History of Street Lighting

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History of street lighting
Before incandescent lamps, gas lighjting was employed. The earliest lamps required that a lamplighter tour the town at dusk, lighting each of the lamps, but later designs employed ignition devices that would automatically strike the flame when the gas supply was activated. The earliest of such street lamps were built in the Arab Empire, especially in Cordoba.
The first electric street lighting employed arc lamps, initially the 'Electric candle', 'Jablochoff candle' or ' developed by the Russian Pavel Yablochkov candle in 1875. This was a carbon arc lamp employing alternating current, which ensured that the electrodes burnt down at the same rate. Yablochkov candles were first used to light the Grand Magasins du Louvre Paris, where 80 were deployed. Soon after, experimental arrays of arc lamps were used to light Holborn Viaduct and the Thames Embankment in London - the first electric street lighting in Britain. More than 4,000 were in use by 1881, though by then an improved differential arc lamp had been developed by Friederich von Hefner-Alterneck of Siemens & Halsk. The United States was swift in adopting arc lighting, and by 1890 over 130,000 were in operation in the US, commonly installed in exceptionally tall moonlight towers.
Timişoara, in present-day Romania, was the first city in mainland Europe to have electric public lighting on the 12th of November 1884. 731 lamps were used.
Arc lights had two major disadvantages. First, they emit an intense and harsh light which, although useful at industrial sites like dockyards, was discomforting in ordinary city streets. Second, they are maintenance intensive, as carbon electrodes burn away swiftly. With the development of cheap, reliable and bright incandescent light bulbs at the end of the 19th century, they passed out of use for street lighting, but remained in industrial use longer.
Incandescent lamps used for street lighting until the advent of high-intensity discharge lamps, were often operated as high-voltage series circuits. To avoid having the entire street go dark if a single lamp burned out, each street lamp was equipped with a film cutout, a small disk of insulating film that separated two contacts connected to the two wires leading to the lamp. If the lamp failed (an open circuit), the current through the string became zero, causing the entire voltage of the circuit (thousands of volts) to be imposed across the insulating film, penetrating it . In this way, the failed lamp was bypassed and illumination restored to the rest of the street. (This is the same principle used in Christmas tree lights.) The circuit usually contained an automatic device to regulate the voltage in the circuit, preventing the current from increasing as additional lamps burned out , preserving the life of the remaining lamps. When the failed lamp was replaced, a new piece of film was installed, once again separating the contacts in the cutout. This style of street lighting was recognizable by the large porcelain insulator that separated the lamp and reflector from the light's mounting arm. The insulator was necessary because the two contacts in the lamp's base may have operated at several thousands of volts above ground/earth.
Today, street lighting commonly uses high-intensity discharge lamps, often HPS high pressure sodium lamps. Such lamps provide the greatest amount of Photopic illumination for the least consumption of electricity. However when Scotopic/Photopic light calculations are used, it can been seen how inappropriate HPS lamps are for night lighting. White light sources have been shown to double driver peripheral vision and increase driver brake reaction time at least 25%. When S/P light calculations are used, HPS lamp performance needs to be reduced by a minimum value of 75%. This is now a standard design criteria for Australian roads.