Interpretation ID: nht88-1.57

TYPE: INTERPRETATION-NHTSA

DATE: FEBRUARY 26, 1988

FROM: SHIMAZU, KUNIO -- TOYOTA GENERAL MANAGER

TO: ERIKA Z. JONES -- NHTSA CHIEF COUNSEL

TITLE: INTERPRETATION -- FMVSS 208 -- AUTOMATIC SAFETY BELT PLACEMENT

ATTACHMT: OCTOBER 3, 1988 LETTER FROM JONES TO SHIMAZU

TEXT: Toyota seeks NHTSA's concurrence with its interpretation of the belt placement requirement of FMVSS 208 applicable to automatic safety belts during dynamic testing.

Sec. 10.5.2, setting forth the belt path requirement, states:

S10.5.2 Automatic safety belts. Ensure that the upper torso belt lies flat on the test dummy's shoulder after the automatic belt has been placed on the test dummy.

However, this section does not clearly specify the belt path or how the belt is to be positioned on the dummy's shoulder. We are concerned that test personnel may feel that they are prohibited from adjusting the belt path after the door has been shut , unless the belt fails to lie flat on the test dummy's shoulder.

Compliance tests should not only be repeatable, but conducted under conditions which simulate as closely as possible those of

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the real world. However, the belt path, immediately after the door has been shut, may not be appropriate for compliance testing if it differs from the real world belt path.

This difference occurs because a human occupant moves to operate controls (ignition key, transmission lever, seat adjustment, door lock, etc.) and adjusts the belt for optimum comfort after the belt has first been positioned across the torso. As show n in the video tape and Appendix attached to this letter, the initial belt path after the door closing is changed by occupant movement, and afterward the belt path remains in this new position.

NHTSA recognizes this in the note at the end of FMVSS 208 which states;

NOTE: The concept of an occupant protection system which requires "no action by vehicle occupants," as that term is used in Standard No. 208, is intended to designate a system which will perform its protective restraining function after a normal proce ss of ingress or egress without separate deliberate actions by the vehicle occupant to deploy the restraint system. Thus, the agency considers an occupant protection system to be automatic if an occupant has to take no action to deploy the system but wo uld normally slightly push the seat belt webbing aside when entering or exiting the vehicle or would normally make a slight adjustment in the webbing for comfort.

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Therefore, automatic belts that need slight adjustment by the occupant upon entry or for comfort, are recognized as such under this standard. Accordingly, in the case of this type automatic belt (where slight adjustment is needed) the initial belt pa th immediately after the door is shut differs from that after it is adjusted by the occupant.

For these reasons, we believe that the belt path on the test dummy should be adjusted by test personnel in the manufacturer's and NHTSA's compliance tests to ensure that the belt path simulates that of the real world.

There may be several methods to adjust the belt on the dummy to simulate a real world position. For example, moving the upper torso by grasping the dummy's head, pulling the belt some inches forward from the dummy's chest and releasing it, etc.

However, based on our experience, the results obtained through those procedures may vary. Accordingly, in order to achieve consistency before conducting a compliance test, NHTSA could request the manufacturer to provide its belt position procedure (a s it already now does in specifying its "normal design riding position" of an adjustable seat back).

Incidentally, we believe the most appropriate objective method is to place the belt over an imaginary straight line running from the upper to lower anchorage as seen from head on.

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To test an automatic safety belt vehicle after merely closing the door is not only not repeatable but is not representative of real world conditions and, therefore, would not accurately measure the crashworthiness of the vehicle's occupant protection system.

Enclosures

INVESTIGATION OF BELT PATH

Using a TOYOTA Cressida and a Volkswagen Golf, we investigated whether the belt path on a dummy (the Hybrid III dummy) would differ from that of a human occupant. The Cressida is equipped with a typical motorized automatic belt system, whose shoulder an chorage is motor-driven along the roof side rail. The Golf, on the other hand, is equipped with a typical non-motorized belt system whose non-movable shoulder anchorage is attached to the door frame.

The video tape which accompanies this letter shows the results of our investigation.

Golf

Dummy

The Volkswagen Golf is shown first. After the dummy has been positioned according to the standard, the door is then shut to place the belt across the dummy's torso (please note test personnel made no adjustment to the dummy or the belt after the closing of the door). As the video shows, the belt catches on the dummy's upper shoulder.

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Human Occupant

The same test is then carried out using a human occupant, equivalent to a 50th percentile adult male. Although the belt may lie improperly across the shoulder immediately after the door is shut, when the occupant moves forward to turn the ignition key, operate heater controls, etc. the belt will then move from that position to the middle of the shoulder. Under the same conditions, using a 95th percentile adult male, the belt lies across the middle of the shoulder after the door is shut.

This demonstrates that the unadjusted belt position on the dummy does not represent the normal riding belt position on a human occupant.

Cressida

The Cressida was tested under the same conditions as the Golf.

Dummy

After door closing, the belt lies higher on the dummy than the typical position marked on the chest based on our real world experience. The belt moves more than 30mm downward and stop when test personnel move the dummy's upper torso back and forth by gr asping the head.

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Human Occupant

In the case of the human occupants equivalent to the 50th and 95th percentile adult males, the belts initially lie on the body at high positions. However, through body movement the belt moves to a lower position.

Summary

1. The belt path on a human body right after the door has been closed is, in most cases, quickly changed by occupant movement.

2. The belt path on a test dummy right after the door has been closed differs substantially from the belt path on a human occupant after movement.