Method of Setting Exit Advance Guide Signs in Highway Tunnels Based on Driver’s Eye Movement with Markov Chain

 While the number of highway tunnels is increasing, the current Chinese criteria and Uniform Traffic Control Equipment Manual (MUTCD) 2009 guidelines provide no clear method for the setting of exit advance guide signs in highway tunnels. To solve this problem, this paper proposes separate guide signs, consisting of location and distance signs. Location signs on tops of tunnels use Chinese characters with a height of 40 cm and 20 cm. Distance signs are 62.6 m from location signs, with a character height and width of 1.5 m, and a total sign length of 22.5 m. Four schemes were tested, in which the distance sign was on the left or right wall of the tunnel, and the vehicle was in the left or right lane. A Markov chain was used to analyze the driver’s eye movement characteristics to evaluate the effect of separate guide signs. The results are as follows. In the left lane, when a distance sign on the left wall of the tunnel appeared, the driver’s fixation points were relatively balanced except in the left area. After the sign disappeared, the driver’s fixation points were no different than before, except in the front area. However, when a distance sign appeared on the right wall, 77.84% of the driver’s fixation points were concentrated in the front and right areas, which decreased driving safety. Similar results were obtained in the right lane. Therefore, distance signs should be placed on the left wall of the highway tunnel. This study can forewarn a driver in a tunnel of the exit location and distance, and facilitate leaving the highway safely.