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The suburban railway
system on which Mumbai is heavily dependent, has been rightly
called ‘the lifeline of the city’. Railway operations present a
huge range of problems to work on. For over six years, our group*
at IIT Bombay has been working on various aspects of suburban
railway operations management. The areas of study include Capacity
Studies and Planning, Timetable Construction, and Rake Management.
Line Capacity Simulator
To represent the
operational features of trains in selected sections, we have
developed a simulator for the Indian Railways Institute of Signal
Engineering and Telecommunications. The simulator can help
estimate the capacity of long-distance track segments on the
railway network under complex traffic conditions. It is also
useful in changing time-tables, analyzing the effect of adding
scheduled trains in a section, evaluating investment at a local
level (such as additional loop lines and platforms), and studying
the effects of signal failures and train delays. Essentially the programme uses priority-based scheduling of trains along with the
operating constraints of track occupancies and platform
availability.
The simulator allows
realistic analyses by reproduction of the operational logic of
railway movement, and related engineering details. It also records
train speeds that depend on track signal conditions, which in turn
depend on the status of several trains ahead of the signal. The
simulator can display train movements on a distance vs. time graph
with details of individual trains.
Presently,
experiments are being carried out in the suburban section of the
Mumbai division of Central Railways, and in the mixed traffic
conditions on the Virar-Dahanu Road section of the Mumbai division
of Western Railways. The former study is aimed at spacing signals
for achieving a desired frequency of train service, while the
latter study allows preparation of temporary timetables in the
event of major maintenance work, which usually imposes
restrictions on train movement and speed.
Timetabling for Suburban Railway
Operations
Preparing suburban
railway timetables is a highly skilled and complex task entailing
months of data collection and analysis before finalization. Inputs
from numerous quarters such as: commercial, operations, safety,
signalling, track, civil and electrical departments are essential
pre-requisites.
We have designed a
semi-automated support for a variety of planning decisions
involved in the preparation of such timetables. Already
implemented in the Western Railway division of Mumbai, the
simplest one is for visualization and monitoring of current
timetables and platform occupancies with facilities for enabling
gradual changes as needed. Currently, we are developing a tool
that will allow a high degree of automation in timetable
generation.
Rake Management System (RMS)
The Rake Management
System (RMS) is a set of utilities and tools designed for analysis
and decision-making on the overall use of rakes vis-a-vis their
deployment, operation, and maintenance cycles for suburban train
services. Additionally, it provides occupancy profiles of trains
at terminals, platforms, and sidings. Thus, it is also useful in
operations planning, time-tabling, maintenance plans and crew
scheduling. The RMS consists of the Rake Linker and
Post-Processor.
Rake Linker:
The Rake Linker allocates rakes to services so that the
number of rakes used to run all services, and the total distance
run by all the rakes is optimal. In technical terms, the approach
involves a minimum-cost flow network flow optimization. Further,
it models the various linkage possibilities (including empty rake
movements, and movements to and from car-sheds and terminals),
assigns costs to them, and picks the ‘best’ overall set of
linkages.
Post-Processor: The Post-Processor
summarizes information about ‘stabling line’ and car-shed
movements in accordance with the availability of stabling lines,
and optimizes the total distance run by the rake in these
activities. For example, if there is more than one car-shed, and
if the rake can be moved to any of them, then these movements are
optimized. It also generates the occupancies of the rakes at every
station and track. The RMS also provides for extensions in the
areas of rostering, i.e. the assignment of actual rakes to a
starting service each day, so that the overall balance of rakes at
various car sheds is satisfied. Finally, a higher level analysis
which examines the possibilities of savings by small changes in
operating parameters, can also be done. The RMS therefore provides
a comprehensive set of tools for optimal rake operation and
maintenance.
The techniques used
in our work on railway operations planning are applicable to
several other areas such as: fleet management, vehicle scheduling,
personnel scheduling, distribution management and so on.
Obviously, each of these problems need customized approaches. IITB
currently has research programs in these areas as well.
*Faculty members involved in this
effort are Narayan Rangaraj (Industrial Engg. and Operations
Research,
narayan@me.iitb.ac.in), Milind Sohoni (Computer Science and
Engg.,
sohoni@cse.iitb.ac.in, Abhiram Ranade (Computer Science and
Engg.,
ranade@cse.iitb.ac.in), K M Moudgalya(Chemical Engg.,
kannan@che.iitb.ac.in)
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