Achieving Efficient Bus Scheduling using
RTS Modeling in Ptolemy
Kim, Dunam
Park, Yangbae
Lee, Jae Woong
Abstract
RTS (Regional Transport Service) in Gainesville, FL, transports many people by scheduled buses,
provided well-operated tracking service. The people, mostly students, check the tracking
website online, and get to the bus stop in time. But they are not always online to know when
the buses are coming or unexpected traffic might be able to cause some delays. Either way,
they should still wait at the bus stops. In other word, it is yet to be guaranteed that the buses
are running efficiently so that has minimum waiting time. This project is to simulate current RTS
system, and to find out how much passengers are waiting each moment. Also it suggests the
efficient bus schedule, which can reduce the waiting time. Through the bus simulation models,
the proper bus intervals are fine-tuned to reach the smallest average waiting time.
Introduction
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Motivation beyond real world problem
Simulation Modeling
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Modeling the real world activity
Flow chart, architecture of simulation
Description of actors which are mainly used
How to Work
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How to design bus system
The bus system roughly consists of two parts. The first one is implemented as a
Ptolemy model, which reads schedule of bus and people and executes simulation. The
second part is a Silverlight animation, which reads an xml file, an output of the first part,
and shows an animation of people’s and bus’s arrival and departure as time flows.
Iteration of SDF director used in this project means passed minutes after a starting
time. For example, if the initial time of this simulation is 11:01, the first iteration means
the time 11:01, and the second iteration means 11:02 and so on.
Display Average
Waiting Time,
Standard Deviation
Schedule
Text File
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Ptolemy
Model
Result
Xml File
Silverlight
Module
Animation of
Simulation
How to start simulation
The Ptolemy model consists of RTS Simulator and Performance Analyzer. RTS
simulator reads text files and simulates the bus stop model and write xml file.
Performance Analyzer calculates the average of waiting time and its standard deviation.
RTS Simulator
Performance
Analyzer
RTS Simulator
Four kinds of Python actors were implemented in this model. The first actor
BusStopEventSource reads schedule data from file and send signal of arrival of people
and bus to the next actor. The second actor BusStopActor stores waiting people in its
queue and pops people when buses come. Then, the actor sends results to Xml Writer
Python actor and WaitingTimeEventSource. The Xml Writer Python actor write xml file
for Silverlight module. And WaitingTimeEventSource sends data to normal Ptolemy
actors in order to calculate average and standard deviation. We will explain
BusStopEventSource and BusStopActor in more detail.
BusStopEventSource
This actor reads data from 4 text files bustop_x.txt. Each text file contains data for
each bus stop. This file contains data about when each passenger arrives at the bus stop and
wants to take which bus and when buses come. In an initialize event handler, the actor reads all
data from 4 files and sorts them. While each iteration, it sends corresponding time’s data to all
Busstop actors.
BusStopActor
This actor receives data from BusStopEventSource and filters data that match its
bus stop id which is an attribute of the actor. The actor pushes arriving passengers into its
queue and pops passengers when their bus comes. Pushing passengers into the queue, it sends
the arriving passengers’ data to XML Writer. Popping out passengers, it sends waiting time to
WaitingTimeEventSource for getting average and standard deviation. At the same time, it sends
coming bus’ data and departing passengers’ data to XML Writer.
Ptolemy Actors
Ptolemy actors receive data from WaitingTimeEventSource and calculate the
average of waiting time and standard deviation. Average actor is used for getting
average. And equation of standard deviation is
μ is average and Xi is value.
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How to see graphical simulation
Experiment
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Data collection
Evaluation of simulation
Conclusion
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Conclusion
Future work
Reference
Appendix
- CD/DVD