Underglow Lights and Ground Effects Lighting

A car with blue underglow ground effects lighting
Underglow can create a dramatic effect after dark.

miggslives/Flickr/CC BY 2.0

Although it’s completely invisible during the daylight hours, underglow lighting is one of the most striking customizations you can make on your car. Also known as ground effects lighting, these systems consist of either neon or LED lights that are mounted to the chassis of a vehicle.

This can create the illusion that a car is floating on a bed of brightly colored light after the sun goes down, which essentially makes underglow the visual equivalent of a thumping subwoofer.

There are a couple of different types of underglow light systems, and the complexity can range from professionally designed and installed systems to LED light bars that any competent DIYer can install over a weekend. However, there are a couple of potential legal issues to consider before installing one of these systems.

Five Underglow Mistakes to Avoid

It's always a good idea to check into the laws where you live before you install underglow lighting on your car, but here are five things that can get you in trouble in a lot of places:

  1. Turn your underglow lights off while you're driving. Underglow looks cool, but it creates an unnecessary distraction on the road. Even if it's legal to install underglow lighting on your car where you live, it's probably illegal to drive with it on.
  2. Avoid restricted colors. Most places place some type of restrictions on aftermarket lighting on vehicles. The most commonly restricted colors are red, blue, and green because these colors are often used by police and emergency services. In the worst case scenario, you could be charged with impersonating a police officer.
  3. Don't use flashing lights. Flashing lights, other than turn signals, are typically illegal on civilian vehicles. Even if you leave your underglow off while driving, you could be cited while parked if it's illegal and the police see your underglow flashing.
  4. Don't use exposed bulbs. Exposing the bulbs in your underglow makes it more obvious that your car has underglow lighting installed, so you could possibly get pulled over even if you don't have the lighting turned on. The halo effect is still visible when you place the lighting where it can't be seen.
  5. Direct your lights downward. In locations where it's legal to drive with underglow lighting turned on, make sure that your bulbs are not only hidden, to avoid glare but that the light is also directed down toward the road.

Types of Underglow Lights

Underglow systems can be broken down into two main categories based on the type of lighting that they use. The first ground effects lighting made use of colored neon tubes, which aren’t ideally suited for the purpose.

While neon ground effects lighting is very bright, and it is possible to achieve strobe effects with specialized modules, neon tubes are very fragile. That makes neon underglow better for vehicles that aren’t driven on a lot of rough roads since even driving over a speed bump may break one of these tubes.

The other type of underglow lighting makes use of LEDs. These systems use hundreds of light emitting diodes, and there is a pretty big range in quality. Early LED ground effects suffered from spotty lighting issues, but higher quality systems create the same type of solid light pattern seen from neon underglow.

Lower cost LED underglow systems also tend to be dimmer, but it is possible to achieve a high level of brightness from LEDs.

The main benefit of using LEDs in ground effects lighting is that they are much sturdier than neon tubes. Light emitting diodes are a type of solid-state lighting that use semiconductors to generate light instead of superheated gas in a glass tube. They also consume less power than neon tubes and can create complicated patterns like chasing and fading.

Installing Ground Effects Lighting

While you can have an underglow light system installed professionally, this is a popular DIY project for people who enjoy customizing their own vehicles. Both neon and LED ground effects kits are available from a variety of aftermarket sources, and they typically come with everything you need to perform an installation. Of course, you’ll also need to have a few key tools and basic knowledge of electrical wiring.

Installing a neon underglow kit typically consists of wiring in a transformer and bolting the lighting assemblies to the chassis. Some neon underglow kits are also compatible with specialized modules that can be wired into the audio system, which will cause the lighting to change along with whatever music is being played. Since neon lights require high voltage to operate, wiring in the step-up transformer might be a little different from other DIY car wiring projects.

Since LEDs can run on 12 volt automotive electrical systems, LED underglow lights are typically easier to install. The simplest LED underglow light kits can be hooked up with a single power wire, although there are more complicated options available. Additional wiring is required if you want your underglow lighting to respond to your sound system, engine RPM, or other cues.

Are Underglow Lights Legal?

The question of ground effects lighting legality is complicated since the law differs from one jurisdiction to another, and it hinges on a handful of different issues.

There are a number of areas where installing underglow lights is illegal, so it’s important to check before you install one of these systems. Even if underglow itself isn’t technically illegal, there may be a law on the books that could allow the police to write you a costly ticket.

In some places, it’s illegal to have any type of neon lighting on a car. In other areas, it’s illegal to have certain colors of lighting installed on a private car, or flashing lights may be prohibited in order to differentiate them from emergency services vehicles.

Other laws specifically forbid any modification that illuminates the ground underneath a vehicle, which is obviously targeted squarely at underglow lights. So before you install this type of systems, it's important to check out the specific laws where you live.