Iowa: Is it legal to put a train horn on a car?
Iowa bans horns that make an unreasonably loud or harsh sound or a whistle, which a typical train horn likely fails.
Iowa requires a working horn audible from at least 200 feet, but no horn or other warning device may emit an unreasonably loud or harsh sound or a whistle. The law does not name air or train horns, but a locomotive-style horn is likely to be treated as unreasonably loud. Drivers may use the horn only when reasonably necessary for safe operation.
Conditions
- Horn may not be unreasonably loud or harsh
- Horn use only when reasonably necessary for safety
What the law says
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 or a whistle.
Sources
- Iowa Code § 321.432 (2026) Official · legis.iowa.gov
Confirm with the state
- Agency
- Iowa Department of Public Safety (Iowa State Patrol)
- Phone
- 515-725-6000
- Website
- dps.iowa.gov
How bordering states compare
- Illinois Allowed with limitsIllinois bans horns that make an unreasonably loud or harsh sound or a whistle, which a typical train horn likely fails.
- Minnesota Allowed with limitsMinnesota bars horns that are unreasonably loud or harsh or that whistle, and only emergency vehicles may carry sirens, whistles or bells.
- Missouri Allowed with limitsMissouri allows a horn or whistle but bars unnecessary noise and any other sound-producing signaling device, which may cover an added train horn.
- Nebraska Allowed with limitsNebraska bans sirens and exhaust whistles on vehicles and bars unnecessary or unreasonably loud or harsh horn use, which likely covers train horns.
- South Dakota Allowed with limitsSouth Dakota bans exhaust horns, sirens and harsh whistles, and forbids unreasonably loud or harsh horn sounds, but does not name air horns.
- Wisconsin Allowed with limitsWisconsin bans sirens and compression or exhaust whistles, and forbids unreasonably loud or harsh horn sounds, but does not name air horns.