Does a Texas vehicle with a diesel turbine engine still need a muffler?

Plain-English summary

Phil Garrett, the Palo Pinto County Attorney, asked the Attorney General whether motor vehicles with a diesel turbine engine are excepted from the rule that all vehicles have a muffler. The question grew out of how the Transportation Code defines "muffler."

Section 547.604 of the Transportation Code requires a motor vehicle to be equipped with a muffler in good working condition that continually operates to prevent excessive or unusual noise. The code defines "muffler" as a device that reduces noise using either (A) a mechanical design, such as a series of chambers or baffle plates, to receive exhaust gas from an internal combustion engine, or (B) turbine wheels to receive exhaust gas from a diesel engine. Some had suggested that the second branch of the definition, the turbine-wheels branch, somehow excludes a "diesel turbine engine" from the muffler requirement.

The opinion rejected reading the definition as an exception. Whichever noise-reduction mechanism a particular muffler uses, section 547.604 still requires a vehicle to have a device, a muffler, that reduces noise. The opinion acknowledged the underlying factual dispute, that some contended a diesel turbine engine is itself the equivalent of "turbine wheels to receive exhaust gas from a diesel engine," and said whether a particular diesel turbine engine satisfies the statutory muffler definition is a fact question outside the opinion process. But the legal bottom line was clear: to comply with section 547.604, a motor vehicle must have a muffler that reduces noise. There is no diesel-turbine exception to the requirement itself.

Currency note

This opinion was issued in 2011. Subsequent statutory amendments, court decisions, or later Attorney General opinions may have changed the analysis. Treat this page as historical context, not current legal advice. Verify current law before relying on any specific rule, deadline, or remedy mentioned here.

What the opinion meant for those who asked

The county attorney and local enforcement (as the opinion held for them): The opinion told them that the muffler requirement in section 547.604 applies to every motor vehicle, with no carve-out for diesel turbine engines. A vehicle must have a noise-reducing muffler.

On the diesel-turbine argument (where the opinion stopped): The opinion did not decide whether a specific diesel turbine engine itself counts as the "turbine wheels" form of muffler. It treated that as a fact question outside the opinion process.

Vehicle owners and operators (as the opinion described it): Under the opinion, having a diesel turbine engine did not relieve a vehicle of the obligation to be equipped with a muffler that reduces noise.

Common questions

Is there an exception to the Texas muffler law for diesel turbine engines?
No. The opinion concluded that section 547.604 requires every motor vehicle to have a noise-reducing muffler, with no exception based on having a diesel turbine engine.

What does Texas law count as a "muffler"?
The opinion quoted the definition: a device that reduces noise using either a chambered or baffle-plate mechanical design for an internal combustion engine, or turbine wheels to receive exhaust gas from a diesel engine.

Does a diesel turbine engine itself satisfy the muffler requirement?
The opinion did not decide that. Whether a particular diesel turbine engine meets the statutory muffler definition is a fact question that falls outside the AG opinion process.

What is the practical requirement?
The opinion stated that, to comply with section 547.604, a motor vehicle must be equipped with a muffler that reduces noise.

Background and statutory framework

Section 547.604 of the Transportation Code requires a motor vehicle to be equipped with a muffler in good working condition that continually operates to prevent excessive or unusual noise. Tex. Transp. Code Ann. § 547.604 (West 1999). For purposes of subtitle C, title 6 of the Transportation Code, "muffler" is defined as a device that reduces noise using either (A) a mechanical design, including a series of chambers or baffle plates, to receive exhaust gas from an internal combustion engine, or (B) turbine wheels to receive exhaust gas from a diesel engine. Id. § 541.203. The opinion treated whether a particular diesel turbine engine satisfies that definition as a fact question outside the opinion process, while reading section 547.604 to require, in all events, a noise-reducing muffler.

Citations

Statutes:

• Tex. Transp. Code Ann. § 547.604 (West 1999)
• Tex. Transp. Code Ann. § 541.203

Source

• Landing page: https://www.texasattorneygeneral.gov/opinions/greg-abbott/ga-0873
• Original PDF: https://www.texasattorneygeneral.gov/sites/default/files/opinion-files/opinion/2011/ga0873.pdf

Original opinion text

Best-effort transcription from the official PDF. Minor extraction artifacts were corrected; the linked PDF is authoritative.

ATTORNEY GENERAL OF TEXAS
GREG ABBOTT

August 9, 2011

The Honorable Phil Garrett Opinion No. GA-0873
Palo Pinto County Attorney
Post Office Box 190 Re: Whether there is an exception for diesel
Palo Pinto, Texas 76484 turbine engines to the requirement that all vehicles
have a muffler (RQ-0949-GA)

Dear Mr. Garrett:

You ask whether motor vehicles equipped with a diesel turbine engine are excepted from the requirement that all vehicles have a muffler.[1]

Section 547.604 of the Transportation Code provides, in relevant part:

(a) A motor vehicle shall be equipped with a muffler in good working condition that continually operates to prevent excessive or unusual noise.

TEX. TRANSP. CODE ANN. § 547.604 (West 1999). For purposes of subtitle C, title 6 of the Transportation Code, of which section 547.604 is a part, a "muffler" is defined to mean "a device that reduces noise using: (A) a mechanical design, including a series of chambers or baffle plates, to receive exhaust gas from an internal combustion engine; or (B) turbine wheels to receive exhaust gas from a diesel engine." Id. § 541.203. Your request letter indicates that some have suggested that the second definition of "muffler" excludes a "diesel turbine engine" from the separate muffler requirement described by the first definition. Notwithstanding the type of noise reduction mechanism utilized by a specific muffler, section 547.604 requires that a vehicle have a device, specifically a "muffler," that "reduces noise."

Under section 547.604 of the Transportation Code, a motor vehicle is required to be equipped with a "muffler" and the statute directs that the term "muffler" may consist of either one of the following: "(A) a mechanical design, including a series of chambers or baffle plates, to receive exhaust gas from an internal combustion engine; or (B) turbine wheels to receive exhaust gas from a diesel engine." See id. § 547.604. As we have noted, your request letter indicates that some have contended that a "diesel turbine engine" is itself equivalent to "turbine wheels to receive exhaust gas from a diesel engine." Whether a particular diesel turbine engine satisfies the statutory definition is a fact question that falls outside the purview of the opinion process. However, section 547.604 plainly requires that motor vehicles "have a device that reduces noise." Accordingly, to satisfy this provision of the Transportation Code, motor vehicles must have a muffler that reduces noise.

SUMMARY

A motor vehicle must be equipped with a "muffler," which is defined in part as "a device that reduces noise." Accordingly, in order to meet the requirement of section 547.604 of the Transportation Code, a vehicle must be equipped with a muffler that reduces noise.

Very truly yours,

GREG ABBOTT
Attorney General of Texas

DANIEL T. HODGE
First Assistant Attorney General

DAVID J. SCHENCK
Deputy Attorney General for Legal Counsel

JASON BOATRIGHT
Chair, Opinion Committee

Rick Gilpin
Assistant Attorney General, Opinion Committee

[1] Letter from Honorable Phil Garrett, Palo Pinto County Attorney, to Chairperson, Opinion Committee, Attorney General of Texas at 1 (Mar. 3, 2011), https://www.oag.state.tx.us/opin/index_rq.shtml ("Request Letter").