Texas mud flap laws require trucks, trailers, road tractors, and truck-tractors pulling semitrailers to have safety guards or flaps behind the rearmost wheels whenever the rear axle carries at least four tires or two super single tires. The flap has to hang within eight inches of the road while the vehicle is moving, and driving without compliant flaps is a misdemeanor carrying a fine of up to $200 under Texas Transportation Code § 547.606.
Which Vehicles Need Mud Flaps
Section 547.606 applies once a vehicle has four tires, or two super single tires, on the rearmost axle. That covers:
- Trucks, whether used commercially or privately
- Road tractors
- Trailers, and truck-tractors pulling semitrailers (flaps go on the rearmost vehicle in the combination)
- Semitrailers in combination with a towing vehicle
A super single is a wide-base single tire that replaces two standard tires on one axle. The 2011 amendment to § 547.606 confirmed that vehicles using super singles still need mud flaps.1State of Texas. Texas Transportation Code 547-606 – Safety Guards or Flaps Required
Heavy-duty pickups with dual rear wheels fall under the rule too. The dual setup puts four tires on the rear axle, and the statute draws no line between commercial and personal use. If you tow with a dually, you need flaps.
Two exemptions exist. A truck-tractor operated by itself, with no trailer attached, does not need flaps. Pole trailers are also excluded.1State of Texas. Texas Transportation Code 547-606 – Safety Guards or Flaps Required
How the Flaps Must Be Installed
The statute is short on detail. It calls for flaps of a type prescribed by the department, located behind the rearmost wheels, and suspended within eight inches of the highway surface.1State of Texas. Texas Transportation Code 547-606 – Safety Guards or Flaps Required The DPS commercial vehicle inspection manual supplies the rest.
Ground Clearance
Eight inches is the on-road standard. While the vehicle is operating on a highway, the bottom of the flap cannot sit more than eight inches above the road. During annual DPS safety inspections, the manual uses a twelve-inch threshold as the rejection point: an inspector fails a vehicle whose flap bottom is more than twelve inches off the surface.2Texas Department of Public Safety. Commercial Motor Vehicles Safety Inspection Manual – Chapter Six Install the flap well under eight inches and you satisfy both.
Width and Material
Each flap must be at least as wide as the tires it protects. If any tread extends past the edge of the guard, the vehicle fails inspection. Acceptable materials are metal, rubber, rubberized material, or any other substantial material heavy enough to stay in place behind the wheels under its own weight while the vehicle is moving.2Texas Department of Public Safety. Commercial Motor Vehicles Safety Inspection Manual – Chapter Six Flaps that sail backward at highway speed or won’t stay reasonably vertical don’t block debris and won’t pass.
What Fails a DPS Inspection
During a safety inspection, a vehicle is rejected for any of the following mud-flap problems:
- No flap or guard installed
- Flap not firmly mounted
- Flap narrower than the protected tires
- Flap split, torn, or deteriorated to the point it no longer blocks debris
- Bottom edge more than twelve inches from the road
When combinations are inspected, each trailer is treated as a separate vehicle. Every trailer in the combination needs its own compliant flaps on its rearmost axle.2Texas Department of Public Safety. Commercial Motor Vehicles Safety Inspection Manual – Chapter Six
Federal Rules for Commercial Trucks
Commercial motor vehicles operating in interstate commerce also fall under 49 CFR § 393.86, administered by the Federal Motor Carrier Safety Administration. The federal rule requires splash guards on trucks, truck-tractors, and trailers on public roads, and it runs alongside Texas law. When the two standards differ, the stricter one controls.
Fines and the Fix-It Dismissal
Operating a vehicle that doesn’t meet Chapter 547 equipment standards is a misdemeanor. Where no specific penalty applies, § 542.401 sets a fine between $1 and $200.3State of Texas. Texas Transportation Code 547 – Vehicle Equipment Court costs are added on top, so what you actually pay at the courthouse usually runs higher than $200.
Section 547.004(c) gives personal-vehicle owners an out. A court may dismiss the charge if you fix the defect before your first court appearance and pay a reimbursement fee of no more than $10.4State of Texas. Texas Transportation Code 547-004 – General Offenses Fix the flap, bring proof, and the ticket goes away for the price of a coffee run.
That option is not available for commercial motor vehicles. If you’re driving a CMV, there is no fix-it path and the violation stays on the record.4State of Texas. Texas Transportation Code 547-004 – General Offenses
CSA Scores and Civil Liability
For motor carriers, a roadside mud-flap violation feeds into FMCSA’s Safety Measurement System under the Vehicle Maintenance BASIC. The system pulls from 24 months of inspection data, and every violation raises a carrier’s percentile rank in that category. A high enough percentile triggers interventions that range from warning letters to full investigations.5Federal Motor Carrier Safety Administration. Vehicle Maintenance BASIC Factsheet One missing flap looks minor by itself. It compounds.
Missing flaps also cut into civil defense. If a rock from an unprotected rear axle cracks a windshield or forces a following driver to swerve into a crash, the absence of a required safety device is direct evidence of negligence. The conversation with an insurer or a jury shifts from whether the driver was careless to the fact that the driver was already violating a specific safety statute, and for commercial operators, a pattern of non-compliant equipment can even trigger policy exclusions.