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4 CHAPTER 1 Introduction This guidebook presents methods to measure, predict, and Which of these competing improvement projects will most report travel time, delay, and reliability using data and analytical favorably affect system congestion and/or reliability? methods within the reach of a typical transportation agency. This analysis framework allows consideration of many, though These methods and measures are useful in system plan- not all, of the multiple dimensions of surface transportation ning, corridor development, priority programming, and system performance: time of day; transit and highway modes; operations to improve transportation system performance passenger and freight vehicles; and levels of aggregation such as and to enhance the customer's experience and satisfaction facility type and system/corridor/segment perspectives. An with the system. analytical framework oriented to the planner or analyst faced The framework presents various data collection methods, with typical questions about system performance, such as iden- analysis approaches, and applications that most effectively tifying existing or future system deficiencies, spotting and support transportation planning and decision-making for reporting trends, evaluating the effectiveness of proposed or capital and operational investments and for quality-of-service completed improvements, comparing alternative courses of monitoring and evaluation. The methods can be applied in action to address a problem or need, and improving the opera- settings with different levels of complexity, including agencies tions and productivity of a fleet of vehicles such as transit buses ranging from those with continuous data collection proce- or trucks, has been developed. dures and sophisticated data processing and analysis capabil- The analysis framework and methods defined below will ities, to those with more limited resources. Data collection and allow users to develop and apply measures of travel time, processing techniques are provided that will allow calculation delay, and reliability that relate to the user's perspective, but of travel time- and delay-based performance measures in a that also are valuable to the decision makers with responsibil- variety of agency settings. ity for planning and operating transportation facilities or serv- Estimating or forecasting the reliability of a transportation ices. While performance measures of all kinds are useful in facility or system, defined here as the variability in travel time management and performance reporting by the responsible or delay, effectively requires continuous data collection agencies, travel-time-based measures are of special interest to sources. The guidebook does not provide a method for the traveling public and elected decision makers because these estimating travel-time reliability for data-poor situations. measures relate directly to the user perspective, such as: Research and analysis of available data conducted for this proj- ect concluded that agencies must have continuous surveillance How long will a trip take? capabilities, or nearly so, in order to provide useful estimates How much longer/shorter will it take if I leave earlier/later? of reliability. How large a cushion do I need to allow if I cannot afford to be late at all? 1.1 Why Measure Travel-Time Performance? Similarly, these methods can be used by system planners to provide answers to decision maker's questions, such as: State departments of transportation (DOT), metropolitan planning organizations (MPO), transit authorities, and other How much longer will a typical trip take if a particular transportation stakeholders are increasingly turning to per- trend continues? formance measures to gain and sustain public and legislative