§FMCSR.com
Historical textIn force on Oct. 1, 2004Source: annual CFR editions 1996–2004

§ 393.40 Required brake systems.

Wording first on file in the 1996 annual edition, superseded by the 2005 annual edition.

govinfo, 2004 edition ↗
Before Jan. 1, 2017 the record is one snapshot per annual CFR edition, revised as of October 1. This is the 2004 edition's wording. An amendment that took effect between Oct. 1, 2004 and Oct. 1, 2004 would not appear until the next edition, so check the citations below and the Federal Register for exact effective dates.
49 CFR § 393.40 — Required brake systems.. Text in force on October 1, 2004. This wording effective October 1, 1996 to October 1, 2005. Source: govinfo, 2004 edition, https://www.govinfo.gov/app/details/CFR-2004-title49-vol4/CFR-2004-title49-vol4-sec393-40. Retrieved from FMCSR.com, https://fmcsr.com/reg/393.40?asof=2004-10-01, on October 26, 2026. Unofficial compilation; verify against the official source.

(a) General. A bus, truck, truck tractor, or a combination of motor vehicles must have brakes adequate to control the movement of, and to stop and hold, the vehicle or combination of vehicles.

(b) Specific systems required. (1) A bus, truck, truck tractor, or combination of motor vehicles must have—

(i) A service brake system that conforms to the requirements of § 393.52; and

(ii) A parking brake system that conforms to the requirements of § 393.41.

(2) A bus, truck, truck tractor, or a combination of motor vehicles manufactured on or after July 1, 1973, must have an emergency brake system that conforms to the requirements of § 393.52(b) and consists of either—

(i) Emergency features of the service brake system; or

(ii) A system separate from the service brake system.

A control by which the driver applies the emergency brake system must be located so that the driver can readily operate it when he/she is properly restrained by any seat belt assembly provided for his/her use. The control for applying the emergency brake system may be combined with either the control for applying the service brake system or the control for applying the parking brake system. However, all three controls may not be combined.

(c) Interconnected systems. (1) If the brake systems specified in paragraph (b) of this section are interconnected in any way, they must be designed, constructed, and maintained so that, upon the failure of any part of the operating mechanism of one or more of the systems (except the service brake actuation pedal or valve)—

(i) The vehicle will have operative brakes; and

(ii) In the case of a vehicle manufactured on or after July 1, 1973, the vehicle will have operative brakes capable of performing as specified in § 393.52(b).

(2) A motor vehicle to which the emergency brake system requirements of Federal Motor Vehicle Safety Standard No. 105 (§ 571.105 of this title) applied at the time of its manufacture conforms to the requirements of paragraph (c)(1) of this section if—

(i) It is maintained in conformity with the emergency brake requirements of Standard No. 105 in effect on the date of its manufacture; and

(ii) It is capable of performing as specified in § 393.52(b), except upon structural failure of its brake master cylinder body or effectiveness indicator body.

(3) A bus conforms to the requirements of paragraph (c)(1) of this section if it meets the requirements of § 393.44 and is capable of performing as specified in § 393.52(b).

[36 FR 20297, Oct. 20, 1971, as amended at 37 FR 5251, Mar. 11, 1972]

Amendment history

4 distinct wordings on file since Oct. 1, 1996
  1. Oct. 1, 2009 → presentannual editions 2009–2016diff vs. previous
    [70 FR 48048, Aug. 15, 2005, as amended at 72 FR 9870, Mar. 6, 2007]
  2. Oct. 1, 2007 → Oct. 1, 2009annual editions 2007–2008diff vs. previous
    [70 FR 48048, Aug. 15, 2005, as amended at 72 FR 9870, Mar. 6, 2007]
  3. Oct. 1, 2005 → Oct. 1, 2007annual editions 2005–2006diff vs. previous
    [70 FR 48048, Aug. 15, 2005]
  4. Oct. 1, 1996 → Oct. 1, 2005annual editions 1996–2004viewing
    [36 FR 20297, Oct. 20, 1971, as amended at 37 FR 5251, Mar. 11, 1972]

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.