Examination of Methods That Adjust Observed Traffic Volumes on a Network

Abstract

As the models of transportation planning and engineering become more and more sophisticated, the quality of data that is used as input to the models is of critical importance to the integrity of the analysis. Several methods that adjust the field-traffic-volume data so that they become consistent and useful information for the subsequent analysis steps are examined. Consistency as satisfaction of flow conservation and other relationships underlying the network flow in question are defined. Six methods, including the manual method, are presented, and the logic and computational process are explained for each method. Except for the manual method, the methods are grouped into two general categories and discussed—one considers inconsistency in the data as a result of the statistical error and uses the classical-regression approach, and the other considers the observed value as the approximate value and uses the fuzzy-set theory. These methods are compared for their performance using an example problem. Transportation analysts’ alternative methods for volume adjustment are provided, and the analysts’ theoretical and practical implications are explained.