Research Note 95-18: Topic = Indirect sources of emissions - strategies for control

No. 95-18
September 1995
California Environmental Protection Agency Brief Reports to the Scientific and Technical
Air Resources Board Community

Research Division, John R. Holmes, Ph.D., Chief P.O. Box 2815, Sacramento CA 98512

Goals And Strategies For Indirect-Source Control Programs

Transportation-related land use strategies are identified that can be used by builders, local governments, planning organizations, and air districts to reduce community-wide vehicle use and emissions from indirect sources. Information on implementation mechanisms for local governments is presented, and reasonably attainable performance goals for urban, suburban, and exurban communities are suggested. This study was conducted by JHK and Associates.


An indirect source of emissions is a land use, such as a shopping center, that generates or attracts mobile source activity that results in emissions of a pollutant for which there is a State ambient air quality standard. The California Clean Air Act of 1988 requires air districts in areas with moderate, serious, or severe air pollution to include in their air quality management plans provisions for developing an indirect-source control program to attain state ambient air quality standards at the earliest practicable date. This study was conducted to identify reasonable indirect-source control strategies, to develop goals for reductions in vehicle use and emissions, and to identify implementation mechanisms available to local governments.
Methods: The investigator conducted an extensive review of the literature, gathered data from travel surveys from communities in California, Oregon, and Canada, and analyzed detailed information from a recent study of travel behavior, land use, and transportation characteristics of communities in California. Performance goals that specify rates of use of alternative transportation and annual reductions per household in vehicle trips, vehicle miles traveled, and emissions of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) are recommended for indirect-source control strategies appropriate for use by urban, suburban, and exurban communities. Three ranges of performance goals for urban and suburban communities and two ranges for exurban communities are specified, allowing local jurisdictions to select a performance goal level that reflects the amount of reduction desired from indirect-source control programs.
Results: The most significant finding of this study is that it is possible to develop recommendations for combinations of transportation-related land use strategies, and to suggest performance goals that are based on quantified data available from actual communities in California with urban, suburban, or exurban characteristics. Literature sources with the most complete and defensible quantification of impacts are identified and reviewed in an annotated bibliography. The final report for this project is available for immediate use by builders, local governments, planning organizations, and air districts seeking to reduce community-wide vehicle use and emissions from indirect sources.

The investigators found that although it is difficult to predict the effects on vehicle use and emissions from individual indirect-source strategy elements, implementing comprehensive strategies is a reasonably reliable method for achieving quantifiable reductions in emissions from mobile sources. A wide range of recommended strategy elements is currently in place in many communities around the state, supporting the conclusion that the strategy packages recommended in this report are reasonable, effective, and acceptable. In addition, institutional and organizational methods for implementing the recommended strategies are often readily available to communities and, in many cases, already in place.
Significance and Application: The information provided in this report can be used by organizations and individuals interested in developing indirect-source control programs needed to attain and maintain ambient air quality standards. The report will help users determine appropriate indirect-source control strategies for a particular type of community and set goals for the amount of emissions reductions desired from indirect-source control programs.
Related Projects: The ARB has funded two studies related to indirect-source activity: Analysis of Indirect Source Trip Activity: Regional Shopping Centers (contract no. A132-094) and Mobility and Livable Communities (contract no. A132-103).

This research was conducted under contract with JHK and Associates (ARB Contract No. 92-348). Comments or questions can be directed to the contract manager, Fereidun Feizollahi, by mail, FAX (916) 322-4357, phone (916) 323-1509, or e-mail: For an index of Research Notes, call (916) 445-0753 or FAX (916) 322-4357.
Copies of the research report upon which this Note is based can be ordered from:
National Technical Information Service
5285 Port Royal Rd
Springfield VA 22161
Request NTIS No. PB96-115704
Title: Transportation-Related Land Use Strategies to Minimize Motor Vehicle Emissions: an Indirect Source Research Study
Author: Deborah Degang and David Early.