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  • § 325.1
    Scope of the rules in this part.
  • § 325.3
    Effective date.
  • § 325.5
  • § 325.7
    Allowable noise levels.
  • § 325.9
    Measurement tolerances.
  • § 325.11
    Issuance, amendment, and revocation of the rules in this part.
  • § 325.13
    Inspection and examination of motor vehicles.
  • § 325.21
    Scope of the rules in this subpart.
  • § 325.23
    Type of measurement systems which may be used.
  • § 325.25
    Calibration of measurement systems.
  • § 325.27
    Use of a windscreen.
  • § 325.31
    Scope of the rules in this subpart.
  • § 325.33
    Site characteristics; highway operations.
  • § 325.35
    Ambient conditions; highway operations.
  • § 325.37
    Location and operation of sound level measurement system; highway operations.
  • § 325.39
    Measurement procedure; highway operations.
  • § 325.51
    Scope of the rules in this subpart.
  • § 325.53
    Site characteristics; stationary test.
  • § 325.55
    Ambient conditions; stationary test.
  • § 325.57
    Location and operation of sound level measurement systems; stationary test.
  • § 325.59
    Measurement procedure; stationary test.
  • § 325.71
    Scope of the rules in this subpart.
  • § 325.73
    Microphone distance correction factors. 1
  • § 325.75
    Ground surface correction factors. 1
  • § 325.77
    Computation of open site requirements—nonstandard sites.
  • § 325.79
    Application of correction factors.
  • § 325.91
    Exhaust systems.
  • § 325.93

Part 325

§ 325.93: Tires.

(a) Except as provided in paragraph (b) of this section, a motor vehicle does not conform to the visual tire inspection requirements, 40 CFR 202.23, of the Interstate Motor Carrier Noise Emissions Standards, if inspection of any tire on which the vehicle is operating discloses that the tire has a tread pattern composed primarily of cavities in the tread (excluding sipes and local chunking) which are not vented by grooves to the tire shoulder or circumferentially to each other around the tire.

(b) Paragraph (a) of this section does not apply to a motor vehicle operated on a tire having a tread pattern of the type specified in that paragraph, if the motor carrier who operates the motor vehicle demonstrates to the satisfaction of the Administrator or his/her designee that either—

(1) The tire did not have that type of tread pattern when it was originally manufactured or newly remanufactured; or

(2) The motor vehicle generates a maximum sound level reading of 90 dB(A) or less when measured at a standard test site for highway operations at a distance of 15.3 meters (50 feet) and under the following conditions:

(i) The measurement must be made at a time and place and under conditions specified by the Administrator or his/her designee.

(ii) The motor vehicle must be operated on the same tires that were installed on it when the inspection specified in paragraph (a) of this section occurred.

(iii) The motor vehicle must be operated on a highway having a posted speed limit of more than 56.3 kph (35 mph).

(iv) The sound level measurement must be made while the motor vehicle is operating at the posted speed limit.

Citation: [40 FR 42437, Sept. 12, 1975, as amended at 60 FR 38743, July 28, 1995]


Although we make every effort to assure that the information we provide is complete and accurate, it is not intended to take the place of published agency regulations. Regulations issued by the U.S. Department of Transportation and its Operating Administrations are published in the Federal Register and compiled in the U.S. Code of Federal Regulations (CFR). Copies of appropriate volumes of the CFR in book format may be purchased from the Superintendent of Documents, U.S. Government Printing Office, or examined at many libraries.

The CFR may also be viewed online at

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