\label{rad_sig} Turbulent line width on a 1 pc scale, $\sigma_0$, as a function of the GMA's distance from the galactic centre, $R_\mathrm{gal}$. Blue triangles represent nuclear clouds, green circles represent inter-arm clouds and purple diamonds represent arm clouds. Turbulence is highest in nuclear clouds and the same, on average, for arm and inter-arm populations.