.For the two lower tunnels, the wind speed ratios corresponding to the azimuthal range of 315–0 (360) are found to be less than one, which indicates a reduction of wind speeds in the tunnels.This is possibly attributed to the shelter effects from a group of building located on the northwest of Pearl River Tower (Fig. 6b). As given in Table 2, the wind speed ratios obtained in Case 1 for tunnel-1 and tunnel-2 are typically lower than those for the two upper tunnels.