Several interesting algorithms have been proposed for the
Rail and Intermodal problem space. This is a complex system composed by
different transport networks, infrastructures, different transport means and
operators, such as dryage operators, terminal operators, network operators and
others. Intermodal means there are lots of decision makers who must work in a
coordinated manner for the system to run smoothly. If intermodal transport is
to be developed, it will require more decision-making support tools to assist
the decision-makers and stakeholders.
When train operations are perturbed, a new conflict free
timetable must be recomputed such that the deviation from the original must be
minimized. This scheduling problem is modeled with an alternative graph
formulation and a branch and bound algorithm is developed. Some approaches use
an integrated framework which deals with signal layout optimization, train
scheduling optimization at microscopic level, and others.
Heuristic approaches include a look-ahead greedy heuristic
and a global neighborhood search algorithm, in terms of railway total train
delay. Scheduling additional train services to be integrated into the current
timetables is a problem that is modeled as a hybrid job shop scheduling
techniques that operate upon a disjunctive graph model of trains.
One approach develops a train slot selection model based on
multicommodity network flow concepts for determining freight train timetables.
This helps to schedule rail services along multiple interconnected routes. This
model seeks to minimize operating costs incurred by the carriers and delays
incurred by the shippers. The schedules and demand levels are ensured to be
mutually consistent. When the model is embedded in a simulation, it can be used
iteratively and together with the output of the scheduling solution.
Another approach solves the freight transportation on hybrid
rail networks used to transport both passengers and freight. It uses a
preferred timetable as input for each freight train. Some overrides are
permitted such as specifying a path different from the one in the ideal
timetable. Its objective is to introduce as many new freight trains as possible
by assigning them timetables that are as close as possible to the ideal ones.
An integer linear programming method is used in the model.
A third approach specifically considers the double-track
train scheduling. It focuses on the high-speed passenger rail line in an
existing network and minimizes both the expected wait times for high-speed
trains and the total travel times of both speed trains. Using the priority for
speed, the problem is translated as multi-mode resource project. It is then
solved for scheduling with a branch and bound algorithm and a beam search
algorithm.
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