Mobile Source Ozone Precursor Emissions Characterization and Modeling
The objective of this program is to characterize mobile source emissions which are one of the largest sources of tropospheric ozone precursor emissions (CO, NOx, and Volatile Organic Compounds (VOCs)) in the U.S. Due to the dynamic operation of motor vehicles, emissions are highly variable as a function of the mode of operation which is influenced by the driver, the type of vehicle, the roadway grade and the passenger or other load carried or pulled by the vehicle. As a consequence, the spatial distribution of emissions from one of the largest sources of ozone precursor emissions is poorly understood. Although average emissions over several square miles may be estimated by existing models, these models are not adequate for evaluating highway design and traffic effects. This program is researching and developing a new modal emissions model that can give detailed analyses of highway transportation control systems and is expected to provide important input on the effectiveness of future highway intelligent control systems.
Mobile Emissions Assessment
System for Urban and Regional Evaluation (MEASURE)
The Mobile Emissions Characterization Team's research objective is to develop
and validate an air pollutant emissions estimation model for highway vehicles
in order to gain a better understanding of the complex relationships between
vehicle activity factors and emissions. In cooperation with our research partners
at the Georgia Institute of Technology (GIT) and the North Carolina Department
of Transportation (NCDOT), the model is being implemented for the Research
Triangle Park area of North Carolina. The model, MEASURE, is built in
a Geographic Information System (GIS) framework and goes beyond the capabilities
of traditional mobile emissions models by estimating emissions for specific
vehicle and engine operating modes (engine starts, acceleration, deceleration,
idling etc.). The premise is that this approach can produce more accurate
estimates of actual on-road emissions, provide better spatial and temporal
resolution of the emissions, and be sensitive to how changes in highway design
and functional characteristics affect emissions rates. The model can be used
to produce more accurate emissions data for input to air quality dispersion
models and the evaluation of the effectiveness of alternative mobile source
emissions control scenarios. To support model development and validation,
the team develops data acquisition strategies and conducts field studies to
collect real-world vehicle activity and emissions data. The team employs remote
sensing devices, automobiles and trucks
equipped with on-board instrumentation, and other techniques to collect these
data.
Remote Sensing
Remote sensing of automobile emissions is a technique developed in the late
1980s. The remote sensing device (RSD) uses infrared (IR) and, in some cases,
ultraviolet (UV) spectroscopy to measure the concentrations of pollutants
(e.g., CO2, CO, HCs, and NO) in exhaust emissions as the vehicle
passes a sensor on the roadway. The RSD
consists of IR and UV instruments that measure
the exhaust emissions as the vehicle passes through the IR/UV beams and a
monitoring station inside a van. RSDs have
been used to develop a profile of the emission characteristics of the overall
fleet of motor vehicles in metropolitan areas and/or to identify those vehicles
known as "super emitters," which are responsible for much of automotive emissions.
In addition to the source and detector, remote sensors may be equipped with
meteorological stations and speed/acceleration systems which are important
in interpreting exhaust measurements by the RSD.
Additional U.S. EPA Resources
EPA's Emissions Characterization and Prevention Branch:
Mobile Source Instrumented Vehicle Program
EPA's Office of Transportation and Air Quality
Additional Resources Outside the U.S. EPA Domain
Georgia Institute of Technology:
- Transportation/Air Quality Home Page
- Air Quality Laboratory
- North Carolina Department of Transportation
Contact
For further information, contact Sue Kimbrough (kimbrough.sue@epa.gov, 919-541-2612)