Atmospheric and wind tunnel studies of gaseous dispersion near roadways have identified new concepts regarding the influence of roadway traffic and stimulated the development of a versatile yet simple simulation model, ROADMAP. Influences of site geometry and roadway configurations were observed and quantified. Two effects found to be particulary significant to microscale dispersion were (a) thermal turbulence and buoyancy caused by vehicular waste heat and (b) mechanical turbulence from highway traffic. ROADMAP simulates two-dimensional gaseous dispersion patterns for various roadway configurations including grade-level, vertical, and slant-wall cut, fill, and viaduct sections. Development of the model is first detailed for a uniform, grade-level freeway. Dispersion patterns were obtained up to heights of 14 m and to downwind distances of 100 m by a sampling array that measured meteorological conditions and concentrations of carbon monoxide and two artificial tracer gases relaeased in the traffic. Comparison of equivalent field and wind-tunnel tests for grade-level roads shows good agreement except for acute wind-roadway angles. ROADMAP's capability for varied site geometries was evaluated by analyzing field and wind tunnel tests for 20 roadway configurations. Comparisions of ROADMAP to independent cabon monoxide data (i.e., data not used in developing the model) from the grade-level field tests resulted in high values of the linear correlation coefficient: 0.91 for neutral stability, 0.67 for stable atmospheric conditions, and 0.80 for unstable conditions. Values for the cut and elevated-section tests in the wind tunnel ranged from 0.69 to 0.93. /Author/

Media Info

  • Media Type: Print
  • Features: Figures; Photos; References; Tables;
  • Pagination: pp 43-55
  • Monograph Title: Air quality analysis in transportation planning
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00193365
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: May 26 1979 12:00AM