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Embargoed until 2016-07-31
Copyright: Islam, Md Kamrul
Embargoed until 2016-07-31
Copyright: Islam, Md Kamrul
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Abstract
This thesis investigates stochastic factors influencing reliability of public transit (particularly bus
transit) and examines performance indicators using probabilistic considerations such as the effect
of randomness in passenger arrival, boarding, alighting and vehicle travel time on the regularity
of headway along the route with multiple stops. The primary objective of this research is to
develop an analytical modeling framework to evaluate transit service performance under
stochastic environment.
This research lays out an approach to study stochastic effects of public transit operation based on
results from theory of bulk queues. Stochastic flows over the system are characterized by the
flow of passengers, with particular interest on the headway distribution of vehicles. Waiting
passenger line at stops are described as individual queues and the theory of bulk queues are
applied to find statistics of performance measures over a particular segment of a route. Three
types of passenger waiting behavior have been taken into account to develop formulations. These
passenger behavior are: (a) passengers wait for the first bus after they joined the queue and
abandon the system if unable to board the bus, (b) passengers wait at transit stop until they are
served and (c) passengers are unwilling to wait for bus if they do not receive service within their
expected limit of waiting time budget. Based on passenger waiting behavior, polynomial
equations and probability generating function of probability vectors of waiting passengers are
derived along with moments of queue length for random outbound capacity of vehicles.
Moreover, mean and variance of headway and occupancy, covariance of occupancy and headway
for a given capacity of vehicles are derived. New performance measures are proposed.
A single route consists of two terminals with multiple intermediate stops are considered for the
analytical modelling purpose. Empty buses of same size begine to serve passengers from the first
stop to the last stop allowing passenger boarding and alighting in intermediate stops in one
direction. Step by step procedure for implementation of analytical model as a computer program
is described. Application of the models is illustrated with number of numerical examples offering
insights into factors that affect reliability of bus transit systems. The inputs of models are
passenger boarding and alighting demand at stops, marginal boarding and alighting time of
passengers, mean and variance of travel time between stops, mean headway and vehicle size.
The models produce a range of outputs that are interest of transit operations such as mean,
variances and covariance of headway and occupancy, distribution of passenger load on bus,
mean of number of waiting passengers, delay of passenger leftover and abandoned passengers at
stops and utilization of transit routes. The developed modelling framework can be applied, in
general, for various transit operating strategies in a cheaper and convenient means over
simulations. More particularly, the computer application programs based on the analytical model
constitute a research tool that would assist to accomplish planning and analyzing tasks within
public transit domain with detailed analysis at stop and route level.
The analytical modeling framework, in its mathematical study of dynamics of bus route
operations is a significant contribution to the states of the art. This investigation provides a
better understanding of determinants of reliability of public transit systems and the model can be
used as an analysis tool by transit planners to evaluate effectiveness of various policies.