Dear Mr. Sharp:
We have received your letter of May 12, 1995, requesting an interpretation of Motor Vehicle Safety Standard No. 108 on behalf of your client, NYTAF Industries. You are concerned that installation of a NYTAF lighting system on the rear of trailers might be considered to impair the effectiveness of the required rear lighting equipment within the meaning of paragraph S5.1.3.
The NYTAF Auxiliary Rear Lighting System
NYTAF has developed "an auxiliary signaling system for heavy duty vehicles" which "displays a verbal message appropriate to the particular potential hazard." According to Exhibit A of your letter, a draft information brochure, the specific words displayed are: "Wide Turn", "Braking", "Wide Load", "Caution", "Help", "Backing", and "Long Load". In addition, right and left facing arrowheads indicate the direction of turning. Drivers cannot alter these messages or program the system to accept personal messages. The brochure depicts the message unit "on the rear of the trailer frame directly below the trailer body in the center putting the display panel on approximately the same horizontal plane as the tail lights and brake lights." Words are provided by light-emitting diodes (L.E.D.). According to your letter, the L.E.D. display "is somewhat more intense than existing brake lights, turn and tail lamps."
Exhibit B "Operation Summary" explains how the system operates with respect to each message, e.g., "Braking" is "activated and illuminated in conjunction with brake lights."
Applicable Requirement of Standard No. 108
Paragraph S5.1.3 of Standard No. 108 states that "No additional lamp, reflective device or other motor vehicle
equipment shall be installed [before first purchase of a vehicle in good faith for other than resale] that impairs the effectiveness of lighting equipment required by [Standard No. 108]."
Prior Interpretations of S5.1.3 Relating to Message Boards
In the past, the agency has advised that the determination of impairment is initially made by the manufacturer of the motor vehicle on which the supplementary equipment is installed, when it certifies that the vehicle complies with all applicable Federal motor vehicle safety standards. Unless that determination is clearly erroneous, NHTSA will not question it. Thus, NHTSA's interpretations are generally cautionary in tone rather than prohibitive.
I enclose copies of two interpretations relating to message boards intended for the rear parcel shelves of passenger cars. The first is a letter of August 17, 1989, to Alan S. Eldahr ("Eldahr"). The relevant language of Eldahr is that a rear window message board "sending messages unrelated to vehicle stops, could confuse and distract a driver following, and in that sense impair the effectiveness of the center lamp." The second is a letter dated August 13, 1993, to Kenneth E. Ross ("Ross"). The Ross letter discusses the relation of message boards to the aftermarket, as well as the notification and remedy obligations which would fall upon NYTAF as a manufacturer of automotive accessory equipment.
Relationship of Eldahr to NYTAF
Eldahr indicates that there is less possibility of impairment existing if the message visible to a following driver is related to the lamp function that occurs simultaneously, as happens, for example in the NYTAF system, when stop lamp activation is accompanied by the word "Braking." We suggest that vehicle manufacturers installing the NYTAF system follow this guideline in their determinations of whether impairment exists.
NYTAF might also wish to reconsider the intensity of the L.E.D. display which you say is "more" than that of the existing rear lighting equipment, especially as it may affect reaction to the stop signal. The intensity should not be so great as to divert driver attention to the message rather than to the stop signal.
There are several areas of Exhibit B "Operation Summary" which require more specific comment. "Caution" is activated in conjunction with the hazard warning system. Standard No. 108 requires these systems to simultaneously flash all turn signal lamps, and not sequentially as Exhibit B states. Exhibit B should be corrected to reflect this if it is to be distributed publicly, as we do not understand that the NYTAF system is intended to create sequential flashing of turn signals when operated in the hazard signal mode. The sole explanation of "Help" is that it is to be activated manually. In our view, a flashing "Help" while the trailer is in motion would be more likely to impair rear lighting equipment than if it is operable only when the trailer is at rest. In addition, Exhibit B does not indicate whether the "Help" message is overridden by other messages when related lighting systems are activated.
We are unsure of the purpose of "Clearance Marker" which is operated "in conjunction with parking lights." Standard No. 108 does not require truck tractors to be equipped with parking lamps. We believe that you meant taillamps. We do not view this lamp as having an impairing effect upon the taillamps. The name of the lamp is somewhat misleading, as it would be mounted at the center of a vehicle whereas a "clearance lamp" is intended to indicate a vehicle's overall width.
Additionally, on certain trailer designs the three identification lamps are mounted around the vertical centerline in the same location in which you have stated the NYTAF system will be mounted. With respect to the close proximity of the two lighting systems, we believe that the brightness of the NYTAF device compared with that of the identification lamps could impair their ability to signal the presence of a large vehicle in the roadway ahead, the intended function of these lamps.
Finally, we note that the color red would indicate a backing function. Although trailers are not required to have backup lamps, Standard No. 108 specifies that the color white shall be used for backup lamps, and we believe that the public has come to associate an activated white lamp on the rear of a vehicle as indicating that the vehicle is in reverse gear. Your client may wish to reevaluate this function in light of possible liability concerns.
We hope that these guidelines will be helpful to NYTAF. If you have any further questions, Taylor Vinson will again be happy to answer them (202-366-5263).
John Womack Acting Chief Counsel