With the increasing emphasis on environmental protection being manifested by the federal government and the general public, highway planning agencies are now required to assess in detail the impacts of proposed facility improvements and newly located roads on corridor ambient air quality. Experience on numerous projects throughout the nation has shown that such assessments generally require lengthy, comprehensive evaluations of corridor meterology, preconstruction ambient air quality, post-construction traffic growth and redistribution effects, gross emission generation, and pollutant dispersion characteristics. The definition of the several elements required for a comprehensive highway air quality impact assessment must be undertaken at the earliest project planning stage so that all necessary studies and field surveys can be initiated in parallel with other aspects of the location study or environmental impact evaluation. This paper describes a novel procedure by which the transportation planner can determine whether detailed air quality studies are warranted for a proposed route alternate under consideration. The environmental capacity of critical average daily traffic of a given roadway is defined as a function of readily available highway planning parameters. A series of capacity curves and planning criteria are presented that describe maximum average daily traffic volumes that can be tolerated under generalized, most adverse meterological conditions before the national ambient air quality standards for carbon monoxide and hydrocarbons will be exceeded at a given distance from the edge of the roadway. Use of this methodology has proved to afford a direct, valid means for structuring highway air quality studies and for direct assessment of air quality impact of proposed highways in suburban and rural environments. /Author/

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    • Publication of this paper sponsored by Task Force on Highways and the Environment. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved.
  • Authors:
    • Rocco, Vincent A
  • Publication Date: 1973

Media Info

  • Media Type: Digital/other
  • Features: Figures; References;
  • Pagination: pp 67-74
  • Monograph Title: Air pollution controls for urban transportation
  • Serial:

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Filing Info

  • Accession Number: 00157795
  • Record Type: Publication
  • ISBN: 0309021995
  • Files: TRIS, TRB
  • Created Date: Sep 28 1977 12:00AM