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  • Green lights on a car indicate it’s with either Homeland Security, Transportation, volunteer firefighters and first responders, command post vehicles, or emergency crowd control.
  • In most states, putting green lights on your car isn’t legal.
  • Other emergency vehicle lights include red, blue, white, amber, and purple lights.

The color of the emergency light flashing from the top of a vehicle usually tells you who operates the machine. Red lights adorn the roofs of vehicles that belong to the fire department, such as fire trucks and fire engines. Meanwhile, police cars mount light bars with either half or the entire lighting accessory featuring blue-colored lamps.

In recent years, you might have seen emergency response vehicles with green lights on their rooftops. They’re as official as fire trucks and police cruisers. But what do green lights on a car mean? What government agency do their occupants answer to? And what emergency services do they provide?

What Do Green Lights on Cars Mean?

Like other emergency lights, green lights show that the vehicle is for emergency use. The most likely places to see cars with green emergency lights are government facilities and towns with volunteer firefighters.

The following are the agencies that usually put green lights on their cars:

Department of Homeland Security

The Department of Homeland Security (DHS) handles American public security. Its portfolio includes counterterrorism, border security, immigration and customs, and disaster prevention and management.

If you see cars with green flashing lights patrolling around a government facility, chances are they’re DHS.

Department of Transportation

The Department of Transportation (DoT) handles federal transportation projects. It also sets safety regulations for all modes of transportation, ranging from cars and trucks to aircraft.

DoT vehicles might have green flashing lights. Their road maintenance vehicles often have green lights to alert drivers.

Volunteer Firefighters and First Responders

Many states operate volunteer groups of firefighters and first responders like emergency medical technicians (EMTs). In Indiana and Washington, volunteers and first responders drive vehicles with green flashing lights.

Command Post Vehicles

Command post vehicles serve as mobile headquarters. They carry the necessary equipment to manage and coordinate large groups during major operations like disaster response and firefighting.

Depending on the design, a command post vehicle can have green lights that indicate its importance in organizing and controlling operations.

Emergency Crowd Control

If you live in Montana, you’ve probably seen a police cruiser with a green light making the rounds. So what do green lights on a cop car mean? That cruiser belongs to the emergency crowd control department, which plans, organizes, and monitors large gatherings of people to keep them safe from dangers like stampedes.

Is It Legal To Put Green Lights on Your Car?

Generally, no. Many states enforce laws that make it illegal to install any lights on your car or truck that other drivers might mistake as emergency vehicle lights. These laws also cover green lights used by some emergency vehicles.

It’s illegal to pass your car off as an emergency vehicle. Furthermore, if someone mistakes you as a first responder, they might waste invaluable time trying to contact you for assistance.

If that wasn’t bad enough, some green lights have a similar color to the green signal light in traffic lights. There’s a chance that a distracted driver might mistake an illuminated vehicle light as the go-signal.

One exception is North Dakota, where you can install green lights on your car or truck. However, the lamps mustn’t flash like emergency lights. Furthermore, the lights must remain invisible when viewed from the front of your vehicle. Other states might have similar laws that permit limited use of green lights.

If you plan to install green lights, consult your state’s local laws and see if it’s illegal to modify your vehicle that way.

Other Emergency Vehicle Light Colors

Emergency vehicles feature different colored lights to identify themselves and their purposes. Aside from green, emergency lights come in the following colors:

Red Lights

Emergency vehicles carry red lights that point forward for maximum visibility in that direction. Police cars, fire trucks, and ambulances all have forward-facing red lights.

Red is a vivid color that quickly grabs attention. It usually indicates danger and wordlessly warns drivers to slow down or stop. When you see red lights, you don’t have to hit the brakes immediately. Instead, pay attention to the vehicle and decide on the right action.

Depending on the state, red lights can indicate if the police car belongs to a city, county, or state.

Many police vehicles add a second light with a different color to their red one. In states like California, police cars use a solid red light and a flashing blue light. Other states, such as Nevada, have police cars with a flashing red light and a solid blue light. Police departments in New York and North Dakota pair the red light with a white light instead of a blue one.

Fire department vehicles in Nebraska have a red light and a white light to distinguish them from police vehicles.

Other vehicles that might carry red lights include funeral hearses, school buses, and tow trucks.

Blue Lights

Americans often associate the color blue with law enforcement. Unsurprisingly, police cars in the United States often have blue lights.

Most police cars with blue lights combine them with either red or white lights. In a handful of states like Arkansas, police cruisers can sport blue lights exclusively.

White Lights

White lights are usually deployed alongside another emergency light of a different color, usually a red light like the ones seen on many police cars. A white light contrasts with a red light, making the latter easier to notice among many other red-colored lights on the road, such as brake lights.

School buses, postal delivery trucks, and rail transportation service vehicles are examples of vehicles that might only have flashing white lights.

Amber Lights

Amber lights tell other drivers to slow down or stop. They differ from other colored lights in that they’re warning lights instead of emergency lights. You don’t have to halt for or give way to a vehicle with illuminated amber lights, but you should also consider taking the appropriate action.

You can usually find amber lights on slow-moving vehicles. Garbage trucks, postal vehicles, and snow plows relied on these lights. Tractor-trailers designed to handle wide loads also have amber lights. Given the size, slow speed, and poor response times of these vehicles, you should slow down and give them room.

Purple Lights

Purple lights appear on some funeral hearses. Vehicles who are participating in a funerary procession might install these lights. Coroners and medical examiners might also put a purple light on their cars to indicate their status.

Why Do Some Emergency Lights Have Two Different Colors?

Some emergency and warning lights are split between two colors. For example, some police cars have red and blue lights. Manufacturers mix these colors to help people with color blindness see the emergency lights.

Color-blind people can see either blue or red. Emergency lights include both colors to make it easier for everyone to spot and recognize an emergency vehicle.

About The Author
Written By Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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