Comparison of the non-thermal velocity dispersions (i.e., σ_NT in units of the sound speed at 10 K) obtained directly from the observed FWHM (upper panel) and after corrections of the opacity broadening (lower panel) for the three regions studied in Fig. 7: Region A using ¹²CO (A_V ~ 1; >1100 spectra); Region B using ¹³CO (A_V ~ 2; >1100 spectra); and the L1495-B213 filament using C¹⁸O (A_V> 5; 23 000 spectra Hacar et al. 2013). The opacity corrected values of σ_NT,corr were obtained from the intrinsic linewidths ΔV_int after correcting the observed linewidths using Eqs. (4) and (7). Subthermal excitation values (i.e., T_ex = 6 and 8 K) are used for the opacity correction for those points in Regions A and B, in agreement with Goldsmith et al. (2008). Owing to the expected increase of the gas kinetic temperature in the cloud outskirts, the observed values for σ_NT in Regions A and B correspond to upper limits of the intrinsic velocity dispersion of the gas. Only points with S/N ≤ 3 are considered.