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“Underglow” or “ground effects lighting” is a stylistic aftermarket mod for cars and trucks. It consists of a telltale pool of light spilling onto the pavement beneath a vehicle. It is caused by a series of lights mounted beneath the chassis of a sports car or lifted truck. Because it can be distracting, or even confused with an emergency vehicle, underglow is illegal in many places.

You will want to read your local laws carefully. Certain colors and styles of underglow are illegal in many states, or even individual municipalities. Sometimes they can’t be turned on on a public road. Other times they can’t even be installed.

The biggest category of underglow lights that are illegal are blue and red setups. This is because in most places, blue and red lights are reserved for police cars or fire trucks. In other places, green is reserved for vehicles such as ambulances.

Purple car with green custom ground effects lighting kit by Underglow parked in front of palm trees.
Custom car Underglow | Unsplash

Another often outlawed type of underglow is a setup with a flashing strobe effect. Some advanced underglow systems can flash, even in time with music playing from your vehicle. As cool as this effect could be at a car show, on a public road it could be mistaken for an emergency vehicle.

In California, installing underglow. You just can’t turn them on while you are driving or parked on a public road. But California specifies that you can’t install the aftermarket lights within 12 inches of factory-installed lights. This state is an interesting one, because it actually has outlawed other forms of accessory lighting such as rooftop marker lights (similar to what semi trucks have) on pickup trucks.

In Vermont, the law specifically states that you can’t turn on underglow while driving. It is unclear whether this applies to private property. But there would be no way to enforce the law on private property.

Alaska specifies that underglow, like all other civilian vehicle lighting, can only be white, yellow, or amber in color. Ohio allows underglow, but specifies that it must be under 300 candlepower.

The states of Michigan, Massachusetts, Maine, Connecticut, Illinois, Pennsylvania, Virginia, and Washington have gone out of their way to prohibit ground effects lighting. That’s right, underglow is illegal all across these states. But remember, your city may have its own guidelines in addition.

Next, see how underglow kits are installed in the video below: