(1) Every motor vehicle, when operated upon a highway, shall be equipped with a horn in good working order and capable of emitting sound audible under normal conditions from a distance of not less than two hundred feet, but no horn or other warning device shall emit an unreasonably loud or harsh sound, except as provided in section 42-4-213 (1) in the case of authorized emergency vehicles or as provided in section 42-4-222. The driver of a motor vehicle, when reasonably necessary to ensure safe operation, shall give audible warning with the horn but shall not otherwise use such horn when upon a highway.
(2) No vehicle shall be equipped with nor shall any person use upon a vehicle any audible device except as otherwise permitted in this section. It is permissible but not required that any vehicle be equipped with a theft alarm signal device which is so arranged that it cannot be used by the driver as a warning signal unless the alarm device is a required part of the vehicle. Nothing in this section is meant to preclude the use of audible warning devices that are activated when the vehicle is backing. Any authorized emergency vehicle may be equipped with an audible signal device under section 42-4-213 (1), but such device shall not be used except when such vehicle is operated in response to an emergency call or in the actual pursuit of a suspected violator of the law or for other special purposes, including, but not limited to, funerals, parades, and the escorting of dignitaries. Such device shall not be used for such special purposes unless the circumstances would not lead a reasonable person to believe that such vehicle is responding to an actual emergency.
(3) A bicycle, electrical assisted bicycle, electric scooter, or low-power scooter shall not be equipped with, nor shall any person use upon a bicycle, electrical assisted bicycle, electric scooter, or low-power scooter, a siren or whistle.
(4) Snowplows and other snow-removal equipment shall display flashing yellow lights meeting the requirements of section 42-4-214 as a warning to drivers when such equipment is in service on the highway.
(5) (a) When any snowplow or other snow-removal equipment displaying flashing yellow lights is engaged in snow and ice removal or control, drivers of all other vehicles shall exercise more than ordinary care and caution in approaching, overtaking, or passing such snowplow.
(b) The driver of a snowplow, while engaged in the removal or control of snow and ice on any highway open to traffic and while displaying the required flashing yellow warning lights as provided by section 42-4-214, shall not be charged with any violation of the provisions of this article relating to parking or standing, turning, backing, or yielding the right-of-way. These exemptions shall not relieve the driver of a snowplow from the duty to drive with due regard for the safety of all persons, nor shall these exemptions protect the driver of a snowplow from the consequences of a reckless or careless disregard for the safety of others.
(6) (a) Any person who violates any provision of this section commits a class B traffic infraction; except that a person commits a class A traffic infraction if the person passes an authorized service vehicle snowplow that is operated by a state, county, or local government, displaying lights as authorized in section 42-4-214, and performing its service function in echelon formation with one or more other such snowplows.
(b) As used in this subsection (6), unless the context otherwise requires, echelon formation means a formation in which snowplows are arranged diagonally, with each unit stationed behind and to the right, or behind and to the left, of the unit ahead.
Source: L. 94: Entire title amended with relocations, p. 2259, � 1, effective January 1, 1995. L. 2005: (1) and (2) amended, p. 196, � 3, effective July 1. L. 2009: (3) amended, (HB 09-1026), ch. 281, p. 1276, � 47, effective October 1. L. 2019: (3) amended, (HB 19-1221), ch. 271, p. 2560, � 6, effective May 23; (6) amended, (HB 19-1265), ch. 203, p. 2175, � 2, effective August 2.
Editor's note: This section is similar to former � 42-4-221 as it existed prior to 1994, and the former � 42-4-224 was relocated to � 42-4-227.
42-4-225. Mufflers - prevention of noise - applicability - exceptions - penalty - definition. (1) Every motor vehicle subject to registration and operated on a highway shall at all times be equipped with an adequate muffler in constant operation and properly maintained to prevent any excessive or unusual noise, and no such muffler or exhaust system shall be equipped with a cut-off, bypass, or similar device. No person shall modify the exhaust system of a motor vehicle in a manner which will amplify or increase the noise emitted by the motor of such vehicle above that emitted by the muffler originally installed on the vehicle, and such original muffler shall comply with all of the requirements of this section.
(1.5) [Editor's note: This version of subsection (1.5) is effective until July 1, 2027.] Any commercial vehicle, as defined in section 42-4-235 (1)(a), subject to registration and operated on a highway, that is equipped with an engine compression brake device is required to have a muffler.
(1.5) [Editor's note: This version of subsection (1.5) is effective July 1, 2027.]
(a) As used in this subsection (1.5), commercial vehicle has the meaning set forth in section 42-4-235 (1)(a).
(b) A person shall not operate a commercial vehicle subject to registration without a muffler. The muffler must be located on the commercial vehicle in a manner that allows the muffler to be visually inspected to ensure it is present, intact, and functioning properly unless subsection (1.5)(c) of this section applies.
(c) The commercial vehicle need not have a muffler that is visible for inspection as required in subsection (1.5)(b) of this section if the following documentation is within the vehicle and available for inspection by a peace officer:
(I) Evidence that the commercial vehicle has had a muffler installed that, when installed, complied with the manufacturing noise standards for the model year of that vehicle as adopted by the federal environmental protection agency;
(II) The vehicle identification number of the commercial vehicle on which the muffler was installed; and
(III) Documentation that contains the following for the muffler described in subsection (1.5)(c)(I) of this section:
(A) The date of purchase;
(B) The make and model; and
(C) The name of the business that sold and installed the muffler.
(d) This subsection (1.5):
(I) Applies only to a commercial vehicle that is powered by an internal combustion engine; and
(II) Does not apply to a farm vehicle.
(2) A muffler is a device consisting of a series of chamber or baffle plates or other mechanical design for the purpose of receiving exhaust gas from an internal combustion engine and effective in reducing noise.
(3) [Editor's note: This version of subsection (3) is effective until July 1, 2027.] Any person who violates subsection (1) of this section commits a class B traffic infraction. Any person who violates subsection (1.5) of this section shall, upon conviction, be punished by a fine of five hundred dollars. Fifty percent of any fine for a violation of subsection (1.5) of this section occurring within the corporate limits of a city or town, or within the unincorporated area of a county, shall be transmitted to the treasurer or chief financial officer of said city, town, or county, and the remaining fifty percent shall be transmitted to the state treasurer, credited to the highway users tax fund, and allocated and expended as specified in section 43-4-205 (5.5)(a), C.R.S.
(3) [Editor's note: This version of subsection (3) is effective July 1, 2027.]
(a) A person that violates subsection (1) of this section commits a class B traffic infraction.
(b) A person that violates subsection (1.5) of this section shall, upon conviction, be punished by a fine of one thousand dollars. Fifty percent of any fine for a violation of subsection (1.5) of this section occurring within the corporate limits of a city or town, or within the unincorporated area of a county, shall be transmitted to the treasurer or chief financial officer of the city, town, or county, and the remaining fifty percent shall be transmitted to the state treasurer, credited to the highway users tax fund, and allocated and expended as specified in section 43-4-205 (5.5)(a). A court shall not impose the fine if the owner or operator provides the documentation described in subsection (1.5)(c) of this section demonstrating that a muffler was in place prior to the citation. A court shall reduce the fine by fifty percent if the owner or operator of the commercial vehicle provides proof that an appropriate muffler was installed within thirty days after the citation was issued.
(4) This section shall not apply to electric motor vehicles.
Source: L. 94: Entire title amended with relocations, p. 2260, � 1, effective January 1, 1995. L. 97: (4) added, p. 393, � 2, effective August 6. L. 2000: (1.5) added and (3) amended, p. 1100, � 1, effective August 2. L. 2005: (3) amended, p. 149, � 26, effective April 5. L. 2025: (1.5) and (3) amended, (HB 25-1039), ch. 197, p. 873, � 1, effective July 1, 2027.
Editor's note: (1) This section is similar to former � 42-4-222 as it existed prior to 1994, and the former � 42-4-225 was relocated to � 42-4-228.
(2) Section 3(2) of chapter 197 (HB 25-1039), Session Laws of Colorado 2025, provides that the act changing this section applies to offenses committed on or after July 1, 2027.
Cross references: For the penalty for a class B traffic infraction generally, see � 42-4-1701 (3)(a)(I); for the penalty and surcharge for equipment violations of subsection (1), see � 42-4-1701 (4)(a)(I)(D).