Abstract
According to the U.S. Environmental Protection Agency (EPA), in 2010 mobile sources in the U.S. contributed 58% of carbon monoxide (CO), 56% of nitrogen oxide (NOx), and 33% of Volatile Organic Compounds (VOCs). Onroad sources also emit a variety of air toxics, including benzene, toluene, and xylenes. The case study presented here determines a safe roadway buffer width to protect human health from nitrogen dioxide (NO2) exposure along an arterial in Grand Prairie, Texas. NO2 health effects include eye, nose, throat, and lung irritation; cough; shortness of breath; tiredness and nausea. In the Dallas Fort Worth region, where Grand Prairie is located, on-road vehicles contribute about half of NOx emissions. Vehicle NOx emission rates along Great Southwest Parkway were measured using a Horiba 1300 OBS onboard emission measurement system, to determine a maximum g/mile emission factor for the corridor. Hourly DFW meteorological data for a 5-year period was processed using CAL3QHCR to determine the 10 worst-case hourly meteorological combinations. The maximum emission factor and worst-case meteorological conditions were input into the line source dispersion model CALRoads View to determine worst-case NO2 concentrations at 5- m intervals away from the roadway. CALRoads View output was post-processed in Arc View GIS to plot concentrations at receptor locations. Worst-case concentrations were compared to the 1-hour NO2 National Ambient Air Quality Standard (100 ppb). For the current Great Southwest traffic volume, it was found that the standard would not be exceeded. Additional CALRoads View runs were conducted to determine how much the traffic volume could increase, and still avoid exceedances outside a 20-foot buffer width, which is a common setback distance in residential areas. It was determined that the traffic volume could increase by a factor of 10 and still protect human health from NO2 impacts, using a 20-foot buffer.
Highlights
Despite stringent exhaust emissions standards, increases in the number of vehicles in use and a corresponding increase in Vehicle Miles Traveled (VMT) mean that vehicles still account for a large percentage of U.S air pollutant emissions
The purpose of this case study was to determine a safe roadway buffer width to protect human health from nitrogen dioxide exposure along an arterial located in Grand Prairie, Texas
Nitrogen Oxide (NOx) emissions data was collected along Great Southwest Parkway in Grand Prairie, Texas, from Abram Street to Fairmont Street as part of a study, described elsewhere, to measure changes in vehicle emissions before and after traffic signal retiming [38]
Summary
Despite stringent exhaust emissions standards, increases in the number of vehicles in use and a corresponding increase in Vehicle Miles Traveled (VMT) mean that vehicles still account for a large percentage of U.S air pollutant emissions. According to the U.S Environmental Protection Agency (EPA), in 2010 mobile sources in the U.S contributed 58% of Carbon Monoxide (CO), 56% of Nitrogen Oxide (NOx), and 33% of Volatile Organic Compounds (VOCs). Interest has emerged determining in roadway buffer widths needed to protect human health [33-36]. In many regions across the US, on-road vehicles such as cars, motorcycles and light duty gasoline trucks contribute 50% of nitrogen oxide (NO + NO2 = NOx) emissions [2]. NO2 is one of six criteria pollutants for which the U.S Environmental Protection Agency has issued National Ambient Air Quality Standards (NAAQS). The purpose of this case study was to determine a safe roadway buffer width to protect human health from nitrogen dioxide exposure along an arterial located in Grand Prairie, Texas. CALRoads View to determine an appropriate buffer width for Great Southwest Parkway in Grand Prairie, Texas
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