Disclaimer. This page summarizes publicly available Maryland statutes as of April 2026 and is published for general informational purposes only. It is not legal advice, and nothing on this page creates an attorney–client relationship. Statutes change, enforcement is active in the Baltimore and Washington-DC-metro corridor, and individual circumstances matter — always verify the current text and consult a licensed Maryland attorney before making installation or use decisions.
- Legal status
- Mounted only
- Install tolerated, use restricted
- Statute
- §22-401
- Md. Transp. Title 22
- Audibility required
- 200 ft
- Factory horn minimum
- Specific dB cap
- None
- "Unreasonably loud" test
- Siren/whistle ban?
- Yes
- Emergency vehicles exempt (500 ft)
- Penalty
- Traffic fine
- Infraction
Are train horns legal in Maryland? Short answer
Installing an aftermarket train horn on a private vehicle in Maryland is not expressly prohibited, but active noise enforcement along the Baltimore–DC metro corridor puts Maryland in the “mounted-only” category in practice. Maryland train horn law is in Md. Transp. §22-401 — “Horns and warning devices.” The statute tracks UVC: 200-ft audibility, “unreasonably loud or harsh sound or a whistle” ban, strict use-limitation, siren/whistle/bell prohibition outside emergency vehicles (500-ft audibility).
Install is legal; public-road use in Baltimore, Montgomery County, Prince George’s County, Anne Arundel County, or Howard County invites citation.
What Md. Transp. §22-401 actually says
Every motor vehicle when operated on 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 200 feet, but no horn or other warning device may emit an unreasonably loud or harsh sound or a whistle. The driver of a motor vehicle shall, when reasonably necessary to insure safe operation, give audible warning with his horn, but may not otherwise use the horn when on a highway. No vehicle may be equipped with nor may any person use on a vehicle any siren, whistle, or bell, except as otherwise permitted in this section.
Operative rules:
- Every motor vehicle on a highway must have a horn audible at 200 feet.
- No horn may emit “an unreasonably loud or harsh sound or a whistle.”
- Horn use is limited to cases “reasonably necessary to insure safe operation.”
- No sirens, whistles, or bells on non-emergency vehicles.
- Theft-alarm exception: vehicle may carry a theft alarm that cannot be used as an ordinary warning signal.
- Emergency vehicles: device audible at 500 feet.
Does the factory horn need to stay working in Maryland?
Yes. §22-401’s 200-ft audibility rule applies to the vehicle’s equipment. Disconnecting the OEM horn is an equipment violation regardless of train-horn install.
Keep factory horn wired; put train horn on a separate dedicated switch.
Is a train horn a “whistle” under Md. Transp. §22-401?
Maryland bans any horn emitting “a whistle.” UVC term — single-tone pressure device — not a multi-trumpet chord.
- ·Siren — continuous variable-pitch tone
- ·Whistle — single-tone pressure device
- ·Bell — fire / warning bell
- ·Emergency vehicles exempt (500-ft audibility)
- ·Multi-note chord, not a whistle tone
- ·Install not banned
- ·Use subject to "unreasonably loud" test
- ·DC-metro enforcement is active
Portable and battery-powered train horns in Maryland
§22-401 regulates “a horn or other warning device” without distinguishing power source. Portable horns on Milwaukee M18, DeWalt 20V, Ryobi ONE+, and Makita LXT platforms fall under the same rules.
Enforcement in practice
Maryland is actively enforcing in the DC-metro corridor and Baltimore. Montgomery County, Prince George’s County, Anne Arundel, Howard, Baltimore City / County see routine equipment inspections during traffic stops. Rural Eastern Shore and Western Maryland counties see less enforcement.
Practical Maryland train horn compliance
- 01 Keep the factory horn wired and functional
Non-negotiable. DC-metro enforcement routinely checks OEM horn function during stops.
- 02 Put the train horn on a separate switch
Distinct from the OEM button. Covered or keyed switches add install discipline.
- 03 Do not use on DC-metro / Baltimore public roads
Montgomery, PG, Anne Arundel, Howard, Baltimore City / County all have active enforcement.
- 04 Reserve use for off-road / events / private property
Maryland has substantial farm land (Eastern Shore) and off-road venues where §22-401 does not apply.
- 05 Watch local noise ordinances
Baltimore City §19 + Montgomery / PG County noise codes layer on state law.
- 06 Hearing protection when testing
140+ dB causes immediate damage at close range.
How to verify this page
Maryland Transportation Article sections can be amended. Before acting on anything here, verify the current text of §22-401 on the Maryland General Assembly’s official statute portal and consult a licensed Maryland attorney for your specific situation. If you notice this page is out of date, please send a correction — we update within 48 hours when a cited source is provided.
Nearby states & related laws
All 50 states →Virginia
Virginia train horn law (Va. Code §46.2-1060): vehicle horn rules, Virginia Beach / Richmond enforcement, aftermarket horn regulations. Plain-English guide.
Delaware
Delaware Code §4306 covers vehicle horns. Install is not prohibited; unnecessary or unreasonably loud use is citable. Plain-English statute summary.
Pennsylvania
Pennsylvania train horn law (75 Pa.C.S. §4535): vehicle horn rules, Philadelphia / Pittsburgh enforcement, aftermarket horn regulations. Plain-English guide.
New Jersey
New Jersey train horn law (N.J.S.A. 39:3-69): vehicle horn rules, active NJ enforcement, aftermarket horn regulations. Plain-English guide.
Continue on Train Horn Hub
All 50 states
Full state-by-state legality index with statuses, citations, and decibel caps where defined.
Decibel distance calculator
Inverse-square-law tool that shows perceived loudness at any distance from the horn.
Battery-powered platforms
Horns organized by cordless-tool battery — Milwaukee M18, DeWalt 20V, Ryobi, Makita.
HornBlasters Shocker XL review
154 dB four-trumpet flagship kit — measured output, install notes, and verdict.
Sources & Citations
- [1] Maryland General Assembly — Transportation Article (official portal)
- [2] Maryland MVA — Vehicle Equipment
- [3] Md. Transp. §22-401 — Horns and warning devices (Justia secondary)
Educational content. Not legal advice. Verify current statutes with your state DMV or a licensed attorney before installation.