Pokolenie tunelu jest właśnie dlatego, żeoświetlenie drogowemusi przechodzić przez całość, więc jego dwie strony i góra są zamknięte, a naturalne światło mogą docierać tylko do otworów na obu końcach tunelu. Ta specjalna konstrukcja spowoduje różnicę jasności między sekcją wejściową do tunelu a sekcją środkową. Aby dostosować się do różnych różnic jasności, ludzkie oczy będą miały różne problemy ze wzrokiem, więc sekcja wlotu do tunelu ma różne cechy wizualne.
In the daytime, when the driver approaches the tunnel entrance, due to the high brightness outside the tunnel entrance, the driver will see a black hole, which is a "black hole" phenomenon. Entering from a bright tunnel into a dark tunnel is dark adaptation, and the human eye cannot immediately perceive the details of the space, that is, the "adaptation lag phenomenon" occurs. This is because the dark adaptation time of the human visual system is longer than that of light adaptation. In the process of dark adaptation, the eye goes from light to dark with low sensitivity at first, then gradually increases, and finally reaches stability and clarity. Although the human eye's visual system can adapt to a huge drop in the brightness of the surrounding environment, the length of this adaptation time depends on the magnitude of the decrease in brightness. The greater the difference in brightness, the longer the adaptation will take. This means that at a certain driving speed, the greater the difference in brightness between inside and outside the tunnel, the longer the driver needs to adapt to the vision.
In the middle section of the tunnel, due to the relatively closed structure, automobile exhaust gas and dust are not easily dissipated in time, and the accumulation will form smoke, which affects the visibility of the driver. There is also the influence of mesoscopic visual effects in the middle segment. During the transition from photopic vision to scotopic vision, the spectral sensitivity of the human eye changes gradually, and the entire spectral sensitivity curve gradually shifts from long waves to short waves. The sensitivity of the human eye to yellow and red light (poor scotopic spectrum) decreases significantly as adaptive brightness decreases, while the response to green light (rich scotopic spectrum) greatly increases. This is why at dusk when the brightness is low, we perceive blue and green light in the shortwave direction to be bright. In addition, blue-green light will inhibit the secretion of melatonin in the human body, improve the body's response ability, and affect the pupil size of the human eye, which will directly affect the driver's reaction time, that is, affect the visual performance.