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Owing to the special tubular structural characteristics of highway tunnels, drivers typically experience a significant change in visual luminance when entering tunnels, which seriously impacts driving safety. This paper proposes a lighting scheme based on optical fiber technology to introduce natural light into the tunnel portal section. First, an on-demand lighting scheme based on the use of daylight is designed by developing an optical fiber lighting system, lighting demand algorithm, and an on-demand lighting control scheme. Furthermore, the scheme is applied to a physical tunnel, and the safety and energy-saving potential of the scheme are analyzed based on the obtained data. The results indicate that the average luminance and luminance uniformity in the tunnel portal section appear to improve with the application of the proposed scheme; the luminance uniformity is particularly increased by 0.18. The correlative color temperature (CCT) of the environment inside the cave changes in real time with the CCT value of the phase pair outside the cave. Compared with the explicit use of electrical lighting, the lighting energy consumption during daytime can be reduced by 34.7% with the application of the proposed scheme, and the highest reduction of 79.8% can be achieved at 13:00.