Interpretation ID: 86-2.33

TYPE: INTERPRETATION-NHTSA

DATE: 04/23/86

FROM: AUTHOR UNAVAILABLE; Erika Z. Jones; NHTSA

TO: ANONYMOUS

TITLE: FMVSS INTERPRETATION

TEXT:

Dear

This is in reply to your letter of October 31, 1985, asking for confirmation of your interpretation that the location of a proposed motorcycle rear turn signal system meets the requirements of Motor Vehicle Safety Standard No. 108.

Table IV of Standard No. 108 requires motorcycle turn signal lamps to be located "at or near the rear" and to have "a minimum horizontal separation distance (centerline to centerline of lamps) of 9 inches." Further, the "minimum edge to edge separation distance between lamp and tail or stop lamp is 4 inches." The diagram you have attached shows that the minimum horizontal separation distance between the turn signal lamps is 12 inches, and therefore complies with that requirement of Standard No. 107. However, the turn signal lamps are not mounted adjacent to the stop/taillamp which is on the rear of the vehicle on what appears to be the body but forward of it so that in a two-dimensional side elevation the edge to edge separation distance of the stop/taillamp and the turn signals is 3.75 inches. A plan view indicates that the horizontal separation distance between edge to edge is 2 inches. The actual edge to edge separation distance as measured by a continuous straight line is 5 inches, and you believe that this satisfies the standard's requirement for a minimum edge-to-edge separation of 4 inches.

We do not agree with this interpretation since it is premised on a frame of reference different from that used in Table IV to express the location requirements for turn signals. The frame of reference used in Table IV is that of a rear elevation in which the motorcycle is bisected by a vertical centerline. This is the appropriate frame of reference since it implements the safety rationale giving rise to the location requirement. Standard No. 108 specifies a minimum separation distance to minimize the possibility that an observer will be confused as to a lamp's function. A motorist approaching directly from the rear will perceive an edge-to-edge separation distance between the stop/tail and turn signal lamp of only 2 inches if your configuration is used. Therefore, each turn signal lamp must be relocated 2 inches further outboard if it is to comply with Standard No. 108.

Your request for confidentiality is honored, to the extent that the copy of this letter made publicly available will include neither the identification of you and your company, nor the diagram you provided.

Sincerely,

Erika Z. Jones Chief Counsel