Addendum to Final Report, Optimizing Traffic Counting Procedures

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.

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