Alternatives for Estimating Seasonal Factors on Rural and Urban Roads in Florida
Seasonal Factor (SF) plays a key role in estimating traffic volumes since this factor is used in calculating not only Average Annual Daily Traffic (AADT) but also PSCF and MOCF. Currently, SFs are calculated for each week of the year at each continuous count station (known as TTMS) where the true AADT information is available. The SF categories are determined based on similarities in traffic characteristics of roads using data collected from the TTMSs. There are 178 SF categories based on the 1999 traffic data. The weekly SFs for a specific category are obtained by calculating the arithmetic averages of the factors from the TTMSs in the same group during the same period of time. FDOT districts then assign a seasonal factor category to each short-term traffic count site according to the site’s geographical location, assuming that seasonal variability and traffic characteristics at the short-term and permanent count sites are similar.
An underlying characteristic of the TTMS grouping process is that the more groups there are, the more likely it is to obtain more accurate seasonal factors, which means greater data collection and processing efforts. Additionally, TTMSs are currently grouped into categories according to subjective criteria, and only the geographic location of a short-term count site is considered when a SF category is assigned. This research is aimed at investigating and evaluating the traffic patterns and roadway classifications obtained from the current and alternative approaches for seasonal factor estimation. The goal is to develop an improved approach that is less data intensive and provides better SF estimates for obtaining AADT from short-term traffic counts.