Division of Planning
Office of Technical Services
Seasonal Adjustment Factors
The values in these tables are used to adjust short term traffic counts (24 or 48 hours in duration) to an Average Daily Traffic (ADT) volume. The average seasonal adjustment factor is shown by functional classification of highway. The seasonal adjustment factor is shown for the day of week, weekday, or average day.
Each page of the report contains the factors for that specific functional class. A factor is calculated for each site for each day of the week, by taking the three year average traffic volume for each day of the week and dividing by the ADT averaged over the latest three years. All sites in the same functional classification are then combined to develop an average factor for the day of the week for the given month.
These factors are intended to be used to adjust daily traffic counts. Hourly data was not analyzed to derive these factors. Therefore, they should not be applied to individual hours of the day. In addition, when using these factors, judgment should be used when atypical traffic patterns are encountered, such as volumes near major recreational areas (e.g. King’s Island, Cedar Point, shopping centers, football and baseball stadiums, etc.)