When you buy a new or used car, dealerships are obligated by U.S. law to ensure the vehicle is “street legal,” or designed and assembled according to government standards that allow it to be driven legally on public roads. Generally, if a car is street legal, it has the features the law requires for it to be driven legally on roadways.

Automobiles and parts, including aftermarket parts and modifications, are regulated by two federal agencies: the National Highway Traffic Safety Administration, which sets vehicle safety standards, and the Environmental Protection Agency, which sets emissions standards. States and local jurisdictions may also establish their own laws and regulations, as long as they do not conflict with federal laws.

While there is not an official list of street-legal car laws nationwide, there are general features and specifications that all vehicles must have to be roadworthy and legal on the road.

Vehicle Type: Street-legal vehicles in the U.S. include cars, trucks, and motorcycles. Vehicles not typically sold for on-road driving, such as golf carts or ATVs, can be adapted for street use in compliance with state laws.

Steering Wheel: A circular steering wheel that is at least 13 inches across its outside diameter is standard on most vehicles. Although there is no law that specifically regulates steering wheel size or shape, a butterfly steering wheel or a fighter jet-like joystick is not typically street legal.

Horn: A vehicle must have a horn that is audible for at least 200 feet. It can generally be any note, sound, or song, as long as it meets certain volume requirements. A car horn cannot produce an unreasonably loud or harsh sound or a whistle.

Hood: An engine hood is mandatory to be street legal. Hood scoops and air intakes on the hood are also regulated and cannot be more than 4 inches higher than the hood surface in most jurisdictions.

Bumper & Fender: Bumpers are one of the first vehicle safety measures, and they are required in vehicles in most states. Most states require fenders, splash guards, or mud flaps.

Windshield: Most states don't allow a tinted front windshield, or only allow the uppermost portion to be tinted. Side windows must allow between 40% and 70% light transmittance, depending on the state. Many states prohibit mirrored tinting entirely.

Windshield Wipers: A set of windshield wipers is essential for visibility in rainy or snowy conditions, and they are required for a car to be considered street legal.

Seat Belts: Seat belt laws vary by state, but the safety devices must be installed in all vehicles under federal law.

Functional Brakes: Working brakes are essential for a car to be street legal. That also includes a functioning parking brake.

Headlights, Tail Lights, Stop Lights & Turn Signals: Every vehicle must have headlights, tail lights, stop lights, and turn signals that comply with federal laws. Original lighting equipment and replacement parts must meet these standards.

Headlights must maintain at least 22 inches of ground clearance, and bulbs must be pointed downward and slightly away from oncoming traffic. Many states regulate obstructions to lights or the use of lighting on the vehicle undercarriage, hood, and wheels.

Side View and Rearview Mirrors: At the minimum, a driver's side-view mirror and an interior rearview mirror are usually required in most vehicles. Box trucks or other vehicles where an interior mirror's view would be obstructed require two outside mirrors on both sides.

License Plate: All vehicles must have a spot to mount a license plate, and that area must be illuminated, unobstructed, and visible from 100 feet. Some states require a license plate on the front and back of a vehicle, while others only require one rear license plate. Plates must be current, valid, and clearly visible wherever displayed.

Reflectors: Vehicles must have side and rear reflectors, which are often built into the lights. Side reflectors must be amber in color, and rear reflectors must be red.

Mufflers, Exhaust & Emission Control Systems: Exhaust and emission control systems were mandated to control pollution and are required for a vehicle to be street legal. A muffler is designed to reduce the amount of noise emitted by the exhaust and is also required. Each of these components becomes very hot during vehicle operation and must be installed so that a passenger does not burn themselves getting in and out of a vehicle.

Tires: Vehicle tires must be installed in a way that reduces the likelihood of expelling debris toward other vehicles. Most vehicles meet tire requirements at the time of purchase. However, most states require the top half of rear tires on modified vehicles to be covered by fenders or mud flaps.

Ground Clearance: Most states have a minimum ground clearance requirement, which is the amount of space between the vehicle and the roadway. Ground clearance may be measured from bumper height, wheel rim height, or the lowest point of the vehicle (usually the center point of a vehicle's undercarriage), depending on the jurisdiction. See “Low Riders” and “Lifts,” below.

What Typical Modifications Make a Car Not Street Legal?

Different states and municipalities have varying laws that govern vehicle specifications and vehicle equipment. In most states, drivers can receive traffic tickets for operating a vehicle that has been modified in violation of those laws.

Modifying your vehicle to suit your style can be a fun way to express yourself, but some of those modifications are not street legal. These are some of the most commonly regulated or unlawful vehicle modifications.

Neon Lighting: Many states regulate obstructions to lights or the use of neon lighting on the vehicle undercarriage, hood, and wheels. In most states, red and blue colored lights are not typically permitted for use on civilian vehicles since they can be confused with first responder vehicles.

Neon Underglow: Underglow refers to neon or LED lights on a vehicle's undercarriage that illuminate the ground. Although lightbulbs aren't directly visible, underglow is still considered vehicle lighting, and its use is restricted in certain jurisdictions.

In some states, just installing undercarriage lights is illegal, whether they are turned on or off while driving. Some states allow for the use of underglow while on private property or while parked but prohibit its use on public roadways. Other states allow underglow as long as the lights are white, yellow, or amber.

Flashing Lights: Flashing lights are considered a distraction to other drivers and are banned in almost every state. Vehicle lighting laws may also apply to rotating, oscillating, moving, or otherwise unsteady lights in some states.

LED Headlights: LED headlights are street legal if they are white or yellow and properly installed. LED headlights that are too bright, an unapproved beam color, or improperly fitted to a vehicle are not legal.

HID Bulbs: High-Intensity Discharge (HID) bulbs are not street legal. At 55 watts (compared to the 35 watts of a standard headlamp bulb), HID lights give off a very bright, bluish-white light that can make it difficult for other drivers to see.

License Plate Frames: Decorative license plate frames are street legal in most states as long as they do not cover up any part of the numbers, letters, state names, or stickers.

License Plate Covers: A plastic license plate cover that deflects light and prevents traffic cameras from reading the license plate is against the law in many states.

Muffler/Exhaust Noise: A muffler that emits excessive or unusual noise is illegal in many states. However, some states take it a step further by prohibiting after-market modification that causes a muffler to emit more noise than the original, factory-installed muffler.

Exhaust Pipe Emissions: Modifying or removing emissions equipment from a vehicle to change its appearance or performance is against the law in every state under the Clean Air Act.

Rolling Coal: Rolling coal is a modification made to diesel vehicles where more fuel is taken into the engine than necessary, producing huge rolling black clouds of smoke out of the exhaust. The act of rolling coal is illegal in all states under the Clean Air Act. Some states have gone a step further and passed laws that ban the modification itself and impose fines on anyone caught with it.

Studded Tires: Metal tire studs improve grip and traction while driving in snowy or icy conditions, but they are hard on roads and illegal in 11 states, including Alabama, Florida, Illinois, Louisiana, Mississippi, and Texas. Some states permit tires with rubber studs.

Only six states permit the use of studded tires without limitation: Colorado, Kentucky, New Hampshire, New Mexico, Vermont, and Wyoming. Most of the remaining states allow studded tires with weather or date restrictions.

Wheel Modifications: There aren't many laws that regulate wheel size unless a modification violates ground clearance requirements. Negative cambered wheels or “hellaflush”, a modification where wheels are angled inward, is generally considered an illegal vehicle modification.

Low Riders: Some states allow vehicle height modifications that affect ground clearance as long as specific safety requirements are met. Any changes that could cause the vehicle body or undercarriage to come into contact with the ground, expose the fuel tank to damage from collision, or cause the wheels to come into contact with the vehicle body are illegal. Lowered vehicles like low riders are usually equipped with hydraulics that allow height-adjustable suspension, but most jurisdictions prohibit the use of hydraulic lift systems while a vehicle is moving or traveling above speeds of 15 mph.

Lifts: Every state regulates vehicle lift limits. Oversized tires, elongated suspensions, or lift kits that affect vehicle height and ground clearance are illegal in some jurisdictions because they affect rollover stability and could potentially cause a vehicle to ride over other vehicles.

Spoilers: A rear spoiler or rear wing, designed to improve a car’s aerodynamic performance, is street legal. However, it cannot block the driver's sightline through the rear window or significantly exceed the size of the body of a vehicle. Generally, the dimensions cannot exceed three inches on each side of the vehicle or six inches from the roofline.

Evasion Devices: Anything designed to evade law enforcement is generally illegal. Smokescreens, caltrops, oil slicks, and anything else meant to obscure views or damage other vehicles are prohibited.

Does Car Insurance Cover Modified Vehicles?

Most insurance companies have underwriting rules that list types of vehicles that they consider “unacceptable risks,” which often include vehicles that have been modified. That means an insurance company might choose not to issue a policy insuring a modified car. Plus, if modifications are made after your policy is in-force, your policy probably has exclusions whereby certain coverages will not apply if it’s found the vehicle was modified.

Some insurance companies offer a custom parts and equipment (CPE) add-on coverage that protects permanently installed parts and equipment other than those installed by the vehicle’s original manufacturer. Your car insurance policy must include comprehensive and collision coverage for you to be able to purchase CPE.

From explaining what makes a car street legal to getting you the auto insurance you need to be legal on the road, Direct Auto is here to help. Call 1-877-GO-DIRECT (1-877-463-4732), Request a quote, or come by a Direct Auto location near you to get a free car insurance quote today!

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