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
Since their introduction in the 1940s, single beacons have become widely accepted as a means of attracting attention to one's vehicle. Although the use of a single beacon in law enforcement has dropped since the introduction of light bars, the single beacon 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 continues to employ a traditional single beacon on their patrol cars is the Michigan State Police. Single beacons may also be seen as secondary lights on a vehicle with a full light bar, either mounted on the vehicles top or inside the vehicle, facing out the windshield or rear window. Beacons are also commonly used on utility and construction vehicles when a full-sized lightbar is ill-suited or impossible to attach to the vehicle.
[edit] Rotating light
These revolving lights usually contain one or several lamps (commonly called light bulbs) around which a curved mirror is spun, creating a rotating beam of light. To protect the workings of the beacon, a plastic dome covers the assembly. These domes usually come in solid colors, but in some cases the front and back halves of the dome are different colors. Other beacons use a clear dome with colored lamps or reflectors inside. Especially in the last case, these rotating beacons have been nicknamed "gumball machines".
[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 firefighters, or managers at freight yards who get a company car but need an amber light for safety. These magnetic-mount beacons are often round or teardrop shaped, and are often referred to as "Kojak" lights after the popular 1970's TV series that used one.
[edit] Full Size Lightbars
[edit] Evolution
Just as the introduction of the single beacon was a great leap forward in vehicle visual warning devices, the practice of using multiple beacons (and thus multiple colors) was a natural progression. In order to utilize two single beacons it became necessary to install a bar across the roof to establish a level platform, and then attach the beacons to this bar, often with a siren speaker and/or "lollipop" lights between the beacons. This was the origin of the term "light bar".
The very earliest light bars appeared in the 1960s and were generally custom-built by the agency using them. This was accomplished by fabricating a bar to attach to the vehicle's roof, and then attaching individual components (beacons, lollipops, speakers, oscillating lights, etc.) to the bar. The beacon manufacturers quickly caught on and began producing off-the-shelf complete "light bars".
The next progression from the individual component design was to integrate the elements of the lightbar into a single contiguous unit. The colored dome over the beacon was extended toward the center of the bar to accomodate fixed beam lights (in place of lollipops), or one or more mirrors to enhance the flash pattern of the beacon. An enclosure for the siren speaker bridged the gap between the beacon lenses and resulted in the first true contemporary lightbar design.
[edit] Modern Lightbars
Today's modern lightbars combine various elements deemed worthwhile for the specific applications they are applied to. These elements may include: halogen/incandescent rotating lights with or without accompanying mirrors, strobe lights, LED panels, two-tiered (above/below) lights, fixed-beam "takedown" flashing lights, side-facing "alley" spotlights, directional traffic advisory arrows, siren speakers, and more. Several manufacturers have incorporated programmable flash patterns into their lightbars. Some lightbar variations are specialized to meet certain desires of the agency utilizing them, such as those in a "V" shape design which presents additional flashpower to the side of the vehicle, and those designed to hug the roof of a vehicle to minimize air resistance and/or present a lower profile for "stealth" purposes. The modern trend of locating sirens and other audible warning devices at the front of emergency vehicle has also resulted in almost all lightbar models being offered in an "all-light" configuration, with continuous lighting options available across the entire width of the lightbar.
[edit] Slick-tops
The aerodynamic properties of light bars can be important on police cruisers, as fuel efficiency and drag are concerns in patrol and pursuit. 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] 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, with blue used almost exclusively for police vehicles. In western Europe the emergency color tends to be only blue, with amber as a warning color for construction equipment etc. In eastern Europe emergency vehicles use blue, or a combination of blue and red.
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. Blue is specific to emergency vehicles only, while red is very common in traffic, in traffic lights, brake lights etc.
[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 color is reserved for snowplows. There is currently a push in Ontario to allow use of blue lights on police/emergency vehicles due to the fact that blue is more visible at night. Some police agencies can already be seen using blue lights, such as Peel Regional Police [1] 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] Finland
All emergency vehicles use blue lights to alert others of an emergency. Law enforcement vehicles have an additional forward-facing red flashing light. The red light indicates that the vehicle in front must pull over and stop. Amber lights ares for non-emergency warning use on e.g. tow trucks, construction equipment and the like.
[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, colors are generally regulated at the state level, but there are some commonalities.
- Red almost always denotes an emergency vehicle if the lights are facing forward.
- 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 is usually the most permissively regulated color.
- White is often used as an optional color on lightbars, though it may be restricted to emergency vehicles in some states. It is rarely used as the only color on a lightbar, though Rhode Island and Wisconsin require flashing white beacons on school buses.
- Green on a fire chief's car or a mobile command post denotes the command vehicle on scene; this usage derives from the use of green flags in the Incident Command System. Green can also denote a volunteer firefighter or EMT's vehicle in some states. Sometimes green is used by private security guards.
- Blue is exclusively used for law enforcement in some states, while in others it is used by volunteer firefighters. In New Mexico, tow trucks have blue lights. Arizona, Colorado, and Minnesota also use blue lights on snowplows. [1]
- Purple is allowed in some states to denote a funeral vehicle.
[edit] by Service
[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.
[edit] Fire and EMS
In the USA, the National Fire Protection Association publishes the NFPA-1901 standards for fire vehicles, which specifies the degree of lighting on various parts of the vehicles, with some flexibility as to color. There is also a GSA specification for ambulances known as KKK-A-1822, which many local authorities follow. Generally, fire vehicles use red and ambulances use red and white. Both often show an amber light facing the rear.
[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. In Detroit, Michigan, Angel's Night volunteers will patrol neighborhoods with yellow lights to help deter vandalism during Devil's Night and Halloween. Typically these lights are the single beacon kind, although lightbars have been used for vehicles of this type, especially on wreckers/tow trucks.
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.
[edit] Optional colors
Often while certain colors are customarily used by different services, there are other colors that are optionally used, such as amber and white. Sometimes this is done to satisfy particular regulations; for example, California requires a solid red light facing forward and a flashing amber light facing rearward on every emergency vehicle.
[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.
[edit] References
- ^ Stidger, Ruth W. "Safer Winter Maintenance". Better Roads Magazine (October 2003).
