The two ships in this study spent an average of 17.0 h (Ship A) and 30.5 h (Ship B) of their total time in port waiting for various activities to start. Relative to these times, four hours of reduced waiting time seems moderate. However, in practice, harnessing a larger share of the total potential might be fraught with some difficulty. The constant repositioning of vessels and the risk of late arrival to port have led to a situation where it is difficult to optimise the speed of a particular ship. The short planning horizon implies that the vessels often arrive at port when it is closed instead of traveling at the most energyefficient speed. The increased share of spot contracts in the last few years has reduced the planning possibilities further. As shown in Section 4.1.3, a senior manager did not agree that a more just-in-time arrival was always worth striving for due to the risk of losing future commercial opportunities.