ID: nht74-2.36

DATE: 05/06/74

FROM: AUTHOR UNAVAILABLE; Richard B. Dyson; NHTSA

TO: Questor Juvenile Products Company

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your April 9, 1974, petition to substitute the proposed performance requirements for child harness testing under Standard No. 213, Child seating systems, for the performance requirements of Standard No. 209, Seat belt assemblies, to which Questor's Model 275 child harness is presently subject. As reasons for the substitution, you cite the inappropriateness of attachment hardware requirements (S4.3(c)) and the configuration of the test device (Figure 7) of Standard No. 209 as well as the desirability of testing to dynamic performance requirements which may become a part of Standard No. 213.

The Standard No. 213 dynamic test values which you recommend are only proposals at this time. Interested parties have not had a full opportunity to comment on them and the NHTSA has not, of course, had the opportunity to fully evaluate them. For these reasons your petition to substitute these new dynamic tests for the Standard No. 209 static tests is denied.

You state that testing of the Model 275 to the assembly performance requirements of Standard No. 209 (S4.4(c)) is complicated by the configuration of the test device for Type III harnesses, which is not suited to test a child harness such as the Questor No. 275 that utilizes the adult front lap belts and the rear adult lap belt or the package shelf as attachment points.

Paragraph S5.3(c)(2) of Standard No. 209 directs that in such a case "attachment shall be . . . in accordance with the [manufacturer's] installation instructions". As adherence to Model 275 installation instructions requires a front and rear adult belt installation (and in some cases a package shelf) the use of an actual vehicle bench seat in a passenger car would be an appropriate method to evaluate the assembly under S4.4(c) of Standard No. 209. Moreover, because the 12-inch extension requirement for an assembly tested under S4.4(c) is based on zero deflection of the test device, the actual vehicle seat should be modified to eliminate deflection.

The NHTSA has previously determined that the requirements of S4.3(c) of Standard No. 209 do not apply to bolts used to secure an adult upper torso restraint, other than the continuous loop type. Similarly, we interpret this provision not apply to the child harness upper torso restraint described in your letter. The bolts would be regulated with respect to strength only by the assembly performance requirements of S4.4(c).

Yours truly,

ATTACH.

April 9, 1974

Richard B. Dyson -- Office of Chief Counsel, National Highway Traffic Safety Administration Dear Mr. Dyson:

Questor Corporation has recently developed a novel child restraint harness that is to be marketed under the brand name "Infanseat Model 275 Child Restraint Harness." This restraint system has been under development for over two years to provide maximum dynamic performance at least possible cost to the consumer.

The Infanseat Model 275 Child Restraint Harness has closely approached the dynamic performance objectives proposed by the DOT to be effective September 1, 1975. When tested with a standard Sierra three-year-old child dummy, this restraint limited head excursion to 18.8 inches in a 30 mph frontal barrier impact test. Additional improvements in design have been made which will further reduce head excursion.

The unique design characteristics of this harness, which provide exceptional dynamic performance, also present difficulties in determining its compliance with FMVSS 209 for Type 3 seat belt assemblies. These problems were discussed with Messrs. R. Jasinski, J. Gilkey, T. Herlihy, and M. Peskoe during a personal visit to Washington on April 4. Mr. Jasinski also reviewed the situation in a phone conversation with Mr. R. Hitchcock. It was suggested after these conversations that this letter be written to you, outlining the areas of concern relative to FMVSS 209.

The design of Infanseat Model 275 Child Restraint Harness departs radically from child harnesses commercially available to date. Current harnesses require mounting to the floor of the automobile to restrain the child and vehicle seat back from movement during impact or load. Inasmuch as this floor anchorage could inadvertently be used by the present automobile owner or subsequent owners for an adult lap belt attachment point, it is understandable that FMVSS 209 would require the strength of this anchorage to be no less than 5,000 pounds, paragraph S4.3 (c) (1).

It is further recognized that currently available child harnesses loop over the adult backrest of automobiles, prior to being themselves anchored to the vehicle floor, and thus largely rely upon the strength of the automobile backrest to reduce movement of the child in an accident situation and/or also restrain the backrest. The assembly performance criteria of FMVSS 209 paragraphs S5.3 (c) (1) through (4) provide some degree of simulating this installation, and yet the force requirement that the complete assembly is required to withstand is 2,000 pounds, 100 per cent greater than the force requirements of FMVSS 213.

The Model 275 Child Harness is shown in accompanying Figures 1 and 2. The significant differences in its installation when compared with existing harnesses are readily apparent.

Firstly, an adult lap belt is used to position the lower portion of the child's harness both laterally and forwardly. Secondly, a back strap, or upper tie-down, connects the child harness at the shoulder strap area to either a rear seat adult lap belt for a front seat installation (Figure 1) in an automobile or to a supplementary anchor installed in the metal portion of the panel between the seat back and the rear window for rear seat installation (Figure 2). Neither the front nor rear seat installations require changes or additions to anchorages at the vehicle floor.

The viability of the upper tie-down attachment has been dynamically demonstrated by a well-known child seating restraint system that not only must restrain the child but also the child seating system itself. The upper tie-down strap most nearly approximates the function of an adult shoulder strap; that is, it keeps the upper torso from pivoting forward in a frontal impact. FMVSS 209 does not specify minimum force requirements for either Type 2, Type 2a, or Type 3 upper torso restraint attachment hardware.

It is suggested, therefore, that the requirements within FMVSS 209 for attachment hardware are neither clear nor appropriate for the Infanseat harness. In addition, the test method for assembly performance does not provide for the recommended installation of this product.

While attempts could be made to modify the simulated seat back shown in Figure 7 of FMVSS 209 to provide for the installation of the Infanseat harness, it is felt that any modification will not adequately reporduce the distribution of forces encountered in real-world situations. Also, any approved simulated static load test of a complete assembly at this time is not felt to be appropriate with dynamic testing of child harnesses soon to be required.

It is respectfully suggested that rather than subject the DOT to possible adverse public criticism by requesting another static test to determine the adequacy of the complete Infanseat harness assembly, it be excluded from the attachment hardware and complete assembly requirements of FMVSS 209. In lieu of these requirements, the Infanseat harness should be required to prevent head excursion of a Sierra three-year-old test device beyond 18 inches in a simulated 30 mph frontal impact test. The Infanseat harness would thus be required to meet the DOT's proposed dynamic performance requirements for child restraints.

Data substantiating the dynamic performance of the Infanseat harness has been independently verified by tests conducted for Consumers Union on prototype harnesses. These tests were not published by CU because the harnesses were not available commercially when their magazine went to press. Additional tests have been conducted to determine the suitability of various materials, installations, and test devices. Significant improvements to the harness are expected to be made, such that it appears likely in the very near future to provide dynamic protection for six-year-old children within the proposed excursion limits desired by the DOT.

As important as the Infanseat harness's dynamic performance is its expected retail selling price. The DOT and child restraint manufacturers are equally concerned that children's restraint devices be affordable by the largest possible segment of the public. It is recognized that the purchase and, therefore, the eventual use of children's restraints are directly related to their cost. The Infanseat harness is expected to be marketed at one-half to one-third of the price of existing restraint systems.

Thank you for your attention to this request for revised interim requirements that would be applicable to the Infanseat harness, and your early response shall be greatly appreciated. It is understood that this product would automatically be required to comply with the proposed revisions to FMVSS 213 when they become effective.

Yours very truly,

QUESTOR JUVENILE PRODUCTS COMPANY;

J. P. Koziatek, P.E. #E-36338 -- Director, Technical Services

Attachments

cc: R. Hitchcock; T. W. Herlihy; M. P. Peskoe; J. C. Gilkey; R. Jasinski

(Graphics omitted)

(Graphics omitted)

ID: 86-2.6

TYPE: INTERPRETATION-NHTSA

DATE: 03/07/86

FROM: AUTHOR UNAVAILABLE; Erika Z. Jones; NHTSA

TO: Stephen T. Waimey, Esq.

TITLE: FMVSS INTERPRETATION

TEXT:

Stephen T. Waimey, Esq. Dean Hansell, Esq. Donovan, Leisure, Newton & Irvine 333 South Grand Avenue Los Angeles, CA 90071

Dear Mr. Waimey and Mr. Hansell:

Thank you for your letter of September 12, 1985, concerning the applicability of S7.4.5 of Standard No. 208, Occupant Crash Protection, to manual Type 2 safety belts in passenger cars. As explained below, S7.4.5 is not currently applicable to manual Type 2 belt systems in passenger cars. However, as a result of a recent amendment to Standard No. 208, the comfort and convenience requirements of the standard will be applied to manual Type 2 belt systems in passenger cars, beginning on September 1, 1989, if the automatic restraint requirements are rescinded.

As you pointed out, S7.4(b) of Standard No. 208 requires vehicles with gross vehicle weight ratings of 10,000 pounds or less to meet the comfort and convenience requirements of the standard, including the requirements of S7.4.5. However, S7.4(b) specifically excludes manual Type 2 safety belts installed in the front seats of passenger cars from the comfort and convenience requirements. Thus, you are correct that a manual Type 2 safety belt installed in the front outboard seating position of a passenger car currently does not have to meet the requirements of S7.4.5.

In April of this year, the agency issued a notice of proposed rulemaking (50 FR 14580) proposing that if the automatic restraint requirements of Standard No. 208 are rescinded for passenger cars, then manual Type 2 safety belt systems in those vehicles would have to meet all of the comfort and convenience requirements, including the requirement of S7.4.5, beginning on September 1, 1989. On November 6, 1985 (50 FR 46056), the agency issued a final rule adopting that requirement.

I hope this information is of assistance to you. If you have further questions, please let me know.

Sincerely,

Erika Z. Jones Chief Counsel

September 12, 1985

Jeffrey Miller, Esq. Chief Counsel National Highway Traffic Safety Administration 400 7th Street S.W. Washington, D.C. 20590

Dear Mr. Miller:

We seek your opinion about a portion of Standard 208. Specifically, we wish to confirm that Part S7.4.5 of Standard 208 is not applicable to passenger cars.

According to Part S7.4(b) of Standard 208, 49 C.F.R. 571.208, vehicles with gross vehicle weights of 10,000 pounds or less must, inter alia, meet Part S7.4.5. However, Part S7.4(b) excludes manual Type 2 seat belts in the front seat. Part S7.4.5, on the other hand, appears to apply only to Type 2 seat belts in the front outboard seating position. Further, there is no reference to Part S7.4.5 in the regulations other than the one in S7.4(b).

Our review of these two standards leads us to conclude that Standard S7.4.5 does not apply to passenger cars, but is rather limited to trucks and buses. Our subsequent discussions with Mr. Oesch in your office have reinforced this conclusion.

We would appreciate your confirming our conclusion.

Yours truly,

Stephen T. Waimey

Dean Hansell

cc: Stephen P. Wood, Esq. Stephen L. Oesch, Esq.

ID: nht92-8.30

DATE: March 9, 1992

FROM: Robert S. McLean -- King & Spalding

TO: Paul Jackson Rice -- Chief Counsel, NHTSA

TITLE: None

ATTACHMT: Attached to letter dated 6/5/92 from Paul J. Rice to Robert S. McLean (A39; Std. 208)

TEXT:

I am writing to request a NHTSA interpretation of two basic sections of Federal Motor Vehicle Safety Standards ("FMVSS") No. 208, Occupant Crash Protection and No. 209, Seatbelt Assemblies (49 C.F.R. S571.208 and S571.209, respectively). My request for interpretation specifically deals with the application of FMVSS 208 and 209 to an occupant restraint system which has a seat belt portion consisting of a two-point automatic motorized shoulder belt and a manual lap belt. This system is of the type used in the 1980-81 Toyota Cressida and also is used on several Nissan and Ford vehicles. Please assume the system is used only on automobiles manufactured before September 1, 1989. For the purposes of this letter, please also assume that this occupant restraint system is certified as complying with the frontal crash protection requirements of FMVSS 208, S5.1 using only the two-point automatic motorized shoulder belt (without the use of the manual lap belt).

We understand that the two-point automatic motorized shoulder belt in the above-mentioned restraint system may be used alone (without the manual lap belt) pursuant to FMVSS 208, S4.5.3 to meet the crash protection requirements of FMVSS 208, S4.1.2.1 (specifically through subsections (a), (b), and (c)(2)) and in place of any seat belt assembly required by that option. FMVSS 208, S4.5.3 states just that: "a seat belt assembly that requires no action by vehicle occupants . . . may be used to meet the crash protection requirements of any option under S4 and in place of any seat belt assembly otherwise required by that option."

The two-point automatic motorized shoulder belt can be used as a "seat belt assembly" to comply with FMVSS 208 pursuant to FMVSS 208, S4.5.3. An automatic belt can be a "seat belt assembly" under FMVSS 208, S4.5.3 without relying on webbing or a lap belt to provide pelvic restraint. This follows directly from the NHTSA interpretation letter to Rembert Ryals, Esq. from Paul Jackson Rice, NHTSA Chief Counsel, dated September 10, 1990 (attached as Exhibit "A" for your convenience), which states that automatic belts certified as complying with the occupant crash testing requirements of FMVSS 208 generally are not required to meet the requirements of FMVSS 209, and that such an automatic belt is not required by FMVSS 208 or 209 to provide a lap belt, either manual or automatic. See also, the NHTSA interpretation letter to Mr. David E. Martin from Erika F. Jones, NHTSA Chief Counsel, dated April 14, 1986 (attached as Exhibit "B" for your convenience). Specifically, the Ryals letter states that FMVSS 209, S4.1(b) does not apply to automatic belts certified as complying with the occupant crash testing requirements of FMVSS 208. Therefore, because a two- point automatic motorized shoulder belt is a "seat belt assembly" under FMVSS 208, S4.5.3 and because such a two-point automatic motorized shoulder belt "requires no action by the vehicle occupants," a two-point automatic motorized shoulder belt can be used, pursuant to FMVSS 208, S4.5.3, to meet the crash protection requirements of FMVSS 208, S4.1.2.1 (specifically through subsection

(a), (b) and (c) (2)) and in place of any other seat belt assembly otherwise required by that option, and need not contain any lap belt.

Therefore, please confirm that (i) the two-point automatic motorized shoulder belt may be used alone (without the manual lap belt) to meet the requirements of FMVSS 208, S4.1.2.1, specifically pursuant to FMVSS 208, S4.5.3 as a "seat belt assembly" to meet the crash protection requirements of FMVSS 208, S4.1.2.1 (specifically through subsections (a), (b) and (c)(2)) and in place of any seat belt assembly required by FMVSS 208, S4.1.2.1 and (ii) the definition of "seat belt assembly" in FMVSS 209, S3 does not apply to the two-point automatic motorized shoulder belt.

Thank you for your help in construing these regulations as they apply to the two-point automatic motorized shoulder belt and manual lap belt restraint system.

If you need any additional information or clarification, please call at (404) 572-3599.

ID: nht76-5.47

DATE: 11/10/76

FROM: AUTHOR UNAVAILABLE; R. L. Carter; NHTSA

TO: Department of California Highway Patrol

TITLE: FMVSS INTERPRETATION

TEXT: Thank you for your August 12 and September 28, 1976, letters to our Office of Standards Enforcement concerning possible noncompliance of certain air-braked school buses with Standard No. 121, Air Brake Systems. At issue is the functioning of a "double check valve" between the two tanks of an air brake system designed to meet S5.7.2 of the standard (as it was in effect prior to September 1, 1976). The valve serves to provide air pressure from either supply reservior to hold off the spring brakes while guarding the air brake system from air loss through either one of the reservoirs. The identified problem stems from construction or installation of the valve such that it does not necessarily operate to seal off the brake system from a loss of air in one of the tanks, permitting loss of air from both reservoirs unless the rate of air loss is substantial. Your letter advises that the State of California is permitting the continued operation of the school buses in question pending receipt of a response from the National Highway Traffic Safety Administration (NHTSA).

I would like to address the findings you raise in the order in which they are listed on page two of your letter. I interpret your first finding to be that the "split system" designs used in compliance with Standard No. 121 may be incapable of meeting the stopping distance requirements set forth in S5.7.2. You question whether S5.7.2 adequately specifies a "back up" braking capability that is not cancelled out by a single failure of air pressure components, citing cases where a substantial rate of loss from one tank (introduced as a failure in accordance with S5.7.2.3) draws down the air pressure in both halves of a split system.

The general requirement of S5.7.2.3 (of the now superseded text) is that the vehicle, in one out of six attempts under specified conditions, must be capable of stopping from 60 mph within a distance of 613 feet "with a single failure in the service brake system of a part designed to contain compressed air or brake fluid. . . ." To provide this performance (and meet the other requirements of S5.7.2) manufacturers have provided "split systems" modulated by the service brake control. As a matter of general compliance with this requirement, you have asked if any single failure (other than failure of common components) can be introduced into the system as a test of its compliance. The answer to your question is yes. The NHTSA does not know the basis of Ford Motor Company's contention that the "failure" introduced in the system must be at least 50 psi/min from an initial reservoir pressure of 120 psi.

A noncompliance with S5.7.2.3 occurs only if the vehicle, with the failure introduced, is incapable of stopping within the prescribed distance in one out of six attempts. Thus, an extremely small failure which is easily overcome by compressor pressure would be one way of testing for compliance with S5.7.2.3, but it would not, in all likelihood, result in the demonstration of a noncompliance. As you noted in the second paragraph of page 3 of your letter, a noncompliance with stopping distance requirements may depend (largely because of a compressor's ability to overcome air loss) on the rate of leakage introduced and the time allowed between introduction of the failure and application of the emergency brake. The standard does not (except for the provision of S6.1.14 for towing vehicles manufactured on or after September 1, 1976) provide detailed specification of procedures, particularly the time between failure and brake application. The agency therefore must utilize a reasonable procedure that does not unfairly test the system. In this case, the agency considers the introduction of any size leak, followed by brake application as soon as the low pressure warning activates, to be a reasonable procedure, approximating what would occur in the event of actual failure on the highway. The agency would find a noncompliance with S5.7.2.3 if the school buses are incapable of stopping within the required distance when the described procedure is followed.

Your second finding is that a particular double check valve installation can cause noncompliance with S5.7.2.3. Consistent with our general discussion of compliance with S5.7.2.3, stopping tests are the means to discover whether the buses in question comply. We are analyzing your data, and a noncompliance investigation has been opened. We have notified Ford Motor Company of its commencement. We have also forwarded data to our Office of Defects Investigation to see if the check valve problem constitutes a safety-related defect apart from the issue of compliance.

Your last three findings address the separate question of whether the concept of a split system is adequately interfaced with the parking brake requirements of Standard No. 121. First you make the general point that, if S5.7.2.3 permits a substantial loss of air from both sides of a split system, the benefit of redundant lines is negated and the split system requirement is unjustified. The agency understands your position and believes that a stricter control on the amount of permissible leakage (perhaps by means of a limitation on compressor replenishment or a longer period before emergency brake application) may be justified. Particularly important is your point that a compressor loses capability as it grows older, and that this is not accounted for in new-vehicle tests. At the same time, however, larger failures do occur and we continue to view the split system as extremely important for these cases. The split system provides extremely good protection against failures such as rupture of a line or brake chamber diaphragm.

With regard to your point that split systems do not guard against failure of components common to the two systems as they are presently constructed (such as the compressor drive belt), I must agree with your point that no brake system can guard against every conceivable failure completely. It is for these cases, in fact, that the agency considers the automatic application of the parking brake system beneficial following loss of the other two capabilities.

You make the further point that, in cases of marginal compliance (i.e., the compressor can replace most but not all air loss from both sides of the split system), the gradual loss of system pressure permits parking brake application that interferes with modulation of the emergency capability. While S5.7.2 was designated as "Modulated emergency braking system", no specification for modulation was set forth in its requirements. The agency intended that a system conforming to S5.7.2 would be controlled by the driver instead of by automatic application. Our review of the systems you tested indicates that they are "modulated systems" as contemplated by the agency.

The present emergency brake requirements only state that the system "be applied and released, and be capable of modulation, by means of the service brake control." While further specification of this requirement may be in order, I believe it is the early application of the parking brake that actually concerns you, as it affects the application and release of the emergency braking capability.

You make the observation that early application of the spring brakes in response to air pressure loss permits them to drag, become overheated, and fade, making them useless before they can be utilized. A related issue is that the spring brakes will apply shortly after emergency brake availability (even before activation of the low air pressure warning), immobilizing the vehicle with no capability to release the parking brakes. You suggest implementation of a parking brake arrangement that would keep the spring brakes off longer or provide an isolated source of air pressure to permit their release when they do lock up.

Analysis of your test reports leads me to agree that some specification to limit the early application of spring brakes would be in order. Of course, as you are well aware, notice to interested persons of any change in the standard is required, along with an opportunity for comment. I believe that such rulemaking could be joined with the earlier rulemaking undertaken in response to a California Highway Patrol (CHP) petition (Docket 75-16, Notice 04).

Your final point is that, as long as early application of the parking brake is permissible, an isolated tank of air should be available to permit release of the parking brake from the driver's position. With regard to an isolated tank, the NHTSA continues to maintain its view set forth in our November 29, 1974, letter to Donald Gibson of the CHP that the second side of the split system provides more capability than the old systems (with an isolated tank) to avoid a lockup following a service brake failure. However, you have clearly demonstrated that the capability can be essentially negated by early application of the parking brake. I believe that limitations on early application of the parking brake would be a superior correction to the problem than the addition of more components (and complexity) to the existing systems.

Because school buses are involved in the problems you cite, you are no doubt aware that @ 103(d) of the National Traffic and Motor Vehicle Safety Act, while preemptive of State regulations or laws of general applicability that are not identical to Federal standards on the same aspect of performance, does not prevent a State or political subdivision from specifying a higher level of brake performance in vehicles "procured for its own use." Thus, the State of California may wish to order school buses with the additional isolated reservoir that you have recommended. The addition of a third tank to a system that complies with the standard's requirements would not be prevented by @ 103(d).

I appreciate the constructive approach being pursued by the State of California in enforcement of Standard No. 121. Our Office of Standards Enforcement will keep you advised of the results of its investigation.

Sincerely,

ATTACH.

DEPARTMENT OF CALIFORNIA HIGHWAY PATROL

September 28, 1976 File No.: 1.A218.A3107

Francis Armstrong -- Office of Standards Enforcement, National Highway Traffic Safety Administration

Dear Mr. Armstrong:

In this Department's letter of August 12, 1976, we brought to your attention a problem with the air brakes on school buses built on Ford chassis. We since have allowed the buses to temporarily continue in operation pending a decision by your agency as to their compliance with FMVSS No. 121.

At a meeting on September 2, in Sacramento with engineers from Ford Motor Company and Bendix-Westinghouse, this Department took the position that the Ford system did not operate as required by FMVSS No. 121 and did not protect the brakes against a single failure. Ford contended that the system was safe and complied with FMVSS No. 121. They further were of the opinion that a leak in a hose, fitting, or diaphragm of less than 50 psi/min from an initial reservoir pressure of 120 psi was not a "failure" as contemplated in FMVSS No. 121 and, in any event, could be overcome by the continuous operation of the air compressor.

The matter was pursued in considerable detail with no meeting of minds. It was found that the vehicle manufacturers' conclusions were based solely on laboratory and static tests and that no failures involving a continuous leak had been simulated on a moving vehicle. They were of the opinion that the usual vibration of the moving vehicle might result in the check valve responding more rapidly in normal service than in static tests. Although we believed the buses did not comply with FMVSS No. 121, we did not desire to keep them out of service if it could be reasonably avoided. On the other hand, we did not wish to allow them to operate if they were imminently unsafe, even if they complied with FMVSS No. 121.

We immediately scheduled dynamic tests for the following day to obtain some of the answers. Our investigation showed that the system did not function any better in tests of the moving vehicle than in stationary tests. The same situation was found to exist on other makes of school buses using similar designs. In our opinion, the systems on these buses do not comply with FMVSS No. 121 or are otherwise deficient for the following reasons:

1. It is highly doubtful that the vehicles can meet the emergency stopping distance in FMVSS No. 121 with a single failure in the air system.

2. Some double check valves are so mounted that they shuttle rapidly in one direction and are essentially inoperative in the other direction.

3. The emergency system is not capable of modulation by the service brake control as required by FMVSS No. 121 when loss of air in the service brake reservoirs results in the spring brakes beginning to apply.

4. If the driver does not react rapidly to a low pressure indication, the spring brakes can drag and overheat so as to be ineffective when they are eventually fully applied.

5. Upon failure of a compressor belt, as in the Martinez accident, the depletion of air in the service brake system upon a few brake applications could cause the spring brakes to lock with the vehicle in a hazardous location such as in a tunnel or on railroad tracks.

The results of our tests on Ford, International and Gillig buses are shown in the enclosed report. We found that all of the buses had insensitive double check valves between the primary and secondary split system. Although the buses were released for operation by the school district, we still have serious concern that this type of system does little good as an emergency brake system.

We ask that you give immediate consideration to a recall investigation to determine if air brakes using the double check valve piping system comply with FMVSS No. 121 and have an effectively-operating emergency stopping system. Our request is based on the following observations during our dynamic tests:

1. The double check valves are not sensitive enough to protect one-half of the dual system against either a mild or substantial air leak in the other half. A leak through a broken hose at a brake chamber with either partial or full foot-brake application did not cause the check valve to shuttle. If the vehicle was going downgrade with the brakes applied, the air would leak out of both systems down to the pressure at which the compressor could keep up with the leak. This ineffective dual system is a waste to the bus or truck operator, as he is no better off than with a single system with no double check valve.

2. It appears questionable whether the vehicles will meet the 60 mph, 613-foot stopping test of Section 5.7.1 of FMVSS No. 121 with a leak equal to the maximum before shuttle movement when the reservoir pressure is stabilized at the compressor output volume. If the vehicles in fact meet this performance requirement under these conditions, the "dual" components are a nonfunctional appendage. With this size leak, the pressure in the "protected" system will eventually be no higher than that in the failed system. Passage of the stopping distance test apparently depends entirely on how quickly the brake pedal is applied after the failure is initiated.

3. Double check valves are installed at the factory in mounting positions that interfere with their operation and any effectiveness that they might have. Some valves were installed with the shuttle axis vertical so that a leak needed to shut off air flow to one reservoir is far less than that at which air flow is shut off to the other reservoir. One ball-check valve was mounted at about a 45-degree angle so the ball immediately shut off a very small leak on the down-hill side but would not shut off the maximum leak that we could reproduce on the uphill side. As a vehicle gets older, contaminates and corrosion products in the system could cause the normally inactive double check valve to hang up when most needed. Even in our tests on a comparatively new vehicle, one of the check valves did not operate nearly as well upon the first simulated leak as on subsequent ones.

4. When a leak occurs, both systems drain down to the point where the spring brakes begin to drag just before the low air pressure indicator comes on. If the driver does not react to the signal, the spring brakes drag more and more as the pressure slowly drops, thereby overheating the linings and drums and destroying the effectiveness of the brakes when they finally are completely on.

5. The driver cannot modulate the brakes with a moderate leak in a supply line in either side of the dual system. The air pressure drops to the point where the spring brakes come on, even with no brake application by the driver. He can then apply the brakes harder by the foot valve, but he cannot release them below the force applied by the spring brakes. The FMVSS No. 121 amendments that became effective September 1, 1976, removed all reference to automatic emergency stopping systems which, if used, were previously required to be releasable by the driver after at least one full application. This feature apparently was intended to be taken care of in the current standard by the modulation requirement. In the systems we tested, the spring brakes could automatically apply with no action by the driver and then could not be released by the modulated treadle valve.

We realize that no system can protect against every conceivable possibility and that compromises are necessary because economical protection against one problem may result in an unavoidable creation of a smaller problem. A brake standard cannot meet every need of users and manufacturers under every possible situation, but the standard should be precise enough so users can follow its requirements and are aware of the limited assumptions on which it is based. To this end, we offer the following items that came to light in our tests. If during your investigation, you also find them to be a problem, you might wish to propose solutions to the Office of Crash Avoidance for consideration during the next revision of FMVSS No. 121.

1. Ford Motor Company contended that a leak through a damaged line, hose, diaphragm, etc., was not a "failure" as intended in FMVSS No. 121 unless the line or hose completely severed to produce a pressure drop of at least 50 psi/min from an initial reservoir pressure of 110 psi. We believe a much smaller initial leak of, say, 6 to 10 psi/min should be considered a failure for which the emergency system must compensate. With these differences of opinion, it is essential that the size of leak that constitutes a failure be specifically defined by NHTSA.

2. The stopping distance test conditions of the emergency system should be spelled out in more detail in FMVSS No. 121. The systems we checked would not isolate the protected half of the dual system under the more common failures of hoses and diaphragms. Also, the functioning of the double check valves was dependent upon their mounting position. A manufacturer's test that might be conducted to show compliance with the stopping distance standard with one system completely vented and the other with full air pressure (as would be assumed if the check valve was sensitive) is not realistic.

3. Ford Motor Company contends that their dual system is modulated as required by the standard. We contend that the system is not modulated, or only partially so, when an air leak developes which stabilizes the pressure at less than the 68-psi spring brake initial pressure. The regulation should spell out test conditions sufficient to control the intended degree of modulation.

4. The Ford system depends on compressor output to limit the extent of pressure drop in the system and, consequently, the amount of uncontrolled spring brake application. A new compressor with a 12 cfm rating can, when in good condition, keep up with a considerable air leak, but the emergency stopping system should not be dependent upon this factor. Some compressors are almost too small for some systems and many lose much of their capacity after they are in service over a period of time.

The deficiencies in the present split-air system would not be so important if a protected air tank was added to allow the spring brakes to release after the automatic application that occurs when one leak causes the air to be drained from both systems. The driver would then be able to release the spring brakes to remove the vehicle from a potentially hazardous location. Other modifications might be desirable such as the use of pressure protection valves shown in the enclosed Bendix-Westinghouse school bus system which was developed in accordance with California law a few years back.

I am sure you are aware of the intense national interest in school bus defects since the Martinez charter bus accident in which 29 persons were killed. The news media is sensitive to matters of school bus operation and may request information concerning our evaluation and recommendations to your agency. The possibility of such inquiry provides additional reason for your expeditious review and resolution of this matter.

I urge you to take immediate steps to require air brake systems of the types described in the enclosed report to be redesigned to comply with FMVSS No. 121 and to effectively protect the vehicles against brake failure.

Very truly yours,

G. B. CRAIG -- Commissioner

Enclosures

DEPARTMENT OF THE CALIFORNIA HIGHWAY PATROL

INSPECTION OF DUAL AIR BRAKE SYSTEMS ON SCHOOL BUSES

ENFORCEMENT SERVICES DIVISION

SEPTEMBER 1976

TABLE OF CONTENTS Page ABSTRACT 1 BACKGROUND 1 PROCEDURE 4 TEST RESULTS 4 I. Tests of 1976 Bluebird School Bus on a Ford Chassis 4 II. Tests of 1976 Superior School Bus on a Ford Chassis 6 III. Tests of 1975 Ward School Bus on an International Chassis 8 IV. Tests of 1976 Gillig School Bus 10 DISCUSSION 11 CONCLUSION 14

[REPORT OMITTED]

ID: nht79-2.37

DATE: 03/22/79

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Blue Bird Body Company

TITLE: FMVSS INTERPRETATION

TEXT:

March 22, 1979 NOA-30

Mr. W. G. Milby Manager, Engineering Services Blue Bird Body Company P.O. Box 937 Fort Valley, Georgia 31030

Dear Mr. Milby:

This responds to your November 29, 1978, letter asking several questions about test procedures conducted in accordance with Standard No. 222, School Bus Passenger Seating and Crash Protection. Your questions concern the impact and contact area test requirements of the standard.

First, you suggest that the head and knee impact tests should be conducted with only one impact allowed per seat back. The standard states in S5.3.1: "A surface area that has been contacted pursuant to an impact test need not meet further requirements contained in S5.3." You apparently interpret "surface area" to mean an entire seat back.

The purpose of the above-cited sentence in S5.3.1 is to assure manufacturers that the agency will not hit the test seat in the identical spot twice during compliance testing. However, it is permissible for several tests to be run on a seat as long as the test device does not impact the same specific area previously contacted by the device in an earlier test. This test method is appropriate because it approximates accident conditions. A seat is likely to be impacted more than once in an accident when the seat immediately behind it is occupied by three passengers. Accordingly, the agency will continue to run multiple tests on a seat back but will never impact the same "surface area" more than once.

In your second question, you suggest that a test sequence is appropriate for contact area testing. The agency disagrees. The agency agrees that the head form and knee form impact tests are different tests for the reasons outlined in your letter. However, nothing in those reasons compels the agency to conclude that a test sequence would be appropriate for contact area testing. In an accident, the impact of children on a seat back may or may not be sequential in nature.

Therefore, the existing test method, which permits the agency to sequence tests in any manner, closely reflects actual accident experiences. Accordingly, the agency will not adopt a specific sequence in its test procedures.

Sincerely,

Frank Berndt Acting Chief Counsel

November 29, 1978

Mr. Joseph J. Levin Chief Counsel National Highway Traffic Safety Administration Washington, D.C. 20590

SUBJECT: FMVSS 222

Dear Mr. Levin:

The purpose of this letter is to seek an interpretation regarding the sequence of testing required by FMVSS 222.

The testing sequence is important because many of the tests required by the subject standard have an interactive effect.

It is obvious that bus seats are an expendable item in a collision. This is attested to by the destructive nature of the requirements of the subject standard.

The head and knee impact requirements of the subject standard are both destructive in nature, and both have interactive effects not only with respect to each other, but also with respect to subsequent impacts within the head requirements or subsequent impacts within the knee requirements.

Because of the interactive effect of these requirements, not only on the immediate contact area, but also the surrounding area, it is not appropriate to conclude that a non compliance exists based on multiple impacts on any given seat. We believe this issue is addressed by S 5.3.1 which states "...a surface area which has been contacted pursuant to an impact test need not meet further requirements contained in S 5.3". It is further addressed by S 5.3.2.2. This section states "When any point ... is impacted...". (Emphasis added). We interpret this singular language to indicate that for compliance test purposes, only one point should be impacted on any given seat. We therefore seek your confirmation of this interpretation.

It should be noted here, as a practical matter, that multiple impacts on a particular seat are appropriate so long as the resulting data do not indicate a non compliance. This is so because multiple impacts on a particular seat constitute a worst case approach; if the seat passes under these circumstances, then it can be assumed it passes if only one impact per seat is made. However, if an indicated non compliance is encountered, it must be verified by impacting a virgin seat in the same location.

The second issue relating to testing sequence is the 3 in2 contact area requirement vs. the HIC and Force Distribution requirements with the head and maximum force requirements with the knee. We interpret the contact area requirements to be distinctly different tests for both the head and the knee for two reasons:

1. S 5.3.1.2 and S 5.3.1.3 require different velocities for the two tests, and

2. S 6.8 requires that the head form, knee form and contactable surfaces must be clean and dry during impact testing.

We therefore seek your confirmation of this interpretation also.

The importance of these issues was raised recently during compliance testing now being conducted by NHTSA at Mobility Systems laboratories. We urge you to resolve these issues by interpretation prior to the issuance of the FMVSS 222 compliance test report on the Blue Bird All American bus currently at Mobility Systems.

Thank you for your prompt reply.

Very truly yours,

W. G. Milby Manager, Engineering Services

sw

ID: nht74-2.11

DATE: 08/19/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: Dura Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Dura Corporation's July 24, 1974, questions whether S5.6 of Standard No. 121, Air brake systems, requires parking brakes on air suspension liftable axles, and whether the "no lockup" requirements of the standard apply to a liftable axle on a "tandem axle rig".

The parking brake performance options of S5.6 do not require parking brakes on an air suspension liftable axle such as you describe. S5.6.2 requires only that the parking brakes installed on a vehicle meet minimum performance levels. S5.6.1 requires parking brake retardation force on "an axle other than a steerable front axle". We do not consider this requirement to apply to an axle which is not on the ground when the parking brake system is activated.

The standard's "no lockup" requirement (S5.3.1) applies to

"any wheel at speeds above 10 mph except for . . .

(b) Lockup of wheels on nonsteerable axles other than the two rearmost nonliftable, nonsteerable axles on a vehicle with more than two nonsteerable axles.

Under this provision, if a vehicle has two nonliftable, nonsteerable axles at the rear which do not lock up (such as an antilock-equipped tandem axle rig) it may be equipped with a liftable nonsteerable axle which does not meet the "no lockup" requirements.

Yours truly,

July 24, 1974

Sidney F. Williams -- Office of Operating Systems, National Highway Traffic Safety Administration, Department of Transportation

Dear Sir:

Dura Corporation is presently involved in manufacturing add-on liftable axle/suspension assemblies which are marketed with OEM and body builders. Due to the impending effectivity dates of FMVSS 121 we are presently preparing to equip our products to comply. Our liftable airide axle/suspension assemblies are applicable to both pusher and tag situations.

The intent of this letter is to request an official interpretation of FMVSS 121. Our present understanding of the standard is as follows:

An anti-lock system will be required with the add-on axle/suspension if added to a single axle rig but not required if added to a tandem axle rig.

II. An emergency/parking spring brake will not be required with the add-on axle/suspension. This supposition is based on a loss of air pressure will automatically lift the axle rendering the spring brake inoperable.

Please indicate if the above statements are correct. Your consideration and cooperation in this matter is truly appreciated.

Sincerely,

Raymond E. Jones, Project Engineer -- DURA CORPORATION

cc: W. Locke

ID: nht71-5.57

DATE: 05/12/71

FROM: AUTHOR UNAVAILABLE; Robert L. Carter; NHTSA

TO: Mercedes-Benz of North America, Inc.

TITLE: FMVSS INTERPRETATION

TEXT: Thank you for your letter of April 20, 1971, regarding an interpretation for seat belt assemblies required by Federal Motor Vehicle Safety Standard No. 208 - Occupant Crash Protection.

It is our intent that an integral (3-point) lap and shoulder belt system, with a sliding attachment, could meet the requirements of the subject standard. Since paragraph S7.1.1 requires automatic adjustment by means of an emergency-locking retractor for this type of integral system (see S7.1.1.3), the sliding attachment friction could not unduly restrict adjusting movements of the belt, however, a nominal friction is permissible and is expected.

The seat belt assembly which you submitted to Mr. Clue Ferguson's Office of Crash Worthiness has been placed in Docket 69-7. This system would appear to have a nominal friction at the sliding adjustment, however, an actual vehicle installation is necessary to enable a full evaluation.

MERCEDES-BENZ OF NORTH AMERICA, INC.

April 20, 1971

Doug W. Toms, Director National Traffic and Highway Safety Administration

Subject: Seat Belt Assemblies According to FMVSS 208

The Motor Vehicle Safety Standard 208 which will be effective January 1, 1972, requires that seat belt assemblies shall adjust to fit the occupant by means of an automatic or emergency locking retractor. The seat belt assembly being considered for installation in our vehicles has been designed to comply with the subject Safety Standard. We would, however, appreciate receiving your confirmation that the design complies with the aspect of performance described in S7.1.1 of the Standard prior to equipping our vehicles.

The subject assembly consists of a single piece of webbing permanently attached at the outboard floor anchorage, with the release/fastening mechanism at the inboard anchorage forming the pelvic restraining loop and a third anchorage behind the shoulder forming the upper torso restraint. The webbing is fed during extension by an emergency locking retractor through the upper shoulder restraint anchorage to provide freedom of movement for the occupant.

Application of this assembly around the occupant is achieved by pulling the "tongue" portion of the attachment hardware from its fully retracted position at the "3" pillar, across the occupant down to the fixed buckle or receptable at the inboard anchorage. The webbing passes loosely through a slot in the tongue to provide a sliding adjustment during this application.

We are requesting your confirmation that this sliding adjustment specifically, will not be considered in non-compliance with your requirement for adjustment by the retractor because of the small amount of friction occuring at the webbing and tongue. It is our opinion that the friction is adequately overcome by the retractor force to provide proper adjustment. Additionally, the assembly when extended for use, will be drawn across the occupant, thus a snug fit across the pelvic region will be provided upon application thereby minimizing the need for further automatic adjustment by the retractor.

A sample of an assembly incorporating this design has been left at Mr. C. Ferguson's office for further evaluation by your staff. Upon receipt of your evaluation of this design we will advise our parent company accordingly.

H. W. Gerth General Manager Product Engineering and Service

cc: Mr. Wilfert Dr. Reidelbach

ID: aiam2281

Dear Mr. Milby: This responds to Blue Bird Body Company's March 29 and 31, 1976, an April 14, 1976, requests for confirmation of several interpretations you have made regarding the new safety standards for school buses and the definition of school bus' as they become effective in October 1976.; Your interpretation is correct that bus passenger compartment' as use in S5.2.3.1 of Standard No. 217, *Bus Window Retention and Release*, means that portion of the bus that is rearward of the forwardmost point on the windshield.; You request confirmation that the requirement in S5.7(a) of Standar No. 220, *School Bus Rollover Protection*, to open emergency exits during the application of force to the bus roof are inappropriate and therefore not applicable in the case of roof exits. Your interpretation is correct, and the NHTSA intends to modify the language of Standard No. 220 appropriately.; You request confirmation that the knee impact requirement of S5.3.2. of Standard No. 222, *School Bus Passenger Seating and Crash Protection*, does not apply to the rear row of seating in a school bus because there is no passenger seating behind this row. Your interpretation is correct. I would like to point out that the seat back of the rear row of seating also is not subject to the requirements of S5.3.1.1 for the same reason. You are also correct that school bus passenger seat' as defined in S4 does not include a wheelchair that is placed in a school bus to transport non-ambulatory bus passengers. Our response on other issues concerning special arrangements for handicapped passengers will be forthcoming as a response to the outstanding Sheller- Globe petition for reconsideration of Standard No. 222.; In your March 31, 1976, letter you asked whether a bus that is sold fo purposes that include carrying kindergarten and nursery school children to and from school or related events would be considered a school bus under the redefinition of school bus' that becomes effective October 27, 1976 (40 FR 60033, December 31, 1975). The answer to your question is yes, because the statutory definition underlying the NHTSA definition of school bus specifically lists preprimary students as passengers of school buses. See 15 U.S.C. S1391(14).; In your April 14, 1976, letter you ask whether the requirement o S5.3.1.3 of Standard No. 222 for a minimum contact area' on a described spherical head form refers to the area of actual contact on the surface of the spherical head form, or the area of contact on the head form as seen in projected view. The contact area' refers to the area of actual contact on the surface of the head form.; Sincerely, Frank Berndt, Acting Chief Counsel

ID: aiam2283

Dear Mr. Milby: This responds to Blue Bird Body Company's March 29 and 31, 1976, an April 14, 1976, requests for confirmation of several interpretations you have made regarding the new safety standards for school buses and the definition of 'school bus' as they become effective in October 1976.; Your interpretation is correct that 'bus passenger compartment' as use in S5.2.3.1 of Standard No. 217, *Bus Window Retention and Release*, means that portion of the bus that is rearward of the forwardmost point on the windshield.; You request confirmation that the requirement in S5.7(a) of Standar No. 220, *School Bus Rollover Protection*, to open emergency exits during the application of force to the bus roof are inappropriate and therefore not applicable in the case of roof exits. Your interpretation is correct, and the NHTSA intends to modify the language of Standard No. 220 appropriately.; You request confirmation that the knee impact requirement of S5.3.2. of Standard No. 222, *School Bus Passenger Seating and Crash Protection*, does not apply to the rear row of seating in a school bus because there is no passenger seating behind this row. Your interpretation is correct. I would like to point out that the seat back of the rear row of seating also is not subject to the requirements of S5.3.1.1 for the same reason. Your are also correct that 'school bus passenger seat' as defined in S4 does not include a wheelchair that is placed in a school bus to transport non- ambulatory bus passengers. Our response on other issues concerning special arrangements for handicapped passengers will be forthcoming as a response to the outstanding Sheller-Globe petition for reconsideration of Standard No. 222.; In your March 31, 1976, letter you asked whether a bus that is sold fo purposes that include carrying kindergarten and nursery school children to and from school or related events would be considered a school bus under the redefinition of 'school bus' that becomes effective October 27, 1976 (40 FR 60033, December 31, 1975). The answer to your question is yes, because the statutory definition underlying the NHTSA definition of school bus specifically lists preprimary students as passengers of school buses. See 15 U.S.C. S 1391(14).; In your April 14, 1976, letter you ask whether the requirement o S5.3.1.3 of Standard No. 222 for a minimum 'contact area' on a described spherical head form refers to the area of actual contact on the surface of the spherical head form, or the area of contact on the head form as seen in projected view. The 'contact area' refers to the area of actual contact on the surface of the head form.; Sincerely, Frank Berndt, Acting Chief Counsel

ID: 11390ZTV

Mr. Tommy Reeder
Loadcraft Manufacturing Corp.
P.O. Box 431
Brady, TX 76285

Dear Mr. Reeder:

This responds to your FAX of November 13, 1995, to Dave Coleman of this agency, with questions relating to rear lights on trailers, and a schematic drawing of the tilt bed trailer that is your concern.

Your first question is this: if the lights are placed on the extreme end of the tilt bed trailer, you say that they will be damaged when the trailer bed is tilted. In its original configuration as a farm trailer, the lamps were mounted on the furthermost crossmember facing the rear of the trailer. You have asked whether the lamps have to be mounted at the extreme end of the trailer.

Standard No. 108, the Federal standard governing lighting requirements, specifies that lamps and reflectors at the back of a trailer shall be located "on the rear". This generally means at the end of the trailer body or bed, or of the rear fender if the trailer is so equipped. It is not necessary to locate lamps literally on the extreme end provided that the photometric and visibility requirements of Standard No. 108 for rear lamps are met in the location chosen. We deem it highly unlikely that the lamps mounted on the rearmost crossmember as shown in your drawing would comply with the photometric and visibility requirements of Standard No. 108.

You have also informed us that you "have started using a drop bar in addition to the lights on the crossmember to increase visibility of the taillights in traffic", and have asked whether this is permissible. The drop bar location for all rear lighting equipment (reflex reflectors, stop lamps, taillamps, and turn signal lamps) would be an improvement, but it is still not certain that such a location would bring the rear lighting array into compliance. There is a 10-degree upward visibility requirement in Standard No. 108, and, depending on the exact mounting angles, the rear edge of the trailer could restrict compliance with this requirement.

There would be a greater likelihood of compliance if the drop bar could be moved rearward to the approximate area where one structural member of the bed begins to angle upward (in your sketch, at the left of the 16 3/4-inch dimension).

If you have any further questions, you may refer them to Taylor Vinson of this Office.

Sincerely,

Samuel J. Dubbin Chief Counsel ref:108 d:1/29/96