Interpretation ID: nht79-2.4

DATE: 03/28/79

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Cars & Concepts, Inc.

TITLE: FMVSS INTERPRETATION

ATTACHMT: 4/21/76 letter from S.P. Wood to Nissan Motor Co., Ltd.

TEXT:

March 28, 1979

Mr. Moe Pare, Jr. Director of Design Cars & Concepts, Inc. 12500 E. Grand River Brighton, Michigan 48116

Dear Mr. Pare:

This responds to your March 2, 1979, letter concerning the definition of the vehicle sub-classification, "convertible." your letter included several Figures of various vehicle designs and asked whether each would be considered a "convertible" by the National Highway Traffic Safety Administration.

While our regulations do not include a formal definition of "convertible," the agency has stated that it considers a convertible to be a vehicle whose "A" pillar or windshield peripheral support is not joined with the "B" pillar (or rear roof support rearward of the "B" pillar position) by a fixed rigid structural member. Therefore, passenger cars equipped with a "sun roof" or a "Hurst hatch roof" do not qualify as convertibles, because they have a fixed, rigid structural member in the described location (April 21, 1976, letter of interpretation enclosed). This interpretation applies, moreover, whether the rigid structural member joining the "A" and "B" pillars is a hidden reinforcing component or whether the structural member is part of the exterior roof panel.

Given this interpretation, only the Fiat X-19 vehicle design illustrated in your Figure 5 would qualify as a "convertible." Each vehicle design in your other illustrations (Figures 1, 2, 3, 4, 6, 7, 8 and 9) include fixed, rigid structural components joining the "A" and "B" pillar sections of the vehicles and, therefore, would not be classified as convertibles. Likewise, the designs would not be considered "open-body type vehicles" (49 CFR 571.3) for the same reason; the structural member, whether hidden or not, would be considered part of the vehicle top. Also, I would point out that the "open-body vehicle" designation generally refers to multi-purpose passenger vehicles such as "jeeps" or "dune buggies."

I hope this clarification is responsive to your inquiry. If you have any further questions please contact Hugh Oates of my office (202-426-2992).

Sincerely,

Frank Berndt Acting Chief Counsel

Enclosure (See 4/21/76 letter from S.P. Wood to Nissan Motor Co., Ltd.)

March 2, 1979

Mr. Hugh Oates Office of the Chief Council N.H.T.S.A. 400 Seventh Street S.W. Washington, D.C. 20590

Dear Hugh:

Per our telephone conversation, I have become confused regarding the legal definition for a "convertible body". At one time I had felt that any vehicle with structure extending from "A" to "B" pillar would not be classified as a convertible; however, I am unable to locate documentation to that effect.

The only definition I can locate is carried in Part 571.3(b) of the Federal Motor Vehicle Safety standards, which defines an "open-body type vehicle" (a term which is used interchangeably with "convertible" in FMVSS No. 208.S4.1.1.3.2. and No. 208.S4.1.2.3.2.) as a vehicle with no occupant compartment top or one which can be installed or removed by the user at his convenience.

By both definitions, I feel that Figure 1, showing a Mazda RX7 with a removable roof panel, does not qualify as a convertible. As this vehicle has roof side rail structures that go directly from "A" to "B" pillar and a full exterior roof stamping, this car, I feel, ought be classified as a coupe.

Similarly, the Renault Gordini (Figure 2) has a much larger opening (extending from "A" to "C" pillar); however, as the "opening" is still surrounded by roof structure (in plan view), I feel secure in assuming that such a vehicle is a coupe also.

Please look at Figures 3 and 4. These photographs show a 1977 Pontiac Grand Prix with a Hurst hatch roof, and a 1979 Chrysler Cordoba with an ASC (American Sunroof Corporation) hatch roof installation. These roofs are similar in that both rely on two "U"-shape openings cut into the roof in a manner that would allow an exterior "roof panel section" along the vehicle's longitudinal centerline. These roofs are installed on "coupe" bodies, but as part of this installation the entire "occupant compartment top" /refer to Part 571.3(b)/, from left, side DLO to right, side DLO, is never removed (either by the manufacturer or user). Again, using both mentioned definitions, I feel these vehicles fall outside the classification of a convertible or "open-body type vehicle".

Now examine Figure 5 showing a Fiat X-19 targa top. As is clear from the photo, this vehicle has "A" and "B" pillars with transverse (to the plan view centerline) structure extending from both "A" and "B" pillars, but clearly has a completely removable "occupant compartment top" with no structure at all between the "A" and "B" pillars (above the beltline). Using both above definitions, this car is clearly a convertible.

Figure 6 shows the roof structure employed on a 1977 Corvette. While this car does have centerline reinforcement member, it is not part of the exterior roof panel sections. Because this center member is not part of the roof panel, and is usually hidden from view, I feel this component takes on the character of a "central (in side view)" reinforcing member and is therefore more closely related to the conventional old style convertible chassis reinforcements than the vehicle's occupant compartment top.

Finally I have come to my real area of concern, shown in Figures 7, 8, and 9. These Cars & Concepts roofs have been granted U.S. Patent No. 4,138,155 which is based largely on the Cars & Concepts installation requirement that the entire occupant compartment top (from right, side DLO to left, side DLO) is completely removed. Similar to the Corvette, our roof also uses a hidden centerline structure which takes the place of the needed chassis reinforcements. Also similar is the "panel to panel" configuration used in our roofs (see Page 2 of Figure 6). These two removable panels comprise (virtually) the entire "occupant compartment top". A basic difference between our roof and that of the Corvette is that our roof has a full width exterior roof panel at the windshield header (as does the X-19), and Chevrolet never actually removes the entire occupant compartment top (including center reinforcement; this center reinforcement is part of the windshield header structure and is basic to the vehicle's construction) of the Corvette.

To summarize, it seems obvious to me that a Fiat X-19 is a convertible, while a coupe with a sunroof is not. It does not seem to me, however, that a car with a Hurst hatch which does not remove the entire occupant compartment top (roof panel) is a convertible. By the same token, a Corvette never exists without an overhead centerline reinforcement member, but the entire exterior roof portion is removable creating a vehicle that fits the N.H.T.S.A.'s criterion for an "open-body". Finally on the Cars & Concepts roof installation, the entire occupant section of a coupe is removed (at this stage it is clearly a targa type vehicle); then in place of chassis reinforcement, we add a centerline structural member and install a removable two piece occupant compartment top.

My question obviously is: between the Fiat, the Corvette, Hurst's roof, and our roof, which (if any) would the N.H.T.S.A. consider a convertible? Thank you for your consideration; please call with any questions.

Sincerely,

Moe Pare, Jr. Director of Design

MP/dma

cc: D. Draper