Interpretation ID: nht89-2.87

TYPE: INTERPRETATION-NHTSA

DATE: 08/30/89

FROM: STEPHEN P. WOOD -- NHTSA ACTING CHIEF COUNSEL

TO: E. H. GALLOWAY -- UNIFORM TIRE QUALITY GRADING TEST FACILITY

TITLE: INFLATION PRESSURES FOR TRACTION GRADING PROCEDURES IN UTQGS

ATTACHMT: ATTACHED TO LETTER DATED 11/01/89 FROM STEPHEN P. WOOD -- NHTSA TO FRANK E. TIMMONS -- RUBBER MANUFACTURERS ASSOCIATION, REDBOOK A34, STANDARD 109, PART 575.104; LETTER DATED 09/28/89 FROM FRANK E. TIMMONS -- RUBBER MANUFACTURERS ASSOCIATION TO STEPHEN P. WOOD -- NHTSA, OCC 3994.

TEXT: In telephone conversations with Steve Kratzke and Marvin Shaw of my staff on August 10, 1989, you requested written confirmation of your interpretation of a requirement set forth in the traction grading procedures of the Uniform Tire Quality Grading Stan dards (UTQGS; 49 CFR @ 575.104). Specifically, you noted that @ 575.104(f)(2)(i)(B) specifies that one "inflate the tire to 24 psi, or, in the case of a tire with inflation pressure measured in kilopascals, to 180 kPa." There is a similar provision for readjusting the inflation pressure of tires during traction testing in @ 575.104(f)(2)(i)(D).

You stated that these provisions are clear as to the appropriate inflation pressure to be used during the testing of tires whose inflation pressure is expressed solely in English units (as pounds per square inch or "psi") or solely in metric units (as ki lopascals or "kPa"). However, you suggested that there is some uncertainty about the appropriate inflation pressure to be used with tires whose inflation pressure is expressed in both English units and the equivalent metric units, an increasingly common practice. You stated that you have been inflating tires whose inflation pressure is expressed in both English and metric units to 24 psi during testing for traction grading, and asked that we confirm that this is the proper inflation pressure for these tires. Your interpretation is correct.

The language of the regulation sets forth a general requirement for an inflation pressure of 24 psi, and a subordinate requirement that tires "with inflation pressure measured in kilopascals" use an inflation pressure of 180 kPa. An examination of the b ackground of this language shows that the alternative inflation pressure of 180 kPa is to be used only for tire sizes that have inflation pressures specified only in kilopascals.

As you know, the UTQGS were originally promulgated with a requirement that all tires use an inflation pressure of 24 psi during the traction testing. This created some problems for tires whose inflation pressure was expressed solely in metric units. In a February 7, 1979 letter to Mr. Leon Conner, the agency stated:

In the situation where no cold inflation pressure exactly equivalent to the specified pressure of 24 psi is stated in [the tire tables] for a tire size designation, the tires to be tested are inflated to the pressure listed for the tire size designati on in [the tire tables] which is nearest to 24 psi, i.e., 180 kPa for tires with inflation pressures measured in kilopascals. The agency plans to issue an interpretive amendment to the regulation clarifying this point.

As indicated in the letter to Mr. Conner, the agency proposed to amend the UTQGS in a notice published October 1, 1979 (44 FR 56389). The preamble to that notice described the proposal as being addressed to tires that do not have any inflation pressure corresponding precisely to 24 psi, and proposing to amend the regulation to provide that those tires should use an inflation pressure of 180 kPa. The final rule adopting this change stated that it was adopting the inflation pressure proposed in the NPRM . See 45 FR 70273, October 23, 1980. This background indicates that the agency intended tires to be inflated to 180 kPa during traction testing only if no information was shown for that tire size under a column for an inflation pressure of 24 psi in the tire tables formerly incorporated in Standard No. 109. The only tire sizes for which information was not shown in a 24 psi column were tire sizes whose inflation pressure was expressed exclusively in metric units. Hence, any tires whose inflation press ure is expressed in both English and metric units should be inflated to 24 psi during the UTQGS traction testing.

Our second comment concerns the fact that in the turn signal mode the unused turn signal lamp would continue to be illuminated when the brake pedal is applied. Thus, an observer would see a flashing turn signal and a steady burning one, whereas with an ordinary vehicle, the observer would see only the flashing turn signal. Whether the presence of the steady burning turn signal on the side of the vehicle opposite the flashing turn signal would detract from the effectiveness of the flashing turn signal, and by obscuring its message make it "partially inoperative", is difficult to judge. Certainly, when a vehicle is signaling a turn, it does not appear necessary to also indicate, to the front, that it is stopping.

These remarks also serve as some comments of this Office as to "safety benefits" that might result from vehicles equipped with your device. Certainly, no standard lighting equipment on vehicles today indicate from the front that the brake pedal is being applied. This is an interesting concept, and we appreciate your interest in enhancing motor vehicle safety.

Sincerely,