Interpretation ID: nht88-1.94

TYPE: INTERPRETATION-NHTSA

DATE: 04/13/88

FROM: AUTHOR UNAVAILABLE; Erika Z. Jones; NHTSA

TO: Robert A. Rogers -- Director, Automotive Safety Engineering, General Motors Corporation

TITLE: FMVSS INTERPRETATION

TEXT:

Mr. Robert A. Rogers Director, Automotive Safety Engineering General Motors Corporation General Motors Technical Center 30400 Mound Road Warren, MI 18090-9015

This responds to your request for an interpretation of Standard No. 101, Controls and Displays, in connection with a design for head up displays (HUD's) that you are planning to introduce in certain future vehicles. The HUD's would protect readings from selected displays so that they appear as if they were located above the front bumper. The displays would initially include the following: speedometer, turn signal, highbeam, hazard, and low fuel warning. You stated that the HUD's would supplement corresp onding instrument panel displays, and would this be 'redundant displays.' You plan to provide the same light intensity for all of the HUD's, which would be variable and could be turned off by the driver.

You noted that section @5.3.4(b) of Standard No. 101 states in part that the telltales and identification for brakes, highbeams, turn signals, and safety belts may not be adjustable under any driving condition to a level that is invisible, and requested the agency's concurrence that variable illumination intensity, including levels at which the displays would not be visible, is permissible for the redundant (but not the other) turn signal and highbeam telltales. This letter provides our concurrence.

By way of background information, the National Highway Traffic Safety Administration does not provide approvals of motor vehicles. Under the National Traffic and Motor Vehicle Safety Act, it is the responsibility of the manufacturer to ensure that its mo tor vehicles meet applicable requirements. The following represents our opinion based on the facts provided in your letter.

Standard No. 101 specifies requirements for the location, identification, and illumination of motor vehicle controls and displays. The purpose of the standard is to ensure the accessibility and visibility of motor Vehicle controls and displays and to fac ilitate their selection under daytime and nighttime conditions, in order to reduce the safety hazards caused by the diversion of the driver's attention from the driving task, and by mistakes in selecting controls.

Standard No. 101 does not itself require that any particular controls or displays be furnished, although several of the controls and displays regulated by the standard are required by other safety standards. The standard instead provides that if certain controls and displays are furnished, they must meet the requirements of the standard. Controls and displays not listed in the standard are not subject to its requirements, except that section 55.3.5 specifies anti-glare requirements for certain sources o f illumination used for the controls and displays not otherwise regulated by Standard No. 101.

No. 101 apply to redundant displays. It is our opinion that where a manufactures provides more than one of a particular display listed in Standard No. 101, e.g., two speedometers, the requirements of the standard for that listed display are met of one of the displays complies with the standard's requirements. The standard's purposes of ensuring the accessibility and visibility of a particular display are fully satisfied by the complying display. Thus, the requirements need not be met again for a redunda nt display. However, redundant gauges, like other gauges not otherwise regulated by Standard No. 101, are subject to the requirements of section @5.3.5. (Telltales are excluded from the requirements of that section.) This interpretation is limited to where a manufacturer provides more than one of a particular telltale or gauge listed in Standard No. 101. We note, for example, that if a manufacturer provides a single fuel level gauge and a single fuel level telltale, neither display would be considered redundant, since gauges and telltales provide different types of information.

With respect to your planned design, it is our opinion that if the turn signal and high beam telltales located on the instrument panel comply with Standard No. 101, the turn signal and high beam telltales provided as HUD's need not meet the standard's re quirements. The light intensities of the turn signal and highbeam telltales provided as HUD's would thus be at the discretion of the manufacturer. Therefore, we concur that variable illumination intensity, including levels at which the displays would not be visible, is permissible for these displays.

Sincerely,

Erika Z. Jones Chief Counsel

March 17, 1988

Ms. Erika Z. Jones Chief Counsel National Highway Traffic Safety Administration Nassif Building Washington, D.C. 20590

Dear Ms. Jones:

This letter is a request for an interpretation from the NHTSA concerning head up displays (HUDs) and the illumination requirements of FMVSS 101 with respect to certain telltales.

General Motors is planning to introduce head up displays in certain future vehicles. The HUD provides redundant selected vehicle information which appears visible through the windshield. The driver can see through the HUD image which is projected to appe ar as if it is located above the front bumper at a height that is adjustable to accommodate varying driver seated heights. Displays which are now being considered for inclusion in the initial HUD are speedometer, turn signal, highbeam, hazard and low fue l warning. The HUD is capable of operation while the ignition is in the ON position, and is not operational when the ignition is in the ACCESSORY, LOCK, OFF or START positions. The illumination of the present design of this display can be varied over dif ferent ranges of light intensity depending upon whether the parking lights are on or off. When the parking lights are on, the greatest light intensity is substantially less than with the parking lights off. A thumb wheel control for HUD illumination is l ocated on the left side of the instrument panel. It is identified by "HUD Dimmer" above the control, with "LO" (Left) and "HI" (Right) indicating the direction that the wheel must be turned to control illumination. This design permits the driver to adjus t the illumination intensity to a comfortable level of visibility for any ancient lighting condition. The HUD can also be turned off at the option of the driver by moving the thumb wheel illumination control to the extreme low end. Our intent is to provi de the same variable intensity for all head up displays, including the turn signal and highbeam telltales. We seek the agency's concurrence that variable illumination intensity, including levels at which the displays would not be visible, is permissible for the redundant turn signal and highbeam telltales. @5.3.4(b) of FMVSS 101 states in part that: " ... the telltales and identification for brakes, highbeams, turn signals, and safety belts may not be adjustable under any driving condition to a level th at is invisible."

As mentioned above, the turn signal and highbeam displays to be included in the HUD are supplemental to primary instrument panel telltales. The primary telltales would comply with the FMVSS 101 illumination requirement cited above. The question, then, is whether the supplemental head up displays are also subject to this FMVSS 101 requirement. Our reasons for believing that the head up displays are not subject to this requirement are as follows:

They are redundant displays. FMVSS 101 does not specifically indicate whether redundant displays are subject to the illumination requirements. In the absence of clear direction from the wording of the standard, we believe a reasonable interpretation of t he standard would allow a HUD design that can be dimmed to an invisible level since no confusion or driver distraction can arise from the absence of a HUD inasmuch as the vehicle still offers the normal telltales. We believe another reason for permitting dimmable head up displays, including those for turn signal and highbeam, relates to the wide variation of lighting conditions in which it must operate. Because the subject displays appear to be outside the vehicle in the driver's forward view, it is imp ortant that the driver be able to control the brightness of the display. Accordingly, we believe that dimmability of the head up displays is more in line with the intent of FMVSS 101 than would be the alternative of maintaining the turn signal and highbe am head up displays at full illumination intensity at all times.

Some drivers may, for whatever reason, prefer conventional instrument panel displays to head up displays. A provision enabling drivers to turn the HUD off will accommodate this important customer satisfaction concern.

- Invisibility of redundant turn signal and highbeam telltales is not inconsistent with rulemaking history. We have reviewed the rulemaking history of FMVSS 100 and 101 and have located nothing which specifically addresses redundant displays of telltales . We have researched previous interpretation letters issued by the NHTSA for guidance in this matter. We have located several letters which the agency has written concerning the applicability of FMVSS 101 requirements to redundant controls; however, we hav e located no interpretation which addresses the applicability of FMVSS 101 to redundant displays. In the interpretations we have reviewed, the NHTSA has generally maintained that redundant controls are subject to FMVSS 101 requirements. An exception was a letter from the agency to Mazda in July of 1984, which distinguished rear seat controls from the visibility requirement of FMVSS 101. In distinguishing secondary rear seat controls, NHTSA explained that a stated purpose of FMVSS 101 (reducing the safet y hazard caused by the diversion of the driver's attention from the road) would not be compromised by the fact that the driver could not see the identification of rear seat controls. In other instances, where NHTSA has indicated that redundant controls a re subject to FMVSS 101 requirements, it has again based these determinations on the purpose of the standard. While there is some potential for misuse of redundant controls, there is no corresponding potential for "misuse" of redundant displays. That is, the subject head up displays will either be visible or invisible to the driver. If they are visible, there is no issue. If the driver chooses to make them invisible, and therefore not use the HUD, it cannot be relied upon or misused. Further, absence of the head up displays will not result in the driver being deprived of turn signal or highbeam information, sin ce this information would continue to be available from the primary instrument panel telltales.

We have located a single interpretation letter from NHTSA with respect to a HUD. It was dated June 19, 1987, and responded to a manufacturer's request for an interpretation of the requirements of FMVSS 205 related to a membrane in the lower left corner o f the windshield that reduced light transmissibility below 708. With regard to the issues discussed in this June 19, 1987 NHTSA interpretation, we would point out that GM vehicles equipped with HUDs will comply with all of the requirements of FMVSS 103, 104 and 205.

In summary, we believe that it is not only permissible, but also preferable, to provide variable illumination intensity for head up displays. Variable illumination for HUDs best satisfies the intent of FMVSS 101 and the interests of customer satisfaction . Furthermore, FMVSS 101, and previous NHTSA interpretations of which we are aware, do not expressly prohibit dimmability of redundant displays.

If further information concerning our planned head up displays would expedite the agency's response to this request for interpretation, we would be pleased to provide such information.

Sincerely,

Robert A. Rogers, Director Automotive Safety Engineering

cc: Ms. Diane Steed, Administrator, NHTSA Mr. Barry Felrice, Associate Administrator for Rulemaking, NHTSA USG 2623