Research Projects

Project at a Glance

Project Status: complete

Report Published March 1977:

Title: Mobile source emission inventory

Contractor: Olson Laboratories, Inc.

Contract Number: 4-956 & 5-434

Research Program Area: Emissions Monitoring & Control

Topic Areas: Mobile Sources & Fuels


This final report documents the methodology and results of the Mobile Source Emissions Inventory Project performed by Olson Laboratories, Inc., for the California Air Resources Board under Contract Nos. ARB 4-956 and ARB 5-434. The objectives of this project included characterization of driving patterns of light-duty passenger cars throughout California's South Coast Air Basin (SCAB), development of driving cycles, and the estimation and measurement of emissions from pre-catalyst vehicles. Exhaust C1 to C10 hydrocarbon composition was also determined for 10 vehicles driven on the EPA Surveillance Schedule and 15 vehicles driven on the composite derived driving cycle.

An instrumented chase vehicle was used to emulate and record driving patterns. Nine routes were selected which provided various freeway and nonfreeway driving conditions. The routes were driven on different days of the week and time of day. The recorded driving pattern data were subsequently computer processed to derive matrices of mode frequency and time-in-mode. Average speeds and mode frequency were similar to previous data obtained in the CRC-APRAC-CAPE-10 Vehicle Operation Survey (VOS) conducted in 1970. However, considerably more time was spent in cruise modes in the current study than in the VOS.

Based on the driving pattern data, driving cycles were developed. One statistically representative cycle was chosen for each of freeway, nonfreeway and composite driving. The driving cycles were plotted and emissions measured from 15 vehicles using the composite cycle. Emissions were also estimated for all three cycles using EPA computer programs and modal emissions data bases. Measured emissions agreed well with the estimated emissions. Over 2,000 driving cycles were selected which, while not statistically representative, provided a range of average speeds. Emissions factors for the range of speeds were calculated using the EPA program and data bases for each route and season. This data was transmitted to TRW for use in calculating speed correction factors.


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

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