Increasing lock throughput in an inland port through simulation–optimisation

A dual lock is considered, in which vessels enter the port from a river and leave the port for the river. Vessels enter the lock when it is open and wait until the locking operation is finished to move forward. A limited number of vessels can be placed in the lock. From a static view, the assignment of locations within the lock is an optimisation problem of the type ‘packing problem’. The decision however is not static but dynamic, as a trade-off must be made between waiting for a newly arriving vessel to enter the lock or starting the locking operation. In the former case the newly arriving vessels face a longer waiting time; in the latter case all vessels already present in the lock face the longer waiting time. The arrivals of vessels at the lock can be described as a stochastic process, both in time as in size of the vessels. Input to the dynamic packing problem is generated by means of a real-life existing simulation model for vessel traffic on the river Scheldt in Belgium.