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3 TECHNICAL APPROACH An extensive literature search and document review was conducted on the current state of the practice related to spare bus fleet ratios and optimal bus fleet sizing. Documents were obtained both through the web (by means of TRIS and other Internet search engines) and, for out-of-print publications, from the TRB archives. The survey of selected transit agencies was designed spe- cifically for this synthesis; and representatives from four case example agencies were interviewed for more in-depth infor- mation and insights. ORGANIZATION OF THIS REPORT Following this introductory chapter, chapter two summarizes the findings of the literature review. Chapter three discusses the survey methodology and results, and chapter four contains summaries of the four case examples. Chapter five reports the synthesis conclusions, including challenges and promising practices, and suggestions for further research; and is followed by references and a bibliography of additional resources. Appendix A contains a copy of the on-line question- naire; Appendix B provides a list of all transit agencies that participated in the survey; and Appendix C contains a pro- posed research problem statement for consideration by the TCRP as a project to further develop applicable resources for transit agency practitioners. Appendix D, available web- only, includes a compilation of individual agency survey responses. Appendix D can be accessed through the follow- ing URL: www.trb.org, search on TCRP Synthesis 109. Since 1995, when TCRP Synthesis 11: System-Specific Spare Bus Ratios was published, significant changes have occurred in the transit industry. Not only have almost all transit agencies replaced their fleets, but new bus con- figurations and alternative propulsion systems have been widely deployed. At the same time, transit vehicles have become more challenging to maintain and operate, owing to the introduction of such features as electronic fare boxes, global positioning tracking systems (GPS), automated stop announcements, and on-board surveillance systems. Anec- dotal information suggests that the increased complexity of transit vehicles and the environmental challenges under which they operate may have resulted in an increased need for spare vehicles, with a corresponding increase in spare bus vehicle ratios. PROJECT OBJECTIVES The purpose of this synthesis is to update the findings of TCRP Synthesis 11 on how various factors affect optimal fleet size. It includes, but is not limited to, the following: ⢠Definitions of spare ratio and transit agency accommo- dations of specific local service factors; ⢠An update of key variables affecting spare ratios today and changes over time; ⢠Documentation of agenciesâ maintenance approaches, programs, out-of-service criteria, practices, and chal- lenges related to maintaining spare ratios; ⢠The influence of service and operating environments on spare ratios; and ⢠Innovative approaches to managing spare ratios. chapter one INTRODUCTION
