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APRAC-3: Emission and diffusion modeling package

The Air Pollution Research Advisory Committee model - APRAC-3 computes traffic pollution mainly in an urban area, given a network of roads. It has been used to simulate the diffusion of hydrocarbons, carbon monoxide and nitrogen oxides. Computationally, it relies on the use of the gaussiam plume approximation, but its more interesting feature is perhaps in the assistance in evaluating traffic emissions.

The model package consists of three modules: a preprocessor of emission factors (based on the program MOBILE1 from the US EPA), the computation of emissions (both along the main traffic paths and in each square of the grid in which the area under analysis must be divided), the computaion of pollutant diffusion with specific attention to the problem of urban canyons.


area: air quality
objectives: simulation, forecasting
description: traffic pollution, gaussian plume,line sources, urban site, hydrocarbons, pollutants from combustion, nitrogen oxides, short term


The model is part of UNAMAP and is available on magnetic tape from:
Computer Products
National Technical Information Service
U. S. Department of Commerce
Springfield, Virginia 22161
Phone (703) 487-4650


P. B. Simmon, R. M. Patterson, F.L. Ludwig, L. B. Jones
Atmospheric Science Center
SRI International
333 Ravenswood Avenue
Menlo Park, California 94025


  • J.L.Heffter, A.D.Taylor, "A Regional Continental Scale Transport Diffusion And Deposition Model" Nat.Ocean and Atmos.Admin, 1975
  • M.E.Holzworth, G.C.Miller, "An Atmospheric Diffusion Model For Metropolitan Areas" J.Air Pollut. Control Association, 1967
  • K.B.Johnson, W.F.Dabberdt, F.L.Ludwig, R.J.Allen, "Field study for initial evaluation of an urban diffusion model for carbon monoxide" EPA, ContractCAPA-3-68, 1971
  • F.L.Ludwig, W.F.Dabberpt, "Comparision Of Two Atmospheric Stability Classification Schemes In A Urban Application" J.Appl.Meteorol., 1976
  • F.L.Ludwig, "Urban Air Temperatures And Their Relation To Extra-Urban Meteorological Measurements" Proc.Semiannual.Meeting Of Am.Soc.Heat.Refrig. and Air Cond.Eng., San Francisco, 1970
  • S.L.Mancuso, F.L.Ludwig, "User's manual for the APRAC-1A diffusion model computer program" CRC and EPA, Contract CAPA-3-68, 1972
  • H.Panosky, "Introduction to Dinamic Meteorology" University Park, Pennsylvania, 1957
  • F.Pasquill, "The Estimation Of The Dispersion Of WindBorne Material" Met.Mag.,90,33,49,1961
  • F.V.Webster, "Traffic signal settings, road research" Technical paper no 37, Road Research Laboratory, H. M. Station Office, London, Engliand, 1958



Estratto dalla banca modelli del progetto CEE GAIA INCO - www.ess.co.at/GAIA