Train Horn on a Snow Plow Truck: Mounting It Out of the Slush and Using It as a Backing and Pass-By Warning

A plow truck gets slush thrown up from below and brine sprayed from behind, and it spends most of the storm backing up in the dark. Here's where to put a battery train horn so it survives that, and how to use it as a short pass-by and pre-backing warning that adds to your backup alarm instead of replacing it.

Why a plow truck is hard on any horn

Air horns usually go low on a pickup, behind the grille or on the frame rails. On a plow rig that's the worst spot. The plow mount, light bar wiring and hydraulic lines already crowd that area, and the blade throws slush, sand and salt brine back onto it every time it pushes a windrow. Iowa DOT notes that the front plow sticks out several feet ahead of the truck, so a horn mounted behind it also has a steel moldboard sitting between it and anyone in front of you.

Three more things work against you:

• Snow soaks up sound. University of Kentucky acoustics researcher David Herrin puts a couple of inches of fresh snow at roughly 60 percent sound-absorbing on average across the audible range. A blast that carries down the block in July carries less in the middle of a storm.
• Trapped water freezes and expands. Ice is about 9 percent less dense than liquid water (USGS), so meltwater that refreezes in a trumpet bell or a diaphragm housing pushes on whatever holds it. Water in the diaphragm also makes a horn squeak, and a couple of short blasts usually clear it.
• Air systems hate winter. A compressor kit adds a tank that collects condensation, plus air lines and fittings that can freeze. A battery horn has no tank or air lines and no wiring through a firewall that already carries plow controls.

Where to mount it on a plow rig

Mount it high and behind the blade, and make it easy to take off. Here's how the usual spots compare on a plow truck:

Two details decide whether the horn makes it through the winter:

• Tip the bells slightly down. Marine horn makers tell installers to point trumpets slightly downward so water drains out. A plow truck needs the same thing, because melted snow that stays in a bell will refreeze there overnight. The trumpet orientation guide goes into more detail.
• Use a mount you can release by hand. Straps or a quick-release bracket let you pull the horn into the cab at the end of a run. If you can't get it off with cold fingers in under a minute, it'll end up living on the truck all winter.

If you haven't picked a horn for the truck yet, the best train horns for trucks roundup compares the dual, quad and Extreme tiers by size and loudness. On a plow rig, the horn also has to fit on the rack beside the light bar.

Backing up: a supplement to the alarm, never a substitute

Most of a plow truck's close calls happen in reverse: stacking snow in a lot, backing out of a dead-end, or pulling back from a driveway apron. TxDOT tells drivers that plow drivers can't see directly behind their trucks and sometimes have to stop or back up. A loud horn is tempting here. Just be clear about what it legally counts as.

• The rule. For construction work, federal rule 29 CFR 1926.601(b)(4) bars an employer from using a vehicle with an obstructed rear view unless it has a reverse signal alarm audible above the surrounding noise, or it backs up only when an observer signals that it's safe. The same section requires an adequate audible warning device at the operator's station, kept in working order.
• The ruling. In 1974, in the Southeast Contractors case, the employer argued that the driver's air horn met the backup-alarm requirement. The Occupational Safety and Health Review Commission rejected that, writing that "an ordinary truck horn does not reveal the direction of travel."

So keep the factory backup alarm and the factory horn working, and use a spotter or camera where your job requires it. The train horn's job is the moment just before you move. One short tap tells anyone shoveling behind you that a truck is about to back up, and then the alarm takes over. If you plow for a town, county or contractor, get any add-on approved by the fleet manager first. Our work truck and fleet guide covers how to ask.

Pass-by warnings: short, deliberate signals

Iowa DOT points out that wing blades are easy to miss when they're down at pavement level in low visibility, and that plows kick up clouds of snow that make it hard for other drivers to see. You can't count on people seeing you. Short horn signals can help them hear you, as long as you keep them short and save them for when there's a real reason:

Use it with restraint. Private plow routes run through neighborhoods in the middle of the night, and a 150 dB blast on a cul-de-sac at 3 AM gets you noise complaints, not safety points. On residential streets, keep the horn quiet unless someone is about to step or drive into the blade.

The horn and the remote

A tool-battery horn works well on a plow truck because there's nothing to plumb or wire, and it comes off the truck between storms. The Extreme Series Train Horn for Milwaukee® 18v Battery is our loudest model at 150 dB. It runs on any Milwaukee® M18™ battery and comes with a wireless remote rated to 160 ft. That covers sounding it from the cab with the horn mounted on a headache rack.

Shop the Extreme Series Train Horn for Milwaukee® 18v Battery →

If a spotter, loader operator or second plow driver needs to sound the horn as a signal, the Long-Range Remote (2,000ft) lets someone outside your truck trigger it. If you already run a different cordless platform, the portable battery train horn lineup covers the other common 18V and 20V packs.

Shop the Long-Range Remote (2,000ft) →

The between-storms routine

Brine is what usually ruins horns over a plow season. Once you're back in the shop:

• Pull the horn and the pack. Wipe the salt film off the housing and trumpets with a damp rag, then dry everything. Don't hose it or pressure-wash it.
• Blow out the bells. A couple of short blasts indoors (or in the garage, with ear protection) clear leftover water before it can refreeze.
• Warm the battery before you charge it. Battery University gives the lithium-ion charging range as 32°F to 113°F and warns that charging below freezing plates metallic lithium on the anode and permanently hurts performance and safety. Using a pack in the cold is fine down to about -4°F, though you'll get fewer blasts. DeWalt® recommends charging its 20V MAX™ packs between 40°F and 105°F, so give a cold pack an hour inside before it goes on the charger.
• Keep the spare pack in the cab, not in the bed toolbox, so the battery you swap in mid-storm is already warm.

FAQ

Does a train horn count as the backup alarm on my plow truck?

No. Under 29 CFR 1926.601(b)(4), a vehicle with an obstructed rear view needs a reverse signal alarm audible above the surrounding noise or an observer guiding it back. The Review Commission held that an ordinary horn doesn't qualify because it doesn't show which way the truck is moving.

Can I leave the horn on the truck all season?

You can, but it won't last as long. Every storm coats it in brine, and every thaw-freeze cycle leaves water in the bells. A quick-release mount and five minutes after each storm add a lot to its life.

Will the battery hold up on an all-night run?

It will give fewer blasts as it gets colder, but discharging lithium-ion down to about -4°F is within the normal range. The damage happens when you charge a frozen pack, so let it warm above 32°F first.

Is it legal to use the horn while plowing public roads?

Horn and noise rules are set by states and towns, and many state vehicle codes only allow horn use when it's reasonably necessary for safe operation. Treat the train horn as a warning device. Use short signals when there's a real hazard, and don't blast it for fun on the route.