Simulation of alternative approaches to relieving congestion at locks in a river transportation system

We construct a discrete-event simulation model to investigate the impact of alternative decision rules and infrastructural improvements to relieve traffic congestion in a section of the Upper Mississippi River navigation system. The model covers a series of five locks that serve commercial tows with widely different barge configurations, as well as private recreational vessels. Mixes and intensities of vessel activity are highly dependent on the time of year, day of week and time of day. The model reveals that some improvement in performance (especially in peak periods) can be achieved by scheduling lock activity with priority given to vessels with shortest average processing and lock set-up times (tempered by the time that vessels have spent in queue). Greater improvement occurs with the use of helper boats and greatest improvement occurs with enlarged locks. The alternative remedies must be evaluated with consideration of their dramatically different capital costs.