Several interesting algorithms have been proposed for the
Rail and Intermodal problem space and this article continues the enumeration of
those that were discussed earlier.
The real-time rail management of a terminus involves routing
incoming trains through the station and scheduling their departures with the
objective of optimizing punctuality and regularity of train service. The
purpose is to develop an automated train traffic control system. The scheduling
problem is modeled as a bicriteria job shop scheduling problem with additional
constraints. The two objective functions in lexicographical order are the
minimization of tardiness/earliness and the headway optimization. The problem is solved in two steps. A heuristic builds a feasible solution by
considering the first objective function. Then the regularity is optimized.
This works well for simulations of a terminus.
A simulation-based approach is also used for tactical
locomotive fleet sizing. Their study shows the throughput increases with the
number of locomotives up to a certain level. After that the congestion is
caused by the movements of many locomotives in a capacity constrained rail
network.
One correlation that seems to hold true is that the
decisions on sizing a rail car fleet has a tremendous influence on utilizing
that fleet. The optimum use of empty rail cars for demand response is one of
the advantages to building a formulation and solving it to optimize the fleet
size and freight car allocation under uncertainty demands.
This correlation has given rise to a model that formulates
and solves for the optimum fleet size and freight car allocation. This model
also provides rail network information such as yard capacity, unmet demands,
and number of loaded and empty railcars at any given time and location. It is
helpful to managers or decision makers of any train company for planning and
management activities. A two-stage solution procedure for solving rail-car
fleet.
Drayage operations are specific to rail. Intermodal
transportation improves when these operations are considered. In the cities or
urban areas, drayage suffers from random transit times. This makes fleet
scheduling difficult. A dynamic optimization model could use real-time
knowledge of the fleet’s position, permanently enabling the planner to
reallocate tasks as the problem conditions change. Tasks can be flexible or
well-defined. One application of this model was tried out on test data and then
applied to a set of random drayage problems of varying sizes and
characteristics.
Tactical design of scheduled service networks for
transportation systems is one where different network coordinate and their coordination
is critical to the success of the operations. For a given demand, a new model
was proposed to determine departure times of the service such that the
throughput time is minimized. This is the time that involves processing,
inspection, move and queue times during demand. It could be considered a hybrid
of some models discussed earlier such as the service network design that
involves asset management and multiple fleet co-ordination to emphasize the
explicit modeling of different vehicle fleets. Synchronization of collaborative
networks and removal of border crossing operations have a significant impact on
the throughput time for the freight.
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