Standardized traffic volume data provide a basis for preliminaryexamination of the underlying distribution of the data. In this study, traffic volume data from permanently installed devices were examined on a daily basis throughout (federal) fiscal year 1989. The examination included computer-based edits and analyst data review. If the edited data were accepted, the data were stored in a computer file for later use. Missing or incomplete days of data were not included. Data were not adjusted on the basis of professional judgment. Thereviewed and accepted data were maintained in a file specifically designed to prohibit intentional or unintentional operator modification of the measurements. These steps were taken to help ensure base data integrity. At the end of the year, all accepted data were analyzed using statistical analysis system software. The traffic volume data from the permanent sites indicate that traffic on many roads is not normally distributed and that site-specific traffic data collected over the period of 1 year may be more variable than previously estimated. This paper appears in transportation research record no. 1305, Finance, planning, programming, economic analysis, and land development 1991.
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