Streetlight systems have developed gradually from candles in the seventeenth century to gas lighting in the eighteenth century and electric lighting in the twentieth century. The first electric lights were electric arc lamps installed in Paris, France. The development of the incandescent lamp, initiated by Thomas Edison, greatly improved street lighting. The modern streetlight system reduces traffic hazards, helps to prevent crime, and enhances the beauty of our surroundings. The incandescent streetlight lamp that was commonly used in the early part of the twentieth century is gradually being replaced by electric discharge lamps of the fluorescent, mercury-vapor, metal-halide, and high-pressure-sodium types. The mercury-vapor lamp has had wide use because of its good efficiency, long life, and good light maintenance. Metal-halide and high-pressure-sodium lamps have a greater light output per watt of electric power input than the mercury-vapor lamps. High-pressure-sodium lamps are currently the most prominent light source for new street-lighting installations. The American National Standards Institute's publication, entitled Practice for Roadway Lighting (ANSI/ANSI RP8), covers street-lighting design for installations in the United States.

Street-Lighting Terms

Light. Aq form of radiant energy. Measurements are based on a unit of luminous intensity equal to the light emitted by a "standard candle" in a horizontal direction.

Lamp. A source of light.

Luminaire. The device which directs, controls, or modifies the light produced by a lamp. It consists of a light source and all necessary mechanical, electrical, and decorative parts.

Candlepower. The amount of light that will illuminate a...