All states have restrictions and requirements related to vehicle lighting systems. However, lots of aftermarket lighting and related modifications are readily available, leading to some confusion for vehicle owners regarding what's permissible. Replacing a burnt headlight is, of course, legal and required. But what about replacing that light with a red bulb or adding red strobe lights under the car? Here are some pointers about how to ensure your vehicle's new look is legal.
Vehicle headlights and taillights are subject to color and brightness restrictions.
Color restrictions. Generally, headlights must be white or amber. Nearly every state prohibits any other color of light that can be seen from the front of the vehicle. It's possible to purchase and use DOT-approved "blue" headlights, although they are not truly blue. In reality, these bulbs produce such a pure white light that only appears slightly blue.
Taillights are subject to even greater limitations. Generally, a vehicle must have only two normal brake lights and a tag light. Vehicles can typically have an overhead brake light (in addition to the two normal lights), back-up lights, and a truck-bed light. But all brake lights must normally be red. In other words, any color customization is generally prohibited.
Brightness limitations. Headlight brightness is primarily governed by federal law. The Code of Federal Regulations indicates that the luminous intensity of headlights must be between 500 and 3,000 candelas. Since very few people know what a candela is or how to measure it, the DOT and SAE certify headlights that are legal for use in the United States. As long as the headlight is labeled as DOT or SAE approved, it's likely legal to use in all 50 states.
Some of the more recent lighting modifications drivers have been installing include neon or LED lights under the vehicle to create an under-glow effect. The laws of some states arguably prohibit under-glow (also called "under-body") lights. But many states still don't have laws that specifically govern these types of lighting effects.
General restrictions. Most states prohibit the use of any flashing lights on non-emergency vehicles. So under-glow lights that flash or strobe are generally prohibited. Under-glow lights might also come under the prohibition against lights visible from the front of a vehicle that aren't amber or white.
Specific restrictions. Some states have created laws explicitly for vehicle under-glow lights. Common restrictions prohibit the use of red or blue lights and require that the bulbs be hidden underneath the vehicle. The laws of a few states prohibit under-glow lights that are visible past 75 feet. Vermont is by far the most restrictive and bans the use of any under-glow lights (above four candlepower) after nightfall.
Most state laws don't directly address the use of LED lights from inside a vehicle. However, many of the general rules discussed above governing headlights and taillights still apply if the LED lights are visible from the front or back of the vehicle.
A few states have exceptions to these rules specific to LED lights inside vehicles. For example, California allows LED lights inside certain vehicles so long as they aren't red in color and don't give off more than .25 candela per square inch.
Fortunately, lighting violations, like most other equipment violations, are typically considered "non-moving" traffic offense. In many states, the non-moving-violation label means the DMV won't assess demerit points to the driver's record for the offense. Fines for lighting violations are normally modest, often around $45. But the real cost would be the money wasted on a modification that now must be removed.