Study On Influence Of Lighting On Driver's Vision When Driving Through Highway Tunnel

Highway tunnel is semi-closed,due to the special geometric structure and the driving environment,“bright adaptation”and“dark adaptation”will occur when drivers driving through it.To ease the bright or the dark adaptation and to improve the driving safety,the luminance levels of the tunnel lighting are stipulated into zones in the Chinese“Guidelines for Design of Lighting of Highway Tunnels”.Based on the process of“perception-cognition-response”,when a driver encounters an obstacle in the tunnel,he will recognize it and take action about how to keep safety,during which the reaction time will be directly affected by the luminance of the tunnel,then influence the road safety.In addition,the light-emitting diode(LED)lamps are more and more popular in the set of the tunnel lighting,however,the set of the correlated color temperature(CCT)in the design of the tunnel lighting is lack of scientific guidance.The impact of CCTs as an influencing factor on the driver's visual recognition and driving safety is also lacking in basic theoretical research.What's more,to alleviate the problem of“dark adaptation”when drivers driving from the outside to the inside of a tunnel and reduce the energy consumption,relevant studies at the present stage generally suggest setting light reduction facilities in the access zone of tunnel.However,the analysises of light reduction facilities generally focus on the disabled glare generated by the direct sunlight,while there is still no theoretical support for the uncomfortable glare,which is directly related to the illumination of the access zone.It is also of practical guiding significance to explore more comfortable shading facilities(tunnel pergola)to reduce the reaction time of drivers and improve the safety of driving in a tunnel.To study the drivers'visual recognition mechanism under the different zones of tunnel lighting,the visual recognition tests of drivers in different tunnel lighting zones were carried out based on the drivers'reaction time.To obtain much safer and more comfortable tunnel lighting environment to promote the drivers'visual ability for recognition,how to improve the comfort of the light reduction facilities in the access zone of the tunnel was studied.The details are as follows:In order to obtain the driver's visual recognition mechanism under the change of lighting environment and under the different CCTs in the interior zone of a highway tunnel,the change of lighting environment in a highway tunnel was simulated using the visual performance method and the self-developed recognition time test system.Taking Zhong Nanshan Tunnel as a reference and according to the Guidelines for Design of Lighting of Highway Tunnels,the luminance change of the lighting environment when the drivers driving into and out of a tunnel at a speed of 70 km/h was simulated,including the luminance of the access zone,the threshold zone,the transition zone,the interior zone and the exit zone.Eight different CCTs(2500 K,3500 K,4500 K,5500 K,6500 K,7500 K,8500 K,9500 K)were selected for the interior zone to study the influence of CCTs on drivers'recognition time during and after the change of luminance in the lighting environment,and the influence of driving time in the interior zone of different CCTs on the reaction time was studied.At the same time,to get the identification mechanism of the drivers in the interior zone under different luminance levels,the targets'recognition experiment of the central vision and the peripheral vision was studied by simulating the lighting environment of the tunnel interior zone.Scenes with different luminance,the targets with different positions or the opening directions on the screen and different staying time were set,and the correct recognition rate and the related reaction time were counted.Finally,to improve the drivers'visual recognition ability when driving into a tunnel,the setting method of light reduction facilities in the access zone of the tunnel and how to improve the glare comfort of common tunnel pergola were studied.The results showed that the driver's reaction time became larger with the decrease of the luminance of tunnel lighting.However,when the driver was in a specific zone of the tunnel lighting,a short“dark adaptation”was helpful to reduce the driver's reaction time and improve the visual performance.When the lighting environment transitioned from the transition zone to the interior zone,it was helpful for improving the driver's visual performance if the CCT of the interior zone near the threshold zone was elevated,but the CCT should not be too high which might lead to a negative effect.Therefore,it was helpful to reduce the energy consumption of tunnel lighting on the basis of safety by appropriately reducing the luminance at the threshold or the transition zones,or increasing the CCT of the lighting at the interior zone.Secondly,based on the cubic spline interpolation model,the safety evaluation index for the interior zone of the tunnel was proposed,the relationship models between the oscillation duration of the converted reaction time and the starting point of unsafe factors with the CCTs were established respectively.Based on the models,the setting method of the CCT of the interior zone was analyzed.Thirdly,when the background luminance was in the range of 0.1-5.0 cd/m~2,the reaction time in the peripheral vision was greater than that in the central vision at the same background luminance,and all indicated a power function relationship with the increase of the luminance.In order to improve the driving safety in a tunnel,the luminance of the sidewall should be higher than that of the pavement,and the lamps with wide distribution curve should be installed on both sides of a tunnel to offer a higher luminance for the sidewall.Finally,in order to reduce the uncomfortable glare caused by the tunnel pergola and improve the visual performance of the driver with the change of the tunnel lighting,the quantitative evaluation method of the uncomfortable glare of the tunnel pergola was established,the calculation formulas of the uncomfortable glare were established for the pergola with equal beam spacing and unequal beam spacing,and the general design method of the tunnel pergola was given considering the uncomfortable glare.