Vehicle emergency lights are available in several kinds, typically as bars or beacons fitted on the roof. They are used to signal others on the road to allow right of way for the emergency vehicle, or as a warning light when the vehicle is stationary. Vehicle emergency lights are often employed in conjunction with other kinds of automotive lighting such as hazard lights. Back-up lamps are Sirens are another popular complement, maximizing effectiveness through the addition of an aural dimension. As can be imagined, the use of such devices is restricted by law in most jurisdictions, reserved for uniformed personnel or utility crews.

Vehicle emergency lights in the United States are regulated by state codes, but common practices abound, such as the use of yellowish amber lighting for utility vehicles and escort vehicles. But in the states of Alaska, Arizona, Colorado, Minnesota, Nebraska, New Mexico, and Texas blue lights are also used for such purposes, whereas elsewhere the color is reserved for law enforcement or emergency rescue. Other local peculiarities include the use of red lights for a funeral hearse - but only during an actual funerary procession - in Iowa. (In other states purple is the color designated for this function.)

Throughout the world, customs vary as much as they are similar. Most of the European Union employs blue lights for law enforcement, but under specific circumstances German, Estonian, Finnish, and Swedish police will use the color red. In Germany and Sweden red also denotes the command post, whereas green is the color found elsewhere. But blue is universally recognized as the color of law enforcement. Ironically, many police officers have complained that the blue lights hurt their eyes and vision!

It is important to acknowledge that once an emergency light is purchased it should comply with the law since there can be accusations of imitation and such. Although it may be used for that exact reason however, it is the duty of law enforcement to abide by the law no matter how small the case or an emotional circumstance which may justify what can and cannot be used for those who are not involved in the force.

There does not appear to be agreement on when emergency lighting for vehicles was first invented. One account traces the devices all the way back to ancient times, when torches were fastened to horse wagons. Many modern accounts find a Mr. Harold E. Edgerton's 1931 employment of flashing lamps to be the first instance of a stroboscope, which was actually used for the study of moving objects and not as emergency lighting. By the 1960s, police and other emergency response vehicles were being mounted with strobe lights, until nearly two decades later bar lights became preferred. This practice was so successful at drawing attention that such lights were being used in other contexts, most notably by tow trucks and other utility vehicles.