USA Banner

Official US Government Icon

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure Site Icon

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Portions of the Department of Transportation are currently in shutdown/furlough status due to a lapse in appropriations. Please continue to monitor this page for updates on DOT’s operating status.
U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Regulatory Guidance

Welcome to the FMCSA Guidance Portal. This web portal is a searchable, indexed database that contains and links to all guidance documents in effect from the Federal Motor Carrier Safety Administration. The guidance documents lack the force and effect of law, unless expressly authorized by statute or incorporated into a contract.

To comment on any guidance document, or to request issuance, reconsideration, modification, or rescission of any guidance document, please identify the guidance document in your request and send it to: FMCSAguidance@dot.gov. NOTE: The FMCSAguidance mailbox is not intended to serve as a mailbox for general inquiries. For inquiries that go beyond the limited purpose of the FMCSAguidance mailbox, please call FMCSA's Information Line (800-832-5660) or visit FMCSA's "Contact Us" page to send your inquiry to the appropriate mailbox.

Subject Agency Identifier Topic Issued Date
Are there established criteria in the FMCSRs to determine the minimum sound level of horns on CMVs? FMCSA-VEH-393.81-Q02 Do FMCSRs specify minimum sound levels for horns?
Is a heat shield mandatory on a vertical exhaust stack? FMCSA-VEH-393.83-Q01 Heat shield on vertical exhaust stack?
Does § 393.83 specify the type of exhaust system, vertical or horizontal, to be used on trucks or truck tractors? FMCSA-VEH-393.83-Q02 Vertical vs. horizontal exhaust systems
May a triangular-shaped flag or device be used by itself to mark an oversized load? FMCSA-VEH-393.87-Q01 Triangular flag to mark oversized load
Does § 393.88 restrict the use of closed circuit monitor devices being used as a safety viewing system that would eliminate blind-side motor carrier accidents? FMCSA-VEH-393.88-Q01 Use of closed-circuit TV to monitor blind spots
For the purposes of § 393.89, would a spline and yoke that is secured by a nut be considered a sliding connection? FMCSA-VEH-393.89-Q01 What is a sliding connection under § 393.89?
On multiple drive shaft buses, does § 393.89 require that all segments of the drive shaft be protected no matter the segments’ length? FMCSA-VEH-393.89-Q02 Protection for multiple drive shafts on buses
How does an existing pillow bearing (shaft support) on a multiple driveshaft system affect the requirement? FMCSA-VEH-393.89-Q03 Pillow bearings on multiple driveshaft systems
If a CMV, other than a motor coach, is equipped with a passenger seat, is a seat belt required for the passenger seat? FMCSA-VEH-393.93-Q01 Seat belt for truck passenger seats
Are pressure gauges the only acceptable means for a visual determination that a fire extinguisher is fully charged? FMCSA-VEH-393.95-Q01 Visual determination that fire extinguisher is charged