Mean radial drift velocity of the dust particles depending on the radius of the particles at r = 5au. This is compared to expected drift velocity for pressure supported discs as given by Eq. (11). Shown are isothermal disc simulation with resolution 1024 × 256 × 64 from 1000 to 2000 yr. Different colours and symbols are used for inward and outward drift. We estimate the error from the radial diffusion coefficient.