Visitor vehicle emissions study : comparison of traffic data at three California national parks

The U.S. Department of Transportation, John A. Volpe National Transportation Systems Center (Volpe Center), Environmental Measurement and Modeling Division, provided technical support to the National Parks Foundation as a part of a National Park Service (NPS) project to evaluate vehicular emissions in the national parks. A Visitor Vehicular Traffic Impact Study (the Study) was performed in three California National Parks between August 2002 and April 2003 – Yosemite National Park, Joshua Tree National Park, and Point Reyes National Seashore - in order to collect traffic count, vehicle tracking, meteorological, Inspection and Maintenance Program, and fuel program data. This data was processed through the Environmental Protection Agency’s (EPA) MOBILE6.2 modeling software to produce park-specific emission factors, and weekly traffic count data was used with these emission factors to produce a weekly emissions inventory for each park. Alternative methods involving modal emissions models were also investigated. Mainly due to their ability to take into account park-specific driving cycles, modal emissions models are likely to provide results that are more appropriate for the National Parks. For further emissions modeling, a simplified approach using a modal emissions model is recommended. This comparison report contains a technical comparison of the three California national parks emissions inventory input data and instructions on how to produce emissions inventories for other parks through a simplified approach.