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Texas Transportation Code chapter 644: commercial truck safety rules explained

The official text of the Texas statute that has the public safety director adopt safety rules for commercial motor vehicles and allows the federal safety regulations to be adopted by reference, with a plain-language explanation. Text last checked October 27, 2026.

10 min readPublished October 27, 2026Last updated October 27, 2026Edited by Joseph Budzinski, CTO, InjuryClaimGuide

The short answer

Texas Transportation Code chapter 644 has the public safety director adopt rules regulating the safe transportation of hazardous materials and the safe operation of commercial motor vehicles, and those rules must be consistent with federal regulations (Transp. Code §644.051). The director may adopt all or part of the federal safety regulations by reference (§644.051(c)). Violating a rule adopted under the chapter is an offense, and knowingly operating a commercial motor vehicle in violation of an out-of-service order issued under 49 C.F.R. Section 385.13(d)(1) carries higher penalties when the vehicle was involved in a collision that caused bodily injury or death (§644.151).

This entry provides general informational guidance and is not legal advice.

Key facts (as of 2026-10-27)

  • Who makes the rules. The public safety director, after notice and a public hearing (§644.051(a)). "Department" in the chapter means the Department of Public Safety (§644.001(2)).
  • Federal rules by reference. The director may adopt all or part of the federal safety regulations by reference (§644.051(c)).
  • Two definitions of a commercial motor vehicle. The federal definition in 49 C.F.R. Section 390.5 for interstate operation, and the Texas definition in Transp. Code §548.001 for intrastate operation (§644.001(1)).
  • Stopping a vehicle. Department officers, and certified city police officers, sheriffs and deputies, may stop, enter or detain a vehicle subject to the chapter and may prohibit its further operation if the vehicle or operator is in violation (§644.103).
  • Offenses. Violating a rule adopted under the chapter is a Class C misdemeanor; knowingly operating in violation of an out-of-service order issued under 49 C.F.R. Section 385.13(d)(1) is a Class A misdemeanor, a state jail felony after a collision with bodily injury, and a second-degree felony after a collision with a death (§644.151).
  • Recent amendments. The most recent amendment anywhere in the chapter is to §644.101 (certification of local officers), by Acts 2025, 89th Leg., R.S., ch. 204 (H.B. 1620). The history line for §644.151 lists Acts 2023, 88th Leg., R.S., ch. 709 (H.B. 2190) as its most recent amendment. §644.051 has not been amended since it was added in 1997.

What counts as a commercial motor vehicle in chapter 644?

The official text of Tex. Transp. Code §644.001, as published by the Texas Legislature:

Sec. 644.001. DEFINITIONS. In this chapter: (1) "Commercial motor vehicle" means: (A) a commercial motor vehicle as defined by 49 C.F.R. Section 390.5, if operated interstate; or (B) a commercial motor vehicle as defined by Section 548.001, if operated intrastate. (2) "Department" means the Department of Public Safety. (3) "Director" means the public safety director. (4) "Federal hazardous material regulation" means a federal regulation in 49 C.F.R. Parts 101-199. (5) "Federal motor carrier safety regulation" means a federal regulation in Subtitle A, Title 49, or Subchapter B, Chapter III, Subtitle B, Title 49, Code of Federal Regulations. (6) "Federal safety regulation" means a federal hazardous material regulation or a federal motor carrier safety regulation. (7) "Port of entry" has the meaning assigned by Section 621.001.

Source: Tex. Transp. Code §644.001, statutes.capitol.texas.gov. Text last checked October 27, 2026.

For a vehicle operated intrastate, the definition comes from §548.001(1):

(1) "Commercial motor vehicle" means a self-propelled or towed vehicle, other than a farm vehicle with a gross weight, registered weight, or gross weight rating of less than 48,000 pounds, that is used on a public highway to transport passengers or cargo if: (A) the vehicle, including a school activity bus as defined in Section 541.201, or combination of vehicles has a gross weight, registered weight, or gross weight rating of more than 26,000 pounds; (B) the vehicle, including a school activity bus as defined in Section 541.201, is designed or used to transport more than 15 passengers, including the driver; or (C) the vehicle is used to transport hazardous materials in a quantity requiring placarding by a regulation issued under the Hazardous Materials Transportation Act (49 U.S.C. Section 5101 et seq.).

Source: Tex. Transp. Code §548.001.

In plain language: which definition applies depends on whether the vehicle is operated interstate or intrastate. For a vehicle operated intrastate, the Texas definition generally covers a vehicle or combination over 26,000 pounds, a vehicle designed or used to carry more than 15 passengers including the driver, and a vehicle carrying hazardous materials in a quantity that requires placards. The federal definition for interstate operation is described in the truck accidents guide.

How does Texas adopt the federal motor carrier safety regulations?

The official text of §644.051:

Sec. 644.051. AUTHORITY TO ADOPT RULES. (a) The director shall, after notice and a public hearing, adopt rules regulating: (1) the safe transportation of hazardous materials; and (2) the safe operation of commercial motor vehicles.

(b) A rule adopted under this chapter must be consistent with federal regulations, including federal safety regulations.

(c) The director may adopt all or part of the federal safety regulations by reference.

(d) Rules adopted under this chapter must ensure that: (1) a commercial motor vehicle is safely maintained, equipped, loaded, and operated; (2) the responsibilities imposed on a commercial motor vehicle's operator do not impair the operator's ability to operate the vehicle safely; and (3) the physical condition of a commercial motor vehicle's operator enables the operator to operate the vehicle safely.

(e) A motor carrier safety rule adopted by a local government, authority, or state agency or officer must be consistent with corresponding federal regulations.

Source: Tex. Transp. Code §644.051.

In plain language: the statute does not list the truck safety rules itself. It directs the public safety director to adopt them, requires them to be consistent with the federal rules, and allows the federal rules to be adopted by reference instead of being rewritten. The department's commercial vehicle rules are published in the Texas Administrative Code, Title 37, Part 1, Chapter 4 ("Commercial Vehicle Regulations and Enforcement Procedures"), on the Texas Secretary of State's website (chapter title checked October 27, 2026). This entry quotes the statute, not those rules, and does not list which federal regulations the rules adopt; the rules change when the department amends them.

Two limits in the statute itself: a rule adopted under the chapter applies uniformly throughout Texas notwithstanding an exemption in the federal safety regulations, other than one relating to intracity or commercial zone operations in 49 C.F.R. Part 395, and it may not apply to three kinds of vehicles operated intrastate: certain machines used in oil or water well servicing or drilling, certain mobile cranes, and vehicles transporting seed cotton (§644.052). Under §644.053(a), a rule may not, among other things, prevent an intrastate operator from operating a vehicle up to 12 hours following eight consecutive hours off.

Which rule applies when Texas and federal rules conflict?

The official text of §644.002(a):

(a) A federal motor carrier safety regulation prevails over a conflicting provision of this title applicable to a commercial vehicle operated in interstate commerce. A rule adopted by the director under this chapter prevails over a conflicting provision of a federal motor carrier safety regulation applicable to a commercial vehicle operated in intrastate commerce.

Source: Tex. Transp. Code §644.002.

In plain language: for interstate trucking, the federal rule controls over a conflicting provision of Title 7 of the Transportation Code (Vehicles and Traffic); for trucking only within Texas, the director's rule controls over a conflicting federal rule. Under §644.002(b), a safety rule adopted under the chapter also prevails over a conflicting local or state agency rule, except a conflicting rule of the Railroad Commission of Texas under Chapter 113, Natural Resources Code.

Who can stop and inspect a commercial vehicle?

The official text of §644.103(a) through (c):

(a) An officer of the department may stop, enter, or detain on a highway or at a port of entry a motor vehicle that is subject to this chapter.

(b) A municipal police officer who is certified under Section 644.101 may stop, enter, or detain on a highway or at a port of entry within the territory of the municipality a motor vehicle that is subject to this chapter. A sheriff or deputy sheriff who is certified under Section 644.101 may stop, enter, or detain on a highway or at a port of entry within the territory of the county a motor vehicle that is subject to this chapter.

(c) A person who detains a vehicle under this section may prohibit the further operation of the vehicle on a highway if the vehicle or operator of the vehicle is in violation of a federal safety regulation or a rule adopted under this chapter.

Source: Tex. Transp. Code §644.103.

In plain language: Department of Public Safety officers may stop, enter or detain a vehicle subject to the chapter on a highway or at a port of entry. City police officers, sheriffs and deputy sheriffs may do the same within their city or county only if they are certified under §644.101, which sets out, mostly by population and location, the kinds of cities and counties whose officers are eligible to apply. The person who detains the vehicle may prohibit its further operation on a highway if the vehicle or its operator is in violation of a federal safety regulation or a rule adopted under the chapter.

What is the offense for breaking these rules?

The official text of §644.151(a) through (c):

Sec. 644.151. CRIMINAL OFFENSE. (a) A person commits an offense if the person: (1) violates a rule adopted under this chapter; (2) does not permit an inspection authorized under Section 644.104; or (3) knowingly operates a commercial motor vehicle in violation of an out-of-service order issued under 49 C.F.R. Section 385.13(d)(1) or owns, leases, or assigns a person to drive a commercial motor vehicle that is knowingly operated in violation of an out-of-service order issued under 49 C.F.R. Section 385.13(d)(1).

(b) An offense under Subsection (a)(1) or (2) is a Class C misdemeanor.

(b-1) An offense under Subsection (a)(3) is a Class A misdemeanor, except that the offense is: (1) a state jail felony if it is shown on the trial of the offense that at the time of the offense the commercial motor vehicle was involved in a motor vehicle collision that resulted in bodily injury; or (2) a felony of the second degree if it is shown on the trial of the offense that at the time of the offense the commercial motor vehicle was involved in a motor vehicle collision that resulted in the death of a person.

(c) Each day a violation continues under Subsection (a)(1) or each day a person refuses to allow an inspection described under Subsection (a)(2) is a separate offense.

Source: Tex. Transp. Code §644.151.

In plain language: violating a rule adopted under the chapter, or not permitting an authorized inspection of a motor carrier's premises under §644.104, is a Class C misdemeanor, and each day it continues is a separate offense. Knowingly operating a commercial motor vehicle in violation of an out-of-service order issued under 49 C.F.R. Section 385.13(d)(1) is a Class A misdemeanor, and the offense level rises if that vehicle was involved in a collision that resulted in bodily injury or a death. That federal rule covers the order the Federal Motor Carrier Safety Administration issues placing a motor carrier's operations out of service when a proposed "unsatisfactory" safety rating becomes final (49 C.F.R. §385.13). The chapter also provides for a civil penalty, payable to the state, for not permitting an inspection (§644.152), and for administrative penalties imposed by the department (§644.153). These are penalties the state imposes; this entry does not address any private claim.

When was this checked, and can it change?

The text above was last checked on October 27, 2026, against the official text published by the Texas Legislature. The Legislature can amend a statute in any session. It convenes in regular session on the second Tuesday in January of each odd-numbered year (Gov't Code §301.001), so the next regular session begins on January 12, 2027. This entry is scheduled to be rechecked against the official text by April 2027 and again after the 2027 regular session ends.

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Frequently asked questions

What does Texas Transportation Code chapter 644 cover?
Chapter 644, titled Commercial Motor Vehicle Safety Standards, has the public safety director adopt rules regulating the safe transportation of hazardous materials and the safe operation of commercial motor vehicles (§644.051(a)), lets certain officers stop, enter or detain a motor vehicle subject to the chapter on a highway or at a port of entry (§644.103), and makes violating a rule adopted under the chapter an offense (§644.151).
Does Texas follow the federal motor carrier safety regulations?
Under Tex. Transp. Code §644.051(b) and (c), a rule adopted under chapter 644 must be consistent with federal regulations, including federal safety regulations, and the director may adopt all or part of the federal safety regulations by reference. Under §644.002(a), a federal motor carrier safety regulation prevails over a conflicting provision of Title 7 of the Transportation Code for a commercial vehicle operated in interstate commerce, and a rule adopted by the director prevails over a conflicting federal regulation for a commercial vehicle operated in intrastate commerce.
What is the offense for operating a commercial motor vehicle in violation of an out-of-service order?
Under §644.151(a)(3) and (b-1), knowingly operating a commercial motor vehicle in violation of an out-of-service order issued under 49 C.F.R. Section 385.13(d)(1), or owning, leasing or assigning a person to drive a vehicle knowingly operated that way, is a Class A misdemeanor. It is a state jail felony if the vehicle was involved in a collision that resulted in bodily injury, and a felony of the second degree if the collision resulted in a death.
Can InjuryClaimGuide tell me whether a trucking company or driver broke these rules?
No. InjuryClaimGuide is a legal advertising service. We do not apply the law to anyone's situation and do not evaluate any claim. An attorney can advise you about your specific situation.

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