The impact of lighting and longitudinal slope on driver behaviour in underwater tunnels: A simulator study

Compared to highway road tunnels, underwater tunnels feature long and steep slopes at the tunnel entrance. This feature, along with a narrow environment and light fluctuation, further compromises driving safety at underwater tunnels. Given more and more underwater tunnels are constructed, it is necessary to examine the impact of slope and light conditions on driver behaviour at underwater tunnels. To this end, the present study set up driving scenarios tailored to typical underwater tunnels. A high-fidelity driving simulator study was then conducted at three levels of luminance (bright, reddish, and dark light) and four levels of longitudinal slopes (2.5%, 3.0%, 3.5%, and 4.0%). Speed, lane-keeping performance, pedal control, eye activity, and physiological arousal were collected. Two-way repeated measures ANOVA and post-hoc analysis were applied. The results showed that slope had a great effect on driving performance, while the luminance level mainly influences the eye movement and heart activities. There were interaction effects on pupil size, in which the impacts of dark light depend on the level of slopes. Besides, it was found that rear-end collision risk was significantly higher under the scenario with dark light and steep slope. The study also investigated the influence of enclosed tunnel environment. The results showed that tunnel environment, without the change in illumination, still resulted in a significant increase in driving workload.