Reddening‐corrected [N II] λ6583/Hα line ratio as a function of Hα line width for the filament measurements. Also shown by the solid lines are predictions of shock models taken from Dopita & Sutherland (1996; DS: shock only; DSp: shock+precursor), Binette et al. (1985; BDT), and Shull & McKee (1979; SMK). In plotting the model predictions, we have equated the shock velocity to the FWHM of Hα.