Experimental Study On The Imporvement Of Optical Illusion At Highway Tunnel Entrance Based On The "Black Hole Effect"

China owns the largest number of highway tunnels worldwide, most of them areoperating in low lighting conditions. In daytime, the drastic variation of illuminationat tunnel entrances causes difficulties on drivers’ dark adaptation, may lead to the“Black Hole Effect”, which means drivers can hardly recognize optical information,and results in over-speeding and rear-end crash. In general improvements suggest tostrengthen tunnel lighting, but it requires more investments and cost, operators cannot afford any improvement plans like this.This study is based on experiments of highway tunnel miniature (1:20), and thesoftware of E-prime2.0to set up experiment platform of illumination transition andhuman psychology, analysis drivers’ visual characteristics with pupil area and visualload; experimental results show:(1) the miniature of highway tunnel can effectivelyimitate the illumination transition on human pupil at highway tunnel entrances;(2)the calculation results indicate that the shading construction ranks from high to lowis: bamboo-truncating with30degrees>45degrees>60degrees>down bamboo-truncating with30degrees>45degrees>60degrees>the grille construction> theretaining wall;(3) the longer the construction is, the better the illumination transits,and to cover the sky gets better shading functions than to cover the road side;(4)when driving into the tunnel entrance, the larger the illumination difference is, theheavier drivers’ visual load is, which may lead to mental tension and “visual vibrate”,which is called optical illusion of the “Black Hole Effect”;(6) the amount of opticalillusion is related to the length of shading constructions when it is covering the samepart of tunnel entrance, and optical illusion trend to lower when it is covering the sky;(7) rebuilding of the optical reference frame can bring drivers effective visualinformation on vehicle speed, but not as well as on vehicle distance.In refer to the shape of celestial “Black Hole”, this study come up with ashading construction called “the cicada shading”, which can ease the illuminationtransition at tunnel entrance and extend the dark adaptation process both in time andspace; with the guidance of edge rate theory, set up retroreflection road marks ofmultiple frequency to improve the perception of vehicle speed, distance and sense of directions, controlling the vehicle in safe speed and relieve optical illusion of the“Black Hole Effect” at tunnel entrance.