The CALPUFF modeling system does not feature a native source type for mobile sources (e.g., vehicles). One way to treat these emissions in the model is to calculate the cumulative emissions of all vehicles which drive on a road and parameterize the road itself into the model as the source. With the introduction of CALPUFF’s Version 7 Modeling System and the release of CALPUFF ViewVersion 8.2.0, users have a few options as to how to model these sources in CALPUFF.
Haul Roads Source Calculator
Several years ago, the USEPA Haul Roads Workgroup issued recommendations for modeling haul roads within the AERMOD air dispersion model. Lakes Environmental used these recommendations to build a source parameterization wizard into AERMOD View – the Haul Roads Calculator. CALPUFF View Version 8.2.0 now features the same Haul Roads Calculator. This utility incorporates all recommendations from the Haul Road Workgroup final report. The user only needs to provide a few simple input values:
Plume height factor (default of 1.7 per the Haul Road Workgroup report)
Lane type (single lane or two lanes)
The calculator uses the report recommendations to apply the appropriate source inputs to each source along the line.
Haul Road Source Calculator
CALPUFF View Source Parameters – Line Volume Source
New Road Source Type
CALPUFF’s Version 7 modeling system also features a native road source. Emissions from roads are generated from individual line segments defined by a sequence of coordinates provided for each road-link. Each link is entered as a discrete source and is defined as a section of the road for which emissions are uniform.
The road is defined as polyline sufficient to resolve curves without the need for uniform spacing. It could be as simple as two points for a straight flat segment, or a series of coordinate pairs can be used to trace a more winding path.
Example of Two Road Sources
The Posting display can be modified using the Graphical Options. From the main toolbar, select the Graphical Options button and then select the Posting options.
The model automatically divides long line segments into shorter segments that are limited by the grid-cell boundaries as no segment may extend across multiple grid cells. One emission rate (g/s/m) for each species is used for the entire road. Near a congested intersection, many short links may be required to resolve the spatial and temporal distribution of emissions. Each is entered and modeled as a discrete source.
Roads can also be specified in the CALPUFF model as an external source file with varying emissions (RDEMARB.DAT). The specifications of this file can be found in CALPUFF View’ Help file.