Fig. 5a and b shows that whether measurements were obtained at the side-type platform or the island-type platform, PM2.5was always higher at the rear of the platform than at the middle position. Similarly, Fig. 5c and d indicates that the PM2.5 concentration at the front of the platform was higher than that at the middle, and Fig. 5e and f shows that the PM2.5 concentrations were similar at the front and rear positions.