Optimization Of Ro-Ro Liner Schedule:A Perspective Of Port Service Time Uncertainty

In recent years,vehicle throughputs at major Ro-Ro terminals in China shows continuous growth,from 3.2 million in 2015 to more than 5.5 million in 2018,with an average annual growth rate of 19.0%.Ro-Ro transport accounts for an increasing proportion in the liner shipping market.Although Ro-Ro transportation is booming,the service itself is not very reliable.In practice,the delay caused by the uncertainty of service time in port will lead to congestion quite often,and in consequence unreliable sailing schedule.This paper aims to optimize the shipping schedule of a Ro-Ro single sailing voyage by considering its operational characteristics,including short service time in port.In so doing,assuming the order of port calls is already known,a mixed integer nonlinear programming model with the consideration of uncertain time in port is constructed by taking into account of the fixed operating cost,fuel cost and delay penalty cost of a single voyage.For ensuring the effectiveness of the developed model,an empirical application is carried out with the practical data obtained from an example Ro-Ro shipping company.Python programming utilized as the tool to obtain the optimized results,and the optimization results and the actual results are analyzed.The results show that the optimization results can satisfy the requirements of the optimization effect and the stability of the schedule.By implementing a large number of numerical experiments,the relative standard deviations of 10 groups are all lower than 6.0%,which indicates that the model has a strong stability.In addition,two sets of examples are added to analyze with the impact of port service time uncertainty at three different port size scales.It can be found that the solution efficiency is still high even for different port size scales.The results show that under the conditions of different port sizes,the Ro-Ro ships choose to shorten the time in port,increase the slack time during the voyage,and reduce the total cost of the Ro-Ro ships as much as possible on the premise of ensuring the departure rate.In addition,more buffer time can be added to the shorter sailing period to improve the reliability of sailing schedule.This research offers not only an effective method in optimizing the Ro-Ro sailing schedule,but also a great potential in practical applications.