Interpretation ID: 1983-2.24

TYPE: INTERPRETATION-NHTSA

DATE: 07/05/83

FROM: Frank Berndt, NHTSA

TO: Koji Tokunaga -- Manager of Engineering, Isuzu Motors America, Inc.

TITLE: FMVSS INTERPRETATION

TEXT:

Mr. Koji Tokunaga Manager of Engineering Isuzu Motors America, Inc. 21415 Civic Center Drive Southfield, Michigan 48076

Dear Mr. Tokunaga:

This responds to your letter of May 26, 1983, asking whether a continuous loop seat belt system you are considering would comply with the requirments of Safety Standard No. 208, Occupant Crash Protection.

Continuous seat belt systems are permissible under Safety Standard No. 208 if certain conditions are met. Paragraph S7.1.1 of that standard requires adjustment of the lap belt portion of Type 2 belts "by means of an emergency locking or automatic-locking retractor" and adjustment in most cases of the upper torso portion "by means of an emergency-locking retractor." The language permits some single retractor, continuous loop systems if the single retractor does "automatically adjust" the tension of the lap belt portion to prevent excessive slack. Because of the danger of submarining due to a slack lap belt, the agency has restricted the acceptability of continuous loop systems under S7.1.1.

To conform to the requirements, the buckle of the assembly must be designed by the manufacturer with a sufficiently low level of friction to qualify the lap portion as automatically adjusting. This means that when the belt is buckled by the vehicle occupant, the retractor must be capable of cinching the lap belt tightly around the occupant's pelvic area (regardless of where the buckle tongue is located along the belt webbing when the belt is fastened). The friction in the buckle tongue cannot be so high that the occupant must manually pull the belt webbing through the tongue to tighten the lap belt.

We note your statement that the one-way frictional bar included in your contemplated belt design "permits the wearer to fasten the lap belt more tightly than the tension from the ELR usually achieves." This is certainly permissible, provided the ELR does tighten the belt sufficiently for the lap belt to be considered automatically adjustable. You will have to make this determination, however. Please note that it is the manufacturer's responsibility to determine whether or not its belt design complies with the standard. The agency does not offer advance approval of any motor vehicle or piece of motor vehicle equipment. Further, the agency does not make determination of compliance of a vehicle or item of equipment prior to the manufacturer's certification of that vehicle or equipment.

I hope this clarification will be of help to you in your design plans.

Sincerely,

Original Signed By Frank Berndt Chief Counsel

Mr. Frank Berndt Chief Counsel

Subject: New Seat Belt System - Compliance with FMVSS 208. S7.1.1

Dear Mr. Berndt:

The purpose of this letter is to request your confirmation on the interpretation of the requirements of FMVSS 208 S7.1.1 in the context of our new seat belt system which we plan to use as soon as possible for the front outboard seating postions on our passenger cars.

This belt system is of a continous webbing loop type with an emergency locking retractor (ELR) installed on the lower part of the B-pillar. The belt webbing goes up from the ELR through a metal ring mounted on the upper part of the B-pillar, then downward diagonally across the occupant's upper torso, through a latch plate which couples the belt to the inboard buckle. Then sideways across the occupant's lap, and to the outboard anchor.

The new feature of this design is a one-way frictional bar incorporated in the latch plate which in effect is the junction between lap and shoulder portions of the webbing. This device permits the wearer to fasten the lap belt more tightly than the tension from the ELR usually achieves, while preventing the lap belt from loosening out as long as the belt is worn. When the belt is worn by the occupant, any slack in the lap belt is removed by his action to pull out the shoulder belt from the retractor. Even when he did not tighten the lap belt snugly, tensions on the shoulder belt caused by his normal motions during vehicle operation work to cause the slack in the lap belt to be taken up by the retractor.

A webbing tension-relieving device is not incorporated in this belt system.

We believe this design meets the intent of FMVSS 208 S7.1.1 because the one-way feature of the latch plates does no interfere with the function of the single retractor to automatically adjust the tension of the lap belt portion ot prevent excessive slack as mentioned in the interpretation letters issued by NHTSA to Renault (dated Sept. 25, 1972) General Motors (dated March 27, 1975) and to Chrysler (dated June 13, 1975).

We request your letter of confirmation regarding this interpretation of FMVSS 208 S7.1.1 in the context of the belt system design described above. Since our final tooling commitments to produce this system must be made very shortly, we would appreciate your prompt review and response.

We are looking forward to hearing from you.

Sincerely yours,

Koji Tokunaga Manager of Engineering