Toomre diagram for the sample of interacting planetary nebulae. The x-axis represents the velocity component (V) in the direction of the galactic rotation, while the y-axis represents the velocity component defined by the galactic centre direction (U) and the direction perpendicular to the Galactic plane (W). All velocity components are corrected from LSR. The semi-circular lines indicate the constant total velocity in steps of 50, 70, 100, 150 km s^-1. The error bars represent the standard deviation in velocity components for the IPNe with multiple determined distances. Regions I, II, and III refer to the objects with total velocities V_S < 50 km s^-1, 70 ≥ V_S ≥ 50 km s^-1, and V_S > 70 km s^-1, respectively.