|
| |
Understanding Car Bumpers
1) What is a bumper?
A bumper is a shield made of steel, aluminum, rubber, or plastic that is
mounted on the front and rear of a passenger car. When a low speed collision
occurs, the bumper system absorbs the shock to prevent or reduce damage to the
car. Some bumpers use energy absorbers or brackets and others are made with a
foam cushioning material.
2) What is the purpose of bumpers?
The car bumper is designed to prevent or reduce physical damage to the front
and rear ends of passenger motor vehicles in low-speed collisions. Automobile
bumpers are not typically designed to be structural components that would
significantly contribute to vehicle crashworthiness or occupant protection
during front or rear collisions. It is not a safety feature intended to
prevent or mitigate injury severity to occupants in the passenger cars.
Bumpers are designed to protect the hood, trunk, grille, fuel, exhaust and
cooling system as well as safety related equipment such as parking lights,
headlamps and taillights in low speed collisions.
3) What are the Federal regulations for bumpers?
49 CFR Part 581, "The bumper standard," prescribes performance requirements
for passenger cars in low-speed front and rear collisions. It
applies to front and rear bumpers on passenger cars to prevent the damage to the
car body and safety related equipment at barrier impact speeds of 2½ mph across
the full width and 1½ mph on the corners.
This is equivalent to a 5 mph crash into a parked vehicle of the same
weight. The standard requires protection in the region 16 to 20 inches above the
road surface, and the manufacturer can provide the protection by any means it
wants. For example, some vehicles do not have a solid bumper across the vehicle,
but meet the standard by strategically placed bumper guards and corner guards.
4) Are all vehicle classes required to meet the Federal bumper
standard?
No. The Federal bumper standard does not apply to vehicles other than
passenger cars (i.e., sport utility vehicles (SUVs), minivans, or pickups
trucks). The agency has chosen not to regulate bumper performance or elevation
for these vehicle classes because of the potential compromise to the vehicle
utility in operating on loading ramps and off road situations.
5) When did the bumper standard first come into effect and how
has it changed over the years?
On April 9, 1971, the agency issued its first passenger car bumper standard
-- Federal Motor Vehicle Safety Standard (FMVSS) 215, "Exterior Protection,"
which became effective on September 1, 1972. This standard called for passenger
cars, beginning with model year (MY) 1973, to withstand 5 mph front and 2 ½ mph
rear impacts against a perpendicular barrier without damage to certain
safety-related components such as headlamps and fuel systems.
In October 1972, Congress enacted the Motor Vehicle Information and Cost
Saving Act (MVICS Act) which mandated that the agency issue a bumper standard
that yields the maximum feasible reduction of costs to the public, taking into
account the cost and benefits of implementation, the standard's effect on
insurance costs and legal fees, savings in consumer time and inconvenience, and
health and safety considerations.
The new requirements under the MVICS Act were then consolidated with
existing requirements in FMVSS 215 and promulgated in March 1976 as a new bumper
standard, which was added to NHTSA's regulations at 49 CFR Part 581. The new
standard which applied to passenger cars beginning with MY 1979, was referred to
as the Phase I Standard. At the same time, a "no damage" requirement (Phase II)
was placed on bumper systems for model year 1980 and subsequent years. (See
question 6 for more information on Phase I and II requirements.)
The most recent revisions to the bumper standard took place in May 14, 1982,
effective for MY 1983 and subsequent model year passenger cars. This amendment
reduced test impact speeds from 5 mph to 2.5 mph for longitudinal front and rear
barrier and pendulum impacts and from 3 mph to 1.5 mph for corner pendulum
impacts. In addition, Phase I damage resistance criteria were substituted for
Phase II criteria and a bumper height requirements of 16 to 20 inches was
established for passenger cars.
6) What do Phase I and Phase II mean? How do they differ and how
much damage does the standard allow?
Phase I and II refer to a two-phased rulemaking action on bumper
requirements. Phase I of the standard became effective on September 1, 1978 for
passenger cars beginning with MY 1979. It incorporated the FMVSS 215 safety
criteria, and added new performance criteria which prohibited damage to all
exterior vehicle surfaces. For MY 1979, the standard required that there be no
damage to safety-related parts and exterior surfaces not involving the bumper
system(e.g., sheet metal; lamps; and fuel, exhaust and cooling systems) with
damage to the facebar and its fasteners at impact test speed of 5 mph front and
rear impacts with barrier and pendulum; 3 mph corner impact with pendulum.
More stringent damage resistance criteria known as Phase II became effective
one year later, on September 1 1979, for MYs 1980 to 1982, and consisted of 5
mph longitudinal front and rear impacts with barrier and pendulum; 3 mph corner
impact pendulum, all with no damage to the bumper itself beyond a 3/8 inch dent
and 3/4 inch set or displacement from original position.
7) Has NHTSA conducted evaluations of the bumper standard? If
so, what were the results?
Yes. NHTSA conducted an evaluation of the bumper standard in 1981. The
evaluation determined the net benefits (the change in costs) to the consumer
attributable to each successive standard (applicable through MY 1980) in
relation to unregulated bumper systems in MY 1972 and prior years. The
evaluation findings were that bumper systems complying with the standard
requirements for model years 1979 and 1980 (most, if not all, bumpers were built
to the 1980 "no damage" standard in 1979) tended to show net consumer losses -
based on a 10-year car life - when compared to unregulated bumper systems. The
costs of the 1979/1980 systems were between $150 and $200 higher than the
unregulated bumpers (1972 and earlier model years).
In 1987, the agency conducted another evaluation of the bumper standard. The
evaluation concluded that: (1) the costs to consumers did not change as a result
of the modification of the bumper standard from 5 to 2.5 mph; (2) the net
effect, over a car's 10 year life, is a small increase in repair costs, which is
offset by a reduction in the cost of the bumpers; and (3) the change in the
bumper standard did not compromise the protection of safety-related parts.
8) Why did NHTSA lower the bumper standard requirements from 5
mph to 2½ mph?
The agency concluded that reducing the impact speed from 5 mph to 2½ front
and rear impact speed best satisfied the statutory criteria that the bumper
standard "seek to obtain maximum feasible reduction in costs to the public and
to the consumer." The agency also concluded that reducing the impact speed to 2½
mph and eliminating the Phase II damage criteria would not have an adverse
effect on safety as measured by the number of crashes, deaths or injuries that
occur annually.
The agency set the protection standard at 2½ mph after studying the
comparable repair costs of a 5 mph bumper that has higher energy absorption
capacity along with additional cost and weight.
After public hearings involving all parties, including consumers and
manufacturers, NHTSA concluded that the public is assured of the largest net
benefits under a standard that requires 2½ mph protection for both the front and
rear bumpers.
9) How does the U.S. the bumper standard compare to the Canadian
and European standards?
Under the Canadian bumper standard, the vehicle is impacted into a
fixed-collision barrier that is perpendicular to its line of travel while the
vehicle is traveling longitudinally forward at 8 km/h (5 mph)
and longitudinally backward at 8 km/h (5 mph), with its engine
operating at idle speed. Every vehicle is impacted twice on the front and rear
surfaces and once on each front and rear corner with the impact line at any
height between 500mm (20 inches) and 400mm (16
inches). While the impact speed in the Canadian standard is higher than
that in the U.S. standard, the Canadian standard has less stringent protective
criteria. Specifically, the protective criteria for the Canadian standard
requires that the vehicle does not touch the test device, except on the impact
ridge with a force that exceeds 2000 lbs. on the combined surface of the test
device.
The United Nations Economic Commission for Europe (ECE) regulation No. 42
requires that a car's safety systems continue to operate normally after the car
has been impacted by a pendulum or moving barrier on the front or rear
longitudinally at 4 kilometers per hour (about 2.5 mph) and on
the front and rear corner at 2.5 kilometers per hour (about 1.5
mph) at 455 mm (about 18 inches) above the ground under loaded and
unloaded conditions.
10) How do I know if my vehicle meets or exceeds the Federal
bumper standard?
Manufacturers self-certify their products in order to meet the bumper
standard, as well as all applicable Federal motor vehicle safety standards.
Since this is a minimum performance standard, the manufacturer may be providing
a greater level of protection. The agency does not require manufacturers to
report the actual performance capabilities of their bumper systems.
Although many manufacturers voluntarily include bumper performance
information on the window stickers of new passenger cars sold in United States,
only California and Hawaii have bumper performance disclosure laws that require
manufacturers to be specific about its performance capabilities.
11) Is there a way to determine how fast a car was going during
a rear end crash based on the damaged bumper(s)?
No. We do not collect any data that would be useful in determining the
impact speed. Many parameters such as vehicle masses, the pre-impact velocity of
both vehicles, impact angles, crush resistance, metallurgical fatigue, etc.,
affect how the bumpers behave during an impact. Each crash must be analyzed with
respect to all of the parameters before an estimate can be made.
12) Does NHTSA conduct any low-speed crash tests of bumpers and
rate their relative performance?
NHTSA does not conduct low-speed impact crash tests of bumpers to rate their
comparative performance due to the costs associated with this type of program.
However, the Insurance Institute for Highway Safety (IIHS) conducts yearly tests
on a number of models for bumper ratings (in terms of strength and repair cost).
Information can be obtained through their web site at: http://www.hwysafety.org or
at (703) 247-1500.
The agency's New Car Assessment Program (NCAP) conducts yearly crash tests
to provide consumers with information about levels of protection when the
vehicles are tested in a frontal barrier crash and when struck in the side by a
moving barrier device. The 'star' ratings that reflect performance on these
tests would better assist a consumer seeking to select a safe vehicle. These
ratings can be obtained through our web site at: http://www.nhtsa.dot.gov
13) Why are bumpers on light trucks or SUVs higher than the
those on passenger cars?
Bumpers are typically higher on light trucks, pick-ups or SUVs than on
passenger cars to provide better clearance for approach and departure of steep
grades or when driving over large rocks and other objects during off road
operations.
14) Does the Federal government specify uniform bumper heights
for vehicles to prevent damage in low-speed collisions?
No, NHTSA regulates the height and impact capabilities of bumpers only of
passenger cars, but not for light trucks, minivans or SUVs. However, some states
and localities have requirements that limit bumper height for other vehicle
types. We suggest individuals contact their local or state agency responsible
for motor vehicle regulations.
15) What is NHTSA doing to address bumper mismatch issue between
passenger cars and SUVs?
The agency is aware that there is a mismatch between the bumpers of
passenger cars and those of some light trucks and vans (LTVs). However, bumper
elevation is not solely responsible for mismatched contact in vehicle
collisions. The effect of braking and interaction of suspension dynamics and
vehicle weight can also be attributed to the mismatch. This issue is being
addressed as a part of the agency's consideration of the broader issue of
vehicle compatibility. Compatibility involves differences in vehicle
characteristics between passenger cars and LTVs such as weight, height off the
ground, geometry and stiffness. To address this issue, the agency is developing
advanced simulation models of vehicles that could be used as tools to understand
crash behavior and interactions between incompatible vehicles and to assess
safety implications of these vehicles fleet wide. This research could lead to
the development of suitable countermeasures for occupant protection in crashes
of incompatible vehicles by transferring loads through structural members which
interact better in crashes and through energy management while maintaining
occupant compartment integrity. Based on the results of the agency's research,
rulemaking actions related to the bumper and/or other Federal standards may be
undertaken to address the vehicle compatibility issue.
| |
|
