Interpretation ID: nht72-3.47

DATE: 10/13/72

FROM: CHARLES H. HARTMAN FOR DOUGLAS W. TOMS -- NHTSA

TO: Mr. Jesse R. Hollins

TITLE: FMVSS INTERPRETATION

TEXT: This is in response to your petition of August 15, 1972, as supplemented by your brother's letter of August 28, 1972, requesting our consideration of your seat belt warning system as a substitute for the warning and interlock systems currently specified in Motor Vehicle Safety Standard No. 208.

As we understand the operation of your system, one of its operating modes resembles the mode presently specified in S7.3.1 of the standard. Your system provides for the operation of a warning signal when the ignition is "on" and the seat belts at occupied front positions have not been operated. Section S7.3.1, considered by itself, would permit such a system, even though that section does not require the warning to operate unless the engine is operating and the vehicle is in a forward gear.

However, your system does not meet the requirement of S7.3.3 that the warning not operate when the vehicle is idling with the transmission in park or neutral position and the belts have not been operated. The argument presented in your brother's letter is that the sudden operation of the warning system when the transmission is placed in a forward gear would be an annoyance to occupants and would result in circumvention of the system.

The NHTSA position is that the convenience of being able to sit unbuckled in a parked car without the warning is such that this "quiet" period should continue to be required. It may be that some occupants will be bothered when the warning begins to sound as they place the car in gear. However, we are persuaded that the current system would be less likely to be circumvented than a system that has no period of non-operation.

The other operating mode of your system has no direct counterpart in Standard 208. As you describe it, returning the ignition to the "off" position will activate the warning system, even after removal of the key, until the belts are returned to their stowed positions. Our letter of August 17, 1972, explained that this will not conform to the requirement of S7.3.2 that the warning must not operate when the belts at occupied front positions have been operated.

We recognize that there are other possible alternative to the required interlock system as a means of encouraging seat belt usage, and several have been suggested. We consider it important, however, that these systems work in a substantially uniform manner, for maximum public safety, acceptance and convenience. On the basis of all the material we have received to date, including yours, we have decided that our present requirements represent the best combination for the alternative to passive restraints in the period 1973-1975. I therefore must deny your petition to substitute your system, or allow it as an alternative, for the interlock system.