Tunnel lighting has long been accomplished using incandescent, fluorescent and High Pressure Sodium lighting technologies. Each of these types of lights have their own advantages and disadvantages. In the last decade, Light Emitting Diode (LED) systems have advanced to a level that economically allows their widespread use in tunnel facilities. While their use has become more widespread in roadway lighting, challenging conditions within tunnels have tempered their acceptance for underground application. Brightness, color, and dispersion of light from LEDs each affect the utility of the lamps. While Roadway and Tunnel Lighting share similar needs, they also each have their own challenges. The enclosed space of a roadway tunnel can accentuate both the positive and negative qualities of a particular light type. This study focuses on tunnel lighting, which differs significantly from roadway lighting. Tunnel lighting was specifically excluded from the ongoing NCHRP Project 05-22: Guidelines for Solid-State Roadway Lighting
The capital cost of LED lighting initially made its use prohibitive when compared to other more energy and maintenance intensive lighting. However, LED costs have dropped very rapidly in recent years, and generally, it is economically competitive with other technologies especially when maintenance frequency and life cycle costs are included. With the rapid advancement and changes in LED technology, it is necessary to study how this new technology of lighting can best be used to meet existing lighting standards and requirements. The rapid advancement of technology has also resulted in obsolescence of early installations of LED systems-forcing owners to retrofit systems well before the end of their expected life because of lack of available replacement parts. The tunnel environment presents unique challenges, both in lighting performance and in reliability. Road salt, constant moisture, and the proximity of the equipment especially when maintenance frequency and life cycle costs are included.
The objective of this project was to develop a guidelines with on the applicability of LED lighting for tunnel use. The guidelines include a catalog the various types of LED lighting techniques commonly available and identify benefits and challenges with each when used to light tunnels including associated cost and maintenance. The guidelines also include a set of recommendations on what will be needed for LED tunnel Lighting for future adoption into the AASHTO Lighting Design Guide 2018. The guidelines is available at:
https://onlinepubs.trb.org/Onlinepubs/nchrp/docs/NCHRP20-07Task425-FinalReport.pdf
(NCHRP Staff: Dr. Waseem Dekelbab)
