Trucking Laws · Nationwide · October 25, 2026

What to Do When Your Semi Breaks Down: A Roadside Checklist

A driver in a yellow safety vest sets out red warning triangles behind a semi on a highway shoulder — Illustration for this story. Not a photo of a specific location.

When a semi quits on the side of the road, the first few minutes matter most. The short answer comes in three steps: turn on the hazard flashers right away, get as far off the road as is safe, and put out warning devices within 10 minutes, as federal rules require. Then call for help: 911 first in an emergency, then dispatch and a repair or towing provider.

The full checklist and the rules behind it follow. This guide is general information, not legal advice.

Quick roadside checklist

Turn on the hazard flashers right away.
Get as far off the road as is safe.
Secure the truck the way your carrier and your truck's manual tell you to.
Put out reflective triangles or fusees within 10 minutes.
In an emergency, call 911 first.
Call dispatch and follow your carrier's breakdown process.
Give the repair or tow provider your exact location and the truck details.
Once the warning devices are out, stay in the cab with your seat belt on if it is safe, or stand well away from traffic.
Log the time the way the hours of service rules and your carrier require.

Make the truck visible and stay safe

Hazard flashers and pulling off

Under 49 CFR 392.22(a), when a commercial motor vehicle is stopped on the traveled part of a highway or on the shoulder "for any cause other than necessary traffic stops," the driver "shall immediately activate the vehicular hazard warning signal flashers." The flashers stay on until the warning devices are set out, and they must be turned on again while the devices are being picked up. The rule allows flashers in addition to the warning devices, "but not in lieu of" them.

Connecticut DOT tells motorists to move into the right shoulder, "entirely off the roadway and away from moving traffic." MassDOT says to move into the breakdown lane to the right of the solid line. Both agencies wrote that guidance for all motorists, not only trucks.

Once stopped, secure the truck the way your carrier and your truck's manual tell you to.

Where to put warning triangles

The federal rule, 49 CFR 392.22(b), says warning devices go out "as soon as possible, but in any event within 10 minutes." Where they go depends on the road:

Two-lane or undivided road: one device on the traffic side, 4 paces (about 10 feet) from the truck, toward approaching traffic. A second goes 40 paces (about 100 feet) behind the truck, in the center of the lane or shoulder the truck occupies. The third goes 40 paces (about 100 feet) ahead of the truck, in the direction away from approaching traffic.
Divided or one-way highway: all three go behind the truck. One goes at 200 feet and one at 100 feet toward approaching traffic, in the center of the lane or shoulder the truck occupies, and one goes on the traffic side within 10 feet of the rear of the truck.
Near a hill, curve or other obstruction: if the truck is stopped within 500 feet of a curve, a hill crest or anything else that blocks the view, a warning device goes "in the direction of the obstruction to view a distance of 100 feet to 500 feet" from the truck.

Warning devices are not required inside a municipality's business or residential district, except when lighted lamps are required and street lighting is not enough to make the truck clearly visible from 500 feet. And if fuel or another flammable liquid or gas is leaking, no flame-producing signal, such as a fusee, may be lit or placed except far enough away to prevent a fire or explosion.

Stay out of traffic

Once your warning devices are out, state transportation agencies such as Connecticut DOT and MassDOT advise staying in the vehicle with your seat belt on if it is safe. Connecticut DOT and State Police say to leave only for a fire or similar danger, moving away from the vehicle and the travel lanes. If you have to be outside, MassDOT says to use the side away from traffic, stand behind a guardrail when possible and put on a reflective vest first.

Who to call, and what to tell them

Call 911 first in an emergency

In an emergency, such as an injury, a fire or a truck stopped in a travel lane, call 911 first. MassDOT says, "Always call 911 first in an emergency," and Connecticut DOT lists calling 911 as its second step, right after getting off the road.

Call dispatch and follow your carrier's process

If your carrier has a breakdown procedure or approved vendors, follow it. For leased owner-operators, FMCSA's leasing rules (49 CFR 376.12) require the lease to "clearly specify the responsibility of each party" for listed costs and to spell out every charge-back item. The rule does not name towing, so read your lease to see who pays. This is not legal advice.

Roadside assistance and mobile repair

Some insurers sell roadside assistance as an add-on. Progressive Commercial, for example, describes an optional heavy truck add-on covering up to $5,000 in towing to the nearest qualified repair facility and up to $500 in labor, with a $250 deductible. Terms vary by insurer and policy.

Find heavy-duty towing and mobile truck repair by state. The truck stop and weigh station map can help pin down nearby landmarks.

What to tell the repair or tow provider

The Towing and Recovery Association of America's vehicle identification guide lists the information a dispatcher needs to send the right towing and recovery unit:

Year, make and model
DOT classification (Class 1 to 8 by gross vehicle weight rating)
Location
Type of tow
2WD, 4WD or AWD
Damage and tire condition
Loaded or empty
Cargo contents
Whether there is a trailer
Whether the keys are with the vehicle
Hazmat placards ("Advise if placarded")

For location, MassDOT suggests noting "the mile marker, last exit number, or the nearest rest area." Give the highway and direction of travel too. Describing any warning lights or fault codes can also help, though that is not on the association's list.

Common semi truck breakdowns: blowout, no-start, air or DEF warning

The same safe approach works for each of these: pull over safely, do not attempt repairs beyond basic checks, and call your carrier or a mobile repair provider.

Tire blowout: pull over safely and call your carrier or a mobile repair provider.
Truck won't start: do not attempt repairs beyond basic checks, and call your carrier or a mobile repair provider.
Air leak or brake warning: pull over safely and do not attempt repairs beyond basic checks.
DEF or aftertreatment warning: your truck's manual and your carrier's maintenance team are the right sources for what a specific warning light means.

For prevention, see the pre-trip inspection checklist.

Hours of service while broken down

Time with a broken-down truck counts as on-duty time. The federal definition in 49 CFR 395.2 says on-duty time includes "All time repairing, obtaining assistance, or remaining in attendance upon a disabled commercial motor vehicle." FMCSA's plain-language driver's guide puts it as "All time taking care of your truck when it is broken down."

The same definition leaves out time "resting in or on a parked vehicle" and time "resting in a sleeper berth." FMCSA's guide says off-duty time requires being "relieved of all duty and responsibility for performing work" and being able to "leave the place where your vehicle is parked." Follow your carrier's logging policy on how to record the wait.

Picking the truck up from a repair shop cannot be logged as personal conveyance. FMCSA says "travel for repair and maintenance work is being done in the furtherance of the business and is considered on-duty time."

To plan the rest of the day around the clock, try the hours of service break calculator, and see the hours of service rules explained for the full picture.

If the truck needs a tow

Heavy-duty towing bills vary widely, and the total depends on the equipment, labor and storage involved. The guide on what it costs to tow a semi covers what goes into a towing bill and how to avoid surprises. Big Rig Daily also lists heavy-duty towing and mobile truck repair by state.

Emergency kit checklist

Required by federal rules (49 CFR 393.95)

Fire extinguisher: a power unit not hauling placarded hazardous materials needs one extinguisher rated 5 B:C or more, or two rated 4 B:C or more. A power unit hauling placarded hazmat needs one rated 10 B:C or more. It must be UL-labeled, have a visual charge indicator, be securely mounted and readily accessible, and use an agent that does not need protection from freezing.
Warning devices: three bidirectional emergency reflective triangles, or at least 6 fusees plus any extra needed to meet the placement rule. Other devices may be used in addition, but not instead.

Fusees and other flame signals are banned on some trucks, including those carrying certain explosives, flammable gas or flammable liquid cargo tanks, and vehicles fueled by compressed gas.

In 2026, FMCSA removed the spare fuse requirement (effective April 20) and dropped liquid-burning flares as a warning device option (effective March 23). The federal options are reflective triangles or fusees.

Suggested, not required

Drinking water
Flashlight
Reflective vest
Work gloves
Phone charger
Spare fuses

Move-over laws: why other motorists must give you room

According to NHTSA, "all 50 states have Move Over laws." Coverage for disabled vehicles differs by state, and many states now include any stopped vehicle with hazard lights on. AAA's August 2026 Slow Down, Move Over chart counts 34 jurisdictions that cover all stopped vehicles and 50 that cover tow trucks. Check the rules in your state.

Big Rig Daily has covered why these laws matter, including an Oklahoma I-35 move-over reminder and a tow truck driver hurt on Virginia I-495.

More tools are on the trucking tools page, including a printable trip log.

This guide is general information, not legal advice. Rules can change, so check the current federal rules, your state's laws and your carrier's policy.

FAQ

How far do you put triangles behind a semi?

On a two-lane or undivided road, 49 CFR 392.22 calls for one triangle about 10 feet from the truck on the traffic side, one about 100 feet behind and one about 100 feet ahead. On a divided or one-way highway, all three go behind: within 10 feet, at 100 feet and at 200 feet.

How long do you have to put out warning triangles?

Federal rule 49 CFR 392.22(b) says warning devices must go out "as soon as possible, but in any event within 10 minutes." The hazard flashers go on immediately and stay on until the devices are out. Flashers may be used along with the triangles, but the rule says not in place of them.

Should I stay in my truck after a breakdown?

Put out your warning devices first, since federal rules require it within 10 minutes. After that, Connecticut DOT and MassDOT advise staying in your vehicle with your seat belt on when it is safe, or standing well away from traffic, behind a guardrail if there is one. Leave the cab for a fire or similar danger.

Does breakdown time count against my 14-hour clock?

Yes, it counts. FMCSA defines on-duty time to include "all time repairing, obtaining assistance, or remaining in attendance upon a disabled commercial motor vehicle," and the 14-hour window runs on consecutive hours, so it keeps running while you wait. Only qualifying sleeper berth periods are left out. Follow your carrier's logging policy.

Who pays for a breakdown tow, me or the carrier?

It depends on your lease or employment agreement and your insurance. FMCSA's leasing rules require owner-operator leases to spell out who pays which costs and what can be charged back, so read yours. Company drivers should follow their carrier's breakdown policy. This is general information, not legal advice.

What should be in a semi truck emergency kit?

Federal rules require a fire extinguisher of the right rating and three reflective triangles or at least 6 fusees. Spare fuses have not been required since April 20, 2026. Sensible extras, suggested but not required, include drinking water, a flashlight, a reflective vest, work gloves, a phone charger and spare fuses.