Many of us believe that we can easily find our way at night. Before electric street lights were used in the late 1870s, this task was much more difficult and dangerous. Let’s take a closer look at the history of commercial street lighting fixtures. The oldest electric street lamps are illuminated by arc lamps. The arc lamps contain two carbon rods which, when touched, complete an electrical circuit. As the rods separated, the current continued to flow through the gap in a light-producing spring.
In 1912, with the invention of incandescent lamps that have a long lamp life and are easy to maintain, arc lamps became unusable. Incandescent lamps are hung on curved poles in the shape of a “neck” like today’s street lamps. Similar to modern incandescent lamps, these gas-filled street lamps contain spiral tungsten that glows when heated by the current flowing through it.
Over time, most incandescent lamps were replaced with fluorescent lamps. Fluorescent lamps produced cool white light for excellent white color reproduction. Other advantages include high luminous efficiency and long lamp life. Fluorescent street lamps were popular in the mid-1950s until the 1970s when they were replaced by high-pressure sodium and metal halide lighting sources. The latter two remain the most common municipal and industrial lighting sources today.
Different street lights consume different amounts of energy. Incandescent lamps typically range from 25-150 watts, fluorescent lamps 18-95, metal halide lamps 50-400 watts, and high pressure sodium lamps 50-400 watts.