Support of the speed decision in liner operation by evaluating the trade-off between bunker fuel consumption and reliability

In liner container shipping, the optimization of bunker fuel costs and reliability can theoretically be achieved by steaming the distance in the available time at average, constant speed. However, in reality bunker fuel costs and reliability are mutually contradictory objectives. Due to incidents (e.g. technical problems on board of vessels, bad weather conditions, piracy) speed ups are necessary to arrive on schedule or at least to mitigate the delay. In this paper, a new approach to liner speed management is proposed. In order to manage the trade-off between bunker fuel consumption and reliability of services, a preventive buffer structure is built up to secure the schedule against delays. However, any analytical calculation of the structure and its effects can only be achieved with disproportionate effort. Therefore, a “discrete event simulation” is applied. Although a heuristic attempt does not provide the exact solution, reasonable and wide-ranged solutions are offered. Different decision alternatives are outlined, structured and tested to find appropriate speed profiles. For the evaluation of speed profiles three measures of reliability and deviation ($\alpha$-reliability: ratio of punctual vessels [in%], $\beta$-deviation: average positive deviation from the schedule [in hours], $\gamma$-deviation: average negative deviation [in hours]) and costs are illuminated.