Abstract
An LED Counter Beam Light (CBL) with a free surface secondary lens is proposed to enhance the safety and efficiency of tunnels. The secondary lens was designed and produced to be mounted on a 50 W white-light LED array to generate the targeted counter beam pattern, in order to meet the standards for enhanced tunnel road lighting of the CIE (Commission Internationale de l’Eclairage)—CIE 88:2004—in a trial tunnel lighting scheme. Through the simulation of a road tunnel in Northern Taiwan using the LiteStar four-dimensional software, it was shown that the proposed LED light can serve as a qualifying CBL to generate an average road tunnel surface luminance (Lav) of 182.76 cd/m2, which is better than the 138 cd/m2 that commercial High-Pressure Sodium (HPS) tunnel lights can provide and the 181 cd/m2 minimum stipulated in the CIE 88:2004 regulations. The results also show that the proposed LED light accomplishes a contrast revealing coefficient qc of 1.03, which is above the minimum regulatory level of 0.6 for a qualified CBL, as well as a luminance uniformity Uo of 0.89 (regulatory minimum, 0.4), longitudinal luminance uniformity UL of 0.99 (regulatory minimum, 0.6), and glare factor TI (threshold increment) of 7.24% (regulatory minimum, 15%). In order to test the feasibility of the LED CBL for future commercialization, the proposed LED CBL was prototyped and measured; the results demonstrate that an average road surface luminance (Lav) of 184.5 cd/m2, intensity of the luminance uniformity Uo of 0.7, intensity of the longitudinal luminance uniformity UL of 0.94, glare factor of 7.04%, and contrast revealing coefficient qc of 1.38 can be achieved, which are all above the levels required by the CIE 88:2004 regulations.
Highlights
Through optical simulation experiments in a trial tunnel in Taiwan, the light-emitting diode (LED) light was demonstrated to be suitable for use as a Counter Beam Light (CBL) and able to meet the CIE 88:2004 regulations for tunnel lighting with appropriate light arrangements [19,20,21]
Through optical simulation experiments in the trial tunnel performed in LiteStar4D, it was shown that the optimized LED light can accomplish a contrast revealing coefficient of 1.03, which is higher than the minimum regulation level of 0.6 for a qualified Counter Beam Light (CBL), and an average street surface luminance (Lav ) of 182.76 cd/m2, which is better than the CIE 88:2004 regulation standard of 181 cd/m2
Based on the layout shown in Figures 5–7; the output reports show that the qc is 1.38 (>0.6), which means that the optimized LED CBL can function as a counter beam illuminator and
Summary
Based on the CIE 88:1990 regulations, the L20 method has been used for designing tunnel road lighting, defined as the luminance of a tunnel’s entrance and surrounding areas creativecommons.org/licenses/by/. LED Counter Beam Light (CBL) is proposed and demonstrated in this paper for reducing the electrical power consumed in tunnel lighting. Considering the cost and financial issues, the invention of the LED Counter Beam Light (CBL) is essential for tunnel lighting, because the higher contrast revealing coefficient qc of CBLs can reduce Lth , decreasing both the power consumption and cost of tunnel lighting. Through optical simulation experiments in a trial tunnel in Taiwan, the LED light was demonstrated to be suitable for use as a Counter Beam Light (CBL) and able to meet the CIE 88:2004 regulations for tunnel lighting with appropriate light arrangements [19,20,21]. A comparison of the lighting performance between the initially designed LED CBL and the optimized tunnel light LED CBL within the tunnel threshold region will be presented
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