The study of beam transport is of central importance to the design and
performance assessment of modern particle accelerators. In this paper, we
benchmark two contemporary codes, DIMAD and BDSIM, the latter being a
relatively new tracking code built within the framework of GEANT4. We consider
both the 20 mrad and 2 mrad extraction lines of the 500 GeV International
Linear Collider (ILC) and we perform particle tracking studies of heavily
disrupted post-collision electron beams. We find that the two codes give an
almost equivalent description of the beam transport
