Luminance stepped decreasing ratio of the tunnel entrance enhanced lighting based on visual performance

To achieve a safe and comfortable entrance enhanced lighting environment of tunnels, visual performance experiments under the dynamic and static luminance environments were carried out to investigate the influence of the luminance variation forms and stepped decreasing ratio k^' of the tunnel entrance enhanced lighting on the driver's comprehensive visual performance. The application effect was further verified by real vehicle experiments and field luminance measurements. The results of the dynamic and static experiments show that compared with the continuous and smooth decrease of the luminance according to the International Commission on Illumination (CIE), when facing the stepped decrease of luminance, drivers tend to withstand greater visual operation stress and a more tense psychological state. After the stepped decrease of the luminance, the driver's average and instantaneous reaction both slow down, while the amplitude of the slowdown decreases with the increase of k^' and increases with the increase of the luminance level. The results of the real vehicle experiments show that increasing k^' of Threshold Zones 1 and 2 and Transition Zones 1 and 2 to 0.7, 0.6, 0.5, and 0.5, respectively, can effectively relieve driver's psychological tension and enhance the visual performance. For practical engineering applications, it should be combined with daylight reduction facilities, thus avoiding the increase of energy consumption of the tunnel entrance enhance lighting.