Interpretation ID: 23729.ztv
Mr. Kevin Thies
26713 138th Place, SE
Kent, WA 98042-8056
Dear Mr. Thies:
This is in reply to your letter of October 4, 2001, asking for an interpretation of Federal Motor Vehicle Safety Standard No. 108. We regret the delay in responding to you.
You quoted S5.5.4 which states in pertinent part "The stop lamps on each vehicle shall be activated upon application of the service brakes." You report that the stop lamps on your vehicle "will turn on upon initial application of the service brakes." However, "as I come to a stop, I let up a little bit on the brake pedal for a smooth stop. When I let up that little bit of pedal pressure, the brake lights turn off even though the service brakes are still applied." You ask whether your vehicles performance complies with S5.5.4.
Without conducting specified compliance testing, we do not have an opinion on the behavior of your particular vehicle. Manufacturers are required in good faith to certify that their vehicles meet all applicable Federal motor vehicle safety standards. We will, however, comment on the general question of whether stop lamps may be deactivated while the service brakes are applied.
Standard No. 108 requires, as you have noted, that the stop lamps be activated upon application of the service brakes. We have also stated that implicit in the requirement that stop lamps be activated upon application of the service brakes is the requirement that they must be deactivated when the service brakes are not applied (letters of June 3, 1991 to Norman H. Dankert and of September 22, 1997, to Senator Phil Gramm, copies enclosed).
In interpreting S5.5.4, a distinction must be made between depression of the brake pedal by a driver and application of the service brakes. In a letter of May 8, 1991, to John E. Calow (copy enclosed), we observed that when a brake pedal is depressed, there may be a small amount of "free play" before the service brake begins to apply. We went on to say that we would consider lamp activation required "as soon as any measurable brake torque occurs." Consistent with this opinion, we would say that stop lamps should remain activated whenever any measurable brake torque exists.
Sincerely,
Jacqueline Glassman
Chief Counsel
Enclosures
ref:108
d.6/10/02