  In this paper, we show how a fixed point based boundary layer analysis can be
used to understand phases and phase transitions in asymmetric simple exclusion
processes (ASEPs) with open boundaries. In order to illustrate this method, we
choose a two-species ASEP which has interesting phase transitions not seen in
the one-species case. We also apply this method to the single species problem
where the analysis is simple but nevertheless quite insightful.
