  We introduce a model for active transport on inhomogeneous networks embedded
in a diffusive environment and investigate the formation of particle clusters.
In the presence of a hard-core interaction, cluster sizes exhibit an
algebraically decaying distribution in a large parameter regime, indicating the
existence of clusters on all scales. The results are compared with a diffusion
limited aggregation model and active transport on a regular network. For both
models we observe aggregation of particles to clusters which are characterized
by a finite size-scale if the relevant time-scales and particle densities are
considered.
