rithms. The general idea is to incorporate all ships within an n-hour horizon into the choice of a moor- ing point for an incoming ship. Given the fact that for some ship types waiting is more expensive than for others (e.g., dependent on the type of cargo, the ship’s capacity or crew size), adequate priority rules might reduce total costs induced by waiting for available mooring points. Also an enumeration algorithm may be applied to select the optimal allocation schedule of all possible schedules within the look-ahead time window. In general, this is a time-consuming approach. In this paper we use the ATA information gained from the pre-arrival notices to implement a simple priority scheme with two priority classes (high and low), in which long ships get high priority, and short ones get low priority. The time horizon is 36 hours, i.e., the pre-arrival notice is received 36 hours before the ship's ATA. The priority scheme makes reservations for the high-priority ships based on their ATA. The assignment of a ship to a mooring point can be done as follows. A high-priority ship entering the port is in principle assigned to a free mooring point that suits its cargo type and length. If all suitable mooring points are occupied, the ship is placed in a queue before the mooring point with the smallest workload. For low-priority ships, the situation is similar, apart from an additional condition. To explain this, let s be a low-priority ship, let t be the current time, let Wi(t) be the workload of mooring point i at time t, and let Di(s) be the time that ship s needs if serviced at mooring point i. Then mooring point i is considered reserved if a high-priority ship arriving within a 36-hour horizon will need mooring point i between t and t + Wi(t) + Di(s). If this is the case, s is not assigned to i, or enqueued before i. Note, that the shorter mooring points at the jetty are never reserved by high-priority ships, since all high-priority ships are too long for these mooring points. Hence, a low-priority ship will always either be assigned to a mooring point directly or placed in a queue before one. In the presentation of the results in section 6, we will make a distinction between model outcomes with and without priority-based mooring point allocation, so that the impact of incorporating such al- location is clearly visible. We will also consider an enumeration algorithm to find the optimal alloca- tion schedule within a 36 hour window.
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rithms. The general idea is to incorporate all ships within an n-hour horizon into the choice of a moor- ing point for an incoming ship. Given the fact that for some ship types waiting is more expensive than for others (e.g., dependent on the type of cargo, the ship’s capacity or crew size), adequate priority rules might reduce total costs induced by waiting for available mooring points. Also an enumeration algorithm may be applied to select the optimal allocation schedule of all possible schedules within the look-ahead time window. In general, this is a time-consuming approach. In this paper we use the ATA information gained from the pre-arrival notices to implement a simple priority scheme with two priority classes (high and low), in which long ships get high priority, and short ones get low priority. The time horizon is 36 hours, i.e., the pre-arrival notice is received 36 hours before the ship's ATA. The priority scheme makes reservations for the high-priority ships based on their ATA. The assignment of a ship to a mooring point can be done as follows. A high-priority ship entering the port is in principle assigned to a free mooring point that suits its cargo type and length. If all suitable mooring points are occupied, the ship is placed in a queue before the mooring point with the smallest workload. For low-priority ships, the situation is similar, apart from an additional condition. To explain this, let s be a low-priority ship, let t be the current time, let Wi(t) be the workload of mooring point i at time t, and let Di(s) be the time that ship s needs if serviced at mooring point i. Then mooring point i is considered reserved if a high-priority ship arriving within a 36-hour horizon will need mooring point i between t and t + Wi(t) + Di(s). If this is the case, s is not assigned to i, or enqueued before i. Note, that the shorter mooring points at the jetty are never reserved by high-priority ships, since all high-priority ships are too long for these mooring points. Hence, a low-priority ship will always either be assigned to a mooring point directly or placed in a queue before one. In the presentation of the results in section 6, we will make a distinction between model outcomes with and without priority-based mooring point allocation, so that the impact of incorporating such al- location is clearly visible. We will also consider an enumeration algorithm to find the optimal alloca- tion schedule within a 36 hour window. 5
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