49 CFR Part 390: Who the Safety Regulations Apply To

49 CFR Part 390 is the gateway rule of the Federal Motor Carrier Safety Regulations: it defines what a commercial motor vehicle is, who counts as a motor carrier, driver, employer and employee, and therefore whether Parts 391 through 399 apply to you at all. It then imposes a handful of obligations of its own — get a USDOT number, mark your vehicles, keep an accident register, produce records on demand, and do not falsify anything.

If you are trying to work out whether you are regulated, this is the part to read first. Everything else in the FMCSRs assumes the answer is yes.

Who do the Federal Motor Carrier Safety Regulations apply to?

The operative applicability text is short. Under 49 CFR 390.3T(a)(1), the rules apply “to all employers, employees, and commercial motor vehicles that transport property or passengers in interstate commerce.”

Three of those terms are defined in 49 CFR 390.5T and each one catches people out:

• Interstate commerce is not just crossing a state line. It means trade, traffic or transportation between a place in a state and a place outside it; between two places in a state through another state or a place outside the United States; or between two places in the same state as part of a movement that originates or terminates outside the state. That last prong is why a purely in-state drayage run from a port can be interstate commerce.
• Employer means any person engaged in a business affecting interstate commerce who owns or leases a commercial motor vehicle in connection with that business, or assigns employees to operate it.
• Employee includes a driver of a commercial motor vehicle — “including an independent contractor while in the course of operating a commercial motor vehicle” — as well as mechanics and freight handlers. Calling a driver a contractor does not move them outside the rule.

Note that the section numbering is untidy here. FMCSA suspended 49 CFR 390.3 and left the parallel 390.3T in force; the same is true of 390.5 and 390.5T, 390.19 and 390.19T, 390.21 and 390.21T. The “T” sections are the operative text. Citations to the non-T numbers still appear throughout the CFR and in FMCSA guidance, and the substantive rules are the same.

What counts as a commercial motor vehicle?

Under 49 CFR 390.5T, a commercial motor vehicle is any self-propelled or towed motor vehicle used on a highway in interstate commerce to transport passengers or property when it meets any one of four thresholds. Meeting one is enough.

Test	Threshold	Cite
Weight	Gross vehicle weight rating or gross combination weight rating or gross vehicle weight or gross combination weight of 4,536 kg (10,001 lbs) or more — whichever is greater	49 CFR 390.5T(1)
Passengers, for compensation	Designed or used to transport more than 8 passengers, including the driver	49 CFR 390.5T(2)
Passengers, not for compensation	Designed or used to transport more than 15 passengers, including the driver	49 CFR 390.5T(3)
Hazardous materials	Transporting material found hazardous under 49 U.S.C. 5103 in a quantity requiring placarding — at any weight	49 CFR 390.5T(4)

Read the weight row carefully. It is the greater of the rating or the actual weight, and it includes combination ratings. A pickup with a 7,000-pound GVWR towing a trailer rated at 7,000 pounds has a gross combination weight rating well past the line. Hot-shot operators discover this constantly.

Read the passenger rows carefully too. The compensation threshold is more than 8 including the driver — a nine-seat van run for hire is a CMV. Without compensation the threshold is more than 15 including the driver.

The hazmat row has no weight floor at all. Placardable quantity in a small van makes it a commercial motor vehicle.

Note also that this Part 390 definition is not the same as the CDL definition in 49 CFR 383.5. A vehicle can be a CMV under Part 390 — bringing the whole FMCSR framework with it — without requiring a CDL to drive. Being a CMV is what obliges you to build driver qualification files under Part 391, run hours-of-service compliance under Part 395, and carry the minimum insurance in Part 387.

Who is exempt?

49 CFR 390.3T(f) lists the exceptions. Unless otherwise specifically provided, the rules do not apply to:

1. School bus operations as defined in 390.5T — except 391.15(e) and (f), 392.15, 392.80 and 392.82;
2. Transportation performed by the federal government, a state, a political subdivision of a state, or a congressionally approved interstate compact agency;
3. Occasional transportation of personal property by individuals, not for compensation and not furthering a commercial enterprise;
4. Transportation of human corpses or sick and injured persons;
5. Fire trucks and rescue vehicles during emergency and related operations;
6. Vehicles designed or used to carry 9 to 15 passengers including the driver, not for direct compensation, provided the vehicle does not otherwise meet the CMV definition — though these operators still must comply with 390.15, 390.19T, 390.21T(a) and (b)(2), 391.15(e) and (f), 392.80 and 392.82;
7. Drivers of vehicles used primarily to transport propane winter heating fuel, or responding to a pipeline emergency, where the rules would prevent response to a qualifying emergency condition.

Separately, 49 CFR 390.39(a) exempts a “covered farm vehicle” and its operator from Part 383 CDL rules and Part 382 drug and alcohol testing, Part 391 Subpart E physical qualifications, Part 395 hours of service, and Part 396 inspection, repair and maintenance. The definition in 49 CFR 390.5 is strict: farm-plated, operated by the farm or ranch owner, operator, employee or family member, used to haul agricultural commodities, livestock, machinery or supplies to or from the farm, and not used in for-hire operations. Above 26,001 pounds the exemption applies within the registration state or within 150 air miles of the farm across state lines; at or below 26,001 pounds it applies anywhere in the United States.

Two important carve-outs on the carve-outs: 49 CFR 382.103(c) states that the 390.3T(f) exceptions do not apply to drug and alcohol testing, and intrastate hazmat carriers are pulled back in for specified parts by 390.3T(g).

How do you get and keep a USDOT number?

Registration in Part 390 is split across two live sections, because FMCSA suspended 49 CFR 390.201 and 390.203 indefinitely (88 FR 80184, November 17, 2023).

New applicants register under 49 CFR 390.200T using Form MCSA-1, the Unified Registration System online application. A “new applicant” is an entity applying for operating authority registration and a USDOT number that has never held an active USDOT, MC, MX or FF number.

Everyone else files under 49 CFR 390.19T. A U.S., Canada, Mexico or non-North America-domiciled carrier conducting interstate operations files the Motor Carrier Identification Report, Form MCS-150 (intrastate hazmat permit holders file MCS-150B; intermodal equipment providers file MCS-150C). Filing is required before beginning operations, and then every 24 months on this schedule:

Last digit of USDOT number	File by the last day of
1	January
2	February
3	March
4	April
5	May
6	June
7	July
8	August
9	September
0	October

The year is fixed by the next-to-last digit: odd means you file in odd-numbered years, even means even-numbered years (49 CFR 390.19T(b)(3)). Failure to complete the biennial update exposes you to civil penalties under 49 U.S.C. 521(b)(2)(B) or 14901(a) and deactivation of your USDOT number (390.19T(b)(4)). Only the legal name or a single trade name may go on the form (390.19T(f)).

Carriers registering vehicles in a state that participates in the PRISM program are exempt from filing separately with FMCSA, provided all required information is filed with the appropriate state office (390.19T(i)). If you are unsure when yours falls, the MCS-150 due date checker works the arithmetic from your number.

What has to be painted on the truck?

Under 49 CFR 390.21T(b), every self-propelled CMV must display:

1. The legal name or a single trade name of the motor carrier operating it, as listed on its MCS-150;
2. The identification number issued by FMCSA, preceded by the letters “USDOT”;
3. If any other person’s name appears on the vehicle, the operating carrier’s information preceded by the words “operated by.”

The physical requirements in 390.21T(c) are specific: on both sides, in letters contrasting sharply with the background, readily legible in daylight from 50 feet while the vehicle is stationary, and maintained that way. Paint or removable devices are both acceptable (390.21T(d)).

Short-term rentals get a narrow accommodation. Under 390.21T(e), a CMV rented for 30 days or fewer — or a leased passenger-carrying CMV on the same term — may display the lessor’s name and USDOT number instead, provided the rental agreement conspicuously carries the renting carrier’s name, address and USDOT number, includes the prescribed law-enforcement cooperation sentence, and is carried on the vehicle for the full term.

What is the accident register, and what belongs in it?

Under 49 CFR 390.15(b), every motor carrier must maintain an accident register for three years after the date of each accident, containing at minimum:

• Date of the accident;
• The city or town, or the nearest one, and the state;
• Driver name;
• Number of injuries;
• Number of fatalities;
• Whether hazardous materials other than fuel spilled from the vehicle’s own fuel tanks were released.

You must also keep copies of all accident reports required by a state or other governmental entity or by insurers (390.15(b)(2)).

The word “accident” is a term of art. Under 49 CFR 390.5T it means an occurrence involving a CMV on a highway in interstate or intrastate commerce resulting in a fatality, a bodily injury where the person immediately receives medical treatment away from the scene, or one or more vehicles incurring disabling damage requiring a tow away from the scene. It expressly excludes occurrences involving only boarding or alighting from a stationary vehicle, and occurrences involving only loading or unloading cargo.

That definition is narrower than “any crash,” and the common error runs in both directions: carriers omit a towaway with no injuries (recordable) and add a parking-lot scuff (not recordable). When in doubt, log it — an over-inclusive register is not a violation.

Separately, 49 CFR 390.15(a) requires you to make all accident-related records and information available to an authorized FMCSA, state, local or third-party representative within the time the request specifies, and to give all reasonable assistance including full, true and correct answers.

What auditors actually check

Part 390 findings tend to be structural — the kind that reframe the whole review.

• Whether you should have been registered at all. If an investigator concludes your operation is interstate under the 390.5T definition and you never filed, everything downstream is unfiled too.
• Biennial update currency. An MCS-150 that has not been touched in three years is visible before anyone arrives, and 390.19T(b)(4) attaches deactivation to it.
• Accuracy of the MCS-150 itself. Cargo classifications, power unit and driver counts, and mileage on that form drive your safety measurement and your expected insurance limit. 49 CFR 390.19T(g) attaches penalties to furnishing misleading information.
• The accident register, against the crash data FMCSA already holds. Investigators arrive knowing your reported crashes; the register is checked against them. Gaps read as concealment even when they are clerical.
• Vehicle markings. Verified on the yard, and one of the easiest violations to write.
• The 48-hour production rule. Under 49 CFR 390.29(b), records held at a regional office or driver work-reporting location must be produced at the principal place of business or another specified location within 48 hours, excluding weekends and federal holidays.
• Record form. 49 CFR 390.31 permits legible copies in lieu of originals, and 49 CFR 390.32 permits electronic documents and signatures — provided electronic records are retainable, accurately reproducible within required timeframes, and accompanied by proof of consent under 15 U.S.C. 7001(c).

Because the 48-hour clock starts when the investigator asks and does not care where your paperwork physically lives, carriers who keep documents, expiry dates and the accident register in one system rather than across a shared drive and three inboxes tend to make that deadline comfortably. That is the problem Fleetive was built around. Before a review, walking through DOT audit preparation is a reasonable rehearsal.

Most common violations

1. Operating in interstate commerce without a USDOT number, usually because the operator believed a pickup-and-trailer combination was under the threshold, or that staying inside one state ended the analysis.
2. A stale MCS-150. The biennial update is missed more than any other filing in the FMCSRs, and it is the one that deactivates your number.
3. Missing or illegible markings — no USDOT prefix, one side only, or a faded decal that fails the 50-foot test.
4. No accident register, or one that only lists crashes the insurer was told about.
5. Misapplying the accident definition, most often by leaving out towaway crashes with no injuries.
6. Blowing the 48-hour production window under 390.29(b).
7. Falsification. 49 CFR 390.35 prohibits fraudulent or intentionally false statements or entries on any application, certificate, report or record required by the subchapter — this is the hook behind back-dated logs and inspection reports, and it is treated far more seriously than the underlying error.
8. Assuming a contractor is not an employee. The 390.5T definition of employee expressly includes independent contractors while operating a CMV, and 49 CFR 390.11 makes the carrier responsible for requiring driver compliance.

Two more prohibitions are worth knowing even though they are rarely cited: 49 CFR 390.13 bars aiding, abetting, encouraging or requiring a carrier or its employees to violate the rules, and 49 CFR 390.36 prohibits harassing a driver using ELD data in a way the carrier knew or should have known would cause a violation of 392.3 or Part 395. Penalties under 49 CFR 390.37 may be civil or criminal; the amounts are inflation-adjusted annually and published in Part 386, Appendix B, so check the current figure rather than a number from a blog.

Where to read the rule

Cornell’s Legal Information Institute mirrors the current text at 49 CFR Part 390, and the definitions section that decides almost every applicability question is 49 CFR 390.5 — remember to read 390.5T alongside it, since that is the operative version.

Once Part 390 tells you that you are regulated, the practical sequence is registration and insurance (Part 387), then driver files (Part 391), then hours of service (Part 395) and vehicle maintenance under Part 396. The DOT compliance guide and the FMCSA regulations overview lay that path out end to end, and every part is indexed in the 49 CFR reference library.

This page is a plain-English summary of a federal regulation, not legal advice. Regulations are amended and section suspensions change; confirm the current text on eCFR or Cornell LII before you rely on it, and consult qualified counsel or your DOT consultant for your specific operation.