Abstract
The inherently spatial nature of transportation-related air quality analysis makes the geographic information system (GIS) particularly well suited to enhancing microscale air quality analysis. GIS provides several features ideal for the type of analysis necessary to determine transportation-related air quality impacts. It is an excellent storage, manipulation, modeling, and mapping tool for spatial data. Spatial information such as street coordinates and accompanying attributes can be exported and manipulated as input to air quality models such as CALINE3 and CAL3QHC. Output from air quality models in the form of pollution concentrations at specified receptor locations can be input to GIS for hot-spot identification, estimation of contributions of off-road mobile sources, and impact analysis. GIS tools applied to air quality analysis include contour generation, classification, thematic analysis, point-in-polygon analysis, and polygon overlay. Several case studies demonstrating these capabilities using TRANSCAD, a transportation-based GIS package, are presented for microscale air quality analysis. Incompatibilities exist between current air quality models and most GIS. Differences in coordinate systems and distance metrics necessitate additional manipulation of data transferred between models and GIS. Other incompatibilities are that street segments are represented as centerlines in most planning applications of GIS and as a series of links in CAL3QHC and CALINE3, and that signalization parameters are represented differently from many common signal-analysis packages, which may necessitate additional data collection.
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