Using Daylight to Light the Access Zone of Road Tunnels

Speaker(s): 
Date: 
March 4, 2003 - 12:00pm
Location: 
Bldg. 90

Lighting guides for roadway tunnels specify relatively high luminances for the "access zone" into the tunnel. They are needed to allow the eyes of the driver sufficient time to adapt during the short period of the transition from the outdoor natural daylight levels to the fairly low luminances along the main length of the tunnel. Usually, the necessary high luminances are provided by rows of costly luminaries which consume a lot of electricity during peak use periods and need a good deal of maintenance. To save some electric power, controls are used to dim the lighting on cloudy hours. Daylight has been used for the access zone in several tunnels around the world, but the solutions have not been very successful. This presentation will report of a successful daylighting design in a new tunnel that was opened in January 2003 in Jerusalem, Israel. Jerusalem enjoys some of the highest levels of solar radiation in the world. Global solar illuminances in summer can reach 110,000 lux. And even the diffuse skylight in the summer may exceed 30,000 lux. Therefore, the option of using daylight for the entrance of new tunnel has been seriously examined. As it is not practical to admit daylight into the tunnel itself, the daylight solution requires an extension of the tunnel. In this project, louver blades were designed in such a way that direct sunlight is totally obstructed, while north skylight can illuminate the shaded length of the access road into the tunnel. A preliminary feasibility examination showed that the extra costs will be returned by electric power and maintenance savings within 18 months. The daylight option has an important built-in advantage. There is no need to control the illuminance level according to the cloud cover since the control is automatically provided by the design. On clear hours, more daylight penetrates into the controlled access zone, while on cloudy hours the illuminance in this zone drops automatically. Thus, a proper adaptation process is achieved. The tunnel was opened in the middle of January of 2003, and the response of the users has very favorable. We shall wait and see how the daylight option will be accepted by the drivers in summer time. Eliyahu Ne’eman is a leading international expert on lighting and daylighting. He has been involved in education, research and practice for over 40 years while working in Israel, UK, Germany and the US (LBNL). He has worked extensively in the area of occupant response in luminous spaces and he has been leading the CIE Task Group that has revised the CIE Museum Lighting Guide.   For more information about this seminar, please contact: JoAnne Lambert 510.486.4835, or send e-mail to JMLambert@lbl.gov

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