What should you do when your semi breaks down on the highway?
Get the truck as far right as it will go, turn on the hazards, and set your three triangles within 10 minutes. Then read the dash lamp and the fault code before you call anyone, because that decides whether you need a tow, a mobile mechanic or just a reset. Then call dispatch, your roadside program, insurance if there is damage, and the tow only when you know where the truck is going.
Step 1: Safety first, by the book
Under 49 CFR 392.22, the moment you stop on the road or shoulder for anything other than traffic, the hazards go on and stay on until the triangles are out. You have 10 minutes to place three reflective triangles:
- One on the traffic side, about 10 feet (4 paces) from the truck, facing approaching traffic.
- One about 100 feet (40 paces) behind the truck, centered in your lane or shoulder.
- One about 100 feet ahead, same lane or shoulder.
On a divided highway or a one-way road, all three go behind you: at 10, 100 and 200 feet. Within 500 feet of a hill crest or curve, move the far triangle out to 100 to 500 feet toward the obstruction. Wear your vest and walk facing traffic.
Seeing a light on the dash? Snap it with DERATE and know if you can keep driving
Step 2: Read the lamp and the code before you call
Photograph the dash with the lamps lit, and scroll the display to the SPN and FMI if the truck shows them. An amber check engine with a steady engine usually lets you limp to a safe exit; a red stop engine lamp or a derate means the engine is protecting itself and the clock is running. A common one on the shoulder is SPN 1569 FMI 31, the engine protection torque derate; the engine derate guide explains how much time you typically have.
Step 3: Who to call, in what order
- Dispatch or your carrier. Give them mile marker, direction, lamp color and code.
- Your roadside program. Ask whether a mobile mechanic can fix it on the shoulder before anyone sends a wrecker; see the mechanic guide.
- Your insurance. Only if there is a collision, a fire, a fuel spill or damage to the load or property.
- The tow. Call last, with a destination shop picked. No destination means storage, and storage is where the bill grows.
- Decide fast with the code. DERATE is an iPhone app that reads a photo of the warning lights or of a scanner screen and gives a free keep-driving, caution or stop verdict; detailed causes, steps and cost ranges come with a plan.
What a Class 8 tow and roadside call typically cost
Heavy-duty towing is billed by the hour. 2026 pricing guides put the hook-up at about $200 to $500 for a semi, with hourly rates from around $250, more when a rotator or a second truck is needed. A straightforward tow to a shop 30 miles away often lands between $600 and $1,500. Recovery after a rollover is a different animal: $5,000 to $15,000 is not unusual, and FleetOwner reported an expected $3,500 recovery that became $18,000 after weekend labor, administrative fees and storage. Storage runs about $50 to $150 per day depending on the state. A mobile mechanic call-out typically costs $100 to $250 plus labor at about $160 per hour. Prices vary by region and provider; ask for the rate sheet before the hook goes on.
Load, reefer and hours of service
- Reefer: confirm the unit runs on its own fuel and log setpoint and box temperature hourly. Down a full day, the reefer tank can run dry.
- Hazmat: keep the shipping papers and emergency response information within reach; the carrier may need to notify the shipper.
- Load transfer: ask dispatch first. A cargo transfer line can run over $1,000, sometimes for freight nobody touched.
Time with a dead truck is on duty unless you are released from all responsibility and log off duty. The adverse driving conditions exception in 49 CFR 395.1(b) allows up to two extra driving hours, but it is written for weather and road conditions you could not have known about at dispatch, not for a truck that quit. Log it honestly and let dispatch replan.
Documents for reimbursement, and what to carry
- Photos of the dash, the mile marker, the triangles in place and any damage.
- Name, phone and arrival time of every vendor.
- Written estimate and itemized invoice from the tow and the shop.
- The fault code printout or screenshot.
- Receipts for fuel, meals and lodging.
In the cab, carry three good triangles, a vest, a flashlight, a power bank, a jump pack, basic hand tools, zip ties, spare fuses, a gallon of coolant and one of DEF, gloves, water and a blanket. A solid pre-trip inspection catches most of what puts a truck on the shoulder.
FAQ
Can I drive to the next exit with a red stop engine lamp?
The red lamp means the engine control module expects damage if you keep going, and some trucks force a shutdown after a short window. If the exit is in sight and your spot is dangerous, crawl to safety. Otherwise, stop.
Who pays for the tow, me or the carrier?
It depends on your lease or employment agreement. Company drivers are usually covered. Owner-operators often pay first and get reimbursed only for carrier-approved vendors, which is why you call dispatch before a wrecker.
How long can I sit on the shoulder before police order a tow?
It varies by state and road. On many interstates, police order a tow within a few hours if the truck is a hazard, and you lose the right to pick the company. Arrange your own tow quickly.