Are Train Horns Legal in Colorado? C.R.S. 42-4-224 and City Noise Ordinances Explained

Colorado has no decibel cap for horns, no safety inspection, and no statute that names "train horn." What it has is C.R.S. 42-4-224, which bans any horn that emits an "unreasonably loud or harsh sound" and limits horn use on a highway to safety warnings, plus city ordinances in Denver and Colorado Springs that stack on top. Here's how they apply to a truck on I-25, a UTV on a forest road, and a horn gun in your hand.

The short answer

You can buy, own, and carry a train horn in Colorado. What the law regulates is a horn on a motor vehicle operated on a highway, and how the driver uses it. Three rules do almost all the work:

• No "unreasonably loud or harsh sound." There is no number attached. The Colorado State Patrol has said publicly that there is no specific upper limit in the statute, only that standard.
• Highway horn use is for safety only. The driver must sound the horn when "reasonably necessary to ensure safe operation" but "shall not otherwise use such horn when upon a highway."
• No extra audible devices on the vehicle beyond what the section permits: a horn, a theft alarm, backup beepers, and emergency-vehicle sirens.

Break those rules and you're looking at a class B traffic infraction: a $15 penalty plus a $6 surcharge, and no license points. Use a horn to deliberately bother people and two other layers apply: the state disorderly conduct statute and city noise codes. Both are covered below.

What C.R.S. 42-4-224 actually says

The statute sits in Part 2 (Equipment) of Article 4, Title 42. Colorado's Model Traffic Code, published by CDOT for cities and counties to adopt, repeats it word for word as section 224. The two subsections that matter:

• Subsection (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 for authorized emergency vehicles. "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."
• Subsection (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."

Two things stand out. First, like Arizona, Colorado sets a 200-foot minimum for audibility and no maximum. Second, subsection (2) is stricter than most states. It doesn't just ban sirens and whistles; it bans "any audible device" that the section doesn't allow. A train horn is still a horn, so a wired-in train horn isn't automatically illegal, but the language gives an officer room to argue that a second, much louder horn is an unpermitted audible device. And the phrase "use upon a vehicle" matters for portable horns: blasting a horn gun out the window of a moving truck is arguably using an audible device upon a vehicle, even though nothing is installed.

Then there's the "unreasonably loud or harsh" test. Under 49 CFR 229.129, a real locomotive horn must produce 96 to 110 dB(A) measured 100 feet ahead of the locomotive. Portable train horn guns are sold at up to 150 dB at the trumpet. A blast at that level at a stoplight on Colfax is exactly what the statute was written for. No meter is needed, only a judge who agrees the sound was unreasonable.

What a horn ticket costs in Colorado

The Colorado Legislative Council's offense guide lists "Horns or warning devices," C.R.S. 42-4-224(6), as a class B traffic infraction. The penalty schedule in C.R.S. 42-4-1701 sets that specific violation at $15 plus a $6 surcharge. The general class B range is $15 to $100, and the statute says the state has "no authority to assess any points" for class B infractions.

The bigger risk is C.R.S. 18-9-106, disorderly conduct. A person commits it if they "intentionally, knowingly, or recklessly" make "unreasonable noise in a public place or near a private residence that he has no right to occupy." That's a petty offense. For offenses on or after March 1, 2022, a petty offense carries a fine of up to $300, up to 10 days in county jail, or both. That's the charge that fits a prank. Hitting a sleeping neighbor's window with 150 dB at 2:00 AM is a criminal matter, not a $21 equipment ticket. We break down the difference between owning a horn and how you use it in Can You Get a Ticket for a Train Horn Gun?

Denver and Colorado Springs add their own rules

State law is the floor. The two biggest cities layer noise codes on top.

• Denver rewrote its noise chapter in 2025 (Council Bill 25-0044). Under section 36-7 of the Revised Municipal Code, no person may "at any time, sound any horn or other audible signal device of a motor vehicle" unless it's needed as a warning to prevent or avoid an accident. That applies "notwithstanding" the city's decibel tables, so a horn blast can be a violation even if it never hits a numeric limit.
• Colorado Springs has no horn-specific section. Instead, City Code 9.8.101 makes it unlawful to create "an excessive or unusually loud noise" or a noise that is "harmful to any person" that can be heard without a measuring device. The vehicle part of the code, 9.8.201, declares noise above 80 dB(A) from a vehicle under 10,000 pounds "excessive, unusually loud, and unlawful."

Outside city limits, Colorado's statewide noise statute, C.R.S. 25-12-103, treats sound crossing a residential property line above 55 dB(A) from 7:00 AM to 7:00 PM, or 50 dB(A) from 7:00 PM to 7:00 AM, as prima facie evidence of a public nuisance. "Periodic, impulsive, or shrill" noise gets a limit 5 dB(A) lower. A train horn blast is about as impulsive and shrill as noise gets, so in a subdivision in Aurora or Fort Collins, assume a 10:00 PM blast earns a knock on the door.

Off the pavement: trails, private land, and the 96 dB OHV rule

Colorado's off-highway vehicle law has a sound limit, but it targets exhaust, not horns. Since July 1, 2010, every OHV operated on public land in Colorado must meet a 96 dB(A) limit measured with the SAE J1287 stationary test, which is an exhaust test. OHVs also need a current Colorado registration or permit from Colorado Parks and Wildlife to ride on public land roads and designated trails.

The key point for horn users: 42-4-224's horn rules apply to a "motor vehicle, when operated upon a highway." They don't follow you up a forest road above Buena Vista or onto your own acreage on the eastern plains. On a two-track, a loud horn is a useful warning at blind corners. What still applies off-highway is disorderly conduct and county nuisance rules. Blast a horn at horses, hikers, or a campground and you've moved from legal to citation. Our guide to train horns on private property vs. public roads covers that line in more detail.

One more line not to cross: never sound a train horn near an actual railroad crossing. Real crossing horns are governed by federal rules, and some Colorado communities have established quiet zones where trains don't sound routinely at all. See how FRA quiet zones relate to aftermarket train horns before you try anything clever near the tracks.

Wired-in vs. carried: why a portable horn changes the picture

Colorado has no statewide safety inspection. Vehicles registered in the Denver metro area and the North Front Range need emissions tests, but nobody presses your horn button at the test station. So the inspection-failure risk that exists in some states doesn't exist here.

What's left is use. A train horn wired into the truck is part of the vehicle's equipment, so every blast on a highway is judged against the safety-only rule, the "harsh sound" language, and subsection (2)'s audible-device ban. A battery-powered horn gun isn't vehicle equipment. It rides in the UTV to the trailhead, goes on the boat at Chatfield or Horsetooth, and comes out on private land or at a permitted event. Off the highway and away from homes, 42-4-224 doesn't reach it at all.

That's the use case the 5-Trumpet Horn Gun for Milwaukee® 18V Battery is built for. It runs on any Milwaukee® M18™ pack you already own, fires from a trigger grip, and needs no compressor, air tank, or relay in the truck. Nothing is installed, so nothing turns your steering-wheel button into a ticket.

The same trigger-grip design is available for DeWalt® 20V MAX™, Ryobi® ONE+™, Makita® LXT™, and most other major cordless platforms, in dual, quad, and 5-trumpet setups. See the full range in our portable train horns collection.

FAQ

Is it illegal to own a train horn in Colorado?

No. C.R.S. 42-4-224 regulates horns on motor vehicles operated on a highway and how drivers use them. It says nothing about buying, owning, or carrying one. A battery train horn gun in your garage, truck bed, or boat breaks no Colorado law.

Is there a decibel limit for car horns in Colorado?

Not in state law. The statute requires a horn audible from at least 200 feet and bans "unreasonably loud or harsh" sound, with no maximum number. Cities can set their own limits; Colorado Springs, for example, caps noise from vehicles under 10,000 pounds at 80 dB(A).

What's the fine for a horn violation in Colorado?

A 42-4-224 violation is a class B traffic infraction: $15 plus a $6 surcharge under the state schedule, with no points. Using a horn to make unreasonable noise near homes or in public can also be charged as disorderly conduct, a petty offense with up to a $300 fine and 10 days in jail.

Can I use a train horn in Denver?

Not as a vehicle horn for fun. Denver's noise code bans sounding any motor vehicle horn or audible signal device except as a warning to avoid an accident, regardless of decibel level. Use a portable horn on private property, on the water, or at events where it's allowed.

For how Colorado compares with the rest of the country, see our state-by-state guide to train horn laws.