Light pipe technology, which was originally used to illuminate buildings of special interest, has been used successfully in several road tunnels, including three in Boston, USA, and one in Monterrey, Mexico. It has been adapted for use in the harsh environments of tunnels with heavy traffic. Light pipe systems combine the linear appearance of fluorescent lighting with the installation and maintenance advantages of point-source lighting. They address the safety and economic issues of tunnel lighting, that have become more important world-wide. A light pipe system consists of a light guide, luminaire, lamp, and ballast. The light guide uses the principle of total internal reflection, and is a clear, durable, hollow plastic tube, lined with a clear optical film containing a continuous series of microprisms. For tunnel applications, each luminaire is double ended, and provides light to two light guides at once. Light pipes provide roadway uniformity-of-lighting levels that can reach 90%. They also avoid the annoying, potentially dangerous, problem where the spacing of lighting fixtures causes drivers at certain speeds to experience an on-off frequency in the light. This modern technology provides high-quality light, and takes advantage of cost savings over the tunnel's whole life.
Samenvatting