Interpretation ID: nht90-4.67

TYPE: Interpretation-NHTSA

DATE: November 29, 1990

FROM: John K. Roberts -- Vice President, Muth Advanced Technologies

TO: Richard Van Iderstine -- NHTSA

TITLE: None

ATTACHMT: Attached to letter dated 1-15-91 to John K. Roberts from Paul Jackson Rice (A37; Std. 108)

TEXT:

Thank you for speaking with me yesterday about FMVSS requirements for automobile and truck mirrors. As I said, Muth Advanced Technologies is developing and marketing a unique vehicle mirror device which may be governed by two or more FMVSS rules (108 an d 111). Correct interpretation of those standards as they apply to this device is very important to us. For this reason, we appreciate being able to speak directly to people who understand the letter and intent of those rules.

For your edification, I have enclosed a brief description of the technology we're working on (presently known as "STM", or "Stop Turn Mirror"). We anticipate STM's being used as safety enhancements on certain vehicles, in combination with (or possibly i n place of) CHMSL's. Hopefully, the enclosed description will give you a clear conception of the device.

Following our conversation, a number of specific questions came to mind regarding the STM and applicable FMVSS Standards:

(1) If the STM satisfies the current explicit requirements of FMVSS 111 and FMVSS 108, is there further NHTSA approval we should pursue before fielding the device?

(2) Would it be reasonable for us to apply for a variance or to seek a change in FMVSS 108, if the STM doesn't meet the letter of FMVSS 108 in certain applications, but demonstrably meets or exceeds the intent of the standard?

(3) Before a pick-up truck CHMSL standard is published, would it be possible to certify the STM as a compliant device and ensure that the wording of the new rule doesn't needlessly prohibit utilization of STM's?

(4) Is it possible that someone at NHTSA would like to see this thing or test it before we go too far in our development and marketing? It may be a useful development in vehicle safety devices with importance to industry and the public. It also may be a ready solution to the difficult issue of requiring CHMSL's on pick-up trucks. We would be happy to support any such investigative effort by supplying a model, information, etc.

If you have any further thoughts on these subjects I would be very interested in hearing them. I'll call next week to follow-up on this.

Enclosure

Muth Advanced Technologies Stop/Turn Mirror The Stop/Turn Mirror (STM) is a system which integrates the functions previously performed separately by rear view mirrors and the Center High Mounted Stop Lamp (CHMSL). The system may be particularly well suited for vans, pick-up and medium duty trucks , sports cars, motorcycles and other vehicles where design of a suitable CHMSL is difficult. The STM offers superior performance as a highly visible stop and turn indication system and simultaneous function as a mirror. Additional benefits are the elim ination of parts and improved aesthetics at a reasonable cost. Field prototypes of the STM will be available by early spring, 1991.

The basis for this product is the observation that vehicle rear view mirrors are placed such that they are quite visible to operators of following vehicles. This same placement is ideal for high visibility stop and turn signals. The STM takes advantage of this geometry by functioning as mirror and a stop/turn lamp.

The STM contains a carefully designed filter and a directional film; these allow the STM to appear as a mirror to a vehicle's driver while appearing as a lamp to the operator of a following vehicle. The filter is a multi-layer dielectric coating applied to the interior surface of the glass to form a dichroic beam splitter or cold mirror. This allows the mirror to reflect a majority of the visible spectrum while transmitting a majority of a discrete band (in this case, red). The directional film conta ins tiny "microlouvers" which allow light rays to radiate directly aft and outboard towards following vehicles. The lamp is actuated by the same circuitry that actuates the standard brake and turn lamps.

Since the STM has an average reflectivity in excess of 65%, it appears to conform with FMVSS 111 requirements for minimum mirror reflectivity.

In some applications, it is anticipated that the STM will directly satisfy the requirements of FMVSS 108, thereby qualifying as a replacement for the standard CHMSL. In other applications, the STM may fulfill the intent of FMVSS 108 without meeting it's explicit requirements. In these cases, the STM may be used in conjunction with an approved CHMSL as an enhancement.

The K.W Muth Company Inc. has applied for US and foreign patents on the STM.