Annual Average Daily Traffic - MDOT SHA Statewide AADT Lines

MDOT SHA Annual Average Daily Traffic (AADT) Lines data consists of linear geometric features which represent traffic count sections along public roadways in the State of Maryland. Traffic counts are performed in order to calculate the annual average daily traffic (AADT), annual average weekday traffic (AAWDT), and AADT based on vehicle class (current year only) for sections along public roadways in the State of Maryland. Overall percent utilization, percent utilization based on vehicle class, and truck-specific percent utilization are showcased as statistical metrics for each road section where applicable. Ten years of historic AADT and AAWDT traffic count information is also available for each road section where applicable.

Annual Average Daily Traffic (AADT) data is collected from over 8700 program count stations and 84 automatic traffic recorders (ATRs), located throughout Maryland. The quality control feature of the system allow data edit checks and validation for data from the 84 permanent, continuous ATRs, and short-term traffic counts. To date, four (4) ATRs have been removed from the ATR Program. Program count data is collected (both directions) at regular locations on either a three (3) year or six (6) year cycle depending on 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 2014), “1” represents the count taken in 2013, “2” represents the count taken in 2012, “3” represents the count taken in 2011 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 State and local government agencies. The data is essential in the planning, design and operation of the statewide road system and the development and implementation of State highway improvement and 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 and efficiently meet MDOT SHA’s long-term traffic data monitoring and 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 2019.

Last Updated: May 2020 (05/21/2020)

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

For AADT data information, contact the MDOT SHA Traffic Monitoring System (TMS) Team
Email: TMS@mdot.maryland.gov

For additional information, contact MDOT SHA Geospatial Technologies,
Email: GIS@mdot.maryland.gov

MDOT SHA Geospatial Data Legal Disclaimer:
The Maryland Department of Transportation State Highway Administration (MDOT SHA) makes no warranty, expressed or implied, as to the use or appropriateness of geospatial data, and there are no warranties of merchantability or fitness for a particular purpose or use. The information contained in geospatial data is from publicly available sources, but no representation is made as to the accuracy or completeness of geospatial data. MDOT SHA shall not be subject to liability for human error, error due to software conversion, defect, or failure of machines, or any material used in the connection with the machines, including tapes, disks,
Organization: State of Maryland
Last updated: 2025-07-26T20:25:17.178634