The wind speed ratio from the southerly winds is averaged at 1.90 for tunnel-1, 1.90 for tunnel-2, 2.08 for tunnel-3 and 2.19 for tunnel-4, whereas the mean values related to the northerly winds are 1.72 for tunnel-1, 1.69 for tunnel-2, 1.86 for tunnel-3 and 1.90 for tunnel-3, respectively.In particular, comparisons of wind speed ratios corresponding to 180 and 0 demonstrate that higher values are always derived when the wind is approaching from 180.