DOT Interface for Project-Level Air Quality Modeling

Focus Area

Air Quality


Air Quality






2-3 years

Research Idea Scope

State Departments of Transportation (DOTs) conduct project-level air quality analyses for the National Environmental Protection Act (NEPA) and to meet the requirements of the Environmental Protection Agency’s (EPA) transportation conformity rule and would greatly benefit from the development of an open-source interface to assist in conducting emission and air quality dispersion modeling for near-road applications. The DOT Interface would facilitate analyses by helping the user to specify project inputs, including traffic volumes, roadway link geospatial coordinates, and emission rates, pre-process those data for input to AERMOD and, following completion of the AERMOD run(s), post-process the output to generate project design values (DVs). It would support analyses for particulate matter (PM), carbon monoxide (CO) and other analyses, including dispersion analyses associated with Environmental Justice (EJ) assessments. It would be structured to facilitate updates over time (e.g., via pooled funds) as NEPA and conformity requirements continue to evolve and grow more complex. The proposed study would be phased, with the first phase addressing the highest priority items and establishing an initial version of the interface to serve as the base for future updates. The first phase would also generate recommendations for work to be completed in the second phase.

Note State DOTs have the expertise with traffic and activity data needed for emission and air quality dispersion modeling and so are uniquely capable of developing the needed roadway link specification and traffic elements of the DOT Interface. The proposed DOT Interface may build upon related work, including NCHRP 25-48, which created a basic open source “Combined Interface for Project Level Air Quality Analysis” but lacks most of the features identified here; the FHWA Cal3i/Cal3Interface for carbon monoxide analyses, which greatly streamlined and facilitated those screening-level analyses; the University of New Mexico “GIS-to-AERMOD” interface or tool for converting roadway GIS data for input to the EPA AERMOD dispersion model; and the Traffic Noise Model 3.1 interface, which allows users to visualize roadway links on a map.

Key features of the proposed DOT Interface by phase would include:


Specification of inputs for the MOVES emission model and AERMOD and CAL3QHC dispersion models, effectively implementing EPA guidance and best practices for project-level air quality analyses.
* Default inputs for NEPA and transportation conformity as appropriate to each model and type of analyses. Tools would be developed as needed for this purpose, e.g., tools to determine release heights and initial vertical dispersion coefficients appropriate for the traffic and highway geometry.
* Traffic inputs, including an ability to compute basic traffic inputs (queue length, delay time that can be used to estimate excess emissions from idling, etc.) as needed for regulatory modeling for each pollutant and facility type (highways, intersections, ports, terminals etc.) Includes use of the FHWA DANA tool and/or other tools as appropriate.
* Links (acceleration, cruise, and queue) for various typical project types, for both the emission and air quality dispersion models, effectively implementing EPA guidance and best practices. This includes capabilities to:
* Import roadway link geospatial data (horizontal and vertical coordinates) and visualize the network in the interface.
* Adjust naming of roadway links and split or combine roadway link segments.
* Calculate and adjust roadway grades
* Receptors for dispersion modeling for all roadway links included in the analysis.
* Generation of input files for the user-specified emission and dispersion models. This includes transferring the output from an on-road emission model (e.g., MOVES or/EMFAC) to the dispersion model and processing the emission rate data, roadway link traffic volumes, roadway link geo-spatial coordinates, and receptor location coordinates to generate the appropriate AERMOD or CAL3QHC input files.

Other tools or capabilities would be provided facilitate the:
* Visualization of links and receptors
* Creation of input data to account for seasonal variation
* Exporting of data for import into a third-party GIS program

* Facilitation of batch operations in addition to individual runs

* Determination of DVs per EPA guidance. This includes generation of tabular output of results with automatic comparison to the national ambient air quality standards (NAAQS) and other user-specified values.
* Generation of graphics including standard sets of charts and tables that may be included in NEPA documentation.

PHASE II (based on successful completion of Phase I and its recommendations for Phase II)

While Phase I would make recommendations for work to be done in Phase II, the following elements are expected to be part of the Phase II work. Note, for planning purposes, the budget and timeframe for Phase II would be similar to that for Phase I. The budget and timeframe proposed for this study is for Phase I only.

Specification of inputs not addressed in Phase I including:
* Affected links for MSATs and GHGs from traffic data
* QA/QC tools including cross-checking inputs against defaults and typical ranges for each input.
* Tools to create equivalent input data for each model and to quality-assure those inputs to support comparisons of the performance of different emission and dispersion models.

Add tools and options not addressed in Phase I, including:
* Tools to facilitate sensitivity testing with batch processing with one parameter varied based on user input. This would also be useful for model testing, e.g., of new beta features.
* Capabilities to work with the EMFAC emission model and potentially other dispersion models for comparison purposes
* Tools to generate XML files for import into the TNM3.1 noise model that includes roadway traffic volume and geo-spatial roadway segment data.

Add tools and options not addressed in Phase I.
* Tools to post-process output for environmental justice (EJ) assessments as needed
* Tools to generate graphics including standard sets of charts and tables that may be included in NEPA documentation.

Co-Authors of the Proposed Scope:
* Christopher Voigt, VDOT
* Roger Wayson, AECOM

Feedback on the scope was provided by the FHWA Resource Center.

Urgency and Payoff

With potential revisions to the national ambient air quality standard for PM under consideration, potential revisions to requirements for MSAT and GHG analyses, and potential EJ considerations, state DOTs need assistance to facilitate analyses that are taking on ever-increasing complexity with reduced margins for error. The development and implementation of a DOT Interface designed for transportation applications would not only help streamline the preparation of project-level air quality analyses and associated environmental documentation, saving time and costs for analyses and improving quality control at the same time, it would also support more efficient reviews of those analyses by state DOTs and FHWA. In short, the proposed DOT Interface is the best way to support the increasingly more complex and challenging air quality analyses that are now required and on the horizon.

Suggested By

Christopher Voigt

[email protected]