Determination Of Safe Buffer Width Of Roadway To Protect Human Health Form Harmful NOx Exposure

According to the 2004 EPA Trends Report, US on-road transportation sources emit 36% of nitrogen oxides (NOx), 63% of carbon monoxide (CO), and 29% of volatile organic compounds (VOCs). This research determines a safe roadway buffer width to protect human health from air pollutant (NOx) exposure. The method was used to determine a buffer width for NOx along Great Southwest Parkway in Grand Prairie, Texas. NOx 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 over 50 % of NOx emissions. Vehicle NOx emission rates along Great Southwest Parkway were measured using a Horiba 1300 OBS on-board emission measurement system, to determine a maximum 2.02 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 meteorological combinations for a 1-hour averaging time, and the 5 worst for an 8-hour averaging time. The maximum emission factor and worst-case meteorological conditions were input into the line source dispersion model CALINE4 to determine worst-case concentrations at 5-m intervals away from the roadway. CALINE4 output was post-processed in Arc View GIS to plot concentrations at receptor locations. Worst-case concentrations were compared to 1-hour NOx standards implemented in Hong Kong. For the current Great Southwest traffic volume, it was found that 1-hour NOx standards would not be exceeded. Additional CALINE4 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 15 and still protect human health from NOx impacts, using a 20-foot buffer.