Development of a modal emissions model using data from the Cooperative Industry/Government Exhaust Emission test program
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2003-06-22
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NTL Classification:AGR-IMPACTS-Environment;NTL-ENERGY AND ENVIRONMENT-Air Quality;NTL-ENERGY AND ENVIRONMENT-Environment Impacts;NTL-HIGHWAY/ROAD TRANSPORTATION-HIGHWAY/ROAD TRANSPORTATION;
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Abstract:The Environmental Protection Agency’s (EPA’s) recommended model, MOBILE5a, has been
used extensively to predict emission factors based on average speeds for each fleet type.
Because average speeds are not appropriate in modeling intersections or other scenarios
involving intermittent travel, emission factors that are specific for vehicle operating modes
(acceleration, deceleration, free-flow, and idle) have been studied in the past. Several models
have been developed that use the concept of acceleration-speed products to serve as input
variables to determine multipliers that can be used to modify constant speed emission factors.
Although relatively simplistic, this process provides results that are considered more accurate
than constant speed emission factors. The Comprehensive Modal Emissions Model (CMEM)
developed under sponsorship by the National Cooperative Highway Research Program
(NCHRP) is based on a parameterized physical approach. While anticipated to be more
accurate, the input requirements to the model are necessarily more complicated.
This paper presents a new modal emissions model based on existing emissions data from the
early 1990s revision efforts of the Federal Test Procedure (FTP). The model updates the older
acceleration-speed product models that were based on data from the 1970s. Using secondby-
second emissions data, several different forms of the modeling equations were developed
and statistically analyzed for predicting multiplying factors for CO. A goal in developing this
model is to serve as a comparison basis for the NCHRP model. The second and more
important goal is to use the model as part of a microscale traffic simulation model that predicts air quality near roadways.
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