Traffic volume summary statistics are foundational to the transportation profession. An historical perspective to estimation and evaluation of annual traffic volume statistics in the united states is provided. During the 1930s there were extensive manual count activities. In the 1940s the transition to mechanical measurement of traffic changed the approach to data integrity. In the 1950s and 1960s dominant personalities gave theoretical direction to calculating annualtraffic summary statistics. The procedures developed during this period were at times questionable but became the unchallenged basis for traffic reports over the next three decades. At the end of the 1980s earlier traffic data assumptions began to be challenged. Among the historical assumptions and procedures being reexamined are the normal distribution of traffic, traffic variability, and data imputation and smoothing. In part it was awareness of problems in historical traffic volume procedures that influenced the development of national traffic monitoring standards. The history of traffic volume summary statistics provides a helpful lesson in designing the future of traffic monitoring. This paper appears in transportation research record no. 1305, Finance, planning, programming, economic analysis, and land development 1991.
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