The wide usage of traffic data item Annual Average Daily Traffic (AADT) places a significant emphasis on providing the best possible value whenever AADT’s are reported. Federal, State, MPO’s, and local agencies rely on AADT values as a fundamental traffic data value for a very wide variety of programs and projects. In practice, agencies use both long term continuous count and short term portable count programs to estimate AADT.

1: To gain a quantitative understanding on how various short term traffic count durations affect and relate to estimated AADT as compared with long term continuous counting program estimations. The ultimate goal is to enable the FHWA to provide the most feasible and technically sound guidance to States and other agencies on this issue. 2: To gain a quantitative understanding on how missing data from long term traffic monitoring data affects the AADT estimation and establish the critical threshold in terms of data usability. In other words, how much data can be missing and what type of data patterns missing can be tolerated in AADT estimation without any special consideration such these steps used in converting short term counts to AADT. 3: To gain a quantitative understanding on traffic monitoring methods from a given segment on an annual basis with a 24 hour traffic count program (counted on a frequency of every year) vs. monitoring the same segment on a once every three year (with every 2nd and 3rd year factored to bring them to current year) basis but with a minimum 48 or 72 hour hour count and how these three different methods can effect AADT data on an annual basis.

Task 1 – Determine the various AADT method accuracies and factoring method accuracies used from permanent long term counters. Use knowledge of various States and local agency specific methods to document what they are doing and any known differences in the methods to calculate AADT values and how they are used in various applications. This task will utilize about 400 random permanent site data provided by FHWA. This task will determine the accuracy of methods commonly used by States, MPO’s and local agencies to obtain AADT values from their permanent traffic data counting sites. Two common methods (straight average of days and the AASHTO method) will be studied along with up to 2 other methods if some are found to be utilized through investigative research. Utilizing these methods, an analysis of the number of days for each month of the year and how using only 7 (every DOW covered), 8-13, 14, 15-20, 21, 22-27, 28 lead to more or less accurate AADT values. This analysis will be done for all roadway types (14 - 7 rural and 7 urban) and at least 25 States. The most reliable and accurate AADT method will be used for the ground truth values in all later tasks. Using this same permanent count data a year-to-year factoring method will also be analyzed that will determine the end-of-year factoring variability. Other factors from permanent site data will also be studied such as the rolling 12 month MOY factor, other MOY factoring, DOW factoring and HOD factoring. The combined MOY, DOW and HOD into one factor will also be studied to see how its accuracy compares to other factoring methods. Finally up to two additional other methods as may have been discovered thru investigative research (contractor knowledge) may also be added to this factoring list. The 400 counter data selection shall cover various geographic areas, roadway functional classes and area types. This key data must be representative of various growth patterns. Task 2 – Determine Portable Counting Duration Variability. Utilizing permanent traffic data from all functionally classified roadways covering all area types for at least 25 States, study the variability of having partial days, 1 day, 2, day, 3 day or 7 day data in AADT estimations. Additionally, the variance by frequency count will be studied by DOW of which it was taken. This is expected to be done using each HOD and DOW with each one of the count durations to fully demonstrate statistically what HOD and DOW combination would yield the best results. Again, data from about 400 permanent traffic counting sites will be supplied by FHWA for this task. This is to document how various short term count based AADT varies statistically as compared with AADT obtained from permanent continuous monitoring data. In other words, this is to determine whether there are any statistical difference among AADTs obtained through various short term count data and the permanent count data. Task 3: Determine the Impacts of Monitoring Method on AADT Data Quality. This task is to evaluate the AADT data accuracy superiority between three different potential counting methods: 1) a 24 hour monitoring program done every year, 2) a 48 hour monitoring program on a every three year counting cycle. With the every three year counting method, AADT data for two of the three years will be factored, modeled and/or estimated and 3) a 72 hour monitoring program on a every three year counting cycle. With the every three year counting method, AADT data for two of the three years will be factored, modeled and/or estimated. Task 4 - study the influence of various duration and frequency factoring methods when utilizing the TMG ADT to AADT process. Included in this research will be year over year factoring for 1, 2, 3 and 6 years. Task 6 - to study influence of special events and holiday travel on AADT estimates.

1 or 2 year commitments are acceptable, study anticipated start date, first quarter of 2014 Each State commitment is expected at $12,000. Polled Fund TPF-5292) is now completed and final reports have been posted to this pooled fund.