§FMCSR.com
Current textIn force on Sept. 30, 2010Source: annual CFR editions 2009–2016

§ 325.75 Ground surface correction factors. 1

Current wording, in the annual edition revised as of Oct. 1, 2009.

govinfo, 2009 edition ↗
Before Jan. 1, 2017 the record is one snapshot per annual CFR edition, revised as of October 1. This is the 2009 edition's wording. An amendment that took effect between Oct. 1, 2009 and Sept. 30, 2010 would not appear until the next edition, so check the citations below and the Federal Register for exact effective dates.
49 CFR § 325.75 — Ground surface correction factors. 1. Text in force on September 30, 2010. This wording effective October 1, 2009 to present. Source: govinfo, 2009 edition, https://www.govinfo.gov/app/details/CFR-2009-title49-vol5/CFR-2009-title49-vol5-sec325-75. Retrieved from FMCSR.com, https://fmcsr.com/reg/325.75?asof=2010-09-30, on October 26, 2026. Unofficial compilation; verify against the official source.

1 Table 1, in § 325.7 is a tabulation of the maximum allowable sound level readings taking into account both the distance correction factors contained in § 325.73 and the ground surface correction factors contained in § 325.75.

(a) Highway operations. When measurements are made in accordance with the rules in subpart D of this part upon a test site which is “hard,” a correction factor of 2 dB(A) shall be subtracted from the maximum observed sound level reading generated by the motor vehicle to determine whether the motor vehicle conforms to the Standards for Highway Operations, 40 CFR 202.20.

(b) Stationary test. When measurements are made in accordance with the rules in subpart E of this part upon a test site which is “soft,” a correction factor of 2 dB(A) shall be added to the numerical average of the recorded maximum observed sound level readings generated by the motor vehicle to determine whether the motor vehicle conforms to the Standard for Operation Under Stationary Test, 40 CFR 202.21.

Amendment history

2 distinct wordings on file since Oct. 1, 1996
  1. Oct. 1, 2009 → presentannual editions 2009–2016diff vs. previousviewing
  2. Oct. 1, 1996 → Oct. 1, 2009annual editions 1996–2008

A new entry appears whenever the regulatory words change between government snapshots. Day-precise from the eCFR (2017 onward); before that, one snapshot per annual CFR edition (revised as of October 1). Bracketed citations are the Federal Register history printed with the section.