Two methodologies for modeling commuter exposures are proposed: computer-oriented approach and a manual approach. Both modeling methodologies require that major commuter routes, or pathways, be identified and that the traffic on the remainder of the roadway network be treated as background pollutant sources. Since the majority of pathway exposure is expected to result from emissions on the pathway itself, the emissions and dispersion of non-pathway source pollutant are handled in a simple fashion. Pathway traffic undergoes a more sophisticated treatment in that congestion and delay due to signalization are accounted for and emissions are computed accordingly. The methodology used to simulate the dispersion of pathway emissions utilizes three separate dispersion treatments, according to whether the roadway is limited-access, non-limited access, or a street canyon.

Project Officer: William Petersen. SRI International "February 1979." "EPA-600/4-79-010."