Figures (6)  Tables (2)

    • Figure 1. 

      Vehicle experiment scene. (a) Exit area of freeway tunnel; (b) exit area of highway tunnel.

    • Figure 2. 

      Contour coefficient for different numbers of clusters at the fixation points.

    • Figure 3. 

      Clustering of fixation points for exits of different grades of tunnels. (a) Exit area of freeway tunnel; (b) exit area of highway tunnel.

    • Figure 4. 

      Percentage of fixation points and cumulative percentage.

    • Figure 5. 

      Boxplot of fixation time.

    • Figure 6. 

      Percentage of scanning speed by interval within each category.

    • Characteristic Freeway tunnel Highway tunnel
      Exit linear Straightness
      Tunnel portal direction Northbound exit
      Tunnel grade Primary Secondary
      Speed limit 100 km/h 40 km/h
      Tunnel structure Dual access 8 lanes
      in both directions      		 Single access 4 lanes in both directions
      Traffic composition Motor vehicles Pedestrian, motor vehicles, non-motorized vehicles

      Table 1. 

      Information on the basic parameters of the tunnels.

    • Section Freeway tunnel Highway tunnel
      0.0−0.05 22.62% 4.58%
      0.05−0.1 5.36% 10.37%
      0.1−0.15 19.64% 17.13%
      0.15−0.2 27.98% 12.47%
      0.2−0.25 8.33% 16.89%
      0.25−0.3 13.69% 38.20%

      Table 2. 

      Exit area of tunnel exit scanning behavior percentage by interval.