A LESS-FLEXIBILITY-FIRST HEURISTIC FOR THE PLACEMENT OF INLAND VESSELS IN A LOCK
Gerrit K. Janssens and Carlo Theunissen,
Operations Management and Logistics,
Limburgs Universitair Centrum (LUC),
Universitaire Campus – Building D,
B-3590 Diepenbeek, Belgium
e-mail: gerrit.janssens@luc.ac.be,
ABSTRACT: Inland vessels move goods along canals and rivers and they visit ports. Due to tides on the rivers, the vessels make use of locks to enter ports or canals. From a port management point of view, a fast access to and from the port and high utilisation of a lock are important objectives. The former relates to low waiting times inbound and outbound the port. The latter relates to a placement of as much vessels as possible in the lock before operating the lock. The use of this objective is inspired by energy savings.
The case study relates to the Van Cauwelaert-lock in the port of Antwerp, Belgium. The policy to access the lock works as follows. Vessels wait in front of the lock. A port administrator assigns a place in the lock based on the knowledge of the vessels’ dimensions. As such, there is no FIFO-discipline, but a ‘group-FIFO’-discipline, i.e. if n vessels are allowed to the lock, they are the first n vessels in the arrival queue.
A heuristic algorithm is formulated for the placement of vessels in the lock. This algorithm supports the decision where to place the vessel in the lock, aiming to place as much as possible vessels from the arrival queue. Simultaneously, it supports the decision to start a locking operation or not, based on information about vehicles, which are announced but not yet arrived at the lock’s entrance. The heuristic is called a ‘less-flexibility-first’-heuristic as it looks for pseudo-placements, showing which flexibility is left for the remaining vessels after placing a vessel. The paper describes the implementation of the heuristic and shows numerical examples. A comparison is made between the heuristic results and the
daily practice, based on real-life vessel movements as registered in the year 2002.
KEYWORDS: Simulation-optimisation, packing problem, lock management
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