Environmental Justice Implications of Roadway Topography

US Transportation Collection2020PDFTech ReportGbologah, FranklinPrendergast, KylaRodgers, MichaelCenter for Transportation, Equity, Decisions & Dollars (CTEDD). University of TexasUniversity of Texas at ArlingtonUnited States. Department of Transportation. Research and Innovative Technology AdministrationUnited States. Department of Transportation. University Transportation Centers (UTC) ProgramCenter for Transportation, Equity, Decisions and Dollars (CTEDD)GeorgiaUnited StatesDispersions (Chemistry)Environmental impactsEnvironmental justiceHighway gradesPollutantsTopographyTraffic congestionTraffic simulationEquity (Justice)EmissionsNear-roadHotspotMotor Vehicle Emissions Simulator (MOVES)AERMODVissimPM2.5CTEDD 019-09USDOT \u2013 69A3551747134Final ReportThis study evaluates environmental justice implications of roadway topography. Most MPOs and transportation agencies use a fixed buffer of 200 meters to identify the population that is at-risk of unsafe exposure to mobile emissions near roadways. Current analysis methodologies are unable to account for the impact that road grade has on emission quantities and therefore, pollutant concentrations in air. This study used Vissim\uae - an advance traffic simulation tool to generate both grade-sensitive and grade-insensitive vehicle speed and acceleration data from a 9-mile high traffic corridor of Atlanta\u2019s Interstate 75. The vehicle activity data was subsequently analyzed with MOVES-Matrix to generate CO and PM2.5 emission rates for about 310 segments that make up the project corridor. The USEPA air dispersion modeling tool \u2013 AERMOD was then used to estimate the distribution of pollutant concentrations at receptors distributed throughout the areas adjacent to the corridor. This concentration data was subsequently used to generate heat maps that facilitated the comparison of the extents of the 200-meter buffer and the extents of a single contour of value equal to the NAAQS limit for the relevant pollutant. For any given scenario, the buffer is deemed adequate if it is able to completely contain contour. The study finds that under free flow traffic conditions, the buffer is adequate for all the scenarios examined. However, for congested traffic conditions the study finds the buffer inadequate for CO dispersion. For PM2.5 dispersion under congested traffic, the findings show that the buffer is adequate. However, it is noted that this study uses only about 50 percent of the Heavy-Duty truck composition in the corridor fleet. HDVs are major contributors to onroad mobile PM2.5 pollution. Furthermore, the findings do not account for background PM2.5 concentrations in the project corridor. These findings are relevant because they indicate that a universal fixed buffer may not be the best way to identify vulnerable populations to near-road emission exposure. Buffer distances should be decided with consideration to the type of pollutant, fleet composition, average speeds, road grade, and local weather.120