Interpretation ID: nht80-2.15

DATE: 04/24/80

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: TRW, Inc.

TITLE: FMVSS INTERPRETATION

TEXT:

April 24, 1980 NOA-30

Mr. Nicholas M. Stefano Manager, Mechanical Device Development Advanced Systems Engineering TRW, Inc. Building E2, Room 4O62 One Space Park Redondo Beach, California 90278

Dear Mr. Stefano:

This responds to your letter of January 7, 1980, in which you described an automotive, electronic display device being designed by TRW and asked for a legal opinion as to its potential compliance with Federal Motor Vehicle Safety Standard No. 127, Speedometers and Odometers. You noted that, upon installation in a motor vehicle, TRW's device would continuously display vehicle and engine speed readings in the form of a bargraph. In potentially hazardous situations requiring the driver to take extra caution or to shut down the vehicle's engine, the TRW device would intermittently interrupt the display of vehicle and engine speeds with sequences of verbal messages. In light of this, you asked whether the fact that TRW's device would not display the vehicle speed during every moment of vehicle operation would prevent it from complying with Safety Standard No. 127.

Based on our understanding of your design, it appears that alternating the display of speed and verbal messages would not violate the standard. Although the future development of electronic digital speedometers was considered in the development of Safety Standard No. 127, the specific type of device described in your letter was not contemplated. The agency had expected that all speedometers would continuously display vehicle speed. While the intermittent display feature would apparently not violate Safety Sandard No. 127 as it is now written, we are concerned about the possible adverse impact upon traffic safety that this feature might have. In particular, we have in mind the effects of a driver's being unable to determine vehicle speed when he or she is approaching or negotiating a curve or exit ramp. Rapid deceleration to a particular speed is typically necessary in auch situations. In the case of a speedometer which periodically does not display vehicle speed for periods of 5 seconds, a vehicle that interval and a vehicle traveling at 40 mph, approximately 300 feet.

Although your alternative mode of operation would reduce this interval through flashing the speed for periods of 0.10 seconds, we question whether such a short period would be sufficient to enable drivers to read their speedometers. We solicit any tests or research that TRW has done on the safety side effects of your design. A member of the agency's accident avoidance division will contact you to discuss this issue further.

In looking at your design, we noted several aspects of it that would apparently not comply with Safety Standard No. 127. The design does not appear to be graduated in both miles and kilometers per hour as required by Section 9.1.2. Further, the design neither has the numeral 55 nor highlights either that numeral or the point at which vehicle speed equals 55 mph as required by section 4.1.5.

Finally, I would emphasize that this letter represents only the agency's opinion based on the information supplied in your letter. The NHTSA does not formally render judgment on the compliance of any vehicle or equipment design with any safety standard before the manufacturer's certification of its product. It is the manufacturer's responsibility under the law to determine whether its vehicle or equipment comply with all applicable safety standards and regulations and to certify its vehicles in accordance with that determination.

I hope that you will find this response helpful and have not been inconvenienced by our delay in sending it to you.

Sincerely,

Frank Berndt Chief Counsel

1272.1-80-02 January 7, 1980

Legal Counsel National Highway Transportation Safety Administration Department of Transportation 400 - 7th Street, S.W. Washington, D.C. 20590

Subject: Federal Motor Vehicle Standard No. 127

Dear Sir:

TRW is in the process of designing electronic display devices for the drivers of automobiles, trucks, tractors, off-highway vehicles, and agricultural equipment. One design concept utilizes a fluorescent display tube with 20 character positions which displays in bargraph form the vehicle speed and the engine RPM. The display is driven by a microprocessor. The microprocessor also collects data from a number of sensors that check the water level in the radiator, the water temperature and engine oil pressure. We intend to use the same display tube that shows speed and RPM to alert the driver to (1) conditions requiring caution on his part; or (2) to "dangerous" conditions requiring shutdown of the engine to avoid serious damage to the engine.

The microprocessor can drive the tube to provide a sequence of displays as shown in Figures 1 and 2 attached. In Figure 1 the top line shows a box for each of the 20 character positions. The speed is 48 MPH as indicated by the top bargraph; and the engine is running at 1220 RPM, as seen from the bottom bargraph in the top display. When the microprocessor detects a "caution" or "danger" condition, it immediately removes both bargraph messages and conveys a message to the driver in a series of 0.9 second ON and 0. 1 second OFF displays, as can be seen by reading the messages on each display line, reading from top to bottom.

In the case of the "caution" message, after 5 seconds the bargraphs return to a steady display condition for 15 seconds. The "caution" message is then repeated for 5 seconds, followed by 15 seconds of steady bargraph display. This message mode is continued until (1) the driver takes some action to change the situation; or (2) the situation changes from a "caution" to a "danger" condition. Figure 2 shows what happens in the latter case.

Subject regulation No. 127 does not offer any guidance to the engineer concerned with these new display concepts since the concepts were not anticipated at the time the regulation was prepared. If the legal interpretation is that the driver must have the vehicle speed displayed to him at every moment, an alternative mode of programming the display would utilize the 0.10 second OFF time slot to display the bargraph for MPH. In this case, the MPH information would not be seen by the driver for only 0.9 seconds (instead of 5 seconds, as in the previous sequence mode).

In either scheme, the basic reason for using one tube to display both MPH/ RPM and caution/danger messages is that the driver is constantly scanning MPH and RPM and will therefore be alerted sooner to a potential breakdown. It is also less costly to the truck purchaser because the cost of the second tube and its associated wiring is eliminated.

We would very much appreciate your guidance in this matter. We have talked by telephone to NHTSA technical personnel at your San Francisco and Washington offices and they have advised that we should seek your legal interpretation.

Very truly yours,

Nicholas M. Stefano

NMS:ml Attachments (2): Figure 1. Caution Message Sequence (Typical) Figure 2. Danger Message Sequence (Typical)