Analyses, Experimental Studies, and Evaluations of Control Measures for Air Flow and Air Quality On and Near Highways: Vol I -- Experimental Studies, Analyses, and Model Development

003457581981Volume 1PDFTech ReportFHWA-RD-81- 51DOT-FH-11-8125AirAir quality managementDepressed highwaysEvaluationExperimentsFlowHighway bridgesHighwaysMathematical modelsMeteorological phenomenaPhotographyTracers (Chemistry)TrafficTraffic speedTraffic volumeWind tunnelsUnited StatesUnited States. Department of Transportation. Federal Highway AdministrationDabberdt, Walter F.Shelar, EugeneMarimont, DavidSkinner, GeorgeSRI InternationalUnited States. Federal Highway Administration. Environmental DivisionUS Transportation CollectionExperimental and theoretical investigations have been made of meteorological and air quality conditions near a broad range of complex roadway configurations. These are described, and some new insights into the interrelationships among traffic, meteorology, and configuration are discussed. The development of a new and versatile dispersion model, called ROADMAP, is also described together with an evaluation of the model's performance relative to measured atmospheric and wind tunnel pollutant concentration data. (Volume II of this final report--FHWA/RD-81/052--is a set of guidelines for the understanding and estimation of air quality conditions for alternative roadway configurations.) The atmospheric experiments were conducted at a grade-level, depressed, and elevated freeway sections; approximately 50 h of meteorological, traffic, air quality, and dual-tracer data were obtained at each site. The wind tunnel tests comprised measurements at nine distinctly different roadway configurations; helium was released at a controlled rate from the model vehicles and was sampled at 20 locations above, upwind, and downwind of the roadway. Wind speed and direction, traffic speed and direction, and ground roughness were varied among the 360 tests. Visual tracers and high-speed photography were also used in the wind tunnel. The experimental data indicates a significant effect of waste heat on near-roadway dispersion. The combined effects of traffic movement and waste heat emissions cause increases in the turbulence intensity of up to 200% across the roadway. However, there is apparently little effect on turbulence caused by changes in traffic volume or speed (for the moderate-to-heavy traffic conditions present during the tests). An aerodynamic or shelter effect is postulated to exist and to be a significant influence for grade-level roads. The semi-empirical roadway atmospheric dispersion model for air pollution (ROADMAP) simulates two-dimensional dispersion patterns for various roadway configurations: grade-level, vertical and slant-wall cut, fill, and viaduct sections. (FHWA).93