Flat towing is not illegal anywhere in the United States, but asking whether flat towing is illegal is the right instinct, because every state attaches its own equipment and safety rules to the practice and the thresholds don’t match from one border to the next. The rule most likely to put you on the wrong side of the law is the weight at which a supplemental braking system becomes mandatory on the towed vehicle, and that number ranges from 1,000 pounds in the strictest states to 4,500 pounds in the most permissive, with a couple of states requiring brakes on any towed vehicle regardless of weight.
Where State Laws Actually Differ
Supplemental braking thresholds are the biggest variable. A large group of states draws the line at 3,000 pounds. Some set it as low as 1,000 or 1,500 pounds. A few let you go up to 4,000 or 4,500 pounds before a brake system is required, and a couple require one on every towed vehicle, period.
Because almost any car you’d flat tow behind a motorhome weighs more than 1,000 pounds, the practical read is simple: if you cross state lines, you need a supplemental braking system on the towed vehicle. Counting on a generous home-state threshold doesn’t help you the moment you drive into a stricter one.
States also differ on maximum tow-bar length, how many vehicles may be in a combination, and whether the towed vehicle needs its registration visibly displayed. A handful lower the speed limit for towing. California caps towing speed at 55 mph. Washington sets a 60 mph limit for combinations over 10,000 pounds. If your route crosses several states, comply with the strictest rule you’ll meet along the way. State DMV sites and the official vehicle codes are the authoritative references.
Equipment the Law Requires
A legal flat-tow setup has five parts working together: a tow bar, a baseplate on the towed vehicle, a supplemental braking system, safety chains or cables, and a lighting connection. Leave any of them out and you’ve created both a safety hazard and a ticket risk.
Tow Bar and Baseplate
The tow bar connects the motorhome’s hitch receiver to the towed vehicle. The baseplate bolts to the towed vehicle’s frame and gives the tow bar arms something to attach to. Baseplates are vehicle-specific by make, model, and year. Tow bars carry a weight rating, commonly 5,000 or 10,000 pounds, and that rating must meet or exceed the towed vehicle’s gross vehicle weight.
Supplemental Braking System
A supplemental braking system presses the towed vehicle’s brake pedal in time with the motorhome’s braking. Without one, the full weight of the car shoves the motorhome every time you slow down, stretching stopping distances and chewing through the lead vehicle’s brakes. Portable floor-mounted units that mechanically press the brake pedal generally cost $1,500 to $1,800. Install one regardless of your home state’s threshold, because the lowest state threshold is 1,000 pounds and essentially every towable vehicle exceeds it.
Lighting
The towed vehicle has to show working tail lamps, stop lamps, and turn signals on the rear, synchronized with the motorhome. Federal regulations for driveaway-towaway operations require the rearmost towed vehicle to carry at least two tail lamps, two stop lamps, and two turn signals, with one of each on each side of the rear.1eCFR. 49 CFR 393.17 – Combinations in Driveaway-Towaway Operations Most setups accomplish this with a wiring harness tapped into the motorhome’s lighting circuit, or with magnetic or suction-cup lights clipped to the rear of the car. Keep the license plate visible.
Safety Chains or Cables
Safety chains are the backup connection if the tow bar fails. Federal rules require at least two chains or cables attached near the bumper-to-frame connection points on each vehicle, crossed beneath the tow bar and attached at or near the crossing point. Crossing them cradles the tow bar tongue if it drops and gives some directional control over the towed vehicle during that moment.2eCFR. 49 CFR 393.71 – Coupling Devices and Towing Methods, Driveaway-Towaway Operations Leave enough slack for turns, not so much that the chains drag.
Not Every Vehicle Can Be Flat Towed
Legality is only half of the question. Many vehicles will suffer serious transmission damage if towed with all four wheels on the ground. In an automatic, the pump that circulates transmission fluid runs off the engine, so a car being towed with the engine off has an unlubricated transmission turning at highway speed. Manual transmissions have a related problem with needle and pocket bearings that don’t get oil when the engine isn’t running. Damage happens in miles, not hundreds of miles.
The owner’s manual is the authority. Manufacturers that build a vehicle to be flat-towable say so and spell out the procedure, which may involve shifting a transfer case to neutral, enabling a flat-tow mode through the infotainment system, or disconnecting the driveshaft. If the manual doesn’t address flat towing, treat the vehicle as not flat-towable and use a dolly or trailer instead.
Licensing and Weight Ratings
A standard driver’s license covers most recreational flat-tow combinations. You need a commercial driver’s license when the gross combined weight rating of the combination reaches 26,001 pounds or more.3Federal Motor Carrier Safety Administration. Driver Operates a Combination Vehicle with a GCWR of 26,001 Pounds or More Most motorhome-and-car combinations stay well under that line, but owners of large Class A diesel coaches towing heavier vehicles should run the numbers. A combination below 26,001 pounds does not require a CDL even if either vehicle on its own is heavy.
Separately from licensing, every tow vehicle has a Gross Combined Weight Rating listed on the door placard, in the owner’s manual, or in the manufacturer’s specifications. The GCWR is the maximum safe weight of the motorhome, the towed vehicle, passengers, fuel, and cargo together. Going over it strains the drivetrain and brakes of the motorhome and voids drivetrain warranties.
Insurance Coverage Gaps
Insurance is where flat towers often learn the hard way. Your motorhome’s liability policy generally extends to damage you cause to other people and their property while the towed car is attached and part of the combination. If the car detaches and strikes someone, those third-party claims typically fall under the motorhome’s liability coverage as well.
What the motorhome policy almost never covers is damage to the towed vehicle itself. Rear-end a car and crumple the towed vehicle’s bumper, or catch a rock in its windshield, and the motorhome’s collision and comprehensive coverage won’t pay. The towed vehicle needs its own active auto policy with collision and comprehensive to handle those losses. Some RV insurers offer endorsements that add limited physical damage protection for the towed vehicle at extra premium, but it isn’t default coverage. Before a trip, confirm with both insurers that the car is covered while being flat towed.
A Pre-Trip Check That Keeps You Legal
About fifteen minutes before you pull out handles most of what state troopers and physics will test. Confirm the tow bar arms are fully seated and locked into the baseplate brackets, and that the hitch pin and clip are in place at the receiver. Check that the safety chains are crossed under the tow bar, attached at the correct points, with slack for turns but not enough to drag. Have someone stand behind the towed vehicle while you cycle brake lights, turn signals, tail lights, and hazards. Activate the supplemental braking system and run its test mode. Follow the owner’s manual drivetrain procedure for the towed vehicle exactly, set the ignition to the position the manual specifies, and verify the steering wheel turns freely. Check tire pressure on both vehicles. If your brake system has a breakaway switch, confirm it’s connected and its battery is charged, because that switch is what locks the towed vehicle’s brakes if the two vehicles separate.
A complete setup, correctly rated and installed, puts you in compliance in virtually every state without having to adjust equipment at each border.