Many air districts throughout the country conduct public education programs during the summer ozone season to encourage the public to reduce their driving on days forecast to violate ozone air quality standards. This research project developed a simple, low cost method for quantifying the travel and emission impacts of these programs, often called "Spare the Air" in Northern California.
The study developed survey methods and collected comprehensive travel data of a random sample of the general population and of individuals who said they responded to the "Spare the Air" message. The data, collected over two summer ozone seasons in Sacramento, allowed researchers to compare the travel behavior of the same individuals on both "Spare the Air" and regular summer days and of "Spare the Air" participants and non-participants. The study found a statistically significant difference between the self-reported vehicle trip reductions and measured vehicle trip changes due to "Spare the Air" programs among the "Spare the Air" participants. This led to the development of a "correction factor" that adjusts average self-reported trip reduction survey results to bring it in line with the observed relationship between self-reported and measured trip reduction.
Applying the results of this study with simple and less costly surveys developed by the research team, air districts will be able to adjust future self-reported vehicle trip reductions and extrapolate them to the entire regional population of drivers within an acceptable margin of error.
In the presentation, Mr. Schreffler will explain the research design, discuss the research findings, present the recommended method developed from the research, and show an application of the method to the summer 2002 "Spare the Air" campaign in the Bay Area.
Eric N. Schreffler is an independent consultant specializing in the evaluation of transportation demand management (TDM) as well as travel and emission reduction programs. He has developed and applied evaluation methodologies for TDM programs for agencies throughout California, the United States, and Europe. For this project, he served as prime contractor and principle investigator, leading a team of consultants that included: Godbe Research and Analysis, K.T. Analytics, ENVIRON, and Gary Hawthorn & Associates. Mr. Schreffler is the Chairman of the Transportation Research Board's Committee on TDM. He holds a Master's in Transportation from M.I.T. and a Bachelor's in Urban Studies from U.C. San Diego.
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