Distribution of CO line widths for the 57 structures. The light and dark blue solid lines show the observed and optical-depth-corrected ¹²CO line widths, respectively. The red solid line represents the observed ¹³CO line widths for the 13 clouds with a projected area ﹩\gt 10\,{{\rm{arcmin}}}^{2}﹩. Vertical dashed lines mark the corresponding mean values for each distribution. The color shadings mark the velocity intervals corresponding to subsonic, transonic, and supersonic regimes for a gas temperature of 10 K.