23-06U

We consider a stochastic lattice model of one-dimensional transport with asymmetric hops to neighbouring sites which admits at most two particles per site. We analyse steady states for periodic and open boundary conditions in the mean-field approximation and we compare our results with Monte Carlo computer simulations. The phase diagram is found to consist of three regions, namely, phases of high density, low density, and maximal current. We also analyse the rarefaction and shock density-profile waves which develop in the infinite chain on large distance and time scales.