Modeling Tip – May 2012

Estimating air quality impacts from haul roads has presented many challenges to air dispersion modelers over the years. From the lack of a true line source to high degrees of variability in emissions estimates, consistent guidance was minimal and confusion was high. Previous releases of AERMOD View sought to reduce some of that confusion by adding tools for modelers such as the Line Volume source. While the AERMOD and ISC models do not contain true line sources, the Line Volume source allowed modelers to easily create a series of volume sources along a path. This source type made it quick and easy to add large sets of volume sources thus reducing time and effort.

On March 2, 2012, the U.S. Environmental Protection Agency Air Quality Modeling Group released a report from the Haul Road Workgroup which recommended an approach for haul road modeling. The Haul Road Workgroup Final Report outlined the advantages and disadvantages to a variety of source characterizations, and it provided details on model sensitivity analyses performed by the Workgroup.

The final recommendations from this report were analyzed by our product specialists and developers to enhance the existing line source tool in AERMOD View. The result was a layout change for the Line Source dialog and the addition of the Haul Road Source Calculator. These changes will help modelers tackle haul road modeling challenges faster than ever before!

AERMOD View Line Source Enhancements

The updated line source window gives more flexibility and adds several new features:

Step 1:Users can now enter a Source ID Prefix (up to 4 characters long) for the volume sources generated along the line. The prefix makes it easier to identify sources when analyzing output or grouping sources.

Step 2: The window now automatically calculates the Total Length of the line’s path.

Step 3: The Line Volume source now allows users to select from Separated or Adjacent configuration.

Step 4: A new Actions menu allows users to Import or Export line source nodes to a comma-separated file (*.csv). This makes it easier than ever to transfer line sources from one project to another. The same menu allows users to manually assign release heights to each node of the line.

AERMOD View Haul Road Source Calculator

AERMOD View Version 7.6.1 also includes the brand-new calculator for modeling haul roads.

The Haul Road Calculator incorporates all recommendations from the Haul Road Workgroup final report. The user only needs to provide a few simple input values:

• Vehicle height


• Plume height factor (default of 1.7 per the Haul Road Workgroup report)


• Lane type (single lane or two lanes)


• Road width


• Emission rate

The calculator uses the Haul Road Workgroup final report recommendations to apply the appropriate source inputs to each source along the line.