Interpretation ID: nht72-4.16

DATE: 10/27/72

FROM: AUTHOR UNAVAILABLE; Richard B. Dyson; NHTSA

TO: Nissan Motor Co., Ltd.

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of September 18, 1972, on the subject of warning system and interlock system operation under Standard No. 208.

The table enclosed with your letter lists all combinations of front seat occupancy and front seat belt usage that are possible in a vehicle with two front seating positions. You ask, as to each of these combinations, whether you have correctly understood the operation of the interlock and warning system. We find that a large majority of the combinations shown in your table are correctly interpreted but that a few are in error or are in need of further clarification.

The primary source of error in the table seems to be confusion as to the effect of the driver's absence from his seat. Under S7.4.1, the conditions under which a failure to operate the belt will require the interlock system to prevent engine operation are specified in S7.4.1(a) and (b). Each of these conditions specifies that the driver's position is occupied, so that if the driver is not in his seat neither condition (a) nor condition (b) is met and interlock system operation is not required.

Applying this interpretation to the matrix in your table discloses that two cases, 18 and 25, are incorrectly interpreted. In each of these cases the driver is not in his seat and the interlock would not be required to operate, even though in both cases the passenger has operated his belt out of sequence and in one case the belt at the vacant driver's position is buckled.

Although interlock operation is not required in cases 18 and 25, a manufacturer would be permitted to design his interlock system to operate in these circumstances. Eighteen and 25 should therefore be treated in the same manner as the other cases in the matrix (11-17, 24) in which interlock operation is shown to be within the manufacturer's discretion.

The warning system, which is required to operate when the ignition is in the start position if the operations required by S7.4.1 to start the engine have not been performed, is on a different footing under conditions where the interlock is permitted, but not required, to operate. Under such conditions, S7.3.5.4 does not require the warning to operate in the start position. We would, however, strongly recommend that the warning system be designed to operate whenever the interlock prevents engine operation, regardless of whether or not S7.4.1 requires operation.

One other case in your table should also be corrected. Under Case 4, you indicate that interlock operation would be within the discretion of the manufacturer. It is our opinion that if the driver has properly operated his belt the interlock and warning system should not operate, even though the belt at the empty passenger's seat has been fastened.

Please advise us if you have further questions.