classified as multi-purpose vehicle or trucks, and thus exempt from the passenger car bumper standards.^[11]

Weakening standards

A BMW front bumper cover (highlighted in red)

Facing pressure from automakers, and operating under the Reagan administration's pledge to reduce regulatory burdens on industry, NHTSA most recently amended the bumper standard in May 1982, halving the front and rear crash test speeds for 1983 and newer car bumpers from 5 miles per hour (8 km/h) to 2.5 miles per hour (4 km/h), and the corner crash test speeds from 3 miles per hour (5 km/h) to 1.5 miles per hour (2 km/h). 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 requirements of 16 to 20 inches (41–51 cm) was established for passenger cars.^[10] At that time, NHTSA promised to conduct research and testing to provide consumers with accurate information on the quality of new car bumpers, but no such information has been provided.

Consumer and insurance groups have decried the weakened bumper standard, saying it has increased consumer costs without any attendant benefits except to automakers.^{[6][12][13][14]}

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.^[15]

The weakened regulations permitted automakers to design bumpers with emphasis on style and low cost; protection dropped substantially and repair costs rose. In 1990, IIHS conducted four crash tests on three different-year examples of the Plymouth Horizon. The results illustrated the effect of the changes to the US bumper regulations (repair costs quoted in 1990 United States dollars):^[15]

• 1983 Horizon with Phase-II 5-mph bumpers: $287
• 1983 Horizon with Phase-I 2.5-mph bumpers: $918
• 1990 Horizon: $1,476

Canada

Canada's bumper standard, first enacted at the same time as that of the United States, was generally similar to the US regulation. However, the Canadian standard was not weakened from 8 km/h (5 mph) to 4 km/h (2.5 mph) in accord with the weakened US standard of 1983. Some automakers chose to provide stronger Canadian-specification bumpers throughout the North American market, while others chose to provide weaker bumpers in the US market, which hampered private importation of vehicles from the US to Canada.

In early 2009, Canada's regulation shifted to harmonize with US Federal standards and international ECE regulations.^[16] Consumer groups are upset with the change,^[17] but Canadian regulators assert that the 4 km/h (2.5 mph) test speed is used worldwide and is more compatible with improved pedestrian protection in vehicle-pedestrian crashes.

Regulatory effect on design

Front bumpers on BMW E28 5-series (top), Audi 90 (middle), Lamborghini Countach (bottom): US (left) and rest-of-world (right). The US bumpers are more massive and protrude farther from the bodywork.

Cars were equipped with bulky, massive, heavy, protruding bumpers to comply with the bumper standards of the 1970s and early 1980s.^[18] By the late 1980s most bumpers were concealed by a painted thermoplastic fascia. The thermoplastic currently in use is a combination of polycarbonate and acrylonitrile butadiene styrene called PC/ABS. The internal aspect of the bumper usually consists of a lightweight foam or polyurethane. This foam does not contribute to the impact absorption factor of the bumper, but serves as a filler and prevents the thermoplastic fascia from cracking upon impact.

International standards

Under the international safety regulations originally developed as European standards and now adopted by most countries outside North America, a car's safety systems must still function normally after a straight-on pendulum or moving-barrier impact of 4 km/h (2.5 mph) to the front and the rear, and to the front and rear corners of 2.5 km/h (1.6 mph) at 45.5 cm (18 in) above the ground with the vehicle loaded or unloaded.^[19][20]

See also

• Automobile safety
• Bumper sticker
• Dashpot
• Headstock

References