Dear Mr. Haenchen:
This is in response to your letter regarding Volkswagen's (VW) plan to introduce ceramic dots on selected areas of passenger motor vehicle windows in order to reduce energy transmission on the car's glazing. I sincerely apologize for the delay in this response.
In your letter, you suggested that one possible means of reducing energy transmission into the interior of cars would be to apply extensive tinting or ceramic dots over extended areas of the glazing on those cars. You provided, in Attachments I and II of your letter, diagrams of the proposed areas of the glazing that would be shaded under your proposal, which included shading at the top (in the shade band areas) of the windshield as well as at the bottom. Shading on side and rear glazing was also shown. You offer a rationale that all of these areas may have less than 70% light transmissibility, and still comply with Standard No. 205, Glazing Materials (49 CFR /571.205).
Your rationale begins with the observation that Section 4.2 of ANS Z26.1 has specifications for items 1 and 2 glazing which refer to footnotes 1 and 3 when specifying Test 2 - Light Transmittance. Those footnotes allow areas of the glazing to have less than 70% light transmittance if the areas are not within the "levels required for driving visibility."
These footnotes are referring mainly to shade bands on the upper edge of the windshield. You also referred to SAE J100 (passenger car glazing shade bands), which defines a "glazing shade band" as "an area of the vehicle glazing through which light transmission is less than required for use at levels requisite for driving visibility by [ANS] Z26.1." SAE J100 recommends shade bands only on the upper edge of the glazing. However, you implied that this recommended practice does not necessarily result from a determination that all other portions of the glazing are at "levels required for driving visibility," the limitation set forth in Standard No. 205.
Instead, your letter set forth a suggested definition of the term "levels required for driving visibility." In a February 15, 1974 letter from this agency to Mr. George Nield, NHTSA said, "We consider the word "levels" in Standard 205 to mean vertical heights in relation to the driver's eyes." You noted that EEC Directive 77/649 specifies levels requisite for driving visibility in the driver's 180 degree forward direct field of vision, and that Section 5.1.3 of this Directive specifies the boundaries for the driver's forward direct field of vision. You stated that this Directive provides guidelines for determining which areas of the glazing are "requisite for driving visibility." You stated that VW has tested its proposed shade bands around the lower edge and vertical sides of the glazing, as shown in Attachments I and II of your letter, according to the specifications of Directive 77/649 and concluded that "ceramic dots in the area defined in [the EEC directive] very well cover the vertical heights in relation to even small drivers' eyes, which are 'requisite for driving visibility'." Based on this information, you asked the agency whether your proposal to include tinted bands or ceramic dots with light transmittance of less than 70 percent in areas beyond the shade band of the windshield would comply with Standard No. 205. The answer to your question is no.
We agree with your observation that neither Standard No. 205 nor ANS Z26 explicitly states how one determines whether or not an area is "requisite for driving visibility." Our February 15, 1974 letter explained that one would make such a determination by considering the vertical height of the glazing in relation to the driver's eyes.
We subsequently considered this subject again in a June 19, 1987 letter to a manufacturer whose identity was kept confidential. I have enclosed a copy of this letter for your information. As you will see, we concluded in this letter that the particular proposed head-up display described in the manufacturer's letter would not be located in an area of the windshield that was "requisite for driving visibility," and therefore vehicles equipped with this head-up display would not appear to violate Standard No. 205. This conclusion was based on the fact that the display would not obstruct the driver's forward visibility any more than typical hood designs or unretracted head lamps.
Applying this reasoning to your plans to tint a band along the bottom of the windshield, it appears that this area is "requisite for driving visibility," except for that portion through which the shortest driver sees the hood or other parts of the vehicle. We again conclude that it is not requisite for driving visibility that the driver see the hood of the vehicle he or she is driving.
You also asked about putting shade bands on the lower edges of all side windows and over most of the surface area of the rear window in the car. These areas cover parts of the glazing through which the driver could see not just parts of the car being driven, but also the road and traffic to the side and rear of the car. In many of our previous interpretations, we have said that all windows in passenger cars are requisite for driving visibility and must, therefore, meet the 70 percent light transmittance requirement in Test 2 of ANS Z26. See, for example, the enclosed letters of April 4, 1985 to Mr. Armond Carderelli and of August 4, 1983 to Ms. Mary Ruth Harsha. This position was taken after considering the number of potential driving situations in which the entire surface area of any of these windows may be needed to allow the driver to analyze the traffic situation and react to it properly and promptly.
As shown by our June 19, 1987 letter to the unnamed manufacturer, it is possible for a party to rebut this presumption. To do so, however, the party must present clear and convincing evidence to show that the area of the window surface in question is at a level that would never enhance driver visibility. We do not believe your letter shows this for the side and rear window area surfaces shown in Attachments I and II.
Your letter attempts to show that the extended shade bands on the side and rear windows are at levels of the glazing that are not requisite for driving visibility by relying primarily on a European Economic Community Directive. We note that this Directive has not been referenced by or incorporated into Standard No. 205. Whatever the ultimate value of this Directive may prove to be in determining what levels on windows are requisite for driving visibility, the agency has not analyzed the recommendations of the EEC directive in detail. Thus, we are not in a position to comment on whether the guidelines established in this Directive are sufficient for defining levels which are requisite for driving visibility, within the meaning of Standard No. 205.
Additionally, another source of information that is not referenced by or incorporated into Standard No. 205 appears to disagree with the EEC directive. This is the Society of Automotive Engineers (SAE) Recommended Practice J100, which indicates that the only levels of windows that are known not to be requisite for driving visibility are bands along the upper edge of the windshield. SAE J100 suggests that the areas along the side and rear window you propose to tint darkly may be at levels requisite for driving visibility. As noted above, NHTSA has not yet evaluated this situation. However, the SAE recommendation suggests that it may not be as simple to determine the levels that are requisite for driving visibility as implied in your letter.
Because of these uncertainties, we cannot conclude that the areas shown in Attachments I and II are not at levels requisite for driving visibility. Accordingly, the presumption that all of the window surfaces in this car are at levels requisite for driving visibility has not been rebutted. This means that if a vehicle has side and rear window portions that do not meet the 70 percent light transmittance requirements, as shown in your Attachments I and II, the vehicle would not comply with Standard No. 205.
I would also like to respond to your assertion that, since your company could block the areas of the side and rear window in question with sheet metal, those areas must be interpreted as not being at "levels requisite for driving visibility," within the meaning of Standard No. 205. We have already considered and rejected this argument in a June 30, 1980 letter to Mr. Hisakazu Murakami (copy enclosed). In that letter, we said, "While there currently are no requirements for the size of window openings, the agency must interpret Standard No. 205 to require window openings that are present to have complying glazing."
Although we have concluded that the areas on the side and rear windows are at levels requisite for driving visibility, we believe that it is appropriate to again re-examine the question of whether we should more precisely specify those areas of windows that are at "levels requisite for driving visibility." As we stated in the enclosed June 19, l987 letter, we plan to initiate a rulemaking action to address this issue, instead of continuing our case-by-case consideration of whether particular areas are at levels requisite for driving visibility.
Again I apologize for the delay in this response. Please let me know if you have any further questions on this subject.
Erika Z. Jones Chief Counsel