What tables, charts, or graphics will be used to communicate reliability?
The basis for all of the reliability measures is route or point-to-point travel times. There are four basic ways in which these travel times can be developed: • Directly calculated from continuous probe vehicle data; • Estimated from continuous point-based detector data; • Collected in periodic special studies (e.g., floating car runs); and, • Estimated using computer simulation, sketch planning, or demand forecasting models. The selection of data collection techniques will be based largely on the intended use(s) of the reliability measure, program scope, and available resources. It is possible that more than one of these data collection techniques could be used to obtain travel time data. Discretion should be used when directly comparing travel times from different methods, as each method may have unique but consistent internal biases. Consider, for example, that travel times along a particular route have been collected for three years using periodic special studies. The deployment of
