Light bar
From Wikipedia, the free encyclopedia
A light bar (or lightbar) is a device designed to make an official vehicle easily identifiable. Lightbars are fitted to nearly every emergency vehicle and most utility vehicles for the purpose of alerting other vehicles and pedestrians of emergency situations or other road hazards.
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[edit] Form Factor
There are two main types of light bars: single rotating or flashing beacons, and larger car-sized lightbars. Both are effective at drawing attention to a vehicle, but since their inception full-size lightbars have increasingly displaced single beacons.
[edit] Single Beacon
First used in the 1940s, single beacons have become universally accepted as a means of attracting attention to one's vehicle. While many agencies have switched to the larger lightbars, the single beacon is still used throughout the world. It's commonly used on utility and construction vehicles when a full-sized lightbar is ill-suited or impossible to attach to a vehicle.
While the term "lightbar" wouldn't be used to refer to a single beacon by itself, two or more placed on the vehicle in question could be considered a lightbar. In some cases several wedge-shaped beacons are mounted in a 'V'-shape to create a lightbar.
[edit] Gumballs
These revolving lights usually contain two or four bulbs with mirrors and an electric motor to rotate them underneath a plastic dome. They usually come in solid colors but in some cases the front and back halves of the dome are different colors while in other cases a clear dome is used with colored lights inside. Especially in the last case, these rotating beacons have been nicknamed "gumball machines"; a name which has stuck throughout the years.
Although their use in law enforcement has dropped since the introduction of lightbars, the "gumball machine" is still used by some police departments because of their lower cost, lower air resistance figures (see below), and in some cases simply due to tradition. One agency that famously continues to employ a traditional single beacon (in a custom hue of red) on their patrol cars is the Michigan State Police.
[edit] Omnidirectional
Single beacons are now more often available as an omnidirectional strobe light with a translucent dome. Some smaller and low-cost models, however, are simply a flashing halogen bulb. LEDs are also used to light some omnidirectional beacons.
[edit] Magnet-Mount
The single beacon is also available with a magnetic mount for situations where permanent mounting is not appropriate. This can include detectives, volunteer fire fighters, or executives for rail or port operators who get a company car but may need an amber light for safety within a working freight yard. These Magnet Mount beacons are usually in the shape of a "tear drop" resembling that off a tear drop when placed on the roof of a car. The strength of the magnet varies from one model to the next; some models lack the strength to adhere to vehicles that are in motion.
Some temporary teardrop magnetic mount, single beacon lights are nick-named "Kojac's" after the popular 1970's TV series that used one.
[edit] Full-size Lightbars
First used in the 1960's, light bars have since become the dominant means of drawing attention to official vehicles, as they are found on nearly every emergency vehicle and on certain other semi-official vehicles (like tow trucks) that require attention. Modern lightbars have several capabilities that can be preprogrammed in, such as traffic control and rotation speed. Usually these arrays are multicolored, and can contain anywhere from six to ten lights, which are rotated by motors within the assembly.
The shape of these larger lightbars can vary radically from very large to very slim, and from one large line to the Federal Signal Vision Lightbar, which is shaped rather like a large letter "V". Usually the size of these fullsized lightbars allows for the lights to be rotated in a certain style, like having all of the lights flash from left to right. Usually these lightbars contain a speaker system for the sirens or for a loudspeaker, which is often located in the middle part of the light bar, about where the space between the driver and passenger would be.
[edit] Other
Many emergency vehicles have alternately flashing "wig-wag" headlights, or have hideaway strobes within their headlights, turn signals, and backup lights.
[edit] Technologies
The lights within a lightbar may be halogen, strobe, or LED. Halogen bulbs may be stationary steady or flashing lights, or they may rotate within the lightbar, similarly to the "gumball" lights.
Strobe lights can put out 1.5 million candle power for roughly 250 microseconds, while lightbars using halogen bulbs can put out a constant 50,000 to 70,000 candle power.
LED-based lightbars are becoming very popular among many emergency agencies for several reasons. The solid-state LEDs are very efficient and draw less current from the car's battery. Their fast on/off transition time enables attention-grabbing pulses. They have no moving parts and are rated for up to 100,000 hours of use reducing downtime for departments. Finally, LED lightbars can be made very thin to offer less wind resistance.
[edit] Colors
Most people interpret the color of a lightbar to denote the type of vehicle or situation, but the relationship between color and service varies by jurisdiction. In North America and Asia the usual emergency colors are red and blue, while in Europe the emergency color tends to be only blue. Research has shown when flashing lights, twice the amount of blue light energy is needed in daylight to be perceived as bright as red. At night, the situation is reversed.
[edit] Australia
Police, Fire and Ambulance (EMS) vehicles use both red and blue in every State. State Emergency Services Rescue vehicles also use red and blue lights in every state, with the exception of Queensland, where they use amber.
In New South Wales the Roads and Traffic Authourity (RTA) traffic commander and traffic emergency patrol units also use red and blue lights when responding to motor vehicle accidents or major traffic situations. Red Cross blood transport vehicles and Mines Rescue units are permitted to use only red lights.
Amber is used by Tow trucks, utility vehicles such as motor breakdown service vehicles, Public utility service vehicles (street sweepers, garbage trucks and elevating platforms) etc. Amber is also required on school buses in New South Wales.
Magenta (purple) is used by Roads and Traffic Authourity (RTA) enforcement vehicles or a vehicle driven by a local Council officer while engaged in monitoring or measuring the weight of heavy vehicles. Purple is also used by some local Council Rangers engaged in parking enforcement duties and by Taxi Council inspectors in Victoria.
A green light indicates a Police/Ambulance/Fire site/incident command vehicle and cannot be used by any other vehicle, or on a vehicle that is in motion.
Volunteer personnel aren't allowed lights on their personal vehicles. White is sometimes used in addition to red/blue in lightbars by Ambulance or Fire vehicles in some States. Most emergency vehicles also use alternating flashing headlights.
[edit] Canada
Generally, red is used for emergency vehicles, amber for utility vehicles, and green for volunteer firefighters. Red and blue are used by police, with the exception of Ontario, which uses red and white. In Ontario, the blue colour is reserved for snowplows. An interesting application of the use of purple lights exists in Ontario, where that colour of light can be used for the lead car in a funeral procession.
[edit] Denmark
As in the United Kingdom, all emergency vehicles use blue lights to alert others of an emergency. Red lights are never used, and amber is for non-emergency use only e.g. trucks.
[edit] United Kingdom
Only emergency vehicles, including police cars, ambulances, fire engines, HM Coastguard vehicles, HM Revenue and Customs vehicles investigating serious crimes and RNLI vehicles launching lifeboats, may use blue flashing lights and flashing headlights, and only then when proceeding to or at the scene of an emergency. (Ambulances may also use blue lights to transport patients to a care facility (e.g. to a hospital, or between hospitals) if the patient's condition necessitates it or transport organs or blood to a patient for transplant ). Vehicles using blue lights are exempt from many motoring regulations, such as being able to treat a red traffic light as a give way sign, driving on the wrong side of the road or a motorway hard shoulder and ignoring the speed limit. They may not, however, ignore no entry signs, drive the wrong way down a one-way street or cross a solid white line in the middle of the road, although some regulations may have to be disobeyed at the professional judgement of the driver. Though no qualification other than a driving license is legally required to use them, most organisations will insist that their drivers are trained in high-speed driving techniques. The common combination of blue flashing lights with two-tone sirens has led to 'blues and twos' becoming a nickname for the emergency services as a whole, as well as the title of a fly-on-the-wall documentary series following them.
Doctors on emergency calls are allowed a green courtesy light. Flashing red lights are not generally allowed on moving vehicles, though some police forces have rear-facing flashing red lights on traffic police cars, which are used to signify that the vehicle is stationary.
Chequered lights denote command and control vehicles - these are red and white for fire, blue and white for police and green and white for ambulance, and are often fitted in the middle of the light bar.
The only form of lighting that may be used by the general public is amber lights, which generally signify slow-moving vehicles, such as utility vehicles, and give no priority, existing purely to advertise the vehicle's presence. They are also mandatory for some vehicles, such as vehicles with a top speed of twenty-five mph (e.g. invalid carriages) on dual carriageways. Volunteer personnel are generally not allowed lights on their personal vehicles.
It should also be noted that UK legislation considers all lights, reflectors and reflective material to be lights, and any colour of light except blue is allowed on any vehicle as long as it is disconnected or covered while on the public highway. Similarly, no distinction is made between lights mounted on light bars and those mounted anywhere else on the vehicle (e.g. headlights, indicators, brake lights) - all are covered by the same regulations.
[edit] United States
In the United States, which color is used for what is left up to the individual states, but there are some commonalities. Red almost always denotes an emergency vehicle. In some states only the police use blue and fire vehicles use red, while in others volunteer firefighters use blue and official public safety vehicles use red. Amber or yellow lights are often used by utility vehicles such as construction or tow trucks that may be stopped or moving slower than the flow of traffic. Amber may also be found as secondary lighting on emergency vehicles
New Mexico is unusual in that tow trucks have blue lights; red is for police, though city police and county sheriff departments do use blue on the passenger side of the vehicle.
Arizona, Colorado, and Minnesota also use blue lights on snowplows.
The state of California requires a solid red light facing forward and a flashing amber light facing rearward on every emergency vehicle, in addition to any other lights that may be fitted.
Other colors sometimes seen on lightbars include clear white, green, and purple. White is often used with red on ambulances, with blue on police cars, and with amber on utility vehicles. Rhode Island and Wisconsin require white lights on school buses, with Wisconsin's law requiring a white strobe light on the roof, over the rear axle(s). Green lights sometimes denote a volunteer fire, EMS, or private security vehicles. On a fire vehicle a green light usually denotes the command vehicle on scene; this usage derives from the use of green flags in the Incident Command System. Purple is used in some states to denote a funeral vehicle.
Many jurisdictions have laws about who may display or operate particular colors of emergency lights. In places that do not enforce specific rules about green or white lights, they are often used by entities like private security companies which may be ineligible to use blue or red lights but wish to distinguish themselves from utility vehicles.
In general, most states restrict red/blue lights to police and fire vehicles. White can sometimes be used for non-emergency vehicles, but it is rare. Yellow can always be used in non-emergency vehicles (with some exceptions, such as California) and green can sometimes be used for private security vehicles. Purple is legal in some states for funeral vehicles.
[edit] Lightbars by Service
Nearly every police department, fire department, and emergency medical service (EMS) use lightbars on their respective vehicles for rapid responses in emergency situations. Often different services will use distinctive color schemes, and different agencies may be interested in different features.
[edit] Police
In the USA, police agencies may use red, white, blue, or any combination there of on their lightbars, depending on the state.
Some police cars have an amber traffic-control stick (also known as an arrow stick, arrow bar, or Arrow Stik (TM)) to direct traffic left or right or around both sides of the vehicle; these most often have 6 or 8 rear-facing lights that flash in sequence.
The aerodynamic properties of light bars are particularly important for police cruisers, as fuel efficiency and drag become issues for patrol and pursuit. A single rotating beacon usually increases a vehicles aerodynamic drag by roughly 2%, while lightbars can increase the aerodynamic drag by up to 7%.[citation needed] Because of this, some police cars do not have roof mounted lightbars. These "slick-top" cars mount their emergency lights within the cruiser, generally at the top and/or bottom of the front and rear windshields. Some slick-top cars are fitted with lightbars that are built into the leading or trailing edge of the roof, covering the extreme top of the front and/or rear windshields. Slick-top police cars are also noteworthy in that their silhouette lacks the shape of a lightbar or beacon, resembling that of a civilian vehicle and making the car harder to identify as a police vehicle.
[edit] Fire and EMS
In the USA, the NFPA (National Fire Protection Association) dictates standards for fire vehicles, which generally specifies red lights of the halogen, LED, or strobe variety, placed on various parts of the vehicles. Depending on area, ambulances may also abide by the NFPA standard, or may have red and blue lights.
[edit] Volunteer Personnel
Almost all states in the US allow volunteer fire and EMS personnel to place emergency warning lights in their personal vehicles for use when responding to emergencies. The laws vary greatly by state.
The degree of lighting is mandated by law and also by local custom in most areas, and can vary from a single rotating light on the dashboard or roof, to a setup much like modern police cruisers. Some states also allow volunteer use of sirens and "fire truck" sounding air horns to clear the right of way.
In some states, volunteers are allowed to use the normal red lights, while in other states volunteers must use some other color, usually blue or green. In the latter case, the lights are used as a courtesy to "request" the right of way and generally do not mandate pulling over. Some states, such as New Jersey, limit volunteer use of red lights to chiefs and captains of squads.
Separate colors may be used for fire versus EMS volunteers. In Connecticut, Indiana, and New York, volunteer firefighters use blue while volunteer EMTs use green.
[edit] Utility Vehicles
Yellow lights have become popular in the civilian arena as a way of drawing attention to a vehicle involved in non-emergency work. Most phone and cable companies, towing services, and certain types of construction equipment mount some type of lightbar; additionally, several local and state vehicles involved in maintenance work for roads, gas and water pipes, electric services, and so forth utilize yellow lights for a higher degree of visibility. Typically these lights are the single beacon kind, although lightbars have been used for vehicles of this type, especially on wreckers/tow trucks.
[edit] See also
[edit] Notes
- ↑ many lifeboats are also fitted with blue lights themselves, but these are mainly for visibility and to indicate official status, and have little legal meaning on the high seas.
- ↑ with the same exceptions as everyone else e.g. to pass a stationary vehicle.
- ↑ this is one of the few situations where a forwards-facing red light may be shown.
