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Proposed Rule

Federal Motor Vehicle Safety Standards; Occupant Crash Protection, Seat Belt Assemblies

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National Highway Traffic Safety Administration (NHTSA), Department of Transportation.


Termination of rulemaking; denial of petition for rulemaking.


In April 2000, NHTSA received a petition for rulemaking requesting that the agency amend its safety standards to require that vehicle manufacturers either offer consumers the option of longer seat belts on new vehicles or make seat belt extenders available for purchase. The purpose of the petition was to accommodate individuals who, because of their size, cannot use the seat belts in the vehicle of their choice. The agency granted the petition on February 28, 2001 and began to gather data on the availability of longer belts and to estimate the underserved population. In August 2002, the agency received a second petition for rulemaking requesting the same amendments.

Based on its analysis of available data, NHTSA is terminating rulemaking on the April 2000 petition, and is denying the August 2002 petition for rulemaking.

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For non-legal issues, you may contact Sanjay Patel, Office of Crashworthiness Standards. Telephone: (202) 366-4583, Facsimile: (202) 366-4329.

For legal issues, you may contact Otto Matheke, Office of the Chief Counsel. Telephone: (202) 366-5263, Facsimile: (202) 366-3820.

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I. Background

On April 18, 2000, Ms. Elizabeth Fisher petitioned the agency to amend Federal Motor Vehicle Standard (FMVSS) No. 209, Seat belt assemblies, to require vehicle manufacturers to provide seat belts that fit all passengers (Docket No. NHTSA-2000-7580-01). Ms. Fisher's petition stated that the existing provisions of FMVSS No. 209 only require belts to fit adult males weighing up to 97.5 kg (215 lbs.) and requested that NHTSA initiate a rulemaking action to require vehicle manufacturers to provide a means for any passenger who fits inside the vehicle to be able to fasten the seat belt. The petition suggested that this could be accomplished either by requiring manufacturers to make longer seat belts available as a vehicle option or by requiring that all vehicle manufacturers make seat belt extenders available to those who wish to purchase them.

FMVSS No. 208, Occupant crash protection, and FMVSS No. 209 require that seat belt assemblies shall be capable of adjustment to fit occupants up to the size of the 95th percentile male, as defined by these standards. These standards define the mass of the 95th percentile male as 97.5 kg (215 lbs.). However, Ms. Fisher, using Body Mass Index (BMI) data from the Third National Health and Nutrition Examination Survey (NHANES III) of the National Center for Health Statistics, argued that more than 22 percent of the U.S. adult population is larger than a Start Printed Page 2481person who is 1.83 meter (6 ft) tall and weighs 97.5 kg (215 lbs.).[1] She believes that belts that just meet the requirements of FMVSS No. 209 would not accommodate these larger Americans.

The agency granted the petition on February 28, 2001, and began to gather data on the availability of longer belts and on the size of the population who cannot currently buckle up. The result of this effort is contained in a NHTSA Technical Report [2] that is available in the Docket for this notice. Another research report upon which we relied in making the decision to terminate rulemaking is “FMVSS 208 Belt Fit Evaluation, Possible Modification to Accommodate Larger People,” Vehicle Research and Test Center (VRTC), 1988. It is also available in the Docket for this notice.

On August 19, 2002, the agency received a second petition for rulemaking on this issue from Mr. Jay Levy. Mr. Levy petitioned for the same amendments to FMVSS No. 209 as those cited in Ms. Fisher's petition. Mr. Levy's petition duplicated the exact arguments stated in Ms. Fisher's petition and did not provide any new information.

II. Reasons for Termination

Both Ms. Fisher's and Mr. Levy's petitions contend that if a person can physically “fit” in a vehicle, the person should also be able to fasten his or her seat belt. However, in establishing minimum performance requirements for seat belts, including the size of these belts, the agency cannot base the applicability of those requirements on such an imprecise guideline. It would be difficult for the agency or vehicle manufacturers to determine what size person can “fit” in each particular vehicle. It would also be difficult, near the outer limits of known dimensions for the vehicle using population, to determine how much longer seat belts would have to be. In order for the agency to develop an objective and reasonable regulation, we would have to know or estimate the dimensions of the largest vehicle users. Therefore, the agency went about determining what would be required to formulate requirements to serve the population that the petitioner believes is not currently served.

In determining the required seat belt length for a particular size person, the most critical measurement is seated hip circumference. The seated hip circumference of an occupant determines the length the belt must travel to come across the occupant to the latch. The seated hip circumference of the 95th percentile adult male referred to in FMVSS No. 209 is 1199 mm (47 in.). The estimated seated hip circumference of the 99th percentile adult person (including male and female) in the U.S. population is 1509 mm (59 in.).[3]

From this seated hip circumference, the agency estimated, using geometric approximation, the additional belt length needed to go around the hips of occupants larger than the 95th percentile male. We determined that a person with the 99th percentile hip circumference from the NHANES III data would need 254 mm (10.0 in.) additional belt length above that needed for a FMVSS No. 209 95th percentile male. Adding an assumption that the 99th percentile person would be wearing bulky winter clothing (which the standard does not require), the agency concluded that the additional belt length needed increases to 348 mm (13.7 in.).

Next, we estimated how many people cannot use their seat belts because the belts are too short to buckle. This involved examining three elements: (1) How many people have a hip circumference larger than the 95th percentile male, but not larger than that of the 99th percentile person from NHANES III, (2) how many vehicle make/models have standard belts that will not accommodate a person larger than the NHANES III 99th percentile male, and (3) how many of these vehicles do not have seat belt extenders or longer belts available.

We estimated from the NHANES III data that the total U.S. population older than 13 years with a hip circumference between that of the 95th percentile male and that of the NHANES III 99th percentile person is 38,191,527 persons or 19 percent. The agency also estimated that 1,980,744 persons, or 1 percent of the population 13 years and older, are larger than the NHANES III 99th percentile person.

Having determined the numbers of people likely to need additional belt length if all belts were no longer than the minimum length required by our standards, the agency then considered the question of how these larger people are currently being accommodated by vehicles now on the market. For many reasons, manufacturers provide additional belt length beyond the minimum required by NHTSA. In response to our inquiry, General Motors, Ford, DaimlerChrysler, and Honda provided extra belt length information about their respective model year 2003 vehicle make/models. The information provided by these four manufacturers covers 136 vehicle models.[4] These manufacturers each provide an average of 18 to 20 inches of extra belt length for the driver and right front passenger positions in their respective model year 2003 vehicles. This extra belt length is more than enough to accommodate our estimate of what is needed for a 99th percentile person, including any additional length to go around the torso of the person. A detailed summary of the additional belt length information by specific make/model from these manufacturers, and all others we contacted, is provided in the Docket for this notice. Based on the available data, it appears that most vehicles can fit all but the largest users with the original belts.

To determine the availability of extra measures beyond standard belts, NHTSA contacted major vehicle manufacturers, to determine if they provide seat belt extenders, optional longer seat belts, or have other means for accommodating large users. A summary of this information is provided in Table 1. From this information, NHTSA calculated that 87.5 percent of vehicle make/models available today offer consumers either seat belt extenders or longer belts as an option. The remaining 12.5 percent do not offer longer belts or extenders but may already offer belts longer than the minimum length required by FMVSS No. 209.Start Printed Page 2482

Table 1.—Availability of Seat Belt Extender or Longer Belts

CompanyExtender availableLength of extender (in)Linkable? (2 or more)Optional longer seat belts?Vehicle sales* (2000)
Honda, AcuraNoNo1,158,860
Volkswagen, AudiNoNo435,851
Land RoverNoYes27,148
Mercedes BenzNoYes, case-by-case205,614
ChryslerYes6, 8Yes2,522,695
MazdaYes8, 9, 12255,526
Toyota, LexusYes6, 9, 12, 15, 181,619,206
GMYes9, 15NoCadillac Catera, 12″ only4,883,040
Nissan, InfinityYes8YesNo752,088
IsuzuYes6, 9, 12, 15, 18YesNo98,066
SuzukiYes9, 15YesNo60,845
Subtotal of vehicles with oversize provisions15,100,873
* The vehicle manufacturers identified the models for which they offer belt extenders or extra webbing. The vehicle sales data from Automotive News were used to quantify the number of vehicles in the fleet.

Given that many vehicles have belts long enough to fit almost all users and that optional longer belts or seat belt extenders are available for 87.5 percent of the fleet, the agency believes that a requirement to increase the belt length in all vehicles is unnecessary. NHTSA's analysis indicates that for almost all of these large individuals, there are few practical obstacles to obtaining that benefit, although they may find it more difficult to do so in some vehicles when compared to others.

Another factor in our decision is a concern that requiring manufacturers to provide either longer belts or belt extenders may have negative safety consequences. In the case of longer belts, the previously mentioned 1988 VRTC report described sled tests conducted with up to 254 mm (10 in.) of extra webbing in the restraint system. All tests were run at a 48 km/h (30 mph) change in velocity using a 50th percentile Hybrid III dummy in the front passenger seating position of a 1982 Chevrolet Celebrity. The amount of belt webbing spool-out increased from 41 mm to 76 mm (1.6 to 3.0 in.) with the increased belt length. Peak head, chest, and pelvic accelerations showed very little change with increased belt length. However, Head Injury Criterion did show an increase of about 12 percent. The greatest change appeared to be an increase of 17 percent in the neck flexion moment. The results of the sled tests also indicated an increase in dummy excursion relative to the vehicle with increasing belt length. The maximum resultant excursion of the head varied from the baseline by 76 mm (3 in.). A linear regression through the data showed a 26 mm (1.02 in.) increase in resultant head excursion for each additional 100 mm (3.98 in.) of belt length. Thus, an addition of 254 mm (10 in.) in belt length translates to 65 mm (2.6 in.) greater head excursion than the baseline.

The results of the VRTC study were obtained from the front passenger seat of a single vehicle without an air bag or seat belt pretensioner. Since belt webbing properties have not changed substantively since the 1980s, these estimates would appear to be reasonable for current belt systems with added webbing on the retractor. Seat belt pretensioners may prevent extra belt spool-out associated with longer belts. However, where pretensioners are not used, increased excursion values due to longer belts may significantly increase the risk of injury due to contact with the vehicle interior.

Belts may also be made longer by the use of belt extenders. Belt extenders, which would only be used by persons needing additional webbing length, would avoid some of the risks of increased spool-out and excursion associated with longer belts. However, as described in the NHTSA Technical Report, proper fit is necessary when using belt extenders. If the location of the extender places the buckle a distance of no more than 152 mm (6 in.) from the occupant's vertical center-line, the shoulder belt will not provide proper torso restraint and may pull the lap belt up onto the abdomen during a frontal impact, possibly leading to greater excursion and/or internal injury. The risks of belt extenders would be accentuated where the extender is not properly sized for the user or where a person of more average size inadvertently used a belt with an extender attached.

III. Options for Larger Persons

NHTSA's decision to terminate this rulemaking does not foreclose opportunities for larger persons to use seat belts that fit. Both vehicles and vehicle occupants are found in a variety of shapes and sizes. A given vehicle may not be able to accommodate all persons. For reasons other than girth, a vehicle may be unsuitable for some users. For example, very tall persons Start Printed Page 2483may need a vehicle with a high roof to afford sufficient visibility and comfort. Particularly short statured persons may need to avoid purchasing vehicles whose design places them in close proximity to the driver's air bag.

Vehicle buyers should take care to be sure that the vehicle they choose is suitable for their needs, including having belts that fit. If the original belts in a vehicle do not fit, it may be possible to obtain longer belts or belt extenders from the vehicle manufacturer. Vehicles with optional longer belts are available as listed in Table 1. Although dealers may not always be aware that longer optional belts or belt extenders are available, vehicle purchasers can and should insist that dealers check with the manufacturer. If available, the purchaser should make their inclusion in the vehicle a condition of the sale.

In those instances in which longer belts or belt extenders are needed and are not available from the vehicle manufacturer, there are means available for modifying the vehicle to accommodate the physical needs of a particular buyer. One option is to purchase belt extenders from an aftermarket supplier or to have belt extenders made. Also, some businesses that modify vehicles to accommodate people with disabilities will modify seat belts.

Another alternative is to have more extensive modifications made on the vehicle itself.[5] Seat positioning can also influence the seat belt fit. For vehicles with at least one end of the belt anchored to the vehicle and not to the seat, an additional 51 mm (2 in.) to 76 mm (3 in.) in belt length is gained for every 25 mm (inch) of rearward seat movement. If a seat position is found that allows the seat belt to fit, but causes the pedals to be out of reach, adjustable pedals may be available as optional equipment. Alternatively, pedal extenders can be obtained.

The agency believes that additional regulatory requirements are not needed to enable larger size persons to find a vehicle that will accommodate their needs and allow them to buckle up. Publication of information on the availability of longer belts as standard equipment [6] and longer belts or belt extenders as options, should allow larger persons to choose models from vehicle manufacturers who are responsive to their needs. Finally, if an individual cannot find a vehicle fitting their needs with a belt that fits, or an available OEM belt extender, a vehicle modifier may be able to fashion a suitable belt extender, produce and install a longer belt, or move the original seat to provide additional belt length.

IV. Conclusion

In accordance with 49 CFR part 552, this completes the agency's review of the petitions for rulemaking. In view of the considerations discussed above, the agency has concluded that there is no reasonable possibility that the amendments requested by the petitioners would be issued at the conclusion of the rulemaking proceeding. Accordingly, rulemaking on the petition from Ms. Fisher is terminated, and the petition for rulemaking submitted by Mr. Levy is denied.

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Authority: 49 U.S.C. 30103, 30162; delegation of authority at 49 CFR 1.50 and 501.8.

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Issued on: January 13, 2003.

Stephen R. Kratzke,

Associate Administrator for Rulemaking.

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1.  As discussed below, NHTSA does not agree that BMI is the appropriate measure for determining dimensions for seat belt fit.

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2.  “Accommodation of Larger Occupants in Current Seat Belt Assemblies,” NHTSA Technical Report, July 2002.

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3.  This dimension is estimated from the standing hip circumference measured in the NHANES III using a calculation described in the NHTSA Technical Report.

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4.  NHTSA does not routinely collect information from manufacturers on belt length beyond what is required for the 95th percentile male, but beginning with model year 2003, the agency does collect information for consumers on whether or not longer belts are available with vehicle make/models in our “Buying a Safer Car” program. NHTSA intends to make this information available on our Web site at​cars/​testing/​ncap/​ by selecting the vehicle of interest and clicking on “safety features.”

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5.  Vehicles are often modified for people with disabilities. NHTSA is not suggesting that large individuals are disabled. However, modifiers are experienced at fitting vehicles to the unique physical characteristics of certain users. The process is described in Adapting Motor Vehicles for People with Disabilities, DOT HS 809 014, and also available at​cars/​rules/​adaptive/​brochure/​index.html.

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6.  NHTSA currently provide information about the availability of seat belt extenders on our Web site at​cars/​testing/​ncap/​.

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[FR Doc. 03-1134 Filed 1-16-03; 8:45 am]