Best Practices for Project-Level Air Quality Analyses

Focus Area

Air Quality


Air Quality






2-3 years

Research Idea Scope

November 2012 Proposal:

Effective December 20, 2012, a new era in air quality
analyses for transportation projects begins as regulatory requirements issued
by the US Environmental Protection Agency (US EPA) for the application of
models (MOVES, CAL3QHCR and AERMOD) and guidance new to the project-level
analyses become effective. Project sponsors (state DOTs and other agencies)
would benefit significantly from the accelerated development of a comprehensive
set of best practices designed to assist modelers in determining how to best
model typical highway and related transit and intermodal projects to meet the
new regulatory requirements in a cost-effective, efficient and transparent
manner. Project sponsors would also benefit significantly from the development
of associated software (“expert” systems) that would serve as an interface to
the regulatory models and guide modelers in the implementation of best
practices, effectively guiding and streamlining the project-level analysis
modeling (and environmental clearance) process to the extent feasible
consistent with federal objectives. The new interface software may build upon
related public domain software as may be identified in the course of this
review or be designed as a new independent interface, and in either case must
meet all applicable federal requirements and guidance for regulatory software
(including those specified by EPA in Appendix W of 40 CFR Part 51 ).


Mandates to address best practices and streamlining
include the Moving Ahead for Progress in the 21st Century Act (MAP-21) (Public
Law 112-141), which was signed on July 6, 2012 . Sections from MAP-21 of
particular interest to this study include:

• Section 1301(b)(2)(A), which makes a general call
“…to develop and advance the use of best practices to accelerate project
delivery and reduce costs across all modes of transportation and expedite the
deployment of technology and innovation”, and • Section 1503(j)(1), which calls
for “advanced modeling technology” that among other objectives can  (-(A)) “…accelerate and improve the
environmental review process…”, and Section 1503(j)(2), which calls for
“…the use of advanced modeling technologies during environmental …


Consistent with the general mandate for streamlining
in MAP-21 is the call to shorten project delivery in the ongoing Every Day
Counts (EDC)  initiative, which was: “…
designed to identify and deploy innovation aimed at shortening project delivery
… and protecting the environment.” See:


Best practices and associated software is also of
widespread interest among key stakeholders:

• A proposal for best practices in support of MAP-21
objectives was presented at the Air Quality, Energy and Climate Change
Subcommittee meeting at the AASHTO Subcommittee on Environment (SCOE) annual
meeting in September 2012 (shortly after MAP-21 was signed) and received broad

• Best practices (and associated software) were also a
major topic of interest at the Transportation and Air Quality Committee (ADC20)
Project-Level Analysis Subcommittee meeting at the Annual Meeting of the
Transportation Research Board (TRB) in January 2012. In a survey of members for
new research ideas, 13 of 32 proposals received addressed best practices and
another 17 addressed the closely-related topic of model improvement . (Only two
did not address either topic.) • Best practices and expert system software for
project-level air quality analyses were also recommendations of the 2012 AASHTO
Air Quality Community of Practice report on the State-of-the-Practice Report on
Project-Level Quantitative Hot-spot Analyses for PM2.5 and PM10 .


Finally, related to the proposed development of
software for best practices, “… the EPA established the Council for
Regulatory Environmental Modeling (CREM) in 2000 in an effort to improve the
quality, consistency and transparency of the models for environmental decision
making.”  One of their stated objectives
is to ensure that the agency:  “…implements
best management practices to use models consistently and appropriately.” CREM
guidance for regulatory software should also be a key consideration in the
development of interface software in this project. See:


Research Objective:


The overall objective is to develop a comprehensive
set of best practices (including associated interface software) for
project-level air quality analyses that project sponsors may apply on a
voluntary basis to help them meet all applicable federal regulatory
requirements including those for both NEPA and conformity in a cost-effective,
efficient and transparent manner. The best practices and software should also
to be designed to facilitate future updates as federal regulations and guidance
are updated and/or additional software features are added. A distinction should
be maintained in the best practices between elements that are required under
regulation and those that are voluntary or included under guidance to be
implemented at the discretion of the project sponsor .


The best practices and software should also support
the following key objectives from federal requirements and guidance:

• MAP-21: “…accelerate project delivery and reduce

• EDC: “…identify and deploy innovation aimed at
shortening project delivery … and protecting the environment.”


The software should additionally support the following
specific objectives from federal requirements and guidance:

• MAP-21: The proposed interface software should be
considered “advanced modeling technology” and accordingly designed to help
“…accelerate and improve the environmental review process…” and support
“…the use of advanced modeling technologies during environmental …

• CREM , which: “…recommends that model developers and
users: (a) subject their model to credible, objective peer review; (b) assess
the quality of the data they use; (c) corroborate their model by evaluating the
degree to which it corresponds to the system being modeled; and (d) perform
sensitivity and uncertainty analyses. Sensitivity analysis evaluates the effect
of changes in input values or assumptions on a model’s results. Uncertainty
analysis investigates the effects of lack of knowledge and other potential
sources of error in the model (e.g., the “uncertainty” associated with model
parameter values). When conducted in combination, sensitivity and uncertainty
analysis allow model users to be more informed about the confidence that can be
placed in model results. A model’s quality to support a decision becomes better
known when information is available to assess these factors.” Excerpt from the
Executive Summary of: US EPA, “Guidance on the Development, Evaluation, and
Application of Environmental Models”, EPA/100/K-09/003, 2009. Direct link:


Consistent with CREM guidance on balancing sensitivity
and uncertainty, a sense of proportionality in the level of detail and
resources allocated to modeling should be addressed in best practices such

• The modeling to be conducted for a given project
should be designed to be just that which is required to respond to the
regulatory question at hand and not involve a level of detail or resources more
than are necessary, and • The modeling resources allocated to each of the major
steps in the modeling chain (traffic, emission, and dispersion) should be
optimized to the extent feasible, considering the time and cost needed to
generate input data for each step and their contribution to the overall level
of accuracy for the modeling chain, and not unduly focus on one step at the
expense of another.


Other objectives for the best practices include
transparency in process and documentation, and quality control and assurance.


Phasing: Depending on funding availability, the study
may be conducted in phases, with the initial phase focusing primarily on the
initial tasks or tasks of this scope of work as defined below. Future phases
would address the subsequent tasks.




1. Gain consensus on focus areas for best practices
and their relative priorities.

a. Meet with the project panel and gain consensus on the
general focus areas for best practices to be addressed in this project. To the
extent feasible, also seek consensus on whether the deliverable for each area
is best accomplished with documentation (a project report) and/or as
incorporated into the interface software to be developed in this project.
Potential focus areas would be expected to include but are not necessarily be
limited to:

v Modeling Traffic for Project-Level Analyses v
Modeling Emissions v Modeling Dispersion v Determining Background Concentrations
(Existing & Future)(including consideration of nearby major sources) v
Mitigation (with Modeling)(including Construction) v Monitoring (Near-Road) v
Programmatic Agreements & Categorical Findings v Consultation (including
the Role of State or Regional Modeling Resource Guides) v Documentation
(covering both NEPA and Conformity) v State or Regional Modeling Resource
Guides v Review and Update Process for Best Practices (for each of the listed
focus areas) v Case Studies (detailed examples of the application of the
recommended best practices to various typical highway, transit and intermodal
projects, including modeling, comprehensive NEPA/conformity documentation,
including the development and use of a Modeling Resource Guide, and budgeting
including time and resource allocation for each of the major modeling steps as
well as consultation and documentation)


For consideration by the project panel, the focus
areas as listed above are generally ones in which:

v future updates can be handled by subject matter
experts, as individual practitioners may have relative expertise in specific
topics such as in traffic, emission or dispersion modeling, v the area
represents a distinct logical step in the analysis process for which specific
guidance or templates can be developed and updated independently (e.g.,
documentation, and modeling resource guides), and/or v the related federal
regulation or guidance may change and corresponding updates to the best
practices guidance or templates will be needed (e.g., background
concentrations, which are linked to EPA’s Exceptional Events Policy, or
programmatic agreements & categorical findings).


b. Conduct a literature review for best practices and
associated software. Identify related research underway or proposed  that may also assist this study (e.g.,
sensitivity analyses, cost estimates for obtaining or generating data for each
step in the modeling chain, etc.). Include consideration as appropriate of
recent proposals submitted for annual TRB meetings (see:


c. Conduct a survey of key stakeholders involved in
the development and/or approval of project-level air quality analyses to
identify needs and recommendations for priorities for best practices and
specifications or key features for the associated interface software. The
survey should include US DOT and EPA representatives (if not already on the
project panel), state DOTs and other project sponsors, TRB Transportation and
Air Quality Committee (ADC20) members, researchers, and other as identified and
agreed by the project panel.


d. Identify and review expert software systems in
place that may serve to inform the development of interface software for this
project. Specifically consider related interface software currently in place
(e.g., CAL3i) or in development that may serve as a starting point for the
design of new software or may readily be enhanced to serve in this capacity.


e. Update and detail the project work plan as
appropriate based on the results of the literature review, survey, and software
review, and panel feedback.


2. Develop best practices for each focus area in the
order of priority identified in the work plan.

a. Conduct supporting analyses  as needed for this purpose, including but not
limited to:

v a sensitivity analysis for the combined or overall
traffic, emission and dispersion modeling chain, v the development of cost
estimates for obtaining or generating key input data for the models as identified
in the sensitivity analysis.

v other


b. Develop outlines for best practices for review and
approval by the project panel. Consider needs and plans for the interface
software to be developed in this project before (in Task 3) finalizing the
draft outline, to maintain consistency between the best practices documentation
and software.


c. Develop draft versions of the best practices for
panel review and approval


d. Finalize the best practices after panel approval.


3. Develop interface software implementing the best
practices identified and developed in Steps 1 and 2 as appropriate.

a. Develop specifications for panel review and
approval for the interface software to meet the needs identified in Step 1, the
best practices as envisaged (in outline form) in Step 2, and all applicable
regulatory requirements and guidance as appropriate. The latter include those
specified in Appendix W of 40 CFR Part 51 
and CREM guidance  for regulatory
software as well as those specific to project-level air quality analyses. Key
requirements for the software design include but are not limited to:

v The software should be designed for use on MS
Windows systems using readily available software.

v The software should be designed as open source and
public domain.

v The software should be designed to allow tools to be
developed and added by third parties, e.g. as is possible with the MOVES model
and tools developed as add-ons using scripts.

v The software should include features designed to
assist in quality assurance and control, including checks on input data.

v The software should provide formatted outputs
(tables and charts) that may be copied directly into project reports.

v The software should allow for scenario testing, i.e.
managing model input and output files to allow the modeler to not only organize
the running of a large number of runs but also to automatically calculate
incremental results from selected runs.


b. Develop a beta version of the software for testing
by the project panel and others as identified in the course of the study.


c. Following the completion of beta testing, finalize
the software and associated user guide or documentation.


4. Prepare a final report for review and approval by
the project panel. Document the overall study approach, results and recommendations
as well as the deliverables. The report may include recommendations for future
work. Deliverables include files in original format (e.g., MS Word, MS Excel,
database, text, executable and all other files) that, as well as an Adobe
Acrobat (pdf) format of the overall study report.

Urgency and Payoff

The development of best practices (or practical
guides) for project-level air quality analyses and associated software tools
would benefit state DOTs and other project sponsors in both streamlining and
improving quality control for environmental clearance processes relating to air
quality. It would facilitate the implementation of EPA and US DOT requirements
and guidance for project-level analyses and at the same time support the
implementation of MAP-21 and the Every Day Counts initiative.

Suggested By

Christopher Voigt Virginia DOT 804.371.6764

[email protected]