Interpretation ID: aiam4355
Division Head
Planning Division
Yue Loong Motor Engineering Center
P. O. Box 510
Taoyuan
Taiwan 330
Republic of China;
Dear Mr. Chen: This is in reply to your letter of June 5, 1987, asking whether certai rear lighting arrangements are acceptable under Federal Motor Vehicle Safety Standard No. 108.; You have submitted a diagram showing four lamps on either side of th vertical centerline of the rear of the car. The most inboard lamps, denoted 'R', are the backup lamp system. Yue Loong contemplates four different functions for the remaining three systems of lamps, 'A', 'B', 'C', and 'D', 'E', 'F' (inboard to outboard) and asks about acceptability.; >>>1. In the first system, ABC or DEF will serve the respective tur signal functions. All lamps would serve as hazard warning signal lamps and stop lamps. Standard No. 108 generally does not prohibit lamp clusters from performing multiple functions. This system is permissible as long as ABC and DEF will serve the respective turn signal functions. All lamps would serve as hazard warning signal lamps and stop lamps. Standard No.108 generally does not prohibit lamp clusters from performing multiple function. This system is permissible as long a ABC and DEF meet all Standard No. 108's requirements for turn, hazard warning, and stop signals when tested in those modes. Your diagram, however, does not indicate which, if any, of these lamps provide the taillamp functions that Standard No. 108 also requires for the rear of motor vehicles. Therefore, lamps ABC and DEF would have to meet the taillamp requirements as well.; >>>2. The second system differs from the first in that the hazar warning system would not operate through the two most outboard lamps. This system is permissible, as Standard No. 108 does not mandate use of all turn signal lamps for the hazard warning signal mode, requiring only 'at least one' on each side of the vehicle, front and rear.; >>>3. The third system differs from the second in that the two mos outboard lamps would no longer be part of the stop lamp system. We view this arrangement as permissible. Standard No. 108 requires that stop lamps, turn signal lamps, and taillamps be located 'as far apart as practicable'. In a literal sense this would appear to require stacking the lamps vertically at the outboard edges of the vehicle, but NHTSA has not adopted a design-restrictive interpretation of this requirement. The determination of practicability is initially that of the manufacturer, but it is subject to review and comment by this agency in instances where such a determination appears clearly erroneous. Where the turn signal system (or part of it) is located at the outboard edges of the vehicle, and the stop lamps and taillamps are adjacent to it, or to each other, we view the 'practicability' requirement as met.; >>>4. The fourth system differs from the third in that the stop lam system would be either that of the systems discussed in items 2 and 3 above, and operating according to Section 3 of your letter. Either system would be acceptable, subject to the operational restriction with turn signal lamps that I shall discuss in my response to section 3.; Next, you have presented four kinds of flashing arrangements for th turn signal lamps. You ask (a) which could meet Standard No. 108, and (b) which could meet Standard No. 108 assuming a flash cycle of 104 seconds. With respect to (a), all four would appear to be acceptable. The standard allows multiple turn signal lamps either to flash simultaneously, or sequentially in the direction of the turn. With respect to (b), Standard No. 108 specifies that a turn signal flasher provide not less than 60 and not more than 120 cycles per minute. This translates to not less than 1 and not more than 2 cycles per second. This requirement would have to be met by all lamps in arrangement (d), i.e. where all lamps operate simultaneously. When operating sequentially, each lamp individually would be subject to the restrictions with the result that the inclusive cycle for a three lamp system would be not less than 3 seconds and not more than 6 seconds. Therefore, arrangements (a), (b), and (c) would meet this requirement assuming a flash cycle of 4 seconds, by arrangement (d) would not, being restricted to a cycle of 2 seconds maximum.; In your third question, or Section 3 as you term it, you have combine the condition of your first two questions and attached a table of 'detailed operating states' of the rear lamps, which incorporated three attached figures, with the question whether it would comply with Standard No. 108. Two of the Operating States illustrated denote the stop lamp 'on' and, individually, the right or left turn signal as 'on'. Standard No. 108 does not allow simultaneous activation of the stop lamp and turn signal lamp when the stop signal is optically combined with the turn signal. In that event, the circuit must be such that the stop signal cannot be turned on in the turn signal which is flashing (paragraph 4.2, SAE Standard J586c *Stop Lamps*, August 1970, incorporated by reference in Standard No. 108). Our other comment concerns 'Fig. a', 'Fig. b', and 'Fig. c' depicting flash cycles of the turn signal lamps. As we noted earlier, the individual lamps are subject to the cycle minima and maxima of 1 to 2 cycles per second, and none of the rates depicted in the three Figures appears to meet the minimum requirement of 1 second. Otherwise, the 'Operating State' table appears acceptable.; I hope that this answers your questions. Sincerely, Erika Z. Jones, Chief Counsel