Traffic Induced Impacts and their Characterization in Air Dispersion Models
The purpose of this research is to evaluate dispersion models and understand their current limitations using data collected from tracer studies conducted at locations with complex real-world traffic flow patterns. The research would be carried out in three phases: (1) identification and gathering of tracer experimental data collected and performed within the near-roadway environment; (2) evaluation of the tracer data for use in model evaluation and the development of a modeling protocol for carrying out an evaluation and (3) model to monitored evaluation to understand if dispersion modeling techniques between different dispersion model formulations and parametrization are both statistically and practically different. The research will ideally include locations with complex vehicle movement such as high volume signalized intersections, freeway interchanges, roundabouts, and urban street canyons. As part of the data gathering effort, the research will gather data from databases of tracer field experiments completed in high traffic volume environments which may include: NCHRP 25-6 tracer studies completed at suburban intersections in Denver, Loudoun County, VA and Tucson; Texas DOT tracer studies done in urban street intersections in Houston and College Station; and street canyon air tracer experiments by the Japan Environmental Management Association in Tokyo as well as other locations. In addition to tracer measurements these studies will ideally include turbulence measurements to enhance the understanding of vehicle induced wake effects. These tracer databases can be used to understand dispersion in high traffic environments and to evaluate the dispersion models under a wide variety of meteorological conditions, locations, land-use, and under conditions with low, moderate and high traffic volume operations so as to determine model disparities and limitations. The study will evaluate dispersion models which are used in the near road environment (e.g., AERMOD, CALINE3, CALINE4, RLINE, ROADWAY-2 and HYROAD). The research will identify current limitations in the dispersion component of these models and the relevant importance of those limitations through model evaluation and testing (e.g., testing with degraded datasets - no turbulence measurements, limited traffic vehicle size characterization). The limitations should identify what are the most important model inputs and the availability of those inputs and future research needed to help address these inadequacies. Similar research elements as to the research proposed here has been completed by the Airport Cooperative Research Program (ACRP) of the Transportation Research Board of the National Academies - ACRP Report 02-58, " Dispersion Modeling Guidance for Airports Addressing Local Air Quality Health Concerns" sponsored by the Federal Aviation Administration, which could provide guidance to the research.
Federal and state air quality standards as well as levels of significance have been lowered many times over the past twenty years and further lowering of the standards may be anticipated. Thus tools to evaluate the future impacts need to reflect air quality impacts with as much accuracy as possible given this lower ceiling. One element not included in most air quality models is near-roadway turbulence. This research will address the importance of vehicle-inducted turbulence and their effects on air pollutants distribution in and near high traffic environment and the impacts on air pollution distribution. The research will identify limitations with current air dispersion models and identify the particular areas in which modeling techniques need to be improved to provide reliable air quality assessments.
March 20, 2017
- items posted in the last 7 days (30 days for TERI)