11 Popular Car Mods That Are Illegal in Most States
Modifying a car might start with practical intentions, but plenty of drivers unintentionally cross the legal line while attempting to boost performance or enhance looks. US state laws differ significantly, so some modifications that are completely banned in one state might just be loosely regulated in another.
These are the car mods that commonly get drivers in legal trouble in different parts of the United States.
Modified Number Plates
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Many areas require plates to remain fully visible and reflective, with clear registration information. States like New York and Texas strictly implement these rules, and violations result in fines. Even decorative plate covers can be flagged during stops. Authorities focus on readability to ensure plates work with toll systems and traffic cameras.
Overpowered Headlights
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It’s frustrating when oncoming headlights hit your eyes like a flashbulb. To address this, federal regulations only permit headlights that emit white or yellow light and meet DOT standards. Several states have taken it further; specifically, Virginia and Pennsylvania have actively issued citations for overly bright or miscolored lights.
Removed Emissions Devices
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Tampering with emissions systems became a national issue in the 1970s, when federal lawmakers began addressing rising air pollution. The Clean Air Act led to strict rules that required vehicles to include components like catalytic converters and diesel particulate filters. The Environmental Protection Agency monitors compliance and has issued large fines to shops and individuals who bypass these systems.
Excessively Loud Exhausts
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Regulating vehicle noise by decibel level helps reduce unnecessary disruption on roads. Some jurisdictions cap exhaust sound at 95 decibels to prevent cars from disturbing residential areas or attracting unwanted attention. Officers in certain areas can issue tickets based on judgment alone, even without measuring equipment.
Lifted Trucks Beyond Legal Height
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Towering trucks might turn heads, but they also raise safety concerns. After all, lifting a vehicle too far changes how it handles weight, alters visibility, and can interfere with headlight and bumper alignment. To avoid issues, owners should check local laws. Some areas permit taller setups with assessment or certification, but others levy strict maximums.
Lowered Suspension with Clearance Issues
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Clearance laws were introduced decades ago to deal with the rising number of cars getting stuck on uneven roads or damaging infrastructure. As suspensions dropped lower for style or handling, cities began setting minimum height requirements to keep vehicles safe and street-friendly. If a car scrapes or its tyres rub, it can be flagged during inspections or routine stops.
Underbody Neon Lighting
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Neon lights glowing beneath a car can look sharp, especially at night, but law enforcement doesn’t share the enthusiasm. Blue and red lighting tends to mimic emergency vehicles, which is exactly why most places ban them while driving. However, if you still want the added visual effect without the hassle, feel free to get static white or amber lights and use them only when parked at shows or events.
Front Window Tints
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In various states, window tinting laws vary by percentage and window position. For example, California requires more than 70% light to pass through front windows, while there are others that allow darker tints. If a car is pulled over and found to have different shades than those allowed, police may slap a fine or order the removal.
Nitrous Oxide Systems
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You are free to use Nitrous oxide kits for tracks, but not on public roads. Just having a bottle connected can violate equipment laws in places like California and Texas. Administration often focuses on whether the system is hooked up, not just installed.
Aftermarket Taillights
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Custom taillights can give a car a distinctive appearnace, but uncertified versions usually don’t meet visibility standards. If you’re caught using them, you might receive a fix-it ticket, be required to swap them out, or fail a safety inspection. This is why you should always check that aftermarket parts are clearly marked and properly installed.
Incorrect Wheel Fitment
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People are generally not aware that changing wheels can affect more than just visual appeal. Fitment that pushes tyres too far out or causes rubbing affects how the car handles and stops. Laws exist to prevent setups that compromise control or safety. Stretching tyres or using extreme offsets can also trigger examination failures.
Hydraulic Lowriders
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Car owners using hydraulic systems need to pay close attention to local laws, especially in states like California and Nevada. These states prohibit vehicles from changing height or bouncing while in motion. The only time hydraulics are allowed is when the car is parked or used in approved shows, but daily driving with active suspension movement is restricted by traffic codes.
Radar Detectors
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Laws targeting radar detectors were introduced to reduce speeding and improve road safety. Officials believed the devices gave drivers the confidence to exceed speed limits without consequence. That concern led to federal restrictions for commercial vehicles and full bans in places like Virginia and Washington, D.C.
Coal-Rolling Diesel Trucks
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Coal rolling involves altering diesel engines to emit thick black smoke, typically by bypassing emissions controls. A number of states—including Colorado, New Jersey, and Illinois—have passed laws directly banning the practice. In other cases, implementation depends on broader environmental or nuisance regulations.
Illegal Window Decals and Obstructions
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Decorative decals, stickers, or objects hanging from the rearview mirror can get you in legal trouble in many states. Laws prohibit anything that blocks or reduces a driver’s clear view through the front windshield or side windows. This includes oversized dashboard items, political or novelty stickers placed in the wrong spot, and even air fresheners in some jurisdictions.