Annual average daily traffic, abbrevated AADT, is a measure used primarily in transportation planning and transportation engineering. It is the total volume of vehicle traffic of a highway or road for a year divided by 365 days. AADT is a useful and simple measurement of how busy the road is. It is also sometimes reported as "average annual daily traffic".
The alternative or second technique is called the short count data collection method also know as the coverage count data collection method. The AADT can be estimated with portable sensors that are attached to the road and record traffic data typically for 2 - 14 days. These are typically pneumatic road tubes although other more expensive technology such as radar, laser, or sonar exist. After recording the traffic data, the traffic counts on the same road segment are taken again in another three years. [FHWA Traffic Monitoring Guide] recommends to perform a short count on a road segment at a minimum of every three years. After collecting the data with a portable traffic counter, the data is converted into an ADT - Average Daily Traffic. This would represent the average day of traffic for the month the data was recorded. Seeing traffic varies throughout the year, with it generally being low in the winter months and high during the summer months, the AADT is estimated by removing this seasonal bias by multiplying the ADT by the Monthly Seasonal Adjustment Factor. Short counts are taken either by state agencies, local government, or contractors. For the years when a traffic count is not recording, the AADT is estimated by applying a factor called the Growth Factor. Growth Factors are statistically are determined from historical data of the road segment. If there is no historical data, Growth Factors from similar road segments are used.
SURFACE TRANSPORTATION BOARD ISSUES ENVIRONMENTAL REVIEW ON UNION PACIFIC RAILROAD - ABANDONMENT - IN CARVER AND SCOTT COUNTIES
Jan 15, 2008; The U.S. Department of Transportation's Surface Transportation Board issued the environmental review: Decision Information Docket...