Mobile Source Emission Inventory -- EMFAC2011 Frequently Asked Questions

This page last updated on January 2013

 

EMFAC2011
EMFAC2011 Web Database
EMFAC2011-LDV
EMFAC2011-HD
EMFAC2011-SG
EMFAC2011 and Project Level Assessment

 

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EMFAC2011

 

EMFAC2011 Web Database

EMFAC2011-LDV

 

EMFAC2011-HD

 

EMFAC2011-SG

 

EMFAC2011 and Project Level Assessment

 

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EMFAC2011

  • What is EMFAC?
    • EMFAC is California’s model for estimating emissions from on-road vehicles operating in California.
    • It is built on decades of vehicle testing and analysis, and is informed by DMV registration data, the Smog Check program, and many other data sources.
    • EMFAC is used as a starting point for developing plans to meet air quality standards, and for assessing the impact of motor vehicle emissions regulations on emissions and air quality.
  • What is EMFAC2011?
    • EMFAC2011 is the latest update to the EMFAC model. The update is required to meet federal air quality and transportation planning guidelines.
    • EMFAC2011 has been updated (January 2013) to provide updated web-tools and training modules that allow easier access to emission factor data and provide some tips for obtaining and using emission factor data for project level assessment. It was also updated to correct the number of starts in several smaller categories of gasoline vehicles in Santa Clara County, which had led to an overestimate of emissions. No other counties were affected and no model algorithms were changed in the update.
    • When EMFAC2011 was originally released in 2011, it was updated
      • with the latest information on vehicle populations and miles traveled in California;
      • to include the impacts of recently adopted diesel regulations including the Truck and Bus Rule and other diesel truck fleet rules: the Pavley Clean Car Standard, and the Low Carbon Fuel Standard; and
      • to reflect the latest emissions inventory methods for heavy duty trucks and buses. These estimates reflect the impact of the economic recession.
  • How is EMFAC2011 structured?
    • EMFAC2011 has been updated with the latest population, activity, and emissions data. It reflects recently adopted rules that were not reflected in EMFAC2007. To achieve these improvements staff modernized the structure of the EMFAC system.
    • EMFAC2011 is composed of three modules:
      • EMFAC2011-LDV (Light-Duty Vehicle): Estimates emissions for gasoline vehicles, diesel vehicles <14,000 pounds gross vehicle rated weight, urban transit buses, and motor homes.
      • EMFAC2011-HD (Heavy-Duty): Estimates emissions for commercial diesel trucks and buses which exceed 14,000 pounds gross vehicle rated weight.
      • EMFAC2011-SG (Scenario Generator): Estimates emissions for alternative air quality / transportation planning scenarios with alternative vehicle miles traveled by speed and vehicle class, using methods consistent with previous EMFAC model versions.
  • How can I access EMFAC2011?
    • Staff has developed a new mobile source emissions inventory web portal, which provides access to emissions inventory methods, data and documentation.
    • Access can be found at the following link: http://www.arb.ca.gov/msei/msei.htm
    • EMFAC2011 output is available on two new searchable databases that provide comprehensive EMFAC emissions and emission rate estimates.
    • Most model users will find it more convenient to use the EMFAC2011 web database tool than using the EMFAC2011 model directly.
    • Data are available for multiple levels of detail to serve most user needs.
    • The three EMFAC2011 modules are available for download.
  • How can I learn more about EMFAC2011?
    • Staff has developed and released on-line training presentations that provide model users with both an overview to EMFAC2011 and specific training on how to use the new EMFAC2011 web database, EMFAC2011-HD, and EMFAC2011-SG.
    • Technical documentation is available that describes how the EMFAC model works, and provides the technical basis for the methods used to calculate the on-road emissions inventory.
    • This information and more is available at the website listed above.

 

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EMFAC2011 and Project Level Assessment

  • What tools have been provided for project-level assessments?
    • Since EMFAC2011 uses a modular emissions modeling approach that departs from the single model approach used by EMFAC 2007, it may now be necessary to use more than one method to obtain the emission rates needed for conducting project-level analyses. The Project-level Assessments are divided into two approaches: (1) Simplified Approach, and (2) Detailed Approach.
    • These approaches are discussed in a new Handbook for Project Level Assessment .(UPDATED February 2013)
    • Since most users do not have project-specific information for (a) regional temperature and relative humidity profiles, (b) vehicle age distributions, and (c) vehicle rest/soak time, ARB has developed a simplified project-level emission rates tool, called the EMFAC2011-PL tool.  The EMFAC-PL tool uses the default inventory from EMFAC2011-SG (Ver 1.1) and generates emission rates based on default fleet distributions in the region for project-level assessments.
    • Where detailed project-specific information is available, projects will need to use a combination of EMFAC2011-LDV and the online emission database tools (http://www.arb.ca.gov/emfac) and the idling rates database (http://www.arb.ca.gov/msei/emfac2011_idling_emission_rates.xlsx).
  • When should I use EMFAC2011-PL for project-level assessment?
    • The simplified approach is appropriate when projects utilize EMFAC default parameters for the following variables (a) regional temperature and relative humidity profiles, (b) vehicle age distributions, and (c) vehicle rest/soak time.  Also, the PL tool only generates one combined output for “All Model Year” age (population/VMT weighted).  Therefore, if the users require model year specific emission rates, then they are recommended to use the Detailed Approach using EMFAC2011-LDV and or EMFAC2011 Web Database
  • What are the system requirements for installing EMFAC2011-PL tool?
    • The EMFAC2011-PL (Ver 1.1) tool requires Microsoft XP or a more recent operating system; and Microsoft Access and Excel 2003 or newer to run the tool.  EMFAC2011-PL also requires that EMFAC2011-SG (Ver 1.1) is installed on user’s computer since the PL tool uses the inventory files from the SG module.
  • When should I use EMFAC2011-LDV for project-level assessment?
    • For vehicles specific to the EMFAC2011-LDV module, if there is more appropriate project-specific information available for either (a) regional temperature and relative humidity profiles, (b) vehicle age distributions, and (c) vehicle rest/soak time, then the user is encouraged to use the detailed approach.
  • When should I use the EMFAC Web Database for project-level assessments?
    • For vehicles specific to the EMFAC2011-HD module, if there is more appropriate project-specific information available for either (a) regional temperature and relative humidity profiles, (b) vehicle age distributions, and (c) vehicle rest/soak time, then the user is encouraged to use the detailed approach.

 

 

EMFAC2011 Web Database

  • What is the EMFAC2011 Web Data Tool?
    • The EMFAC2011 web data tool is two new internet databases which is accessible to all users and provides access to EMFAC emissions and emission rates at varying levels of detail. It is located through the ARB mobile source emissions inventory website: http://www.arb.ca.gov/msei/msei.htm; at http://www.arb.ca.gov/emfac
  • Why access the EMFAC2011 Web Data Tool?
    • Internet database technologies have improved drastically in the past decade, allowing ARB to serve more than 80 GB of data to air quality and transportation professionals at government agencies and in industry. We believe the database provides a more simple and user-friendly way to access information than running the EMFAC model. Because EMFAC2011 is a suite of three modules within one modeling system, we believe accessing the web database will be much easier than downloading and running each module individually.
  • How is the EMFAC2011 Web Data Tool Organized?
    • The user may choose to download emissions or emission rates from the web tool. The emissions database format is very similar to the EMFAC2007 .bdn output, which provides emissions (tons/day), fuel consumption (1000 gallons per day), population, vehicle miles traveled and trips; by pollutant and process; by vehicle class, fuel, model year, and speed. The emissions rate database format is identical to the emissions database format, except that emission rates are provided instead of emissions. Emission rates are expressed in grams/mile for running exhaust and evaporative emissions, and grams per vehicle-day for non-running evaporative processes (hot soak, diurnal, resting), idling, and start emissions.
    • To start selecting data, the user must specify a data type, region type, region, calendar year, and season. Users have the option to download different levels of detail in vehicle categories. The EMFAC2011 vehicle category scheme is highly detailed, providing each vehicle category covered by the EMFAC2011-LDV and EMFAC2011-HD modules separately. There are many individual categories of diesel trucks in the HD module that describe different weights, body types, and vocational categories. Alternately, users have the option to summarize emissions to the EMFAC2007 categorization scheme in which diesel trucks are collapsed just by weight class for medium and heavy heavy-duty diesel trucks. The table at http://www.arb.ca.gov/msei/vehicle-categories.xlsx describes each vehicle class and how it is defined.
    • Then, the tool allows different levels of aggregation of database output including:
      • one vehicle category, multiple vehicle categories (using control or shift keys) or all vehicle categories;
      • one model year, multiple model years (using control or shift keys), all model years, or all model years combined into one row;
      • by speed bin or for all speed bins combined (when speed bins are selected only running exhaust emissions are provided);
      • gasoline fueled vehicles, diesel fueled vehicles, or both.
  • What can I use the EMFAC2011 Web Data Tool For?
    • Most analyses that EMFAC can be used for can be completed using the web data tool. Emissions trends can be queried by viewing data for each individual year of interest. Model year specific emission rates can be viewed over time to see how deterioration is modeled to impact emissions, by selecting multiple calendar years, one at a time. 
    • The emissions rate tool is provided primarily for assisting consultants that need emission rates for performing project level assessments for CEQA, permitting, and other applications.
    • For more information on project level assessment, go here. (UPDATED January 2013)
  • Are there any limitations to the EMFAC2011 Web Data Tool?
    • If you have suggestions for how to improve the database, please send an email to msei@arb.ca.gov.
    • The EMFAC2011 Web Data Tool is based upon the same emissions output that is embedded in EMFAC2011-SG. In some cases, speed distributions provided by local transit agencies do not provide VMT in a speed bin. In other cases a vehicle category may have zero population in a selected region. In these cases emission rates will be zero in the database.
  • How do I calculate Methane (CH4) and Nitrous Oxide (N2O) emissions?
    • Methane (CH4) calculation method
      • Run EMFAC2011-LDV to calculate CH4 for those vehicle categories;
      • Use  CH4 = 0.0408 * TOG = 0.058821 * THC to calculate CH4 for EMFAC2011-HD categories.
    • Nitrous Oxide (N2O) calculation method
      • Use 4.16% of NOx to calculate N2O for all gasoline vehicles, the same assumption as for the emissions inventory for the Advanced Clean Cars Rule;
      • Use 0.3316 g/gallon fuel to calculate for all diesel vehicles as the GHG inventory.

 

 

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EMFAC2011-LDV

  • What is EMFAC2011-LDV?
    • EMFAC2011-LDV is one of three modules of the EMFAC modeling suite. It is used to estimate emissions of gasoline vehicles, diesel vehicles <14,000 pounds gross vehicle rated weight, urban transit buses, and motor homes.
    • It is based on the EMFAC2007 model, and has been updated with 2009 population data from the Department of Motor Vehicles, as well as updated vehicle miles of travel and speed data from regional transportation planning agencies across California.
    • It was updated in October 2012 to correct the number of starts in several smaller categories of gasoline vehicles in Santa Clara County which had led to an overestimate of emissions. No other counties were affected, and no model algorithms were changed in the update.
  • How do I access EMFAC2011-LDV Data?
    • EMFAC2011-LDV emissions and emissions rate data are available through our website: http://www.arb.ca.gov/msei/msei.htm
    • For most users accessing the data directly will provide a simple and user-friendly way to access information. The module can also be downloaded directly from this website, as can a user’s guide and technical documentation.
  • When should I run EMFAC2011-LDV?
    • We recommend all EMFAC users review available data on our web site prior to exercising the model. EMFAC2011-LDV can be used:
      • To generate the ERP files for air quality modeling purposes;
      • To obtain the default mobile source inventories for the light-duty fleet;
      • To generate default or user-defined emission rates for the light-duty fleet;
      • To obtain the default or user-defined hourly emissions inventories for the light duty fleet; 
      • To quantify the effect of modifying the temperature and humidity profiles for the light duty fleet; and
      • To calculate methane (CH4) emissions for vehicle categories in EMFAC2011-LDV.
  • Is there anything else I need to know about EMFAC2011-LDV?
    • Yes. Because EMFAC2011-LDV does not estimate emissions for all on-road vehicles, it cannot be used alone to estimate emissions from all vehicles. In addition the module is not programmed to output carbon dioxide emissions that reflect the Pavley regulation and the Low Carbon Fuel Standard.
    • EMFAC2011 in general and EMFAC2011-LDV in particular does not include the benefits of the Advanced Clean Cars Program.

 

 

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EMFAC2011-HD

  • What is EMFAC2011-HD?
    • EMFAC2011-HD is one of three modules of the EMFAC modeling suite. It is used to estimate emissions of commercial diesel trucks and buses exceeding 14,000 pounds gross vehicle rated weight.
    • Population and activity estimates are identical to those approved by the Board for the Statewide Truck and Bus Rule. Emission factors reflect the same adjustments made for the Truck and Bus Rule, and are generated at a regional level, reflecting regional specific speed and meteorological conditions. The emission factor modeling methods are identical in framework to those used in EMFAC2007.
  • How do I access EMFAC2011-HD Data?
    • EMFAC2011-HD emissions and emissions rate data are available through our website: http://www.arb.ca.gov/msei/msei.htm
    • For most users accessing the data directly will provide a simple and user-friendly way to access information. The module can also be downloaded directly from this website, as can a user’s guide and technical documentation.
  • When should I run EMFAC2011-HD?
    • We recommend all EMFAC users review available data on our web site prior to exercising the model. EMFAC2011-HD can be used to obtain default mobile source inventories for the heavy-duty fleet.
  • What else do I need to know about EMFAC2011-HD?
    • Because EMFAC2011-HD does not estimate emissions for all on-road vehicles, it cannot be used alone to estimate emissions from all vehicles.
    • The module is not programmed to output carbon dioxide emissions that reflect the Low Carbon Fuel Standard; the Pavley regulation does not affect HD categories.
    • The module requires a more complicated installation procedure than EMFAC-LDV, and requires the installation of several free software packages. Detailed installation instructions are provided in the User’s Guide on our web site.
  • What are the system requirements? Users will need:
    • Windows 2007 64-bit;
    • .NET Framework 4;
    • MySQL Community Server 5.5;
    • Mysql-connector-net-6.2;
    • MySQL database manager application program, such as MySQL Workbench;
    • 25 MB space for each sub-area, calendar year combination.
  • What is included in the installation package?
    • The installation package includes the EMFAC-HD module and input files.
  • Where do I get the other software packages that I need?
    • EMFAC2011-HD requires the 64-bit version of Windows 7. If you don’t have this software you may purchase or upgrade Microsoft Windows. Links to the other required software are provided on the EMFAC2011-HD download site.
  • What is the scope of inventory provided by EMFAC-HD?
    • EMFAC-HD provide default emissions for NOx, TOG, ROG, PM10, PM2.5, CO, CO2, and SOx as well as fuel consumption for summer, winter and annual average between calendar years 1990 and 2035 for 69 sub-areas throughout California.
  • Does EMFAC-HD provide daily and hourly emissions?
    • EMFAC-HD only provides daily emissions.
  • Does EMFAC-HD provide by model year and/or by speed emissions?
    • Yes. Users can choose to output by model year and by speed emissions in 5 mile per hour speed bins.
  • Can a user change the VMT and /or speed profile in EMFAC-HD?
    • No. EMFAC-HD provides default runs. EMFAC2011-SG provides the capability of running alternative transportation planning scenarios.
  • Can a user change the temperature and humidity inputs in EMFAC-HD for air quality modeling?
    • No. Emissions from diesel vehicles are not very sensitive to temperature and humidity. Annual, summer, and winter runs are available for each region.

 

 

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EMFAC2011-SG

  • What is EMFAC2011-SG?
    • EMFAC2011-SG is one of three modules of the EMFAC modeling suite. It is used to estimate emissions from all on-road vehicles for alternative transportation planning scenarios. EMFAC-SG takes the output from EMFAC-LDV and EMFAC-HD and applies scaling factors to estimate emissions consistent with user-defined vehicle miles of travel (VMT) and speeds.
  • What is new in EMFAC2011-SG (Ver 1.1)?
    • The new version also allows users to generate output specific to the SB375 vehicle categories (LDA, LDT1, LDT2, MDV), and output in the CEIDARS Transaction File (.ctf) format.
  • I had installed EMFAC2011-SG (Ver 1.0).  How do I replace it with the new version (Ver 1.1)?
    • Delete the EMFAC2011-SG (Ver 1.0) folder from the C Drive
    • Install the EMFAC2011-SG (Ver 1.1) module using the installation procedure in the updated EMFAC2011-SG User’s Guide
  • When should I run EMFAC2011-SG?
    • EMFAC-SG provides air quality planners, transportation planners, and other EMFAC users a tool for assessing emissions under different future growth scenarios. This includes conformity analyses of transportation plans and programs with the State Implementation Plans required by federal law, State Implementation Plan inventories, and alternative growth scenarios associated with regional transportation planning for greenhouse gas reductions (SB375).
  • What are the inputs in EMFAC2011-SG?
    • EMFAC2011-SG has three main inputs, and one optional input:
      • Base Inputs
      • VMT Distribution by Vehicle Category
      • Speed Profiles
      • Regional Scenario (optional)
    • The modeling parameters in all three inputs are defined at the sub-area level. In order to correlate the data in the three input sheets, the module identifies each sub-area case as a “Scenario”. In order to process regional inventories consisting of multiple sub-areas, users are required to classify all the sub-area “scenarios” into regional “groups”; the SG module processes each scenario individually and aggregates data by groups at the end of model execution.
  • How does the SG module work?
    • EMFAC2011-SG reads pre-formatted emissions inventory output data from EMFAC2011-LDV and EMFAC2011-HD modules. These data are included in the installation package. EMFAC2011-SG will output the combined inventory data for a default run, or linearly scale emissions by calendar year vehicle class and speed bin based on user-defined inputs.
  • What do I need to run EMFAC2011-SG?
    • The module is written in a Microsoft Access / Visual Basic for Applications platform; requires Microsoft XP or a more recent operating system; and requires Microsoft Access and Excel 2003 or newer to run the module.
  • How do I modify the speed profile for conformity analyses in the SG module?
    • The SG module allows the users to enter the daily speed profiles for each sub-area "scenario‟. The speed profiles are defined by vehicle category, and are represented as a percent of total VMT in each speed bin for an average day.
    • In order to create an inventory with user-defined speed profile, the sub-area scenario “Speed Profile” entry for the scenario should be set to “User” (in the [Scenario_Base_Inputs] worksheet). The speed profiles are entered in the “Scenario_Speed_Profile” worksheet, and require the following inputs:
      • Group
      • Area
      • Scenario
      • Sub-Area
      • CalYr
      • Season
      • Title
      • Veh & Tech: EMFAC2011 Vehicle Category
      • EMFAC2007 Veh & Tech: EMFAC2007 Vehicle Category
      • 5MPH-70MPH: Speed Distribution (percent VMT at each speed bin) for Speeds 5 - 70 MPH @ 5 MPH increments
        • *Hint: Users may obtain the default speed profile by running the SG module in “Default” mode and exporting the “Default Input Parameters”. This could allow the user to obtain a template, where they may modify the speed profiles for the select vehicle categories. If the same file is used for running a user-defined scenario, the user should remember to set the sub-area scenario “Speed Profile” entry to “User” (in the [Scenario_Base_Inputs] worksheet).
        • *Hint: The SG module also allows users to create an empty template to enter the speed profile (see SG User’s Guide Page 31).
  • How do I modify the VMT distribution by vehicle category for conformity analyses?
    • The SG module allows the users to modify the VMT by vehicle category for each sub-area “scenario”.
    • In order to create an inventory with user-defined VMT by vehicle category, the sub-area scenario "VMT by Vehicle Category‟ entry for the scenario should be set to “User” (in the [Scenario_Base_Inputs] worksheet). The new VMT by Vehicle Category are entered in the "Scenario_VMT_by_VehCat‟ worksheet, and requires the following inputs:
      • Group
      • Area
      • Scenario
      • Sub-Area
      • CalYr
      • Season
      • Title
      • Veh & Tech: EMFAC2011 Vehicle Category
      • New VMT: Daily VMT by Vehicle Category
        • *Hint: Users may obtain the default VMT by Vehicle Category by running the SG module in “Default” mode and exporting the “Default Input Parameters”. This could allow the user to obtain a template, where they may modify the VMT for the select vehicle categories. If the same file is used for running a user-defined scenario, the user should remember to set the sub-area scenario “VMT by Vehicle Category” entry to “User” (in the [Scenario_Base_Inputs] worksheet).
        • *Hint: The SG module also allows users to create an empty template to enter the VMT by Vehicle Category (see SG User’s Guide Page 31).
  • How can I obtain hourly emission estimates?
    • The EMFAC2011-SG module does not output hourly emissions. However, the user may obtain the hourly emissions inventories for the light duty fleet by running the EMFAC-2011 LDV module.
  • How can I quantify the impacts of changes in hourly temperatures and humidity on emissions or emission rates?
    • The EMFAC2011-SG module creates inventories for summer, winter, and annual seasons, but does not allow users to modify the default temperature and humidity. However, the users may modify the temperature and humidity profiles for the light duty fleet in the EMFAC-2011 LDV module.
  • The EMFAC Model Documentation says that the SG module runs at the sub-area level. How can I create regional emission inventories?
    • In order to process regional scenarios, users are required to classify all the sub-area “scenarios” into regional “groups”; the module processes each sub-area scenario individually and aggregates data by regional groups at the end of model execution.
  • Can I create multiple scenarios in the same run?
    • Yes. The SG module allows users to create multiple regional and sub-area scenarios in the same run either by using the Graphical User Interface [recommended (see SG User’s Guide Page 29)] or by defining multiple scenarios in the Input File.

 

 

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