Tracer diffusion of methane molecules in the unidirectional channels of AlPO4-5 has been studied by means of molecular dynamics simulations. A one-dimensional hop-and-cross model is introduced and is shown to be able to reproduce the molecular dynamics results accurately and we profit by extensive speedup in computational time. After elimination of system size effects by using the new model, two regimes can be recognized: a short-time regime where the mean square displacement is proportional to t(0.6), and a long-time regime where the proportionality is linear.