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Project Status: complete

Title: Study of multi-day storage pattens for gasoline-fueled vehicles in the South Coast Air Basin. Final Report.

Principal Investigator / Author(s): Horie, Yuji

Contractor: Valley Research Corporation

Contract Number: A6-196-32

Research Program Area: Atmospheric Processes, Emissions Monitoring & Control

Topic Areas: Field Studies, Mobile Sources & Fuels, Monitoring


New evidence indicates that extended periods of vehicle non-use contribute to overloading the vapor trapping canister in a vehicle and resulting in excess emissions. To incorporate this finding into the ARB's emission model, the Air Resources Board (ARB) is currently developing improved methods of estimating evaporative emissions from on-road gasoline-fueled motor vehicles in the South Coast Air Basin. Critical factors in determining evaporative emissions are the duration and frequency of "multi-day" vehicle storage, lasting 24 hours or longer. To quantify these critical factors for all gasoline-fueled vehicles in the Basin, Valley Research Corporation (VRC) conducted several surveys on storage patterns of both individually-owned vehicles and commercially-owned vehicles. Specifically, VRC designed and implemented the following surveys:

1. Household Survey for individually-owned vehicles;
2. Business Vehicle Survey for both fee-paid and fee-exempt vehicles with commercial license tags; and
3. Facility Survey for unregistered, new vehicles at car dealers and registered vehicles at various facilities such as auto-repair and body shops, and parking and camping facilities.

These surveys have revealed that, of the basinwide population of 8.1 million privately owned vehicles, there are about 2.1 million vehicles daily experiencing multi-day soaking. For the estimated population of 374,000 commercially-owned vehicles in the basin, there are 137,000 (37%) vehicles daily experiencing multi-day soaking. Of these privately and commercially-owned vehicles on multi-day soak, about 7% are soaking at vehicle holding facilities such as auto-repair shops and parking lots. In addition to these vehicles in circulation, there are 154,000 new, pre-registered vehicles soaking for multi-days at new car preparation lots and vehicle dealers.


For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 322-3893

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