Science Inventory

MOBILE EMISSIONS ASSESSMENT SYSTEM FOR URBAN AND REGIONAL EVALUATION

Citation:

Description:

A working research model for Atlanta, GA has been developed by Georgia Tech, and is called the Mobile Emissions Assessment System for Urban and Regional Evaluation (MEASURE). The EPA Office of Research and Development has developed an additional implementation of the MEASURE research model for the Research Triangle Park, NC area. The MEASURE emissions modeling concept will benefit state and local air quality agencies, local metropolitan planning organizations, or academic research organizations to further their understanding of current transportation emissions sources as well as to model future transportation control strategies. At present, MEASURE focuses on estimating emissions for ozone precursor pollutants (volatile organic compounds, nitrogen oxides, carbon monoxide) and has limited emission estimation capabilities for other pollutants. In the future, better characterization of particulate matter and hazardous air pollutant (air toxic) emissions is planned.

MEASURE includes the following advancements to the state-of-the-art highway vehicle emissions modeling:

  • Advanced modeling of emissions rate characteristics of different vehicle technology groups;
  • Advanced modeling of vehicles based on power demand characteristics;
  • Advanced modeling of vehicles as a function of a vehicle's mode of operation;
  • Characterization of physical transportation networks in terms of spatially distributed attributes (e.g., road grade) that affect vehicle modal operations; and
  • Integration of model development and application in a GIS environment, linking spatially arrayed vehicle distribution, vehicle usage, and behavior, and transportation network characteristics and volume flows.
The basis for this model is modal, which refers to the modes of engine operation that a vehicle may be in at any given point in time such as engine start, idle, hot stabilized operation, enrichment conditions (influenced by high acceleration and power demand), hot soak evaporation, etc. Within the current model design, a variety of vehicle activities, environmental factors, vehicle and driver characteristics are considered as well as the spatial and temporal distributions of these vehicle and driver characteristics.

On- and off-network components are included in the model. On-network components refer to vehicle activity on major roadway links such as interstates, major arterials, etc. Traffic volumes, speeds, temporal distributions, and fleet characteristics are included for network components. Off-network components refer to vehicle activity on local roads and streets. Typically, these local roads are aggregated into mini-transportation analysis zones. Off-network activities are derived from socioeconomic and environmental data (i.e., population, housing, employment, land use) and aggregated on a zone basis.

Fleet composition is an important factor in the model. This is due to the numerous vehicle parameters that are used to determine emission rates. These vehicle parameters include vehicle class, emitter class, model year, gross vehicle weight, engine displacement, and fuel injection and control system technology. Additionally, these vehicles have spatial variations throughout an urban area with correlations to certain socio-economic data (e.g., population, housing income). The fleet for a given area is subdivided into various technology groups and these groups are tracked within the model. Emission rates are applied separately to each technology group. The emission rate algorithms included in the model are based upon statistical analysis of emissions data and will be determined for all the modes that are included in the model.

Record Details:

Record Type:MODEL
Product Published Date:11/05/2003
Record Last Revised:03/31/2011
Record ID: 74939