Emergency vehicle lighting

lightbarlight barbeaconsemergency lightspolice lightswarning lightscherry topLight Barsblue lightsblue lights and sirens
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.wikipedia
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Strobe light

strobestrobe lightsstrobes
Some emergency lighting is based on strobe lights similar to those used in flash photography.
Other applications are in alarm systems, emergency vehicle lighting, theatrical lighting (most notably to simulate lightning), and as high-visibility running lights.

Flashtube

xenon flash lampxenon flashflash tube
These xenon flash lamps put out a very brief but very bright flash by discharging a large current through a gas which ionizes the gas.
Because they can generate bright, attention-getting flashes with a relatively small, continuous input of electrical power, they are also used in aircraft warning lights, emergency vehicle lighting, fire alarm notification appliances (horn strobes), aircraft anticollision beacons, and other similar applications.

New Zealand Police

PoliceNew Zealand Police ForceNZ Police
Since 2008 the orange-blue livery is being phased out, and all marked patrol vehicles were expected to have the yellow-blue livery as well as LED light bars by 2014.

Light-emitting diode

LEDLEDslight emitting diodes
Light-emitting diodes are small, completely solid state, very power-efficient, long-lasting (as they have no filaments to burn out) and can be seen very easily even at great distances and in sunlight.
One-color light is well suited for traffic lights and signals, exit signs, emergency vehicle lighting, ships' navigation lights, and LED-based Christmas lights

Hong Kong Police Force

Hong Kong PoliceRoyal Hong Kong Police ForceRoyal Hong Kong Police
Most police vehicles in Hong Kong are equipped with both red and blue emergency vehicle lighting.

Ambulance

ambulancesmedical carMilitary ambulance
Emergency medical vehicles, such as ambulances and paramedic fly-cars, generally use white, amber, and red as well.
For this purpose, they are generally equipped with flashing warning lights and sirens.

Fire engine

fire truckfire enginesfire trucks
Vehicles operated by fire departments, such as fire engines and heavy rescue vehicles, prominently use red, a color with strong cultural associations with the fire service, along with some amber and white.
They are normally fitted with audible and visual warnings, as well as communication equipment such as two-way radios and mobile computer technology.

NHS Blood and Transplant

National Blood ServiceBlood Transfusion ServiceUK Transplant Service
Blood donation vehicles are allowed the use of blue lights and sirens (known commonly "blues and twos") for the use of emergency blood transports.

Automotive lighting

taillightturn signalturn signals
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.
Emergency vehicles usually carry distinctive lighting equipment to warn drivers and indicate priority of movement in traffic.

Wig-wag (automobile)

wig-wagemergency lightsmade to flash
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.

Siren (alarm)

sirensirensfire siren
Often, they are used along with a siren (or occasionally sirens) in order to increase their effectiveness.

World War II

Second World WarwarWWII
The use of the blue emergency light originates in Germany during World War II.

Scattering

light scatteringscatteredscatter
Due to the scattering properties of the blue color, it is only visible to lower altitudes and is therefore less easily spotted by enemy airplanes.

Emergency vehicle

emergency vehiclesemergencydemonstrator
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.

Fresnel lens

Fresnelopticfirst-order
These revolving lights may contain a single, stationary bulb around which a curved mirror is spun (or which is attached to a spinning mirror), or a lamp with a Fresnel lens.

Parabolic aluminized reflector

sealed beamPARPAR cans
Larger rotating lights may contain modular or sealed-beam lamps which rotate as an assembly (commonly 2 or 4 bulbs, but possibly 1 or 3).

Gumball machine

gum machinegumballGumball Dispenser
Other beacons use a clear dome with colored lenses on each lamp; in the latter case, these rotating beacons are sometimes referred to colloquially as ‘gumball machines’ or sometimes ‘cherry tops’ in the case of red lights.

Halogen lamp

halogenhalogen lampstungsten-halogen lamp
Rotating lights often use a quartz-halogen or conventional incandescent bulb, though some rotating beacons are now made with LEDs rather than bulbs.

Incandescent light bulb

incandescent lampfilamentincandescent light
Rotating lights often use a quartz-halogen or conventional incandescent bulb, though some rotating beacons are now made with LEDs rather than bulbs.

Emission spectrum

emissionemission spectraemission spectroscopy
The light produced has a somewhat bluish emission spectrum, which makes red lightbars glow a fuchsia-pink color when lit.

Drag (physics)

dragaerodynamic dragair resistance
LED-based lightbars can be made very thin, reducing wind resistance by around 8-10 percent, or made very flat and used in novel applications, for example to flip up under a sun visor.

Traffic light

traffic signaltraffic lightstraffic signals
In colder inclement climates, this has resulted in LED emergency vehicle warning lights (as well as traffic lights) being obscured by the buildup of frost or snow, raising safety concerns.

Michigan State Police

State PoliceDepartment of State PoliceDepartment of the State Police
One agency that continues to employ traditional red rotating beacons on its patrol cars is the Michigan State Police.

Detective

police detectiveinvestigatordetectives
Examples of such situations would be detectives in unmarked vehicles, volunteer firefighters, or managers at freight yards who use an amber light for safety.