High-mast lighting
{{Short description|Lighting pole for large areas}}
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File:Highway 401 Night Lapse Busy.jpg at night]]
File:Highway 401-Highway 402 interchange.jpg
File:半夜的台南系統交流道.jpg, Tainan, Taiwan]]
High-mast lighting is a tall pole with lighting attached to the top pointing towards the ground, usually but not always used to light a highway or recreational field. It is used at sites that require lighting over a large area. The pole that the lighting is mounted on is generally at least {{cvt|30|m}} tall (under this height it is referred to as conventional lighting system),{{cite web|url=http://onlinemanuals.txdot.gov/txdotmanuals/hwi/conventional_vs_high_mast_lighting.htm|title=Section 4: Conventional vs. High Mast Lighting|last=Lopez|first=Carlos A.|date=1 November 2003|accessdate=31 October 2011|location=Highway Illumination Manual|archive-date=4 October 2011|archive-url=https://web.archive.org/web/20111004090735/http://onlinemanuals.txdot.gov/txdotmanuals/hwi/conventional_vs_high_mast_lighting.htm|url-status=dead}} while the lighting consists of a luminaire ring surrounding the pole with one or several independent lighting fixtures mounted around it. Most units have four, six or eight lights in the ring, with three, five, ten, twelve and sixteen lights used in rarer instances. While most high-mast lights are high-pressure sodium, other lamp types such as mercury vapor, metal halide and LED, have also been used. Some units have the lighting surrounded by a circular shield to prevent or reduce light pollution or light trespass from affecting neighborhoods adjacent to the highway.{{cite web|url=http://www.dot.state.pa.us/Internet/Bureaus/pdDesign.nsf/HighwayLightingconstruction|title=Highway Lighting Unit Construction|accessdate=31 October 2011|archiveurl=https://web.archive.org/web/20070403201916/http://www.dot.state.pa.us/Internet/Bureaus/pdDesign.nsf/HighwayLightingconstruction|archivedate=3 April 2007}}
Maintenance of these systems is done by lowering the luminaire ring from the mast head to the base using a winch and motor to the ground or at a height accessible by a cherry picker and located in areas to allow for easier access without disrupting traffic.
Development history
Prior to the 1960s, highway lighting was often provided by shorter (approx. {{convert|30|ft|abbr=on}}) lighting poles with mercury vapor lamps. Advancements in high-mast illumination took place extensively in the mid-1960s in both Europe and North America. In 1966, the Texas Transportation Institute (TTI) installed a temporary {{convert|120|ft|abbr=on}} tall high-mast tower at a highway interchange in Fort Worth, Texas with exceptional results. That same year, TTI and the Texas Highway Department installed twenty {{convert|100|ft|abbr=on}} high-mast lighting towers at two adjacent interchanges on Loop 410 on the northeast side of San Antonio as part of a study to evaluate the benefits and techniques of various types of highway lighting. Each high-mast tower had ten 1,000 watt floodlights. Participants in the San Antonio Illumination Study traveled through the study corridor multiple times over two nights to observe and report impressions of the lighting, after which they were asked to complete a questionnaire about their experience and rate the different types of lighting. The surveys revealed that high-mast lighting was by far the preferred method of lighting.{{cite news |title=Let There Be Light |url=https://texashighwayman.com/misc/let-there-be-light/let-there-be-light.pdf |access-date=14 December 2024 |work=Texas Highways |date=December 1966}}
By 1967, Europe was known to have high-mast illumination technology in practice. 1968 saw the first permanent US installations of high-mast illumination starting in Auburn, Washington south of Seattle. The first American towers were {{convert|100|ft|abbr=on}} tall with a fixed-in-place lighting system that could not be lowered. A later project in 1968 featured a {{convert|150|ft|abbr=on}} fixed-lighting tower on the Texas-Arkansas state line with two other {{convert|100|ft|abbr=on}} fixed-lighting towers on either side of the state-border. By 1969/70, winch systems for the lighting systems were developed and several {{convert|175|ft|abbr=on}} towers were installed in Dallas and Houston, followed soon thereafter by {{convert|200|ft|abbr=on}} towers. In Canada, {{convert|100|ft|abbr=on}} fixed-lighing towers are standard on freeways in the Toronto and Montreal areas. Houston is believed to be the world's leading city of high-mast illumination along its freeways. Despite this, Belgium is considered to have the world's best-lit freeways.{{cn|date=December 2023}}
Modern high-mast illumination towers typically range from {{convert|125|to|175|ft|abbr=on}} tall and roughly {{convert|700|ft|abbr=on}} in spacing.
Moonlight towers in Austin, Texas served as a major influence on TxDOT's design of some of the first modern high-mast lighting towers in the US during the 1960s and 1970s.{{Cite book|last=Slotboom|first=Erik|title=Houston Freeways: A Historical and Visual Journey|publisher=Oscar F. "Erik" Slotboom|year=2003|isbn=0-9741605-3-9|location=www.HoustonFreeways.com|pages=76–83|language=English}}
References
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See also
{{Commons category|Light towers}}