公路隧道出入口段行车时驾驶员的视觉负荷变化较大，为进一步量化该路段视觉负荷的变化规律，选取10名驾驶员在秦岭终南山公路隧道柞水—西安段进行实驾试验，采集驾驶员在昼间晴朗天气下通过隧道出入口路段的照度、车速、瞳孔面积等数据。通过分析驾驶员在隧道出入口段的瞳孔面积变化特征，参照峰均比(PAR)、频段比(LF/HF)等物理学、医学参数，提出“瞳孔面积相对变化强度”(RCPA)的概念，将其作为视觉负荷的评价指标，划分出该指标取值与视觉舒适度的关系，并建立RCPA与速度、照度的数学模型。结果表明： 1）RCPA可以较好地体现出隧道出入口段视觉负荷渐变累积和急剧震荡的规律； 2）在即将驶入洞口和刚刚驶离洞口时的瞬时视觉负荷最大，超过了生理极限； 3）RCPA与速度、照度的定量关系可为隧道出入口制定安全速度阈值、改善照明环境提供参考依据。
The visual load of a driver changes significantly
while driving through the entrance and exit sections of a highway tunnel. To
quantify the change law of the visual load at these sections, 10 drivers are
selected for conducting a driving test at the ZhashuitoXi′an section of Zhongnanshan highway tunnel
in Qinling Mountains. Data such as illuminance, vehicle speed, and pupil area
of the drivers passing through the tunnel entrance and exit sections on sunny
days are collected. By analyzing the change characteristics of the drivers′ pupil area at the entrance and exit of the tunnel, the concept of
the relative change intensity of pupil area (RCPA) is proposed. The concept is
based on physical and medical parameters, such as the peaktoaverage ratio and frequency band ratio,
which are as evaluation indices of the drivers′ visual
load. In addition, the relationships between the indices and visual comfort are
revealed. Finally, a mathematical model showing the relationships between the
RCPA and velocity and illumination is established. The results reveal the
following. (1) The RCPA sufficiently reflects the law of gradual accumulation
and sharp flatuations of the visual load at the entrance and exit of the
tunnel. (2) The instantaneous visual load of the drivers is the largest when
they are about to enter or leave the tunnel, and this load exceeds the
physiological limits of the drivers. (3) The quantitative relationships between
the RCPA and speed and illuminance can provide a reference for setting safe
speed thresholds at tunnel entrances and exits and improving the lighting
environment in tunnels.
