History of street lighting in the United States
The use of street lighting was first recorded in the city of Antioch from the 4th century. Later it was recorded in the Arab Empire from the 9th–10th centuries, especially in Cordova, and then in London from 1417 when Henry Barton, the mayor, ordered "lanterns with lights to be hanged out on the winter evenings between Hallowtide and Candlemasse." It was introduced to the US by inventor Benjamin Franklin, who was the postmaster of Philadelphia, Pennsylvania. For this reason, many regard Philadelphia as the birthplace of street lighting in the US.
The colonial-era streetlights were lit by candles placed inside a glass vessel, which kept the candle from being blown out by wind. Franklin's design was four-sided, with four separate panes of glass, so that if one pane of glass was broken, the lamp did not need to be entirely replaced, and might not even blow out.
After the invention of gas light by William Murdoch in 1792, cities in Britain began to light their streets using gas. The United States followed suit shortly afterwards with the introduction of gas lighting to Pelham Street in Newport, Rhode Island in 1803. Throughout the 19th century, the use of gas lighting increased. Some locations in the US still use gas lights; see Gas lighting.
After Edison pioneered electric use, light bulbs were developed for the streetlights as well. The first city to use electric street lights was Wabash, Indiana. Charles F. Brush of Cleveland, Ohio wanted to publicly test his new invention the "Brush Light" and needed a city to do so. The City Council of Wabash agreed to testing the lights and on March 31, 1880, Wabash became the "First Electrically Lighted City in the World" as a flood of light engulfed the town from four Brush Lights mounted atop the courthouse. One of the original Brush Lights is on display at the Wabash County Courthouse. By the beginning of the 20th century, the number of fire-based streetlights was dwindling as developers were searching for safer and more effective ways to illuminate their streets. Fluorescent and incandescent lights became 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. Part of New York City's Broadway was nicknamed the Great White Way due to the massive number of electric lights used on theater marquees lining the street.
- 1 History of manufacturers
- 2 Means of electric light generation
- 3 Optical types
- 4 Fixture type identification
- 5 List of streetlight manufacturers and fixtures
- 6 See also
- 7 References
- 8 External links
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 popular Form 400. Westinghouse answered with the OV-20 model.
In 1957, a new breed of streetlight fixture was introduced; the "cobraheads". If viewed from beneath they resembled 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 popular streetlight fixture.
GE later introduced its own cobrahead, called the M400. The original M400 is noted for its pointed front end that protrudes over its bowl-shaped diffuser (also called a refractor). The M400 was the OV-25's main rival. They carried 250–400 watt bulbs and were common on Interstate highways and city boulevards. GE made the M250 which was exactly same design as the M400 but using plastic refractor made for 250 watt. The M250 production ended in 1960 replacing with a M250R.
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 and M250 with its PowrDoor design. Gone was the protruding front end, and the new M400A and M250A were also more streamlined (although the original M400 and M250R continued to be produced until 1970). In 1970, a split-door M400 was introduced that shared the M400A's bodyshell but had a nonvented door held in place with a spring latch, while the M400A's vented door was held in place with a bail latch.
GE and Westinghouse also developed smaller fixtures. A miniature version of the M400 was made for suburban residential streets and alleys. That fixture was called the M250R which replaced the M250 which looked exactly like the M400 but with plastic lens and rated for 250 watt. In the same vein, Westinghouse offered three smaller Silverliners. The OV-12 (whose look resembles a miniature OV-50) came out in 1960, and it became the companion model to the Canadian-market OV-14B, which had been introduced in 1957. The OV-14B looks like a smaller version of the 1957-edition OV-25. Both the OV-12 and OV-14B were 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 high pressure sodium (HPS) lights that came out in 1970. The existing Silverliners could not handle these new lights, so Westinghouse developed a new OV-25, as well as a new OV-15. Both of these new Silverliners (also known as TuDors, and seen as Westinghouse's answer to GE's popular PowrDoor series) now had a flat bottom, and weren't nearly as popular as the originals. However, by 1975, all Silverliners, including the single-door OV-15 and OV-25, were available as HPS units.
More new manufacturers entered the streetlighting industry. ITT (also known as American Electric, or ITT/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).
Earlier versions of the M1000 and OV-50 (and, in very rare instances, the Model 327) 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 around 1970, the company (by then, renamed McGraw-Edison) produced the boxy, rectilinear, more simplified Unidoor 400 (for metropolitan expressways and city boulevards) and Unidoor 175 (for smaller residential streets and alleys).
In 1982, the entire Silverliner line was discontinued, when Cooper Lighting bought 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 and the rarer M250 in 1975. 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.
In 1988, ITT/American Electric 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. While the Model 125 continues production today, the Model 113 was replaced by the American Electric Model 115 in 2003. In 1992, ITT sold American Electric to Thomas & Betts. In 2001, Thomas & Betts sold the street lighting division to Acuity Brands, where it was then spun off as American Electric Lighting.
In the mid-1980s, GE revamped its entire lineup. One, called the M400R2, had a flat bottom reminiscent of the third-generation Silverliners; the other, now called the M400A2, retained the original 1967 design but no longer had the vented door that the previous model did. Also, the M250R2 featured a slightly flatter profile than the M250R it replaced, and the M250A2 now took on the boxy profile that was previously used by the M150. In 1997, the M400 underwent a total redesign, borrowing its styling from the Thomas & Betts Model 125. In 2008, GE resumed production of the M400A2 and M400R2, which are now sold concurrently with the 1997-edition M400 and M400A models.
More recently, teardrop lamps (both existing and reproductions) have been used in favor of cobraheads in both urban and suburban areas. They are usually complemented with bishop's crook poles and more elaborate architectural elements. King Luminaire (a division of the StressCrete Group) manufactures these.
Means of electric light generation
Open Arc lamps were used in the late 19th & early 20th century by many large cities for street lighting. Their bright light required that the early arc lamps be placed on rather high (60 to 150-foot) towers; as such, they might be considered the predecessor to today's high-mast lighting systems seen along major highways. They were also widely used in film and stage. Arc lamps use high current between two electrodes (typically carbon rods) and require substantial maintenance. Arc lights have mainly been used where high lumen light was needed such as lighthouses. Today very few open arc lights remain in operation, primarily in a few lighthouses and some industrial uses. The only remaining examples of original street lighting use are the moonlight tower of Austin, Texas.
A xenon lamp is a high pressure sealed arc lamp, and is in common usage today where extreme brightness in a relatively small space is required, typically in motion picture projectors in theaters, and stage and motion picture lighting. The sealed arc lamps do not suffer from the inefficiency and high maintenance problems of the original open arc lamps, but they are not well suited for most street lighting use.
By far the most recognized type of lighting is the incandescent light bulb using a tungsten filament. These were the first low power electric lights in cities world wide. Some can still be found in streetlight service, although many of them are using more efficient CFL light bulbs and some have been converted to MV or HPS. Others have been installed popular downtown areas of major cities to have a nostalgia effect. They were introduced some 20 years after open arc lamps, and in many cases replaced the higher maintenance arc lamps. Incandescent light also has excellent CRI rated at 100. Color temperature is generally around 2000–3200 K depending on the type of lamp. An incandescent lamp is less efficient when compared to HID and gas discharge lighting such as Neon light.
Tungsten-halogen incandescent lights are more efficient than regular incandescent lights, and are very commonly used in theatrical and motion picture lighting due to their higher efficiency and brightness and better color temperature characteristics. They are little used in street lighting due to their relatively short lifespan.
Standard incandescent lamps are very commonly used in traffic signals, although are increasingly being replaced by LEDs.
The fluorescent lamp first became common in the late 1930s. These lamps are a form of discharge lamp where a small current causes a gas in the tube to glow. The typical glow is strong in ultraviolet but weak in visible light. The glass envelope is coated in a mixture of phosphors that are excited by the ultraviolet light and emit visible light. Fluorescent lamps are much more efficient than incandescent lamps, and for a short time became popular in street lighting both because of the efficiency and the novelty value. Fluorescent lamps for street lighting were first introduced to the public for commercial uses at the 1939 World's Fair.
The major problems with standard fluorescent lamps for street lighting is that they are large, and produce a diffused non-directional light. They are also rather fragile. Therefore the fixtures needed to be large, and could not be mounted more than 20–30 feet above the pavement if they were to produce an acceptable light level.
Fluorescent lamps quickly fell out of favor for main street lighting, but remained popular for parking lot and outside building illumination for roadside establishments.
In 1948, the first regular production mercury vapor (MV) streetlight assembly was developed. It was deemed a major improvement over the incandescent light bulb, and shone much brighter than incandescent or fluorescent lights. Initially people disliked them because their bluish-green light made people look like they had the blood drained from them. Other disadvantages are that a significant portion of their light output is ultraviolet, and they "depreciate"; that is, they get steadily dimmer and dimmer with age while using the same amount of energy, and in a few rare instances, they also cycle at the end of their life cycles. Even rarer is they can burn out, especially when the light is being burned while dim (usually at the end of the life cycle). Mercury lamps developed in the mid-1960s were coated with a special material made of phosphors inside the bulb to help correct the lack of orange/red light from mercury vapor lamps (increasing the color rendering index(CRI)). The UV light excites the phosphor, producing a more "white" light. These are known as "color corrected" lamps. Most go by the deluxe (DX) designation on the lamp and have a white appearance to the bulb. Mercury Vapor Bulbs come in either clear or coated with powers of 50, 75, 100, 175, 250, 400, 700 or 1,000 Watts. The Mercury Vapor lamp is considered obsolete by today's standards.
As of 2008, the sale of new mercury vapor streetlights and ballasts was banned in the US by the Energy Policy Act of 2005, although the sale of new bulbs for existing fixtures do continue, but the bulbs will also be banned in 2016 in the US and Europe. Mercury vapor fixtures can be operated with metal halide lamp (MH) ballasts, and are likely to be rewired with these ballasts in coming years. In response to the ban, some older MV streetlights will most likely be modified to use either high pressure sodium or metal halide lamps in the near future, because they are known to last longer than newer luminaires. In some areas where the MV lights are either failing or being replaced, they are being replaced by either HPS, LED, or Induction fixtures of similar lumen output, but also lower wattages and power consumption as well.
High pressure sodium
Around 1970, a new streetlight was invented: The high pressure sodium (HPS) light. They became common in the late 1980s. It was initially disliked by most residents because of its orange glow, but the sodium vapor streetlight has since become the dominant type on American roadways and most people have become accustomed to the orange/yellow glow. It is by far the most efficient light source available. Color-corrected sodium vapor lamps exist but are expensive. These "color corrected" HPS lamps have lower life and are less efficient.
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 retrofitted to use HPS lights as well. 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, first generation GE M400 and M250 and the second-generation Westinghouse OV-15 and OV-25 Silverliner (although later versions of this model were available from the factory as HPS units) as well as the Line Materials Unistyle 400 and 175/250.
LPS lights are even more efficient than HPS, but produce only a single wavelength of yellow light, resulting in a CRI of zero, meaning colors cannot be differentiated. LPS lamp tubes are also significantly longer with a less intense light output than HPS tubes, so they are suited for low mounting height applications, such as under bridge decks and inside tunnels, where the limited light control is less of a liability and the glare of an intense HPS lamp could be objectionable.
HPS lamps have slightly different electrical requirements than do the older MV lamps. Both HPS and MV lamps require a transformer or ballast to change the voltage and regulate the current, however, HPS lamps also require an electrical "starter" circuit—much like older fluorescent lamps in residential use. MV lamps do not require a separate "starter" circuit because they have a special starter element within the bulb used for striking the arc. MV lamps slowly dim over time, and a 20 year-old lamp may emit a very pleasing, but useless, soft green glow, rather than the powerful blue-white light of a new MV lamp. The yellow-spectrum HPS lamps also slowly dim over time but are known for "cycling," where the lamp cycles on and off when it has reached the end of its life cycle. When cycling, the arc within the lamp extinguishes and the lamp must cool down before the starter circuit initializes a new arc. This has been the most recognized downfall of HPS. Some HPS lamps start to burn a pinkish/reddish color at the end of their life (usually when already cycling), or also burn out at the end of their life cycle whether they cycle or not. HPS fixtures can contain a special photocell or ballast that can sense a cycling lamp and shut off the fixture to prevent damage to the ignitor and ballast.
HPS lamps generally have the same rated lifespan as MV lamps, and they give increased light and efficiency at lower wattages. Usually, when an MV light is replaced, it is replaced with a HPS light of a lower wattage, for example, a 175 watt MV fixture will get replaced with a 100 or 150 watt HPS fixture as that will meet or exceed the lumen output of the 175 watt MV fixture. At end of life MV lamps just become dimmer and sometimes color shift towards the green end of the spectrum but continue to consume the same amount of electricity. HPS lamps begin to suffer end-of-life cycling before the amount of useful light becomes visibly diminished, or just burn out. HPS lights come in wattages of 35, 50, 70, 100, 150, 200, 250, 310, 400, 600, 750, and 1,000 watt sizes, while LPS lights come in wattages of 18, 35, 55, 90, 135, and 180 watt sizes
In recent years, metal halide lamp (MH) streetlights have illuminated roadways and parking lots. Metal halide has long been popular in business installations and 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 counterparts, as it is 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 10,000 to 12,000 hours on average. There has also been a noted issue with the lamps "exploding/shattering" during a failure. Metal Halide light bulbs also tend to dim and/or flicker at the end of their life cycles, and on occasion, cycle. Sometimes, they emit a pinkish glow at or near the end of their life cycle which in this case, the bulb just burns out. 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. Therefore, the use of metal halide is limited mainly to city and high end street lighting. They are available in clear or coated bulbs. Probe start MH lights (which are less efficient and are also soon to be banned, unlike Mercury Vapor lamps) come in wattages of 50, 70, 100, 175, 250, 400, and 1000 watt sizes, while pulse start MH lights come in sizes of 50, 70, 100, 150, 200, 250, 320, 350, 400, 450, 750, and 1,000 watt sizes. The wattages of pulse start metal halide lamps are similar to HPS lamp wattages.
Ceramic discharge metal halide lamp
Ceramic discharge metal halide lamps will probably be the next step in streetlighting, replacing old mercury vapor and high pressure sodium lamps, especially where one wants a more clear white with better CRI (78–96) and light color retention than the blue-white mercury and orange sodium lamps. CDM lamps give five times more light than comparable tungsten incandescent light bulbs (80–117 lm/W) and will probably become more common in cities, unless LED lamps outperform them.
An induction lamp features extremely long lamp life (100,000 hours), energy efficiency, high color rendering index, and a color temperature close to incandescent lights. The life of induction (also known as electrodeless fluorescent) lamps is negatively affected by heat, particularly as the temperature exceeds 35 degrees Celsius (95 degrees Fahrenheit). Since temperatures in this range commonly occur during early night hours in the summer in much of the US, induction lamp applications have not extended beyond test and demonstration projects for street lighting. The larger size of the induction lamps also inhibits the effective control of the light they emit, limiting their use to lower mounting applications. [according to whom?] There are areas in New Jersey that are using induction lighting from US Lighting Tech, Inc (Irvine, CA) to replace very old and even some pre-2008 mercury vapor lights, and have had success in their reliability and output of the fixtures. Beginning in September 2011 the City of San Diego, CA will replace some 35,000 street lights with induction lamps costing $16,000,000.00. In Mexico, the city of Linares and Acapulco also have begun the replacement of 6,500 and 42,000 street lights with induction lamps from Amko SOLARA Lighting (Taipei, Taiwan), selected for their smart controls, since October 2011. A portion of these street lights from Amko will feature smart grid compatibility to allow the lights to be remotely monitored and controlled via the Internet.
Compact fluorescent lamp
Compact fluorescent lamps (CFL) have been used more frequently as time has improved the quality of these lamps. These lamps have been used on municipal walkways and street lighting though they are still rare at this time. Improvements in reliability still need to be made. Some issues with them are limited lumen output, 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 3000 K with its light being "soft white" around that color temperature. Higher color temperatures are available.
Light emitting diodes
Light emitting diodes (LED) have virtually replaced both incandescent lamps and the occasional fluorescent lamp in traffic signal and crossing sign usage. They are rapidly developing in light output, color rendering, efficiency, and reliability. The cost of LED lighting is still extremely high compared to an incandescent lamp used for the same purpose, but the cost is decreasing rapidly. Even with the high per-unit cost, the increase in efficiency and increased lifespan make them very attractive for street lighting use. The reduced cost of electricity and maintenance in many cases can offset the increased cost of the lamp.
LEDs have yet to earn widespread usage in general street, sidewalk, or parking lot illumination as it is thought their brightness does not yet compete well with HPS, MH, or CFL lighting. However, the city of Ann Arbor, Michigan, implemented LEDs in street lighting applications in March 2006 and have since expanded their use. In addition Chapel Hill, North Carolina, entered a 12-month test program and partnership with Duke Energy on March 25, 2009, to evaluate the effectiveness of replacing existing HPS lighting with the more efficient LED street lighting within its vibrant downtown. In late 2008, Anchorage Alaska installed over 4,000 LED streetlights as part of a plan to convert the community's 16,000 roadway lights to efficient white light. In mid-2009, the City of Los Angeles announced a 5-year project with the Clinton Climate Initiative to replace all 140,000 of the city's existing streetlights with LED fixtures. In mid-2010, Seattle City Light began installing LED streetlights in a residential neighborhood as part of a plan to install 40,000 LED streetlights over the next 5 years. Also, Atlantic City Electric in Southern NJ is also testing out LED streetlights made by 2 different manufacturers in 4 communities to evaluate if LED lights are worth using over HPS. The parking lot at Camden County College in Blackwood, NJ is now using LED postlights that replaced the previous HPS flood and shoebox lights. The Cities of Philadelphia and New York have also begun testing LED streetlights. The town of Abington, PA has installed LED streetlights on their main and secondary streets to replace MV fixtures. In spring of 2011, the municipally-owned energy provider for San Antonio, Texas, CPS Energy, entered into contract with GreenStar LED (of Boerne, Texas) for an order of over 25,000 LED street light fixtures. LED street light have been introduced also in smaller cities and communities, for example, in Brisbane, CA.
As with other semiconductors, heat buildup in an LED dramatically reduces its life. The temperature at which this reduction in life occurs is often very near summer evening ambient temperatures. Many of the heat-removal technologies used for other semiconductor applications, such as air conditioning systems, fans, or thermal-transfer fluids, are impractical, maintenance-intensive, or cost-prohibitive for street lighting. Airborne dust from industrial and agricultural activities can impair the functioning of finned heat sinks. Achieving good maintenance-free thermal management in an often hostile environment while keeping product cost competitive is the largest hurdle to the widespread adoption of LED street lights.
The non-cutoff fixtures usually include the globe-shaped lamps that are mounted atop lampposts. These lamps distribute 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 towards the ground. Non-cutoff fixtures are rarely found on roadways because they tend to blind the driver.
This is the most popular street lighting optic. 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 good job of spreading the light towards the ground but some uplight is possible, though not as serious as non-cutoff fixtures. Semicutoff fixtures are often 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 commonly seen with both mercury vapor and HPS lamps (and sometimes metal halide as well).
These optics give more light control than 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 (also called a sag lens) 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).
These lights do not allow any of the light to escape the fixture above 90 degrees. Full-cutoffs distribute their light in a defined pattern, potentially providing more light on the ground at lower power consumption. In recent years, cutoff-type lights have gained popularity. Although full-cutoff fixtures generally use HPS lamps, some metal halide and even a few mercury vapor ones are known to exist.
Semicutoff refractor compatibilities
Small fixtures (175 watts and under)
- Round design: This refractor is shaped like a half-circle, and is usually found on fixtures operating at 150 watts and lower. Examples of round refractors include the ones used by the American Electric Models 113/115 and General Electric M250.
- Flat design: This refractor uses a prismatic design, and has a flat bottom. It is most commonly found on fixtures operating between 100 and 250 watts. Examples of flat refractors include the ones used by the American Electric Models 113/115, Westinghouse OV-15, Crouse-Hinds L150 and OVS and Cooper OVX and OVZ.
- Square design: This refractor is shaped like a square, but some newer incarnations may also have a slightly rounded bottom. Examples of square refractors include the ones used by the General Electric M250, Line-Materials Unistyle 175, McGraw-Edison Unidoor 175/250, Crouse-Hinds L150 and OVS and Cooper OVX and OVZ.
- All three refractor designs are compatible with any small fixture, except the Westinghouse OV-10, OV-12 and OV-14B (which share the same unique refractor design).
Medium fixtures (200–400 watts)
- Round design: This refractor is shaped like a half-circle. Usually found on General Electric M400s made prior to 1997 (and select models from 2008 onward), they are also used by the remote-ballasted GE Form 400 and Revere 400-watt models. Line-Materials/McGraw-Edison used a slightly different round refractor design for the Unistyle 400 and Unidoor 400.
- Prismatic designs: There are many different versions of the prismatic refractor design. A larger version of the flat design is used on the Westinghouse OV-25, Crouse-Hinds L250 and OVM and Cooper OVD. Another popular design features rounded-off corners, and is compatible with Thomas & Betts/American Electric Models 25, 125 and 325, as well as the 1997 and later editions of the General Electric M400.
- The Unistyle 400/Unidoor 400 refractor is also interchangeable with the Model 25, and vice versa.
Large fixtures (up to 1000 watts)
- The Westinghouse OV-50/Cooper OVL refractor is used by the remote-ballasted Westinghouse OV-35 and Revere 1000-watt models, and although there has been very little-known evidence of this, the OV-50/OVL refractor is also interchangeable with the Thomas & Betts/American Electric Model 327, and vice versa.
- The round refractor design as seen on the General Electric M1000 can also be used with the remote-ballasted GE Form 402.
Fixture type identification
Many streetlights are marked with a NEMA wattage label to aid workers in identifying them.
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. The higher the number, the brighter the light.
There are three 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.
- If a sticker reads "3," it describes a 35-watt light.
- Also MH stands for Probe Start Metal Halide, while PSMH stands for Pulse Start Metal halide.
- Blue: Mercury vapor
- Red: Metal halide
- Half Red/Half White: Pulse Start Metal Halide (PSMH)
- Yellow: Older HPS, LPS, and some induction
- Orange: new sticker color, now used for HPS
Colors vary for new LED street lights such as black for Philips Hadco RX1 and RX2 or Green for BetaLED luminaires. The Induction fixtures usually contain a green and white sticker. Frequently seen power ratings:
- "3" sticker - 35 watts (HPS/LPS)
- "4" sticker - 40 watts (Induction)
- "5" sticker - 50/55 watts (MV/HPS/LPS/PSMH)
- "7" sticker - 70 watts (HPS/PSMH/MH/LED/Induction)
- "8" sticker - 80 watts (Induction)
- "9" sticker - 90 watts (LPS)
- "10" sticker - 100 watts (MV/MH/PSMH/HPS/Induction)
- "11" sticker - 110 watts (LED)
- "13" sticker - 135 watts (LPS)
- "15" sticker - 150 watts (HPS/PSMH/Induction)
- "17" sticker - 175 watts (MH/MV)
- "18" sticker - 180 watts (LPS)
- "20" sticker - 200 watts (HPS/PSMH)
- "25" sticker - 250 watts (MV/PSMH/HPS/Induction)
- "27" sticker - 270 watts (LED)
- "31" sticker - 310 watts (HPS)
- "32" sticker - 320 watts (PSMH)
- "35" sticker - 350 watts (PSMH)
- "37" sticker - 37 watts (LED) - New - For BetaLED's luminaires in Boston, MA
- "39" sticker - 39 watts (LED) - New - For BetaLED's luminaires in Boston, MA
- "40" sticker - 400 watts (MV/PSMH/HPS)
- "45" sticker - 450 watts (PSMH)
- "60" sticker - 600 watts (HPS)
- "70" sticker - 700 watts (MV)
- "70" sticker - 70 watts (LED)
- "75" sticker - 750 watts (HPS/PSMH)
- "X1" sticker - 1000 watts (MV/HPS/PSMH)
List of streetlight manufacturers and fixtures
|Fixture name (compatible wattages)||Notes|
American Electric/ITT/Thomas & Betts/AEL
|Model 13-000 (50–250 watts)||Same as the boxier, bulkier looking Model 13 that would follow, but had a similar shape of a Model 113 and had more of a Silverliner appearance.|
|Model 25-000 (250–400 watts)||Same as the boxier, bulkier looking Model 25 that would follow, but more of a Silverliner appearance.|
|Model 327-000 (700–1000 watts)||Same as the boxier, bulkier looking Model 327 that would follow, but more of a Silverliner appearance.|
|Model 13 (50–250 watts)||The smaller companion to the Model 25. A power pad version of this fixture was also available, and it was the immediate predecessor to the Model 313.|
|Model 25 (200–400 watts)||The larger companion to the Model 13, and later inspired an even larger version.|
|Model 327 (700–1000 watts)||A spinoff of the Model 25, and as of this writing it is still in production as AEl's only 1 KW fixture.|
|Model 113 (50–250 watts)||Replaced the Model 13. Has softer, more rounded lines than its predecessor. Its bodyshell resembles a more modernized version of the original Model 13.|
|Model 313 (50–250 watts)||The power pad version of the 113.|
|Model 115 (50–400 watts)||Replaced the Model 113. Introduced in 2003 by Acuity Brands Lighting /American Electric.|
|Model 315 (50–400 watts)||The power pad version of the 115. This small fixture, like the Model 115 and Cooper OVX, also has the option for medium-sized lamps (310-400 watt) often causing shorter lamp life and premature cycling)|
|Model 125 (150–400 watts)||Replaced the Model 25. Has softer, more rounded lines than its predecessor. GE's M400 has used this design since 1997, but with some noticeable differences: The 125 has a slightly smaller housing than the M400 and an internal latch, as evidenced by its indented front end.|
|Model 325 (150–400 watts)||The power pad version of the 125.|
|Model 413 (50–150 watts)||The 413 was created for International customers so they could fit more fixtures per container. The 115 was redesigned so 40 cartons fit on a pallet, thus eliminating the need for the 413.|
|Roadway-Area-SRX (35–90 watts)||AEl's smaller LPS fixture.|
|Roadway-Area-SP2 (90–180 watts)||AEL's larger LPS fixture.|
|Durastar 2000 (50–250 watts)||A semi-cutoff or full-cutoff fixture, manufactured of fibreglass and uses unique Duralock docking station, the fixture is composed of two parts the docking station that contains the slipfitter, and the fixture, the fixture locks on to the mounting station. The durability of this fixture is frequently questioned, as many has been replaced by other AEL fixtures not made our of fibreglass.|
|Durastar 3000 (150–400 watts)||Same features as 2000 series.|
|Corvus CVM (70–250 watts)||Available in either Cutoff or Full Cutoff the Corvus CVM is a small sized cobra head the is slightly more decorative then most others.|
|Corvus CVL (100–400 watts)||Available in either Cutoff or Full Cutoff the Corvus CVl is a medium-sized cobra head the is slightly more decorative then most others.|
|LEDR (70–100 watts)||The LEDR was the first LED fixture manufactured by AEL, it was avabable in either 70 or 100 watts of LED. It was discontinued in 2011 for unknown reasons and replaced by the ATB1.|
|ATB1 (Different LED Configurations)||The ATB1 was introduced in March 2011 to replace the LEDR which was discontinued for unpublished reasons. It features a power door design for easy replacement of electrical components with many different configurations for different roadway sizes.|
|Type 3 STR-LWY-1S-HT (37, 39 or 70 watts)||A small or medium LED street light found in Boston, Massachusetts. Introduced in January 2011.|
|L150 (50–250 watts)||A small cobra head formerly the 4th generation Westinghouse OV-15.|
|L250 (200–400 watts)||A medium cobra head formerly the 4th generation Westinghouse OV-25.|
|OV-15 (50–250 watts)||A small cobra head, was originally the 3rd generation Westinghouse OV-15 Silverliner. It retains the same basic design of the OV-15, however is only available in Canada as a non cataloged product.|
|OV-25 (200–400 watts)||A medium cobra head, was originally the 3rd generation Westinghouse OV-25 Silverliner. It retains the same basic design of the OV-25, however is only available in Canada as a non cataloged product.|
|OVL (700–1000 watts)||A large cobra head, was originally the 3rd generation Westinghouse OV-50 Silverliner. It retains the same basic design of the OV-50, except it is now painted in a light grey finish (the standard color scheme for most new luminaires manufactured after 1970). Cooper still uses the OV-50 designation for its Canadian versions.|
|OVS (50–250 watts)||A small cobra head, replaced the L150, predecessor to the OVZ.|
|OVM (150–400 watts)||A medium cobra head, replaced the L250, predecessor to the OVD.|
|OVG (50–250 watts)||A Small cobra head, semicutoff, smaller version of the OVD.|
|OVG (50–250 watts)||A Small cobra head, cutoff version of OVG, smaller version of the OVY.|
|OVH (50–250 watts)||A Small cobra head, fullcutoff version of the OVG, smaller version of the OVF. Also available with LED lighting.|
|OVD (150–400 watts)||A medium cobra head, Semicutoff fixture, replaced the OVM, this fixture uses the same glass that also appears on the Westinghouse OV-25 Silverliners, OVM and L250, it is the larger version of the OVG.|
|OVY (150–400 watts)||A medium cobra head, the cutoff version of the OVD, it is the larger version of the OVG|
|OVF (150–400 watts)||A medium cobra head, the fullcutoff version of the OVD, it is the larger version of the OVH|
|OVX (50–400 watts)||A small cobra head available in semicutoff or fullcutoff, the OVX was not a direct replacement for any other model, it is slightly controversial in that it is a small cobra head that has the option for medium-sized lamps often causing shorter lamp life.|
|OVZ (50–250 watts)||A small cobra head available in semicutoff or fullcutoff, replaced the OVS.|
|OVC (50–250 watts)||Same as the OVZ except unpainted was used in the Canadian market, however Canada now uses the OVZ.|
|Form 175 (100–250 watts)||Predecessor to the M250. Had the strange cone shaped refractor. (Very Rare!)|
|Form 109 (250–400 watts)||Predecessor to the Form 400.held 600 watt incandescent lamps or 400 watt mercury vapor lamps.made from 1948 to 1955.|
|Form 400 (250–400 watts)||Replaced the Form 109, and predecessor to the M400.also made as the form 400 powerpack an iteragate ballast version of the form 400. made from 1956 to 1959.|
|Form 402 (700–1000 watts)||Predecessor to the M1000.|
|Form 7980||Claw shaped fixture. Similar to the Boston Wheeler crescent moon heads.|
|Form 131VR||Predecessor to the Form 79RV|
|Form 72||Predecessor to the Form 79 luminaire|
|Form 45113||Pendant or span wire mount luminaire for incandescent lamps (extremely rare!)|
|Form 110 luminaire||"Compact" luminaire. uses mercury vapor lamps or incandescent lamps. Also includes photocell.|
|201-SA||Current NEMA luminaire first introduced in the early to mid-1980s and redesigned in 1985.|
|M100 (100–175 watts)||A open bottom companion to the M250, also believed to be the first as a full cutoff.|
|M150 (50–250 watts)||This PowrDoor luminaire, noted for its boxy profile, was introduced in 1980 as a companion to the M250A. In 1986, it was renamed the M250A2, and continues to use that designation today.|
|M250 (1959–1960)/M250R (1960–1970)M250R1 (1970–1985)/M250R2 (1985–present) (50–250 watts)||Introduced in 1959, redesigned in smaller body in 1960 then redesigned in May 1970 (as the M250R1) and 1985 (as the M250R2). The original M250 from 1959 to 1960 was actually a fixture with a M-400 body but with plastic refractor. Additionally, "Crimefighter" versions exist in Chicago, with a cylinder-shaped refractor attached to the 1970 version's bodyshell.|
|M250A (1967–1985)/M250A2 (1986–present) (50–250 watts)||This PowrDoor luminaire was introduced in 1967 as the smaller companion to the M400A, and its bodyshell was a miniature version of the M400A's. A full-cutoff version of this luminaire was introduced in 1975 (Very Rare!). It was redesigned in 1986, taking on the M150's boxy profile, and renamed the M250A2.|
|M400 (1959–1970)/M400R2 (1986–1996 Reintroduced in 2008–present) /M400R3 (1997–present) (150–400 watts)||Introduced in 1959, this single-door luminaire was discontinued around 1970. From 1970 to 1986, the M-400 was virtually identical to the M-400A with the exception of having a non-vented door held in place with a simple spring latch. The ballast components were mounted on the top housing. In 1986, it was revived as the M400R2, with a TuDor-esque flat profile to distinguish it from the M400A2 PowrDoor. The current version (introduced in 1997 as the M400R3) looks similar to a Thomas/Betts 125 except for a slightly bulkier housing and a bail-type latch. As of 2008, both the M400R2 and M400R3 are in concurrent production.|
|M400A (1967–1985)/M400A2 (1986–1996 Reintroduced in 2008–present) /M400A3 (1997–present) (150–400 watts)||This PowrDoor luminaire was introduced in 1967 as the larger companion to the M250A. Earlier versions had a vented door held in place with a more complex bail latch. A full-cutoff version of this luminaire was introduced in 1975. In 1986, it was renamed the M400A2 (this incarnation did not have the vented door of the earlier models), with the arrival of the single-door M400R2. The current version (introduced in 1997 as the M400A3) looks similar to a Thomas/Betts 325 except for a slightly bulkier housing and a bail-type latch. As of 2008, both the M400A2 and M400A3 are in concurrent production.
There are rare 100 watt versions of the M400A3 that exist on the Tobin Bridge in Chelsea, Massachusetts. Additionally, "Crimefighter" versions exist in Chicago, with a bucket-shaped refractor attached to the normal 1975 full-cutoff version's bodyshell.
|M1000 (700–1000 watts)||Introduced in 1959, adopted fins until the mid-1960s, was redesigned in 1978, and discontinued around 1987.|
|GE Evolve LED (80–165 watts)||GE's newest medium cobra head that utilizes LED lighting, equals 70–150 watt HPS.|
|RM-series (50–250 watts)||The smaller companion to the RL-series.|
|RL-series (200–400 watts)||The larger companion to the RM-series, its look bears a resemblance to a Thomas & Betts Model 25.|
|RK-series (400–1000 watts)||The largest of all Hubbell streetlights.|
Joslyn Mfg. and Supply
|MV111 (100–250 watts)||Remote-ballasted fixture, the smaller companion to the MV131. The "MV" designation is said to stand for "Mercury Vapor," and the majority of all Joslyn luminaires still use mercury lights.|
|MV131 (250–400 watts)||Remote-ballasted fixture, the larger companion to the MV111.|
|MV121 (100–250 watts)||The smaller companion to the MV141. It looks like a spaceship with a refractor stuck underneath.|
|MV141 (250–400 watts)||The larger companion to the MV121.|
|MV151 (400–1000 watts)||The largest companion of all the Joslyn streetlamps.|
|TDS2||Lithonia's model # for the Durastar 2000.|
|TDS3||Lithonia's model # for the Durastar 3000.|
|CHE||Same as the American Electric Lighting Roadway 413 luminaire.|
|CHL||Same as the AEL Roadway 115.|
|CHLD||Same as the AEL Roadway 315.|
|CHM||Same as the AEL Roadway 125.|
|CHMD||Same as the AEL Roadway 325.|
|CHX||Same as the AEL Roadway 327.|
|TMM||Same as the AEL Multi-Mount 285.|
|TDR||Same as the AEL Interstate II series 775.|
|TSL||Same as the AEL Signlite 875.|
Line Material Industries/McGraw-Edison
|Ovalite (100–400 watts)||Remote-ballasted fixture, in the tradition of the Westinghouse OV-10/20/35 and GE Form series. The earliest Ovalite had similar style as a GE Form 109 but later it was changed and was still called an Ovalite.|
|Unistyle 175/250 (100–250 watts)||The smallest member of the Unistyle family. Most were Mercury Vapor, but there are HPS ones that exist as well.|
|Unistyle 400 (250–400 watts)||Most people think of the 400 as the largest member of the Unistyle family, but it's the mid-sized fixture. Most were Mercury Vapor, but there are HPS ones that exist as well.|
|Unistyle 1000 (700–1000 watts)||This very rare fixture was the largest member of the Unistyle family.|
|Unidoor 175/250 (100–250 watts)||Replaced the Unistyle 175/250 and designed for HPS lights|
|Unidoor 400 (200–400 watts)||Replaced the Unistyle 400 and designed for HPS lights|
|Spherolite (50-295 watts)||Pendant type luminaire. Uses incandescent or mercury vapor lamps.|
|Suburbanaire (50-295 watts)||"NEMA HEAD" style yard light for incandescent or mercury vapor lamps. Dates back to 1963|
|Dusk-To-Dawner (100, 175, & 250 watts)||Dusk to dawn cobrahead security light for mercury vapor lamps.|
|RX1 (70-110 watts)||A small LED street light found in Boston, Massachusetts. Introduced in June 2011.|
|RX2 (200-270 watts)||A medium LED street light found in Boston, Massachusetts. Introduced in June 2011.|
|Helios HBS (70-250 watts)||The HBS series is a small cobra head manufactured by Lumec Lighting (a subsidiary of Philips Lighting). The HBS features a unique locking system to keep dirt out of the optical chamber which is mounted to the door. The HBS is a more decorative and visually appealing cobra head than most, so it is common used where more decorative lighting is used.|
|Helios HBM (70-400 watts)||The HBM is the medium-sized cobra head of the Helios series, featuring the same features as the HBS. Unlike most medium fixtures however, it will also accommodate all low wattages.|
|B2217 (100-250 watts)||The first small Powerlite fixture designed in the 1960s, this design was the smallest of the first generation or Powerlite fixtures, all used mercury vapour lamps however some remain in High Pressure Sodium|
|B2215 (400 watts)||The medium-sized fixture in the first generation series, the B2215 could accommodate up to 400 watt mercury vapour lamps.|
|B2213 (700-1000 watts)||The B2213 was the largest of the first generation and is the largest cobra head style fixture ever made, at more than 4 feet in length.|
|B2227 *Later known as the R37* (50-250 watts)||The B2227 was the small fixture in the second generation of Powerlite fixtures, introduced in the late 1970s it was shorter than the B2217. Many B2227s where equipped with High Pressure Sodium which replaced less efficient mercury vapour lamps.|
|B2255 (200-400 watts)||The B2255 was the medium-sized fixture in the second generation series, it was commonly used with 200-400 watt High Pressure Sodium lamps. The B2225 was introduced in the 1970s and was manufactured until the early 1990s. The B2255 was the only fixture that had the option on a power door, where the ballast and other electrical components are mounted on a second door on the fixture, allowing for quick repairs.|
|B2228 (1000 watts)||The B2228 used the same housing as the B2255 and featured the same features, however it used a larger reflector inside the fixture to house the larger 1 kW lamps.|
|R47 (50-400 watts)||The R47 was released in 1992 and would end up being one of Powerlite's last designs produced until the company's merger in 2002. The R47 was a small fixture that was about the same size as the B2227 and used the same refractor footprint, it however, was able to accommodate up to 400 watt High Pressure Sodium lamps.|
|R7 (50-400 watts)||The R7 "Roadkat" was the final Powerlite design created in 1996, this fixture feature a more modern slipfitter design and compact size, this fixture still continued to use the same refractor foot print shared by the R47 and R37 (B2227) which is also shared by most small GE, AEL and Cooper Lighting fixtures still made to this day.|
|Twistpak (50-250 watts)||The Twistpak was a post top fixture manufactured from the 1970s onward, the Twistpak use a modular design, where the ballast and all electrical components where mounted on a tray for quick change out if needed, the top refractor would twist off (hence the name) to allow access to the lamp and ballast. There was also a pole integrated version where the ballast was mounted inside the pole and the refractor assembly would mount directly to the top of the pole. The Twistpak design is still manufactured by American Electric Lighting.|
|Revere 400 (250–400 watts)||Resembles a Westinghouse OV-25 Silverliner, but uses an M400-style refractor.|
|Revere 1000 (700–1000 watts)||Resembles a Westinghouse OV-50 Silverliner, but with a shorter neck.|
|AK-10||Incandescent gumball or deep bowl teardrop luminaire|
|OV-10 (100–250 watts)||Predecessor to the OV-12.|
|OV-20 (250–400 watts)||Predecessor to the OV-25.|
|HMA-60 (700–1000 watts)||Companion model to the OV-20|
|OV-35 (700–1000 watts)||Predecessor to the OV-50.|
|MO-8 (100–175 watts)||A flat-bottomed Silverliner in a cobrahead style with internal reflector, believed to be the Westinghouse full-cutoff fixture. Ballast and slipfitter is accessed by simply unscrewing a stainless screw on the top and the top "folds open" revealing a ballast and slipfitter found on the bottom casing.|
|MO-9 (100–175 watts)||A flat bottomed Silverliner with an external stamped reflector and a ballast casing attached.|
|OV-12 (100–250 watts)||Replaced the OV-10, predecessor to the OV-15. Introduced in 1960. This fixture looks like a shrunken-down OV-50.|
|OV-14B (100–250 watts)||Replaced the OV-10, predecessor to the OV-15. Introduced in 1957. It looks like a smaller version of the 1957 design of OV-25. Also those were mostly used in Canada when the United States had the OV-12 but the OV-14B can be found in the USA but is quite rare.|
|OV-15 (50–250 watts)||Replaced the OV-12 and OV-14B as the smallest Silverliner. Introduced in 1965 and redesigned in 1979. This was also modified in the early 1970s to use HPS lamps as well as mercury vapor. The Crouse-Hinds L150 was originally designated as an OV-15. This fixture continues Canadian production as the Cooper OV-15.|
|OV-15 TuDor (50–250 watts)||Introduced in 1970, this split-door luminaire featured a flatter profile and was designed to compete directly with the General Electric M250A Powr/Door luminaire and was Westinghouse's first HPS fixture as the regular single door OV-15 weren't modified for HPS use yet.|
|OV-25 (250–400 watts)||Mid-sized Silverliner, and the most popular streetlight fixture of all-time. Introduced in 1957, redesigned in 1964 and again in 1979. This is believed to be the first-ever integral-ballasted fixture. A remote-ballasted version was also available, with a truncated back as its most notable feature. This was also modified in the early 1970s to use HPS lamps as well was mercury vapor. The Crouse-Hinds L250 was originally designated as an OV-25. This fixture continues Canadian production as the Cooper OV-25.|
|OV-25 TuDor (250–400 watts)||Introduced in 1970, this split-door luminaire featured a flatter profile and was designed to compete directly with the General Electric M400A Powr/Door luminaire. This was also Westinghouse's first HPS fixture as the regular single door OV-25 weren't modified for HPS use yet.|
|OV-50 (700–1000 watts)||The largest Silverliner, introduced in 1963. Adopted fins in the mid-1960s. This fixture continues U.S. production as the Cooper OVL, and it also continues Canadian production as the Cooper OV-50.|
- Note 1: Unistyle luminaires are known for their arched top and sloped front end, while their Unidoor successors have a boxy profile. The 175 designation is used for the smaller versions of both styles by most people, but some use the 250 designation, since they were capable of light sizes of up to 250 watts.
- Note 2: Silverliner luminaires that have been rebuilt and painted light grey are referred to as "Greyliners"/"Grayliners." Usually, they include the single-door OV-15 and OV-25 Silverliners, and the OV-50 was also switched to a Greyliner scheme when Cooper Lighting bought out Westinghouse's streetlighting division in 1982. Its immediate successor, the Cooper OVL, is also considered to be a Greyliner. Although other Cooper/Crouse-Hinds luminaires, like the OVM/OVS and OVX/OVZ, use the grey color scheme, they are not referred to as Greyliners.
- Note 3: It is also very common to reuse older luminaires with newer parts. The most common practice is retrofitting a normal MV luminaire to use HPS lamps. This is being done in most small towns and a few mid-sized cities because it is cheaper to rewire an existing fixture rather than buying completely new ones. Sometimes, normally silver luminaires, like the 1959-era GE M250s/M400s and Line-Material Unistyles/Unidoors, are repainted light grey; the most common examples of these are the aforementioned Westinghouse Greyliners.
- Note 4: GE's revival of the M400A2 and M400R2 designs in 2008 is believed to be the first time ever that a manufacturer has resumed production of a previous design. Despite this, the newer 1997 "American Electric" designs also continue to be in production.
- Note 5: During production of the Westinghouse OV-25, and to a certain extent, the OV-15 as well, Westinghouse utilized four different glass refractor designs during the series run. Three of which, used in the first generation ("flatbottom"), second generation, and third generation (this style is still used today for Cooper luminaires), were manufactured by Holophane, the other design, used for the second generation Silverliner, was manufactured by Corning Glass.
- M. Luckiesh (1920), Artificial Light, The Century Company, pp 153–4.
- Fielding H. Garrison, History of Medicine:
"The Saracens themselves were the originators not only of algebra, chemistry, and geology, but of many of the so-called improvements or refinements of civilization, such as street lamps, window-panes, firework, stringed instruments, cultivated fruits, perfumes, spices, etc..."
- S. P. Scott (1904), History of the Moorish Empire in Europe, 3 vols, J. B. Lippincott Company, Philadelphia and London.
F. B. Artz (1980), The Mind of the Middle Ages, Third edition revised, University of Chicago Press, pp 148–50.
(cf. References, 1001 Inventions)
- "NEWPORT FIRSTS". http://newsroom.discovernewport.org/facts/firsts. Retrieved 9 February 2015.
- Luminous efficacy#Lighting efficiency