National Center for Sustainable Transportation

This report addresses aspects of the California Air Resources Board (CARB)’s current quantification methods for estimating GHG emission reductions from projects that expand transit facilities or service. A number of California Climate Investments programs fund transit projects, including the Low Carbon Transit Operations Program, the Transit and Intercity Rail Capital Program, and the Affordable Housing and Sustainable Communities Program. CARB has developed technical documents for each program, called “Quantification Methodologies,” and associated spreadsheet calculation tools, called “Benefit Calculator Tools,” for program applicants to use in estimating project-level GHG emission reductions and co-benefit estimates for projects proposed for funding. To measure GHG emission reductions from transportation projects, including transit projects, CARB relies on ”CMAQ” computation methods, published by CARB in 2005 with the California Department of Transportation (Caltrans) for evaluating motor vehicle fee registration projects and congestion mitigation and air quality improvement (CMAQ) projects, specifically transit and connectivity (TAC) features. This report addresses how and whether CARB might update default values for two adjustment factors employed in the TAC methods that apply to transit facility and/or service expansion projects.

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