Tunnel lighting differs significantly from standard roadway lighting; its unique characteristics necessitate a primary focus on safety within the lighting system design.
When designing tunnel lighting schemes, factors such as the human eye's adaptation to light and darkness must be considered, with particular attention paid to transition zones. To accommodate the eye's adaptation requirements, transitional lighting is necessary at tunnel entrances to ensure adequate visibility. Conversely, since the adaptation time required at tunnel exits is very short-typically less than one second-no special transitional lighting treatment is usually required there.
Tunnels are enclosed spaces inaccessible to natural light; therefore, continuous artificial lighting is required throughout the interior-even during the day-to ensure driving continuity and the safety of motorists. Lighting is thus an indispensable component of tunnel construction.
Research into energy-efficient tunnel lighting using new light sources has garnered significant industry attention, with substantial progress made in the development of energy-saving LED tunnel lights. LEDs possess inherent advantages for tunnel lighting-supported by research into photopic and mesopic vision theories, as well as the relationship between color rendering and illuminance-leading to their adoption in numerous major tunnel lighting projects across China. While the application of LED fixtures in tunnel lighting has seen breakthrough progress, challenges remain, such as the lack of specific design and installation standards for LED-based tunnel lighting and inconsistent product quality. With 60% of Europe's tunnels located in Italy, the following discussion draws upon a practical application case from a tunnel in Rome.
Tunnel lighting must contend with a harsh environment characterized by factors such as vehicle exhaust, noise, vibration, corrosive gases, and moisture. To provide a safe and comfortable lighting environment for passing vehicles and pedestrians, the following analysis outlines the design concepts and methodologies for tunnel lighting. We utilize SPARK square LED tunnel lights. The LEDs currently employed have advanced to a performance level of 114–122 lm/W at 1 W; operating at a voltage of 3.2 V and a current of 320 mA, the actual operating power of a single LED is 1.024 W. With 56 LEDs, the total light source power is 61.6 W; factoring in a power conversion efficiency of 86%, the total system power is 72.6 W. The 736-meter tunnel is equipped with 103 lights, resulting in a total power consumption of 7,374.8 W (103 × 71.6 W). Based on 24-hour daily operation, the total energy consumption is approximately 215.3 kWh per day, or about 71,950 kWh per year.