2010-2019 Regional Traffic Counts
The above document shows a ten-year history of traffic counts in our region organized by station numbers for each county. The data, collected by the S.C. Department of Transportation (SCDOT), are annualized average daily traffic (AADT) counts; each count represents the average amount of vehicular traffic, in both directions, which passes a given point over a 24-hour period on a typical day in the year. SCDOT counts are seasonally adjusted so that they represent an average of all seasonal traffic.
How accurate are these traffic counts? AADT is a key variable in producing vehicle miles traveled (VMT) estimates, for analyses of crash rates, evaluation of infrastructure management needs, air quality compliance, and validation of travel demand model predictions. This data is frequently used to influence policy decisions. Despite their importance, AADT values are simply rough estimates of traffic counts along major roadway sections. SCDOT calculates these counts using short-period traffic counts (SPTCs) in which one- to three-day samples are taken every few years at select points across the statewide highway network. These counts are factored up to a yearly estimate based on year-to-year trends, sampling season, and day of-week factors developed using data obtained from permanent automatic traffic recorder (ATR) stations. Thus, these traffic counts should be considered estimated figures rather than actual figures.