Radial-motion-distance relation. Radial component of the relative cluster motions (v_r) versus relative cluster distance (r), with e Lup as a reference point. The symbols are colour-coded by formation time, as in Fig. 4. A linear fit to the data is shown as a solid grey line, with the best-fitting slope given in the upper left corner, and the 1-2-3σ fit uncertainties are plotted as shaded grey areas. The two clusters marked by dashed black circles (e Lup, ν Cen) are excluded from the linear fit.