Annual Average Daily Traffic (AADT) data is collected from over 8700 program count stations and 84 ATRs, located throughout Maryland. The quality control feature of the system allow data edit checks and validation for data from the 91 permanent, continuous automatic traffic recorders (ATRs) and short-term traffic counts.  Program count data is collected in both directions (inventory & non-inventory) at regular locations on either a three (3) year or six (6) year cycle depending on the type of roadway. Growth factors are applied to counts which were not taken during the current year and the counts are factored based on the past yearly growth of an associated ATR. Counters are placed for 48 hours on a Monday or Tuesday and are picked up that Thursday or Friday, respectively. The ATR and toll count data is collected on a continuous basis. Toll station data is provided by the Maryland Transportation Authority (MDTA). A special numeric code was added to the AADT numbers, starting in 2006, to identify the years when the count was actually taken. The last digit represents the number of years prior to the actual count. Where “0” represents the current year when data was collected (in 2020), “1” represents the count taken in 2019, “2” represents the count taken in 2018, “3” represents the count taken in 2017 and so forth.

Annual Average Daily Traffic (AADT) data is a strategic resource for the Federal Highway Administration (FHWA), the Maryland Department of Transportation (MDOT), the Maryland Department of Transportation State Highway Administration (MDOT SHA), as well as many other Federal, State & local government agencies. The data is essential in the planning, design and operation of the statewide road system and the development & implementation of State highway improvement & safety programs. The MDOT SHA Traffic Monitoring System (TMS) is a product of the ISTEA Act of 1991, which required a traffic data program to effectively & efficiently meet MDOT SHA’s long-term traffic data monitoring & reporting requirements.

Annual Average Daily Traffic (AADT) data is updated and published on an annual basis for the prior year. This data is for the year 2021.

View the most current AADT data in the MDOT SHA Annual Average Daily Traffic (AADT) Locator