Mobile Source Emissions
Mobile Source Ozone Precursor Emissions Characterization
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 Source Emissions Research Program
The ECPB 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, the Mobile Emissions Assessment System for Urban and Regional
Evaluation (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.
Research Test Vehicle
The research test vehicle is a modified 1993
Chevrolet Lumina Euro. Modifications have included the installation
of gaseous analyzers for the measurement of tail pipe emissions of carbon
monoxide, carbon dioxide, oxygen, hydrocarbons, and oxides of nitrogen.
Control and operation of the gaseous analyzers,
AC/DC power supplies, and data acquisition
are conducted from within the back seat area. Moisture removal, calibration
gas control, and sample controls are located in the trunk.
Engine parameter data are collected for analysis with the emissions. The
research test vehicle supports the development of algorithms for the MEASURE
Model, validation of remote sensing instrumentation, and the correlation
of vehicle emissions data collected with remote sensing instrumentation
and dynamometer facilities.
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 Office of Mobile Sources, Ann
Arbor
Additional Resources Outside the U.S. EPA Domain
- Georgia Institute of Technology: