Galactic height Z_abs versus the peculiar transverse velocity of the OB runaways in Vel OB1. Open triangles refer to candidate runaways (see Table A.2). It shows the expected trend that the fastest runaways reach the largest distance from the Galactic plane. Ten of the OB runaways with an observed bow shock are within 60 pc from the Galactic plane where most of the gas and dust is present. Vela X-1 is at a height of 134 pc and still produces a prominent wind bow shock.