Emergency vehicle lighting
Emergency vehicle lighting, also known as simply emergency lighting or emergency lights, is a type of vehicle lighting used to visually announce a vehicle's presence to other road users. A sub-type of emergency vehicle equipment, emergency vehicle lighting is generally used by emergency vehicles and other authorized vehicles in a variety of colors. Emergency vehicle lighting refers to any of several visual warning devices, which may be known as lightbars or beacons, fitted to a vehicle and used when the driver wishes to convey to other road users the urgency of their journey, to provide additional warning of a hazard when stationary, or in the case of law enforcement as a means of signalling another motorist that a traffic stop is being initiated. These lights may be dedicated emergency lights, such as a beacon or a lightbar, or modified stock lighting, such as a wig-wag or hideaway light, and are additional to any standard lighting on the car such as hazard lights. They are often used along with a siren system to increase their effectiveness and provide audible warnings alongside the visual warnings produced by the lights. In many jurisdictions, the use of emergency lights may afford the user specific legal powers, and may place requirements on other road users to behave differently, such as compelling them to pull to the side of the road and yield right-of-way in traffic so the vehicle may proceed through unimpeded. Laws regarding and restricting the use of these lights vary widely among jurisdictions, and in some areas non-emergency vehicles such as school buses, and semi-emergency vehicles such as tow trucks, may be permitted to use similar lights. Early emergency lights were often red lights mounted to the front or roof of a vehicle. The use of the blue emergency light originates in Germany during World War II. As a result of the "Verdunkelung", a black-out measure for aerial defense from 1935, cobalt blue was regulated to replace the red color used until 1938 in German emergency vehicle lights.