Evaluation of Traffic Signs Information Volume at Highway Tunnel Entrance Zone Based on Driver’s Visual Characteristics

Reasonable and appropriate traffic sign information volume (TSIV) is crucial to ensure road traffic safety, especially at the entrance zones of highway tunnels. This research compares how various levels of TSIV affect both visual characteristics and visual workload of drivers through real road driving tests. Forty participants were recruited to conduct a field driving experiment at six highway tunnels. The eye movement data of drivers were collected by an eye tracker and the effects of TSIV on drivers’ eye movement characteristics, visual stability, visual SampEn (sample entropy), and visual workload intensity were analyzed and evaluated. At the T3 level (48.31 bits) of TSIV, the drivers’ average fixation duration and average saccade duration were both at the lowest value, while the drivers’ average saccade amplitude reached the maximum, and the dispersion of the three eye movement indicators was the smallest. In addition, the drivers’ visual SampEn increased continuously when approaching the tunnel portal, and was the lowest at T3 level. With the increase of TSIV, drivers’ visual workload intensity decreased first and then increased, the minimum being at T3 level. The drivers’ visual behavior is more stable, visual coordination ability is better, and visual workload and psychological pressure are least under the T3 level, which is beneficial to ensure driving safety at the entrance zone of a highway tunnel. Inappropriate levels of TSIV at highway tunnel entrance zones will cause inevitable risks to driving safety.