• 10 Common Car Mods That Are Illegal in the United States

Better be careful what modifications you put in your car

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Car modifications have become integral parts of car culture that it’s hard not to go a day without seeing at least one car that’s received modifications from the automotive aftermarket world. But just because modifications are popular, that doesn’t mean all of them are legal. As the aftermarket industry has evolved through the years, certain modifications began skirting state and federal laws of the U.S.

As such, measures were taken to curtail a lot of these modifications. Some have become illegal in some states while others have become illegal across the board. So before you decide to install a cold air intake or strap on lightbars on your car, consider first which modifications are legal and which ones are illegal in your neck of the woods. Check out this list we made of the most popular modifications performed on cars that are either illegal or, at the very least, frowned upon.

There’s such a thing as being too bright on the road

You would think that having a car with extra powerful lights is a good thing on the road. You know, the brighter the light, the more visible the road, right? While that might be the case for you, bright headlights, spotlights, and light bars are outlawed in a lot of states because of the dangers they pose, not to you, but other motorists.

Lightbars, in particular, are known for being extremely bright and powerful. That’s good news for you if you’re off-road or in dark areas without traffic, but if you’re going to use light bars on populated roads and highways, you’re inviting danger for others and trouble from law enforcement authorities.

Imagine driving on the opposite lane of a highway and then a car driver from the other lane turns his lightbar on. The powerful light could not only temporarily blind you, but it could also divert your attention long enough for you to get into an accident. There are places where light bars are handy, but public roads aren’t one of them.

You’re not James Bond; those automatic license plate covers are inviting trouble

There’s a cool factor that comes with automatic license plate covers, or at least those that we see in movies. Not only can you evade law enforcement authorities with a little trickery, but the possibilities of what you can do with automatic license plate covers will draw out the horns on your heads.

But while this type of equipment is legal to buy and own, it’s illegal to use on the road for the simple reason that covering your plate at the flick of a switch is often used to avoid law enforcement authorities.

No one’s going to use an automatic license plate covers for giggles; it’s often used by people with something heinous planned, and they install a license plate cover on their cars as a precaution for when things awry. Keep your license plates visible at all times, folks. If you get caught with an automatic license plate cover on your car, you could end up in big trouble.

Rolling coal isn’t cool; it’s dirty and illegal

If you’ve ever seen a truck on the road that emits plumes of black smoke from its exhausts, there’s a good chance that you’re looking at a rolling coal truck.

Rolling coal, for those who aren’t familiar, is the practice of modifying a diesel engine for the singular purpose of emitting large plumes of black or grey sooty exhaust fumes into the air.

Those who turn their trucks into rolling coals even go so far as to modify their vehicles using smoke switches and smokestacks. While it is a spectacle in it of itself, the practice is also in violation of the Clean Air Act, which prohibits the manufacturing, sale, and installation of “a part for a motor vehicle that bypasses, defeats, or renders inoperative any emission control device [and] prohibits anyone from tampering with an emission control device on a motor vehicle by removing it or making it inoperable prior to or after the sale or delivery to the buyer.”

A lot of states have banned rolling coal trucks and in Illinois, anybody who is caught removing or altering their vehicle’s EPA emissions equipment will get fined $5,000 on top of any penalties enforced by federal laws. In other words, don’t even think of rolling around town in a rolling coal truck.

Car window tints aren’t illegal; really dark ones are

Car window tints are technically not illegal. There are several manufacturers that design high-quality window tints and you can buy these where they’re available without so much as getting into trouble.

That said, window tints are also one of those car accessories that’s treated differently depending on which state or county you live in. Certain states have laws allowing car window tints that reach a certain lighting threshold.

That means that darker window tints allow less light to enter the car. While that may be good in preventing the interior of your car from turning into an oven, dark tint can also prevent people on the outside from seeing who or what is inside the car. If you have a car with a dark window tint, there’s a good chance that someone from law enforcement will talk to you about it depending on what kind of laws are in place within their jurisdiction. Is it worth the hassle? I don’t think it is.

Be wary of your state’s laws regarding license plate frames

The license plate frame is another example of a car accessory that straddles the line between legal and illegal. Technically speaking, license plate frames are not illegal to have in your car.

According to the 2018 State License Plate Laws, Oklahoma is the only state in the U.S. that explicitly forbids the use of license plate frames.

On the other hand, novelty plate shields are illegal in more states, including the District of Columbia, Illinois, Kansas, Maryland, Massachusetts, Minnesota, New York, Oklahoma, Oregon, Tennessee, and Vermont.

It’s very important to understand the laws of your state with regard to license plate frames and clear plastic covers. In some states, these accessories become illegal when it impairs the readability of the name of the state where the vehicles are registered or the letters or numbers of the license plate at any time. So, if you have a license plate frame that covers any of the aforementioned details, that could get you in trouble.

Police lights will only get you in trouble

Lights modifications are probably the most popular modification done on a car. We already mentioned lightbars as being illegal on populated roads and highways, but at least lightbars can be used in less populated areas and the world of off-roading.

Unfortunately, red, white, and blue lights — or police lights, as they’re more commonly known — are illegal. Expect a heavy fine if you get caught using police lights on your unmarked car. Heck, expect to spend some time in jail, too, because you’re likely going to up there if you’re caught using these lights.

Don’t jam my laser

Laser jammers are technically legal to buy in the U.S., but there are states that prohibit their use on the road, specifically when it comes to preventing law enforcement authorities from using their laser guns to check on the speed of a specific vehicle. A laser jammer is a piece of nifty equipment to have in your car. It has the ability to overwhelm the laser beam coming from laser guns so that the latter registers a faulty speed measurement or, in some cases, no measurement at all.

The purpose of laser jammers in this context is clear. Those who have the equipment in their cars don’t want to get caught by the authorities, especially when they’re breaking speed limits on public roads. Laser jammers have been successful in that regard, and a lot of states in the U.S. have responded in kind by outlawing its use on the road. You can still buy laser jammers; just don’t buy one and use it to try evading law enforcement authorities. Trouble awaits if you get caught.

The ears bleed, too

It’s a common occurrence among car aficionados to have loud exhaust systems. Loud means proud, right? That’s especially true when we’re talking about high-powered sports cars with raspy V-8 engines sitting on idle, ready to wake up and let the entire neighborhood know about it.

Here’s the thing: installing an aftermarket exhaust system is not illegal in the U.S. A lot of aftermarket tuners have even made great businesses out of it.

But just because it’s legal, it doesn’t mean there shouldn’t be limits to it, too. Most states in the U.S. have either banned or set in rules in place to mitigate the use of obnoxiously loud exhaust systems.

In New York, for example, motor vehicles must produce have a maximum sound level of 76 decibels at speeds of 35 mph or less. Go above 35 mph and the legal threshold also goes up to 82 dB.

Other states have stricter laws against loud exhaust systems. Take Colorado, for instance. According to state laws, “no person shall modify the exhaust system of a motor vehicle in a manner which will amplify or increase the noise emitted by the motor of such vehicle above that emitted by the muffler originally installed on the vehicle, and such original muffler shall comply with all of the requirements of this section.”

Cold air intakes straddle the thin line between legal and illegal

Cold air intake systems are one of the most important aftermarket upgrades you can give to your car. Installing one in your ride usually nets more horsepower coming out of the engine, and more power means more fun, right? Well, tell that to state regulatory authorities, a lot of whom have made cold air intake systems illegal within their respective jurisdictions.

Outside of the possibility that cold air intake systems can contribute in more cases of speeding, the basis for its illegal status in states like Arizona, California, Maine, Maryland, New Jersey, New York, Pennsylvania, and others rests on its violation of the California Emissions Standards under Section 177 of the Federal Clean Air Act of 1970.

On the bright side, there are ways to make old air intake systems legal across all 50 states. A specific unit must receive a CARB Executive Order (EO) number, something manufacturers of this aftermarket equipment have to provide for each unit they sell.

Studded tires aren’t everyday tires

Studded tires are another confusing piece of equipment that jumps the fence between legal and illegal depending on the location and situation. In the case of these tires, they’re legal in a lot of places, specifically in places where the winter season could turn those areas into frozen wonderlands. See, studded tires are unique in their capacity to dig into the ice, helping cars get more traction compared to regular tires.

Most states in the U.S. even require car owners to use studded tires in harsh conditions, particularly in areas where snow can get out of hand in the winter. Knowing all this does make you wonder why studded tires can get you in trouble with law enforcement authorities.

The problem in this regard is simple: if you’re using studded tires at any time other than the winter season, you’re going to get in trouble with the authorities.

Studded tires are great for winter, but when it’s not snowing and the roads are clear, studded tires can destroy tarmac and road surfaces. So while you can buy and use studded tires during the winter season, best take those tires out from spring to autumn unless you want to get on the wrong side of the law.

What car mods are illegal?

There are a lot of car mods that are illegal in America. Super loud exhausts, bro trucks, rolling coals, lowrider, underbody neon lights, and super dark car tint are all illegal in the U.S.

What car mods are illegal in California?

California has one of the stricter car modification laws in America, and among the mods that are illegal in the state include underbody neon lights license, extra loud exhausts, radar detectors / laser jammers, license plate covers and frames that obstruct any part of the plate’s numbers, letters, or the state name.

Is it legal to mod your car?

Modifying your car is legal, though there are elements of car modifications that are illegal depending on which state you live in. Cold air intakes, for example, are illegal in Arizona, California, New York, Pennsylvania, and several other states if they don’t carry a CARB Executive Order (EO) number.

Is it legal to have custom exhaust?

Depending on the state you live in, it’s either legal or illegal. Most states do have regulations that allow custom exhaust systems provided they don’t reach specific noise levels at certain speeds. New York, for example, allows a maximum sound level of 76 decibels at speeds of 35 mph or less and up to 82 dB at speeds over 35 mph.

Is NOS legal?

NOS is legal to buy, but illegal — and very dangerous — to use on public roads. Cars that carry NOS typically partake in races, both of the sanctioned and non-sanctioned variety.

Kirby Garlitos
Kirby Garlitos
Automotive Aftermarket Expert - kirby@topspeed.com
Kirby’s first exposure into the world of automobiles happened when he caught Knight Rider on television as a five-year old boy. David Hasselhoff didn’t leave much of an impression on him (that happened later on in Baywatch), but KITT certainly did. To this day, Kirby remains convinced that he will one day own a car with the same ‘spirit’ as the original KITT (not the 2008 monstrosity). He doesn't know when that will be, but until then, he’s committed to expressing his love for KITT, and all cars for that matter, here at TopSpeed.  Read full bio
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