Interpretation ID: nht89-2.8

TYPE: INTERPRETATION-NHTSA

DATE: 06/19/89

FROM: STEPHEN P. WOOD -- NHTSA ACTING CHIEF COUNSEL

TO: JAMES A. LUTES -- ENGINEERING DEPARTMENT KENTUCKY MANUFACTURING COMPANY

TITLE: NONE

ATTACHMT: LETTER DATED 11/09/88 FROM JAMES A. LUTES TO ERIKA Z. JONES -- NHTSA; LETTER DATED 10/28/88 FROM THOMAS A. COZ TO JIM LUTES RE CALIFORNIA CITATIONS HIGH MOUNTED TRAILER STOP LAMPS

TEXT: Dear Mr. Lutes:

This is in reply to your letter asking for an interpretation of Motor Vehicle Safety Standard No. 108 with respect to the location of stop and turn signal lamps. I regret the delay in responding.

Your company has been installing supplemental stop and turn signal lamps approximately 12 feet above ground level on the rear doors of van-type trailers. The standard stop and turn signal lamps are located within the mounting range (15 to 72 inches above the road surface) specified by Table II of Standard No. 108. The photocopies you have enclosed indicate that on at least three occasions the State of California has cited trailers with this lighting configuration because the supplemental lamps are moun ted at a height in excess of 72 inches. You have asked for our interpretation and clarification of this matter.

Paragraph S4.1.3 of Motor Vehicle Safety Standard No. 108 permits the addition of supplemental lighting equipment, before delivery of a vehicle to its first purchaser, provided that it does not impair the effectiveness of the required lighting equipment. Although your high mounted stop and turn signal lamps are located in the vicinity of the identification lamps, we see no problem of impairment (the vehicle in the photo does not appear to have clearance lamps; for purposes of this interpretation we sha ll assume that they are mounted at the same height as the identification lamps, and at either side of the vehicle above your supplemental lamps). When activated, the clearance and identification lamps are steady burning and serve as presence lamps. The supplemental lamps, on the other hand, are activated only when a change in vehicle motion or direction is occurring. If the activation of the supplemental lamps could be said to distract attention from the clearance and identification lamps, the distra ction occurs only at a time when the most important information being communicated by the vehicle's rear lights is that a change in vehicle motion or direction is occurring. Under those circumstances, the required stop and turn signal lamps tend to have the same distracting effect. Further, on heavily-traveled highways where

lamps at standard locations may be hidden by intervening vehicles, signal lamps mounted at higher locations can alert drivers farther to the rear that a large vehicle ahead may be stopping or changing lanes, thus reducing the likelihood of a chain co llision. In summary, your installation of the supplemental lamps is acceptable to this agency under Standard No. 108.

We surmise that the California citations were given on the belief that supplemental lighting equipment must meet the same locational requirements as original equipment. While that is an understandable interpretation, this letter provides the proper inte rpretation of paragraph S4.1.3. We are providing a copy of this letter to the California Highway Patrol in order that the State interpretation may accord with the Federal one.

If you have any further questions we shall be pleased to assist you.

Sincerely,