Light bar

Emergency vehicle lighting is one or more visual warning lights fitted to a vehicle for use 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 driver to stop for interaction with an officer. These lights may be dedicated emergency lights, such as a beacon or a light bar, or may be modified stock lighting, such as a wig-wag or hide-away light, and are additional to any standard lighting on the car such as hazard lights. Often, they are used along with a siren (or occasionally sirens) in order to increase their effectiveness. In many jurisdictions, the use of these 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 so the emergency vehicle may proceed through unimpeded.

Laws regarding and restricting the use of these lights vary widely between jurisdictions, and in some areas non-emergency vehicles (e.g. school buses) and semi-emergency vehicles (e.g. tow trucks) may be permitted to use similar lights. These non-and semi-emergency lights are also discussed here. Research into the usefulness and potential dangers of these lights is also presented.

Emergency vehicle lighting is a sub-type of emergency vehicle equipment.

Emergency vehicle lighting is generally used to clear the right of way for emergency vehicles, or to warn approaching motorists of potential hazards, such as a vehicle that is stopped or moving slower than the rate of traffic, or a car that has been pulled over. It may also be used to provide specific directions to motorists, such as a command to pull over. Some vehicles incorporate a small arrow board to direct traffic.

The use of emergency beacons is restricted by law in many jurisdictions only for responding to an emergency, initiating a traffic stop, bona fide training exercises, or when a specific hazard exists in the road. Most private security agencies have special permits that allow them to use beacons in specific areas. It has yet to be determined whether autonomous vehicles will be required to carry lights, or what colors or patterns they might exhibit to warn off aggressive human drivers.

The optical and mechanical characteristics of the lights used can have a significant effect on the look of the vehicle and how readily it gains attention in emergencies.

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Wikipedia