¹Port Operations, Research and Technology Centre (PORTeC), Centre for Transport Studies, Imperial College London, London SW7 2BU, UK. E-mails: m.g.h.bell@imperial.ac.uk, kbichou@imperial.ac.uk

Abstract

The rate at which vessels are loaded and unloaded has a bearing on turnaround time and therefore on the required size of the fleet. This paper shows that the loading rate also has a bearing on schedule reliability. When schedules are unstable vessel bunching can occur, leading to less frequent services operated by bunches of vessels. This greatly affects the average inventory throughout the shipping supply chain network. It is shown that schedule stability requires the loading rate to be at least twice the rate at which containers to be loaded accumulate in the yard. Analytical expressions are derived for the arrival headways variance at the second and third ports of call. This paper extends on previous work on this topic by considering both loading and unloading of containers. Countermeasures to restore schedule stability are considered.