Influence of luminance and luminance longitudinal uniformity of tunnel lighting on drivers' comprehensive visual performance

The present study aimed to investigate the comprehensive influence of the average luminance Lav and luminance longitudinal uniformity U1 on the diver’s visual performance under the stage of driving in the tunnel’s interior zone during the experiment. Specifically, we collected reaction time, pupil area change rate, and blink frequency from 40 participants through the indoor visual performance experiments. The present study quantitatively characterized the mechanism of the antagonism between luminance intensity and difference, and established the Lav-U1 curve which succeeds in satisfying the safety threshold of the driver's comprehensive visual performance. The results show that the driver's visual performance deteriorated continuously as the test time increases. Increasing the luminance was beneficial for accelerating the reaction speed, but also caused greater stimulation of light and dark changes. The change ratio of reaction speed and the increased amplitude of perceived luminance increased exponentially with the increase of luminance, resulting in an antagonism effect. The visual performance decreased with the increase of average luminance under low uniformity levels, and increased with the increase of average luminance under high uniformity levels. Furthermore, we found that the luminance longitudinal uniformity should match up the luminance in the interior zone, instead of separation under the current specification. Based on our findings, we propose specific recommendations for the luminance longitudinal uniformity under different average luminance levels. For the interior zone of tunnels with an average luminance of 2.5, 4.5, and 6 cd/m2, the luminance longitudinal uniformity should be increased from 0.6 to 0.67, 0.72, and 0.75, respectively. Current findings demonstrate that the implementation of the proposed U1 standard in tunnel lighting design can significantly fasten drivers' reaction time, contribute to a decrease in traffic accidents, and thus improve the safety level of tunnel lighting design in the interior zone of tunnel. These results have significant implications for the design of tunnel lighting.