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Mobile Source Inventories for SIPs. Matt Laurita Air Quality Modeling and Transportation Section EPA Region 4. What You Need. MOBILE6.2 model “Technical Guidance on the Use of MOBILE6 for Emission Inventory Preparation” Vehicle Miles Traveled (VMT) and Speeds

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Mobile source inventories for sips

Mobile Source Inventories for SIPs

Matt Laurita

Air Quality Modeling and Transportation Section

EPA Region 4


What you need
What You Need

  • MOBILE6.2 model

  • “Technical Guidance on the Use of MOBILE6 for Emission Inventory Preparation”

  • Vehicle Miles Traveled (VMT) and Speeds

    • Base year and estimated future values

  • Local data

    • Fleet age distribution, fleet mix, meteorological data

  • Control programs

    • Inspection & Maintenance (I/M), anti-tampering, etc…

  • For PM2.5: AP-42, Chapter 13


What you need1
What You Need

  • NONROAD2004 Model

  • Emissions and Dispersion Modeling System (EDMS) Model

  • “Procedures for Emission Inventory Preparation – Volume IV: Mobile Sources” (EPA420-92-009)

  • Category 3 Marine Diesel Engines - Final Emission Standards Final Regulatory Support Document (EPA420-R-03-004)

  • Final Regulatory Impact Analysis: Control of Emissions from Marine Diesel Engines (EPA420-R-99-026)


Mobile6 2
MOBILE6.2

  • EPA’s approved motor vehicle emissions model

  • MOBILE6.2 is used for

    • SIP development

    • Transportation conformity

    • Emission inventories

    • Special studies


Mobile6 21
MOBILE6.2

  • Computer model that predicts vehicle emissions on a grams per mile basis

  • Freely available (download)

  • DOS based

  • Contains default national data on fleet mix, average speeds, age distributions, etc…

  • User can input detailed local data


General procedure
General Procedure

  • Input local data and run MOBILE6.2

    • MOBILE6.2 will generate Emission Factors (EF)

    • EF are in units of grams per mile

    • EF can be generated for NOx, VOC, CO, NH3, SOx, direct PM, brake & tire PM, and air toxics

  • Using the appropriate EF:

    Emissions = EF x VMT


Required data
Required Data

  • Calendar year (1952-2050)

  • Minimum / maximum temperatures

  • Fuel volatility (Reid Vapor Pressure, RVP)

  • Diesel sulfur content


Important mobile6 2 inputs
Important MOBILE6.2 Inputs

  • Meteorological data

    • Minimum and maximum temperatures

    • Absolute or relative humidity

    • Should be consistent with the modeled episode

  • Evaluation month

    • January (1) or July (7)

    • This only affects the vehicle fleet (i.e. fleet turnover from January to July)

    • Typically use January for CO, July for Ozone


Important mobile6 2 inputs1
Important MOBILE6.2 Inputs

  • PM2.5 emissions calculated as annual emissions

  • Requires MOBILE6 run for each month in an analysis year

  • Example – Calculating emissions for 2005

Note that RVP may vary by month, as well


Local data i m program
Local Data – I/M Program

  • Source: State Air Agency

  • What you need to know:

    • Program type: Two-Speed Idle, ASM, On-Board Diagnostics (OBD)

    • Vehicle model years covered

    • Actual or anticipated start date of the program

    • Compliance rate

    • Waiver rate


Local data vmt mix
Local Data – VMT Mix

  • Source: MPO, DOT

  • Percentage of VMT generated by different vehicle classes (e.g. passenger cars, light-duty trucks, buses, etc.)

  • MOBILE6.2 input uses 16 vehicle classes

    • Local data may not use as many classes

  • You may have to convert! (See Technical Guidance)

  • Each roadway classification can have a different mix


Local data age distribution
Local Data – Age Distribution

  • Source: DMV, I/M Data

  • MOBILE6 includes a default percentage of vehicles of each age from 0 to 25 years old

  • Vehicles older than 25 years are included with 25-year-old vehicles

  • Local data can significantly affect the emission estimates


Local data vehicle speeds
Local Data – Vehicle Speeds

  • Source: MPO, DOT

  • Forecast by travel demand models (TDM) or other methods

  • Can be input as

    • One average speed for each road classification (e.g. Interstate, Other freeway, Principal Arterial, Minor Arterial, Collector, Local)

    • Distribution of speeds on each roadway for each hour of the day


Local data vmt
Local Data – VMT

  • Source: MPO, DOT

  • Often forecast by travel demand models (TDM)

  • If no model: extrapolation of historic traffic counts

  • Typically varies by roadway classification (6 Urban and 6 Rural classes)

  • Reminder: VMT is not a MOBILE6.2 input, but is used for post-processing


What if you don t have local data
What if you don’t have local data?

  • MOBILE6.2 includes national defaults for almost all inputs

  • Minimum data requirements

    • temperature, fuel volatility, and year of evaluation

  • This will give you a less exact estimate for your area

  • Use all local data that is available to you and supplement with defaults where necessary


Federal programs
Federal programs

  • Do you need to worry about Tier 2, low sulfur gasoline and the Heavy-Duty Diesel Rule?

  • No. MOBILE6.2 already accounts for Federal rules.

  • However, areas required to implement reformulated gasoline must specify this input into MOBILE6.2


Notes on pm emissions
Notes on PM Emissions

  • Diesel sulfur content is a required MOBILE6.2 input for PM modeling

  • MOBILE6.2 does not calculate re-entrained road dust or construction dust emissions

    • There is no approved computer model

    • Use the methodology in AP-42, Chapter 13, “Miscellaneous Sources”


Completing the analysis
Completing the Analysis

  • Average Speed vs. Link-Level Analysis

  • Average Speed

    • Treats each road functional classification as a whole

    • Example: One MOBILE6.2 run for freeways with single average freeway speed and VMT mix

    • Freeway EF X Total VMT on Freeways = Emissions from freeway vehicles

    • Repeat for arterials, collectors, etc…and sum the totals


Completing the analysis1
Completing the Analysis

  • Link-Level

    • Multiple MOBILE6.2 runs at different speeds for each roadway classification

    • Create a look-up table of EF based on speed and roadway type

    • Calculate emissions for each segment of roadway (link) based on classification and speed

    • Sum all of the link emissions together


Resources
Resources

  • From www.epa.gov/otaq/m6.htm:

    • MOBILE6.2 User Guide (EPA420-R-03-010)

    • MOBILE6.2 Policy Guidance (February 24, 2004)

    • Technical Guidance on the Use of MOBILE6.2 for Emission Inventory Preparation (EPA420-R-04-013)

  • From www.epa.gov/ttn/chief/ap42/:

    • AP-42, Chapter 13, “Miscellaneous Sources”


Nonroad2004

Airport Ground Support

Agricultural

Construction

Commercial

Lawn & Garden

Logging

Recreational Marine

ATVs

Snowmobiles

Chain Saws

Others

NONROAD2004

  • EPA’s approved emissions model for:

  • Used for SIP development and emission inventories

  • Does not cover Aircraft, Locomotives, or Commercial Marine Vessels


Nonroad20041

Airport Ground Support

Agricultural

Construction

Commercial

Lawn & Garden

Logging

Recreational Marine

ATVs

Snowmobiles

Chain Saws

Others

NONROAD2004

  • EPA’s approved emissions model for:

  • Used for SIP development and emission inventories

  • Does not cover Aircraft, Locomotives, or Commercial Marine Vessels


Nonroad20042
NONROAD2004

  • Contains national data for all equipment categories

    • Equipment populations

    • Load factors

    • Activity levels

  • Can allocate emissions to the state or county level

  • Calculates emissions by year, season, month, or day

    • Also by weekend or weekday

  • Can output emissions of NOx, VOC, CO, SOx and PM


Nonroad2004 local data
NONROAD2004 - Local Data

  • Local data always preferred

  • Source: Surveys

  • What data can you improve?

    • Population estimates

    • Activity estimates

    • Allocations of equipment use by season or day of the week


Nonroad2004 local data1
NONROAD2004 - Local Data

  • Source: NOAA, local sources

    • Temperatures

    • Should be consistent with temperatures used for on-road mobile inventory

  • Source: State Air Agency

    • Specific fuel parameters


Nonroad2004 local data2
NONROAD2004 - Local Data

  • Local data is inputted by adjusting the model’s default data files

  • If sufficient data exists, emissions can be sub-allocated from the county to the sub-county level


EDMS

  • FAA’s emissions model

  • Commercial and general aviation aircraft

  • Ground support equipment (also handled by NONROAD – be careful not to double-count!)

  • Airport roadways (may be covered in on-road inventory)

  • Can also handle airport stationary sources and training fires (N/A for this purpose)


EDMS

  • Default data

    • Aircraft / engine combinations

    • Time-in-mode (e.g. takeoff, climb out, approach, idle)

    • Ground support equipment by aircraft type

    • Takeoff weights and approach angles

    • Mixing height (default 3000 ft above ground level (AGL))


Edms local data
EDMS – Local Data

  • Source: NOAA, local source

    • Average annual temperature

    • Mixing height

  • Source: FAA, Airport Authority

    • Annual Landing-Takeoff (LTO) cycles for each type of aircraft (or aircraft / engine combination for commercial aircraft)

    • Annual number of touch-and-goes (typically general aviation training aircraft)


Edms output
EDMS - Output

  • Annual emissions of NOx, VOC, CO and SOx for aircraft and ground support equipment (GSE)

  • PM10 for GSE (but not aircraft)

  • Aircraft PM calculated by hand – limited data

  • EDMS is also capable of dispersion analysis, but that is not necessary for inventory development


Locomotives
Locomotives

  • Locomotive emissions not covered by a model

  • Procedures for Emission Inventory Preparation – Volume IV: Mobile Sources, page 200

  • Requires all local data


Locomotives local data
Locomotives – Local Data

  • Class I, II, and III railroads

  • Line haul and switchyard

  • Line haul calculation:

    • Emissions = Emission Factor x Annual Fuel Usage


Locomotives local data1
Locomotives – Local Data

  • Source: Interview with railroad operator

  • Class I

    • Must determine the fuel usage in the nonattainment area

    • Fuel Consumption Index = Systemwide Gross Ton Miles / Systemwide Fuel Consumption

    • Fuel Usage = Fuel Consumption Index * Traffic Density in the nonattainment area

    • Class I railroads should be able to provide this information (though they may view it as confidential)


Locomotives local data2
Locomotives – Local Data

  • Class II & III

    • Typically smaller railroads

    • Do not keep same types of records as Class I

    • May be able to estimate fuel consumed in nonattainment area (e.g. by percentage of track in the area)

    • All fuel may be consumed in nonattainment area


Locomotives local data3
Locomotives – Local Data

  • Switchyard Locomotives

    • Emissions = Number of yard locomotives X Annual emissions per yard locomotive

  • Sources:

    • Interviews with yard operators

    • Observation


Commercial marine vessels
Commercial Marine Vessels

  • Developed as part of the National Emissions Inventory (NEI)

  • Emissions estimated by multiplying activity by an emission factor

  • Commercial Marine emission factors and methodologies are found in

    • Final Regulatory Impact Analysis: Control of Emissions from Marine Diesel Engines (EPA420-R-99-026) for Category 1 and Category 2 engines

    • Category 3 Marine Diesel Engines - Final Emission Standards Final Regulatory Support Document (EPA420-R-03-004) for Category 3 engines

  • States encouraged to use local port traffic data to refine the NEI estimates


Resources1
Resources

  • www.epa.gov/otaq/nonrdmdl.htm

    • NONROAD2004 (Draft)

    • Various technical reports

  • www.aee.faa.gov/emissions/EDMS/EDMShome.htm

    • EDMS ($45 to purchase)

  • www.epa.gov/otaq/invntory.htm

    • Procedure for Emission Inventory Preparation - Volume IV: Mobile Sources (EPA420-92-009)

    • Category 3 Marine Diesel Engines - Final Emission Standards Final Regulatory Support Document (EPA420-R-03-004)

    • Final Regulatory Impact Analysis: Control of Emissions from Marine Diesel Engines (EPA420-R-99-026)


For more information
For More Information…


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