Addendum to Final Report, Optimizing Traffic Counting Procedures

Report No: 87-R21

Published in 1987

About the report:

The methodology described in entry 55-14 was used with 1980 data for 16 continuous count stations to determine periods that were stable throughout the year for different short counts. It was found that stable periods for short counts occurred mainly on Mondays, Tuesdays, and Wednesdays, and expansion factors were then developed for short counts of different durations and different starting times for these days. The expansion factors were then used to estimate 1981 AADT's from short counts extracted from data obtained in 1981 continuous counts. The results indicated that relative errors of less than 10% were obtained for AADT's estimated from counts of 6-, 8-, 10-, and 12-hour durations on Mondays, Tuesdays, and Wednesdays. As described in entry 55-15, the overall study entailed breaking down all highways in the primary system into homogeneous links such that the traffic characteristics along any given link were constant. The links in each district were then grouped into clusters such that the links within a given cluster had similar traffic volume characteristics. A counting procedure was then developed based on an accuracy level of ± 10% with 95% confidence. Counting stations were then randomly selected. Entry 55-17 revised some of the data in the final report.

Disclaimer Statement:The contents of this report reflect the views of the author(s), who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Virginia Department of Transportation, the Commonwealth Transportation Board, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Any inclusion of manufacturer names, trade names, or trademarks is for identification purposes only and is not to be considered an endorsement.


  • Sarath Joshua, Nicholas J. Garber, Ph.D.

Last updated: December 30, 2023

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