Interpretation ID: nht73-5.15

DATE: 05/18/73

FROM: AUTHOR UNAVAILABLE; James E. Wilson; NHTSA

TO: Hon. M. J. Rinaldo - H.O.R.

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of April 30, 1973, concerning the requirement of Motor Vehicle Safety Standard No. 121, Air brake systems, that air-braked vehicles be capable of stopping in a specified distance without locking their wheels.

Standard No. 121 was originally proposed in notices of proposed rulemaking published June 25 and 26, 1970. A public meeting was held on October 20, 1970, at which representatives from all interested members of industry and government reviewed the proposal. The standard was issued as a final rule on February 27, 1971, with an effective date of September 1, 1974. Following issuance of the rule, a number of petitions for administrative reconsideration were received, and after lengthy consideration of these petitions the agency responded by amending the standard in a notice published February 24, 1972. This amendment also prompted petitions for reconsideration, which were answered by further amendments on June 24, 1972. The standard has not been further amended since that time.

The antilock requirement to which you refer was a feature of the initial proposal and has remained, with minor adjustments, in all succeeding versions of the standard. it is the third of three performance criteria that a truck or bus must meet in a stop under actual road conditions. The first requirement is that the vehicle must be capable of stopping in specified distances from 60 mph and 20 mph on high and low friction surfaces. The second requirement is that the

2 stops must be made without leaving a straight 12-foot wide lane. The third is that the vehicle must stop without lockup of any wheel at speeds over 10 mph, except for lockup of a wheel controlled by an antilock system.

The aim of each of these requirements is reasonably clear. The stopping distances specified represent a significant improvement in the stopping capability of most air-braked vehicles. The stay-in-the-lane requirement is an important measure of brake balance. The antilock requirement is intended to upgrade the maneuverability of air-braked vehicles in nonlinear braking situations, where locked wheels would result in a partial or complete loss of directional control.

It should be noted that the standard does not require an "antilock system". It requires that a vehicle be capable of stopping without lockup, but it does not require a specific system to accomplish this result. As a practical matter, most manufacturers appear to have chosen antilock systems as the means of meeting the standard, although consideration has been given to other systems such as proportional braking systems in some vehicle applications.

A good deal of attention was focused on the antilock requirements during the rule making process. The agency's conclusion was that, if controlled braking was to remain as a goal of the standard, there was no satisfactory means to achieve this goal except by preventing the wheels from locking. Having chosen to require antilock braking, the agency cannot amend the requirement except through a full rulemaking procedure. If presented with a petition for rulemaking that appeared to have merit, the agency would propose the amendment by issuing a notice in the Federal Register. It would then allow time for public comment before deciding whether to adopt the proposed amendment. At this time we have no petitions under consideration on the subject of antilock braking.

In the rulemaking process followed to develop Standard No. 121, as well as in any rule making to amend it, the other Federal agencies are invited to participate on the same basis as other interested persons. We do not

3 routinely follow special procedures with other Federal agencies, except for the Bureau of Motor Carrier Safety, whose regulations interact closely with ours. As a matter of record, no Federal agency other than BMCS submitted comments during the rule making on Standard No. 121.

The(Illegible Word) has limited research funds and has, partly for that reason, conducted very few tests of specific product designs. The agency is directed under the terms of its legislative authority to issue performance standards, rather than design standards, and such testing as it has done relates to the feasibility of achieving a certain level of performance rather than to the characteristics of a particular product. The agency's staff has reviewed the results of testing done by manufacturers that bears on Standard No. 121, but has not conducted tests itself.

The cost of a typical antilock system is difficult to determine accurately. For competitive reasons, cost data is closely held by the manufacturers, particularly in the period before the systems are actually in production. We have estimated that some systems will be selling in the range of 100 dollars per axle, but there are a great many variables to be considered and we do not know if that figure will prove to be representative of actual prices.

ENCS.

April 30, 1973

James E. Wilson Acting Administrator National Highway Traffic Safety Administration

I would greatly appreciate your cooperation in furnishing me with background information concerning Federal Motor Vehicle Safety Standard No. 121 which, as I understand it, requires the installation of a computerized anti-wheel lock device on trucks and tractor-trailers. Specifically, I would appreciate the following information:

1. A brief statement of the requirements of the standard.

2. The dates on which the standard was adopted and becomes effective.

3. What, if any, alternative devices were studied to accomplish the same objectives prior to the adoption of the standard?

4. What administrative procedures were followed in the consideration and adoption of the standard?

5. What procedures would be required in the event of an amendment or addition to the standard prior to its effective date?

6. Are any such amendments or additions to the standard presently under active consideration?

7. What is the estimated cost per unit of equipping trucks and tractor-trailers with the computerized

2 anti-wheel lock device?

8. To what extent were the needs and experience of other Federal agencies which utilize or operate trucks and tractor-trailers considered in the course of adopting the standard?

9. In adopting standards of this kind, are such Federal agencies regularly consulted?

10. In cases where proposed standards may involve a requirement for the installation of a specific safety device, are such devices and alternative designs ordinarily tested by NHTSA?

11. Under what conditions would NHTSA consider it necessary or useful to conduct tests on newly developed safety devices?

Thank you very much for providing me with this information.

Matthew J. Rinaldo Member of Congress