Green lights on cars aren’t just decorative—they usually serve an official purpose, though their meaning can vary depending on where you live. In many areas, volunteer firefighters and EMS personnel use green lights on their personal vehicles while responding to emergencies. They may also appear on command vehicles at emergency scenes to help responders quickly identify the person in charge.

Green lights can also be used by certain government agencies, private security vehicles, and, in some regions, authorized highway maintenance crews. Their exact purpose depends on local laws, but they generally signal that the vehicle is performing an official duty rather than acting as a standard emergency vehicle.

For most drivers, displaying green lights is not allowed without authorization. Many states prohibit civilians from using them, and doing so can result in traffic stops, fines, or other legal consequences. Even where green lights are permitted, they are usually considered courtesy lights that request, but do not legally require, other drivers to give way.

If you notice green lights on a vehicle, it’s most likely being used by a volunteer first responder, security service, government agency, or authorized maintenance crew. Since regulations differ from one state or country to another, it’s always best to follow local traffic laws regarding emergency and official vehicle lighting.