Abstract: In this paper, the accident distribution law of urban underwater road tunnel is summarized. The factors influencing the driving safety of the tunnel are analyzed from three aspects of driver factor, tunnel light environment and tunnel alignment. The existing security improvement measures and their advantages and disadvantages are analyzed, and the research trend of driving safety optimization of underwater tunnel is prospected, which refers to regarding the improvement of tunnel light environment quality as the key, considering traffic accident forms, causes and influencing factors and as well as the differential visual demands of drivers in different tunnel areas on the basis of ensuring traffic safety. The drivers′ visual demands can be divided into functional, safety and comfort requirements, and correspondingly, the tunnel driving environment can be divided into basic, safe and comfortable visual reference systems. In order to build comfortable visual reference system of urban underwater road tunnel, the tunnel lighting and visual induction technology are combined to alleviate the drastic transition of the reference system of threshold/exit zone and strengthen the weak visual reference in interior area. Finally, the evaluation index system of urban underwater road tunnel driving safety optimization method based on space right of way, human factors and driving tasks, difference and rhythm is established, providing new idea for the optimization of urban underwater road tunnel driving safety.

Key words: urban underwater road tunnel, driving safety, visual demands, optimization method, evaluation index system