ITS Berkeley

This paper and its companion present a study of railroad classification yard strategies that allow for blocks of destinations to be assigned to classification tracks in different ways, depending on the time of day, week or month. With the same number of tracks, more classifications can be handled by this method. The paper examines homogeneous traffic; that is, traffic patterns where all blocks have the same amount of traffic, where cars for all blocks depart equally frequently from the yard and where the overall traffic flow does not change with time. The results represent the beginning of...

This paper examines crane scheduling for ports. It starts with a simple static case and uses it as a building block to develop a better understanding of the dynamic problem with berth length limitations. The paper assumes that ships are divided into holds and that (usually) only one crane can work on a hold at a time. Cranes can be moved freely from hold to hold, and ships cannot depart until all their holds have been handled. In the most general case, ships arrive at different times and must queue for berthing space if the berths are full. The objective is to turn around (serve) all the...

This paper studies single server queueing systems where customers arrive according to a schedule, but not punctually, and where service might be provided in the scheduled order; thus, customers may leave the system in a sequence different to that of their arrivals. The situation arises in connection with maritime container terminals. The steady state solution to the problem follows an integral equation that may be solved numerically. When congestion is light (as is usual in well managed ports) approximate analytic solutions to the integral equation can be found. As an illustration,...

This paper shows how idealized models can be used to obtain cost-effective, implementable solutions to large and complex logistics problems. It advocates the use of fine tuning software to translate the guidelines produced by idealized models into specific feasible solutions. The “traveling salesman” (TSP) and “vehicle routing” (VRP) problems were used to test the approach. For sufficiently large problems the proposed procedure leads to solutions that improve on those produced by either idealized models or numerical methods alone. Simulated annealing (SA) was chosen for fine tuning. This...