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The general purpose of this thesis is to investigate strategies that can be used in order to improve service reliability in urban transit systems. Initially, a very simple model is used to compute the probability of bunching of buses on a route. This result is then used to prove that adding a very large number of buses on an existing line does not necessarily significantly improve the level of service (Chapter II). The second major part of the thesis deals with the problem of control on a bus route. A specific strategy is first selected based on selective holding of buses at a point on a route. A method using elementary calculus to find the best point on the line at which to control is then described (Chapter III). Finally, a practical study is performed on the Harvard-Dudley bus route running between Cambridge and Boston. Using the model developed in Chapter II we prove that the headway standard deviation cannot be more than fifty percent above the mean headway, as is suggested by the data collected. Then we try to show how an operator can use the theoretical results developed previously to improve the service (Chapter IV). THESIS SUPERVISOR: TITLE