Interpretation ID: nht69-1.23

DATE: 08/20/69

FROM: WARREN M. HEATH

COMMANDER ENGINEERING SECTION

TO: ROBERT BRENNER --

ACTING DIRECTOR NATIONAL HIGHWAY SAFETY BUREAU U.S. DEPARTMENT OF TRANSPORTATION

COPYEE: GEORGE GAUDAEN -- SAE

TITLE: REF: 81.A215.A1575

TEXT: Dear Mr. Brenner:

We have a copy of a letter to Mr. Charles W. Heyer of Electrical Testing Laboratories from Mr. Charles A. Baker regarding photometric test procedures. That letter quite clearly points out the method in which the National Highway Safety Bureau desires multicompartment turn signal lamps to be(Illegible Word). However, it raises additional questions concerning procedures to be used both by a laboratory in determining compliance of a device with the Federal standards and by a manufacturer in designing a lamp to meet these standards.

The photometric requirements in SAE(Illegible Word) were developed several years ago before multicompartment lamps were in common use. These standards reasonably well fulfilled the need in upgrading the performance of single-compartment lamps at that time. Later, experience with some of the original multicompartment lamps and complaints about excessive brightness of the taillamps and stoplamps on vehicles brought about a need for revising the standards.

At that time, each section of a multicompartment lamp was treated in the same manner as an individual lamp, since their performance was little different than that of individual lamps set side by side. Therefore, each compartment of a three-compartment lamp had to meet the(Illegible Words) for a taillamp and the 80 candlepower minimum for a turn signal lamp. In addition, each compartment was allowed to have a maximum intensity of 15 candlepower at or above horizontal for the taillamp and 300 candlepower in red for the turn signal lamp.

The above maximum values were reasonable when only one or two lamps were used on each side of the vehicle. Unfortunately, the first three-compartment lamps were built with such high light output that each compartment barely complied with the

maximum. This meant in some cases that the combined taillamp output on each side of the vehicle was over 45 candlepower and the combined turn signal output was barely below the total maximum of(Illegible Word) candlepower, thereby being annoyingly bright to following drivers.

The manufacturers and the(Illegible Word) Lighting Committee recognized this problem and alter a number of demonstrations of systems and rewriting of proposed crafts developed the multicompartment rear lamp specification in(Illegible Words). The original brightness problem appeares to be quote simple and could have been solved merely by reducing the maximum intensities allowed multicompartment lamps; however, the manufacturers were concerned that they would then be squeezed between a high minimum value for each compartment and a low maximum value which did not allow sufficient(Illegible Word) for normal design and production.

The SAE studies indicated that with the types of multiple compartment lamps(Illegible Word) were in use about three years ago, the values in SAE(Illegible Word) applying to the total light output of the multicompartment lamp were reasonable. This standard did not cover every combination of brightness and lens area that might be involved in providing anytime effectiveness while limiting nighttime brightness to reduce annoyance, but it was a first step in this direction.

Manufacturers who have attempted to comply with both(Illegible Words) and SAE(Illegible Word) have differences in interpretation of your requirements. We would like to have the following points clarified so we do not cause the manufacturers unnecessary difficulties when we test devices for compliance with Federal and State standards:

1. Section(Illegible Words) specifies in part that the photometric requirements "shall be provided by one or a combination of the compartments or lamps".

(a) Does this mean that if one compartment or lamp meets the minimum and maximum requirements, the other compartments or lamps can have photometric output either below the minimums required or above the maximum permitted?

(b) Does this mean that one lamp may be used to meet the minimum requirements with the others adding stray light, provided the maximum requirement of 15 candlepower in the case of taillamps and(Illegible Word) candlepower in the case of turn signal lamps is not exceeded when all lamps or compartments are lighted simultaneously?

(c) Does the manufacturer have the choice in interpreting this section as to which method is most favorable to him for his particular design?

2. Mr. Baker's letter of May 12 states that "The sums of the measured candlepowers at the test points of separately photometered lamps or compartments of a combination shall not be acceptable", whereby implying that all lamps or compartments shall be photometered simultaneously.

(a) What was the purpose of stating in Section 3.1.1.7 that photometric requirements shall be provided by "one" or a combination of compartments if individual tests are not permitted to determine whether one compartment actually does comply?

(b) If it is the intent that the compartments shall be measured simultaneously, should not the above section be(Illegible Word) to eliminate the implied alternative of having only one of the lamps comply?

3. FMVSS No. 198 makes no mention of the method of testing multicompartment and multilamp taillamps and steplamps, as Section 3.1.1.7 applies only to turn signals.

(a) Do the standards require each compartment of a taillamp or steplamp to be tested separately to show compliance with(Illegible Word), or are they to be tested simultaneously as required of turn signals?

(b) Must each separate lamp or individual compartment meet the taillamp-to-steplamp ratio, or is it sufficient that the compartments when lighted together meet the ratio even though a particular lamp or compartment does not comply individually.

4. The California Vehicle Code contains a Section(Illegible Word) which prohibits a motor vehicle from being equipped with any lamp or illuminating device not specifically required or permitted by the Code. The manufacturers would like to interpret Section(Illegible Words) as permitting any number of additional taillamps and stoplamps on each side, provided only the lamp meets the requirements of J575c. The only limitation they propose is that all of the lamps taken together do not exceed the maximum candlepower requirements(Illegible Words), as an example of nonimpairment of the effectiveness of the single required lamp. They would also use photometric data showing that the total stoplamp to total taillamp output complies with the ratio requirements of J575c; again, to prove nonimpairment.

(a) Do the Federal standards preempts states from enforcing present requirements that each rear lamp on a vehicle must perform a specific function and to approved for that function?

(b) Are all of the separate lamps in the multiple rear lamp arrangement considered by the Bureau as comprising one lamp and(Illegible Word) to be taken as such by the states in enforcing identical standards?

(c) Does the Federal standard merely require the minimum of one stoplamp and taillamp on each side of the vehicle to meet the requirements of(Illegible Word), with the additional optional lamps to be provided at the manufacturers discretion regardless of whatever standards the states may have for any such supplemental lamps?

5. Some modern designs of multicompartment lamps have three compartment configurations where the large(Illegible Word) compartment is a backup lamp and on each side of it is a taillamp-stoplamp combination. Other configurations include a three compartment lamp centered on the rear of the vehicle where the middle compartment as a taillamp-stoplamp combination and the compartments on each side of it perform only taillamp functions.

(a) Where one rear lamp compartments are separated by a backup lamp compartment, as the entire lamp to be tested as a single unit as though the rear lamp sections were adjacent to each other?

(b) With respect to the device where a taillamp is on each side of a center-mounted stoplamp, are the taillamps considered a part of the physically integral three-compartment center lamp for the purposes of determining compliance with minimum and maximum specifications and ratio requirements? Or, is the taillamp on each side of the stoplamp to be tested simultaneously with the other taillamps on that particular side of the vehicle for the purposes of determining compliance?

The manufacturers have been quite ingenius in developing different variations of multiple lamps and multicompartment lamps and each has his own interpretation as to how his particular arrangement might be considered as complying with a specific Federal or SAE standard. We have been asked a number of questions such as those above as a result of our program of purchasing and testing devices for conformance to the standards.

We would very much appreciate your giving consideration to this problem and providing us with specific information that we can use in answering inquiries from foreign and American manufacturers and on using the correct test procedure for determining compliance of a specific device with the requirements.

Very truly yours,