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Ambient Monitoring Technology Information Center (AMTIC)

NO2 Monitoring - Near Road Monitoring

This webpage is intended to provide information regarding ambient air pollution monitoring stations in the near-road environment known as the near-road monitoring network.  The near-road monitoring network was initiated as part of the 2010 NO2 NAAQS review and has become a multi-pollutant monitoring network.  Materials to be provided on this webpage include the list of near-road monitoring sites, the Near-road NO2 Technical Assistance Document, the Near-road NO2 Pilot Study, materials used in support of the near-road NO2 pilot study, and other related near-road monitoring resources.  Additional near-road monitoring resources, particularly those regarding research, can be found on EPA’s Office of Research and Development’s Near Roadway Research webpage.

Near-road NO2 Monitoring Sites

The EPA, in cooperation with state, local, and tribal air agencies has tracked the installation of near-road NO2 monitoring stations across the country. As part of this effort, the Agency has created a list of sites and captured critical meta-data about the sites, their target roads and general operations.  These meta-data include:

  • The Core Based Statistical Area (CBSA) in which the site exists
  • The EPA Region in which the site exists
  • The population of the CBSA
  • The installation phase of the near-road site
  • Optional site identification information
  • The AQS ID
  • The name of the target road
  • The Annual Average Daily Traffic (AADT) counts of the target road
  • The relative AADT ranking within the CBSA
  • The Fleet Equivalent AADT count (a novel metric accounting for both traffic volume [AADT] and fleet mix [diesel vs gasoline vehicle count])
  • The relative FE-AADT ranking within the CBSA
  • The distance between the monitor probe and the target road (meters)
  • The height of the monitor probe above the ground (meters)
  • The approximate start-up date of the monitoring site (where NO2 is the first pollutant required to be measured)
  • The latitude of the site (decimal degrees)
  • The longitude of the site (decimal degrees)

More information on many of these meta-data, including detailed definitions, data sources and derivations, and their importance on near-road monitoring placement can be found in the Near-road NO2 Monitoring Technical Assistance Document, which is linked on this webpage.

The Agency intends to update this list of near-road sites periodically. Data from these sites, and all State and Local Air Monitoring Stations reporting data to the EPA, may be obtained through EPA’s AirData website ( or accessing EPA’s AQS database. 

Near-road NO2 Technical Assistance Document (TAD)

The Near-road NO2 Technical Assistance Document (TAD) has been developed to aid state and local air monitoring agencies in the implementation of required near-road NO2 monitoring stations. The June 2012 version of the TAD reflects the collaboration between partner state and local air monitoring agencies and associations, partnering state departments of transportation, the Federal Highways Administration, and the EPA. This document also reflects feedback, concepts, and suggestions from two reviews conducted by the Clean Air Scientific Advisory Committee (CASAC) Ambient Monitoring and Methods Subcommittee (AMMS). In addition to the TAD, the EPA has provided here a link to a recorded webinar (circa December 2011) that provides a walk-through of the TAD and includes interaction with state and local participants.

Near-road NO2 Pilot Study

In conjunction to the development of the Near-road NO2TAD, a near-road NO2 pilot study was initiated by state and local air monitoring stakeholders to evaluate, improve, and document the near-road monitor siting process with EPA, and to provide firsthand experience to several air agencies in the full installation of a near-road NO2monitoring station.  The near-road NO2 pilot was organized between the National Association of Clean Air Agencies (NACAA), volunteer state and local air agencies, and the EPA.  The experiences gained in the pilot study are intended to be shared by those air agencies participating in the pilot with the air monitoring community.  Materials provided here are products of the pilot activities, including the final study report (which includes sample data) and the Quality Assurance Project Plan.