Research Projects

Project at a Glance

Project Status: complete

Title: Study of driving and storage patterns of nonprimary private vehicles in the South Coast Air Basin

Principal Investigator / Author(s): Horie, Yuji

Contract Number: A0-073-31


Research Program Area: Emissions Monitoring & Control

Topic Areas: Mobile Sources & Fuels


Abstract:

Every post-1970 California vehicle is equipped with an evaporative emission control system (EECS). The main component of the EECS is a canister filled with activated charcoal which is designed to trap gasoline vapor from the carburetor after the engine shutoff or from the fuel tank when the vehicle is not used for several days. It is suspected that current EECS may not be very effective for a nonprimary vehicle: vehicles which are used primarily for shorter trips than 7.5 miles each way or driven three days or less per week. The objectives of this study are to estimate the size of such nonprimary vehicle population and determine their typical driving and storage patterns through a telephone questionnaire survey. The survey was conducted for 800 households, which were randomly selected from white page listings of the 15 telephone directories covering the South Coast Air Basin (SCAB). Results of the survey indicate that the nonprimary vehicles constitute 52.6 percent of all vehicles or 2.95 million vehicles over the SCAB region. A cursory analysis of their driving and storage data and the recent laboratory test data on hot soak emission and purging has identified four distinct driving and storage patterns: low hot soak class of vehicles with long driving distance and small number of trips per week, moderate hot soak class of vehicles with moderate driving distance and large number of trips, high hot soak class of vehicles with short driving distance and large number of trips and diurnals dominated class of vehicles with long driving distance and small number of days used per week.


 

For questions regarding research reports, contact: Heather Choi at (916) 322-3893

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