An Evaluation of the Bumper Standard - As Modified in 1982

Warren G. La Heist and Frank G. Ephraim

An evaluation of the Bumper Standard was conducted to determine actual benefits and costs and cost effectiveness of changes made (in 49 C.F.R. Part 581) in 1982. These changes, effective with the 1983 model year, reduced required damage resistance for passenger car bumpers from 5 mph longitudinal front and rear barrier and pendulum impacts and 3 mph corner pendulum impacts to 2.5 and 1.5 respectively. The requirement that there be no damage to the bumper itself beyond a 3/8 inch "dent" and 3/4 inch "set" (or displacement) from original position was changed to allow damage to the bumper itself while still requiring no damage to safety-related parts and exterior surfaces not involving the bumper. The evaluation was conducted under requirements of Executive Orders 12291 and 12498.

The evaluation compares collision damage experience and bumper system costs of 1983/84 models (post-standard modification) to a two year baseline of 1981/82 models (pre-modification). Manufacturers were selective in implementing the now minimum requirements, with only 35 percent of the cars sold in the U.S. in 1983 being equipped with bumpers that were changed in a way which reduced collision damage resistance when compared to the predecessor 1981/82 models. By the 1984 model year, slightly over 50 percent of models sold were equipped with bumpers changed in comparison to 1981/82 models.

The principal conclusions are:

(1) The costs to consumers have not changed 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 cost, which is offset by a reduction in the cost of the bumpers.

(3) The change in the bumper standard has not affected the protection of safety-related parts.

On April 9, 1971, the National Highway Traffic Safety Administration (NHTSA) issued its first regulation on passenger car bumpers. Federal Motor Vehicle Safety Standard (FMVSS) 215, "Exterior Protection," was initially effective on September 1, 1972, and imposed requirements which prohibited damage to specified safety-related components such as headlamps and fuel systems in a series of perpendicular barrier impacts, at 5 mph for front and 2.5 mph for rear bumper systems.

Under subsequent legislation and regulations, performance requirements were changed several times. For the 1979 model year, the standard required that there be no damage to safety-related parts and exterior surfaces not involving the bumper system--a requirement known as Phase 1--at impact test speeds of 5 mph. The most stringent requirements were in effect for 1980 to 1982 models, and required 5 MPH longitudinal front and rear barrier and pendulum impacts, as well as no damage to the bumper itself beyond a 3/8 inch "dent" and 3/4 inch "set" or displacement from original position. These latter requirements which limited damage to the bumper are referred to as "Phase II." The last change in the bumper standard took place on May 14, 1982 when the requirements were modified, reducing the test impact speeds from 5 mph to 2.5 mph for longitudinal impacts and from 3 mph to 1.5 mph for corner pendulum impacts. The Phase II damage requirement was dropped and replaced with the previous Phase I requirement.

Drawing on the best available data and public comments, NHTSA completed a Final Regulatory Impact Analysis (FRIA) in support of the final rule amending the bumper standard to the 2.5 mph, Phase I requirement. The new requirement became effective on July 6, 1982, affecting 1983 and subsequent model year cars.

Executive Order 12291, dated February 17, 1981, requires Federal agencies to perform evaluations of their existing regulations, including those rules which result in an annual effect on the economy of $100 million or more. The objectives of an evaluation are to determine the actual benefits and costs of equipment, systems and devices installed in production vehicles in connection with a regulation -- and to assess cost effectiveness. Evaluation of standards is also consistent with, and part of, the Regulatory Program initiated under Executive Order 12498, dated January 4, 1985.

This evaluation compares the collision damage experience and bumper system costs of 1983 and 1984 models to a two year baseline consisting of 1981 and 1982 models which correspond to the period before the standard was modified. An important aspect of this comparison is the fact that manufacturers were selective in implementing the new minimum requirements of the regulation. In 1983, for example, only 35 percent of the cars sold in the United States were equipped with bumpers that, upon close scrutiny and analysis, were, changed in a way which reduced collision damage resistance -- in comparison to their 1981 and 1982 model predecessors.

In 1984, additional models were found to incorporate strength reducing changes, and other models, whose front bumpers had been reduced in 1983, now also were given reduced strength rear bumpers. By the 1984 model year slightly over 50 percent of the models sold were equipped with changed bumpers when compared to 1981 and 1982 models. Most of the changes were made to both the front and rear bumpers of a model.

It is important to define the term "changed," since the technique used for evaluating the effect of the bumper standard modification relies entirely on the difference between "changed" and "unchanged" bumper systems and comparing each of these populations to their 1981 and 1982 predecessors. Changed bumper designs are those make/model bumpers which in 1983 and/or 1984 were reduced in strength when compared to their 1981/1982 predecessors. Reduced strength was determined on the basis of a detailed examination of bumper designs and parts; it was not measured directly (i.e., by impact test). Unchanged bumper designs are the make/model bumpers which in 1983 and/or 1984 were essentially identical to their 1981/1982 predecessors. The cars with unchanged bumpers serve as the control group in the experimental design for the evaluation.

When referring to changes, alterations to general styling, aerodynamic flow shape and other "cosmetic" changes are excluded from the analyses and only the energy management components -- the major portion of a bumper system -- are considered. Consequently, the changes found in 1983 and 1984 bumpers were categorized into four mutually exclusive groups:

• Facebar thinning or downgauging

• Structural reductions or eliminations involving mounting brackets, reinforcements, end caps, etc.

• Energy absorber replacement with rigid brackets

• A combination of structural and energy absorber changes

The fifth category is composed of those bumpers which were left unchanged from their 1981 and 1982 predecessors that had to meet the 5 mph, Phase II standard. Overall, the population of cars with changed bumpers averaged a curb weight of 2,690 lbs. in contrast to 2,920 lbs. for cars with unchanged bumpers. There appears to have been a tendency to change bumpers on the smaller models -- subcompacts and compacts -- more often than on intermediates and standard sized passenger cars.

As has been the practice for evaluations of regulations, the analyses of weight, cost and component identification were supported by "teardown" methodology, a complete disassembly and analysis performed under contract, on an average of 60 make/models for each of the four (1981 through 1984) model years in the study. Each year this number represented at least 85 percent of domestic production and 55 percent of import sales, or approximately 80 percent of the combined fleets. These data form the primary basis for the cost side in the benefit-cost analysis.

Estimation of benefits is based on differences in both damage frequency and repair cost between changed and unchanged systems, in 1983 and 1984, relative to their respective 1981 and 1982 predecessors, in low-speed collisions.

To focus on low-speed, bumper-related collisions two data sets are needed. One is obtained from a national survey of incidents not reported to insurance companies. The other is derived from a sample of insurance claim files screened to exclude incidents involving injuries and cases where the vehicle had to be towed from the scene. These sources and procedures are essentially the same as those used in the bumper evaluation published in April 1981.

The primary conclusion of the evaluation is that after two years in which certain design changes were made to a growing population of bumpers -- in response to a modified bumper regulation -- the road experience in terms of low-speed bumper-related collisions for the cars with changed bumpers has remained the same as the experience with cars equipped with bumpers manufactured to the previous 5 mph standard.

The principal findings and conclusions of the evaluation are the following:

Bumper System Weights and Costs

• Combined front and rear bumper systems that were changed -- that is reduced in strength -- after the standard was modified, weighed less than their 1981 and 1982 model predecessors. The 1983 model bumpers weighed 72 lbs. compared to 85 lbs. for the 1981/82 models. In 1984, the average bumper that was changed, weighed 74 lbs.--a slight gain over 1983 models.

• Costs of bumpers decreased from $138 (1984 dollars) for the 1981/82 models to $114 for 1983 models. By 1984, bumper costs went back up to $125 because more energy-absorbing materials were added to certain bumper designs, and in some cases, aluminum was substituted for steel in facebars.

• In 1984 more than 50 percent of the new passenger car fleet was equipped with bumpers that incorporated a design change which reduced the strength of the bumper.

• The dominant design change was a reduction in the number of structural bumper parts such as reinforcements to facebars, brackets and end caps. In 1984, one quarter of the cars produced had bumpers with this change. They were 13 lbs. lighter and cost $21 less than their 1981/82 model predecessors.

• Another design change was the thinning of the main bumper strength member--the facebar. This was done on 14 percent of the 1984 passenger car fleet and resulted in a 6 lb. weight drop and a $7 cost reduction relative to 1981/1982 models.

• A combination of changes was made on 10 percent of the 1984 production fleet, including the replacement of hydraulic or similarly actuated plunger-type bumper energy absorbers with rigid brackets. Selected structural parts were also eliminated. The substitution of rigid brackets for hydraulic energy absorbers would normally result in a cost reduction and little or no change in weight, but due to the use of more costly high impact absorbing plastics instead of standard plastics for the fascia, prospective cost savings were offset to yield only a net reduction of $3. Weights of this group of bumper designs dropped by 7 lbs. due solely to the elimination of structural parts.

• In 2 percent of the 1984 production fleet, the only design change affecting energy management was the substitution of rigid brackets for hydraulic energy absorbers. This group also included the use of aluminum in place of steel for facebars or reinforcements. The added cost of this change in material offset most of the drop in costs for replacing the energy absorbers with brackets yielding a net reduction of $6. A substantial weight reduction of 18 lbs., relative to 1981/82 predecessor models, was due entirely to the material substitution.

Collision Damage Frequency

• The 1984 and combined 1983 and 1984 changed bumper models did not encounter a significantly different rate of damage frequency, compared to unchanged bumper models, in low-speed unreported collisions.

• Based on collisions for which an insurance claim was filed, there was an increase of 6 percentage points (from 59 to 65 percent) in the proportion of bumper-related damage claims for 1983/1984 changed bumper-equipped models. Most of the increase was attributable to claims for rear end damage. Beyond a fairly low impact speed, a bumper offers little or no protection. In frontal collisions, the bumper is less of a factor in preventing damage since these generally involve higher impact speeds than rear collisions. Therefore, increased damage is more likely when rear bumpers are built to a reduced standard.

Damage Repair Cost

• In unreported low-speed collisions, the average cost to repair damage is $450. There was no significant difference in damage repair cost between changed and unchanged 1983/1984 bumper models, relative to their 1981/1982 predecessors, when front and rear bumper systems are combined.

• Bumper-related damage that is severe enough for an insurance claim costs, on the average, $1,000 to repair. This average value is based upon reported incidents involving both changed and unchanged bumper systems for the whole range of 1981 through 1984 models. Repair costs of 1983/1984 changed models showed a statistically significant reduction of $62 when compared to their 1981/1982 predecessors.

Damage to Safety Other Parts

• In unreported low-speed collisions, there is no statistically significant difference in the damage frequency of safety-related and other bumper protected parts in models equipped with changed bumpers compared to models with unchanged bumpers.

• The insurance data revealed that parts such as lamps, radiators, trunks and fuel tanks showed no significant change in damage frequency in cars protected by changed bumper systems. Only hood latches incurred a higher rate of damage in cars protected by changed bumper systems. Past-studies have shown that hood latches rarely malfunction and when hoods fly open, they seldom cause collisions.

Override and Underride

• The bumper standard modification did not change bumper height requirements. The difference in bumper contact frequency of 1983/1984 changed bumper systems (86 percent) and their 1981/1982 predecessors (83 percent) is not statistically significant.

Benefits and Costs

• Collision damage repair costs dropped for both changed and unchanged 1983/84 models, relative to their 1981/82 predecessors. The unchanged model repair costs dropped more, but the $36 difference between these and the changed systems is not statistically significant. The Final Regulatory Impact Analysis (FRIA) prepared in 1982 projected a $76 increase (in 1984 dollars) in lifetime collision damage repair cost for bumpers designed to meet the 2.5 mph standard.

• The lifetime cost of the combined front and rear bumpers of changed systems relative to unchanged systems dropped by $44. The FRIA in 1982 projected a bumper system cost reduction of $91 (in 1984 dollars) for bumpers designed to meet the 2.5 mph standard.

• The net benefit of changed versus unchanged systems is $8 ($44 decrease in bumper cost minus the $36 increase in lifetime collision damage repair), over the life of a car, but this change is not statistically significant. There still were no significant differences in net benefits between changed and unchanged bumper systems even when benefits and costs were disaggregated by facebar, structural, energy absorber and a combination of structural and energy absorber changes. The 1982 FRIA projected a $15 net benefit.

Time and Inconvenience

• The driver survey of low-speed, unreported collisions yielded estimates of the average time spent in connection with incidents involving damage, as follows:

  At the scene: 35 minutes

  Filling out forms: 78 minutes

  Getting repair estimates: 4 hours

  Getting car repaired: 1.5 days

  Time without use of car: 2 days

  There was no difference in the amount of time expended per incident between cars with changed bumpers compared to cars with unchanged bumpers. However, on a lifetime basis, given the respective collision damage rates of changed and unchanged cars, there is a net increase in cost of $4 for cars equipped with changed (reduced strength) bumpers.

• The costs to consumers have not changed as a result of the modification of the bumper standard from 5 to 2.5 mph.

• The net effect, over a car's 10 year life, is a small increase in repair cost, which is offset by a reduction in the cost of the bumpers.

• The change in the bumper standard has not affected the protection of safety-related parts.