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The use of street lighting was first recorded in London in 1417 when Sir Henry Barton, the mayor, ordered lanterns with lights to be hanged out on the winter evenings between Hallowtide and Candlemasse. However it was introduced to the United States by famed inventor Benjamin Franklin, who was the postmaster of Philadelphia, Pennsylvania. Because of this, Philadelphia is regarded by many as the birthplace of street lighting in the United States.

The colonial-era streetlights were lit by candles shining inside their boxes. After the invention of gas light by William Murdoch in 1792, cities in Britain began to light their streets using gas and the United States followed suit shortly afterwards with the introduction of gas lighting to the streets of Baltimore in 1816. Throughout the nineteenth century, the use of gas lighting increased. After Edison pioneered electric use, light bulbs were developed for the streetlights as well. The first city to use electric street lights was New York City, in 1886.

By the beginning of the 20th century, the number of candle-lit streetlights were dwindling as developers were searching for safer and more effective ways to illuminate their streets. The fluorescent and incandescent lights became very popular during the 1930s and 1940s, when automobile travel began to flourish. A street with lights was referred to as a white way during the early 20th century.

History of manufacturers

The two main competitors in the street lighting industry were General Electric and Westinghouse. During the 1950s, GE lit roadways with its Form 109 and, later, the wildly popular Form 400. Westinghouse answered with the OV-20 model.

In 1957, a new breed of streetlight fixture was introduced. These fixtures were called "cobraheads" as if you looked at them from beneath they looked reminiscent of a cobra's flared neck. Westinghouse dubbed its cobraheads the Silverliners, which remained in production over the next 25 years. The OV-25 remains a very popular and most-beloved streetlight fixture.

GE later came out with its own cobrahead, called the M400. The original M400 is noted for its pointed front end that protrudes over its bowl-shaped diffuser. The M400 was the OV-25's main rival. They carried 250-400 watt bulbs, and therefore, were common on Interstate highways and city boulevards.

In 1964, Westinghouse produced an updated version of the OV-25, with a more-rounded look. Only the diffuser was left unchanged.

In 1967, GE updated its M400. Gone was the protruding front end, and the new M400 was also more streamlined.

GE and Westinghouse also developed smaller fixtures. A miniature version of the M400 was made for suburban residential streets and back alleys. That fixture was called the M250. In the same vein, Westinghouse offered two smaller Silverliners. The OV-12 (whose look resembles a miniature OV-50) came out in 1960, and it was replaced by the OV-15 in 1965. These smaller fixtures carried 100-250 watt light bulbs.

The second-generation M400 and M250 were the first fixtures to sport the new sodium lights. The existing Silverliners could not handle these new lights, so Westinghouse had to develop a new OV-25, as well as a new OV-15. Both of these new Silverliners (also known as Tudors) now had a flat bottom, and weren't nearly as popular as the originals.

More new manufacturers entered the streetlighting industry. Thomas & Betts (also known as American Electric) developed two new fixtures, the Model 13 and Model 25. The Model 25 was later the basis for a larger lookalike, the Model 327. All three fixtures had a boxy look that usually sported grinning diffusers, a nod to the OV-15s and M250s. (Of the three fixtures, only the Model 327 is still in production.)

The Model 327, along with GE's M1000 and Westinghouse's OV-50, sported 700-1000 watt lights (see table). These behemoth fixtures are scattered throughout different parts of the country.

Earlier versions of the M1000 and OV-50 are noted for having fins on top of the fixture. As newer ones were made, the fins were eliminated.

Some well-known light fixtures came from the Line Material Company. In the 1960s, during the height of the mercury lights' popularity, Line Material produced the Unistyle 400 and the smaller Unistyle 175. Both of these fixtures combined various characteristics of the Silverliners and GE M-series fixtures. When the sodium era began, the company answered with the boxy, more simplified Unidoor 400 (for metropolitan expressways and city boulevards) and Unidoor 175 (for smaller residential city streets and alleys).

In 1982, the entire Silverliner line was discontinued, when Cooper Lighting bought out Westinghouse's streetlighting division. Today, Cooper still makes the OV-50, now called the OVL. It also continues to manufacture the OV-15 and OV-25 models for sale in Canada.

GE and Cooper continued to take streetlighting to new heights. GE was a pioneer in the full-cutoff arena, when it created a spinoff of the popular M400. This fixture is noted for its pointed front end and lack of a diffuser. In addition, high-mast assemblies were developed for the light towers that were springing up along Interstate highways.

Thomas & Betts also created spinoffs of its Model 13 and 25. These new fixtures, called the 113 and 125, had a more-rounded look than their respective predecessors. They have become the most popular fixtures not manufactured by GE or Westinghouse.

In the mid-1980s, GE unveiled an updated M400, with a flat bottom reminiscent of the third-generation Silverliners. In 1997, the M400 underwent a total redesign, borrowing its styling from the Thomas & Betts Model 125.

Means of light generation

Incandescent light

By far the most recognized type of lighting, your common household bulb. These were the first low power electric lighting in cities world wide. Some can still be found in streetlight service to this day. Others have been installed popular downtown areas of major cities to have a nostalgia effect. Incandescent light also has excellent CRI rated at 100. Color temp is generally around 2-3K depending on type. Incandescent light is also the most inefficient when compared to HID and gas discharge lighting such as Neon light. About 98% of the energy used by incandescent lighting is wasted in heat.

Arc lamp

Arc lamps were used in the late 19th & early 20th century by many large cities for street lighting. The bright light of Arc lamps required that the early Arc lamps be placed on rather high (60 to 150 foot) towers. (They were also widely used in film and stage.) Arc lamps use high current between two carbon rod electrodes and require substantial maintenance. Arc lights have mainly been used where high lumen light was needed such as lighthouses. Today very few arc lights are in operation for actual light use. Again mainly in lighthouses (few) and industrial uses.

Mercury vapor

In 1948, the first regular production mercury vapor(MV) streetlight assembly was developed. It was deemed a major improvement over the old incandescent light, and shone much brighter than incandescent or fluorescent lights. Initially people disliked them because their bluish-green light made people look like they had their blood drained from them. Other disadvantages are that a significant portion of their light output is ultraviolet — both a waste and a safety hazard if the glass breaks, they "depreciate" — get steadily dimmer and dimmer with age while using the same amount of energy. Mercury lamps were developed in the early/mid 60s coated with a special material made of phosphors inside the bulb to help correct the lack of orange/red light from MV lamps(increasing the CRI). The UV light excites the phosphorus producing a more "white" light (really producing some "reds" in the light spectrum). These are known as "color corrected" lamps. Most go by the "DX" designation on the lamp and have a white appearance to the bulb. They're a major improvement over their "clear bulb" counter parts.

Many towns/cities still have their MV streetlights in operation, though they're slowly being replaced by HPS lamps. Debates still rage whether this is truly a wise move given the maintenance cost and quality issues of HPS lighting.

Sodium vapor

Around 1970, a new streetlight was put into service: The high pressure sodium(HPS) light. It was initially disliked by most residents because of its ugly orange glow, but the sodium vapor streetlight has since become the dominant type on American roadways and most folks have become used to the orange/yellow glow. It is by far the more efficient light source when compared to Mercury Vapor(MV) or Metal Halide (MH). Color Corrected Sodium Vapor Lights exist but are very expensive. These "color corrected" HPS lamps have lower life and are less efficient in lumens output.

There are two types of sodium vapor streetlights: high-pressure(HPS) and low-pressure(LPS). Of the two, HPS is the more-commonly used type, and it is found in many new streetlight fixtures. Sometimes, older (pre-1970) fixtures may be modified to use HPS lights as well. This process is known as retrofitting. Virtually all fixtures that are converted to HPS have previously been lit with mercury vapor. Examples of retrofitted fixtures for HPS use include the GE Form 400 and the second-generation Westinghouse OV-25 Silverliner (although later versions of this model were available from the factory as HPS units).

NOTE: While HPS lamps have been in operation for several decades now, their shortcomings are becoming apparent. Initial intent was to replace all existing street lamps with HPS due to their lower cost and greater efficiency. But there are quality control issues with these lamps (e.g. short life cycle, "cycling" lamps, etc.). This issue has increased overall cost to municipalities when compared to Mercury Vapor.

Note 2: HPS lamps have slightly different electrical requirements than do the older-technology MV lamps. Both HPS and MV lamps require a transformer to raise the voltage of the electricity used to power the fixture. However, HPS lamps also require an electrical "starter" circuit to start--much like the older fluorescent lamps in residential use. MV lamps do not require a "starter". On the other hand, MV lamps slowly dim over time, and a twenty-year-old lamp may emit a very pleasing, but useless, soft glow, rather than the powerful blue-white light of a new MV lamp. On the other hand, the yellow-spectrum HPS lamps are known for "cycling" or intermittent lighting where the lamp cycles on and off. This tendency is most commonly seen in lamps that are reaching the end of their life cycle. The arc within the lamp extinguishes and the lamp must cool down before the starter circuit initializes a new arc.

HPS lamps do not last as long as do MV lamps, but they do give increased light and efficiency. Many prefer the blue-white light of the MV lamp to the yellow-white light of the HPS lamp.

Metal halide

In recent years, Metal halide lamp(MH) streetlights have illuminated the roadways and parking lots. Metal halide has long become popular in business installations, as it can be found in warehouses, schools, hospitals and office buildings. Unlike the old mercury lights, metal halide casts a true white light. It is not nearly as popular as its sodium or mercury counterparts, as it's newer and less efficient than sodium.

Metal halide lights have also been used for retrofitting. Virtually all fixtures that are converted to metal halide have previously been lit with high-pressure sodium (HPS). Examples of retrofitted fixtures for metal halide use include the Thomas & Betts Model 25 and Model 327, as well as full-cutoff versions of GE's M400. MH lamps suffer color shift as they age though this has been improving. Actual life expectancy is about 10-12K hours on average. There has also been a noted issue with the lamps "exploding/shattering" during a failure. High cost and low life hours has kept them from becoming popular municipal lighting sources even though they have a much improved CRI around 85.

Compact fluorescent lamp

CFL or "compact fluorescent lamp/lighting" has been used more and more frequently as time has improved the quality of these lamps. These lamps have been used on municipal walkways and street lighting though rare at this time. Improvements in reliability still need to be made. Some issues with them are high heat build up in the self contained ballast, low life/burnout due to frequent cycling(on/off) of the lamp, and the problem where most fluorescent sources become dimmer in cold weather (or fail to start at all). CFL efficiency is high and CRI is excellent around 85. CFL produces a color temperature around 3K with its light being "soft white" around that color temp. Higher color temps are available.

Optical types

Non-cutoff

The non-cutoff fixtures usually include the globe-shaped lamps that are mounted on top of lampposts. These lamps distribute their light in all directions. A major problem is created by the light pollution and glare, as they shoot their light upwards into trees and towards the sky rather than down towards the ground. Non-cutoff fixtures are not found on roadways because they tend to blind the driver.

Semicutoff

This is the most popular streetlighting optic of all-time. The semicutoff fixtures usually refer to the cobraheads, but they can also apply to some lamppost-mounted fixtures that do not emit their light upwards. Most of the light can be emitted below 90 degrees, but as much as 5% of the light can also be emitted above 90 degrees. These fixtures do a very good job at spreading the light towards the ground, but some uplight is possible, though not as serious as non-cutoff fixtures. Often, the semicutoff fixtures are mounted on tall poles. Examples of semicutoff optics include the bowl-shaped diffuser on GE's M400s made prior to 1997, and the prismatic one shared by the Westinghouse OV-25, Crouse-Hinds L250 and OVM, and Cooper OVD. These fixtures are very commonly seen with both mercury vapor and HPS lamps (and sometimes metal halide as well).

Cutoff

These optics give more light control over semicutoffs. Less than 2.5% of the light can leave the fixture above 90 degrees. Cutoff fixtures have gained popularity in recent years, as they are available from manufacturers like GE and American Electric. The cutoff lights have a wider spread of light than full-cutoffs, and they generate less glare than semicutoffs. The cutoff lenses consist of a shallow curved glass that is visible just below the lighting area on the fixture. As with the semicutoffs, these fixtures are very commonly seen with both mercury vapor and HPS lamps (and occasionally with metal halide as well).

Full-cutoff

These lights do not allow any of the light to escape the fixture above 90 degrees. Full-cutoffs distribute their light in a defined, tight pattern. In recent years, cutoff-type lights have gained popularity. To achieve the same result as cutoff or semicutoff fixtures, more full-cutoff fixtures would have to be installed, or they would have to be mounted higher. Although full-cutoff fixtures generally use HPS lamps, some metal halide and even a few mercury vapor ones have been known to exist.

Fixture type identification

Many streetlights are marked with stickers to aid workers in quickly identifying them. However the "code" isn't that hard and can be read by anyone for fun, say on a long road trip.

The system is as follows: The color of the sticker indicates the type of light, the number is one tenth of the power in watts. More power roughly corresponds to a brighter light.

There are two exceptions to this rule:

  • A "17" sticker adds a five to the power rating, and therefore, the light is rated at 175 watts.
  • If a sticker reads "X1," it describes a 1000-watt light.

Sticker colors:

Frequently seen power ratings:

  • "4" sticker--40 watts
  • "5" sticker--50 watts
  • "7" sticker--70 watts
  • "10" sticker--100 watts
  • "15" sticker--150 watts
  • "17" sticker--175 watts
  • "20" sticker--200 watts
  • "25" sticker--250 watts
  • "31" sticker--310 watts
  • "40" sticker--400 watts
  • "70" sticker--700 watts
  • "X1" sticker--1000 watts

See also

External links

Economic history of the United States | History of science and technology in the United States | Street lighting

 

This article is licensed under the GNU Free Documentation License. It uses material from the "History of street lighting in the United States".

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