Mobile Source Emission Factors

Mobile Source Emission Factors Used in Statewide and Metropolitan Planning Organization Air Quality Analyses 

Table of Contents

Overview

Mobile source emission factors are used to assess the air quality impacts of transportation projects included in MassDOT’s State Transportation Improvement Program (STIP) and in the Commonwealth’s Metropolitan Planning Organizations’ (MPOs’) individual Transportation Improvement Programs. Emission factors are developed for mobile sources including automobiles, trucks, buses, and transit vehicles. Emission factors are developed using the U.S. Environmental Protection Agency’s (EPA) MOtor Vehicle Emission Simulator (MOVES) model and are required as inputs into MassDOT’s air quality calculations for transportation projects.

Through consultation with the Federal Highway Administration and EPA, it was agreed that emission factors would be developed using specific inputs for the MOVES model for a representative county in Eastern Massachusetts (Middlesex County) and one for Western Massachusetts (Hampden County). Factor outputs were developed for the years 2019, 2020, 2025, 2030, 2040, and 2050. Idle emission factors were also developed for the year 2025 to be used in analyzing air quality benefits of intersection improvements.

Emission factors are developed for specific vehicles, types of roadways, average operating speeds, months of the year, and time of day. A more detailed explanation of how these factors were developed can be found in documentation compiled by the Central Transportation Planning Staff, which is the staff to the Boston Region MPO.

Input Requirements for EPA’s MOVES model

Input files have been developed through coordination with the Massachusetts Department of Transportation, the Massachusetts Department of Environmental Protection, and the Central Transportation Planning Staff, which is the staff to the Boston Region MPO. Input files have been developed for the years 2019, 2020, 2025, 2030, 2040, and 2050. These files include county specific data for the year of the analysis, as shown below.

  • Vehicle Type Population
  • Age of Vehicles
  • Vehicle-Miles of Travel by Vehicle Type
  • Vehicle-Miles of Travel by Roadway Type
  • Meteorology of the Area
  • Fuel Supply Information
  • Vehicle Inspection and Maintenance Characteristics

 

2019 Input Files

2020 Input Files

2025 Input Files

2030 Input Files

2040 Input Files

2050 Input Files

Emission Factor Outputs from the MOVES model

A detailed explanation of how the emission factors were developed can be found in documentation compiled by the Central Transportation Planning Staff, which is the staff to the Boston Region MPO. As shown in the documentation, three separate output files are created:

  • Rates per Distance provides kilograms per vehicle per distance (referred to as emission factors below) and presents the exhaust and evaporative emissions that occur when vehicles are on roads
  • Rates per Profile provides kilograms per vehicle and presents the vapor venting emission from parked vehicles
  • Rates per Vehicle in kilograms per vehicle and presents the emissions from vehicle starts and extended idle

Rates per Distance

Codes for the emission factors displayed in the rates per distance emission factor files are shown below.

Factors by Average Speed—speed bins include the following:

  1. Less than 2.5 miles per hour (mph)
  2. 2.5 mph ≤ speed <7.5 mph
  3. 7.5 mph ≤ speed <12.5 mph
  4. 12.5 mph ≤ speed <17.5 mph
  5. 17.5 mph ≤ speed <22.5 mph
  6. 22.5 mph ≤ speed <27.5 mph
  7. 27.5 mph ≤ speed <32.5 mph
  8. 32.5 mph ≤ speed <37.5 mph
  9. 37.5 mph ≤ speed <42.5 mph
  10. 42.5 mph ≤ speed <47.5 mph
  11. 47.5 mph ≤ speed <52.5 mph
  12. 52.5 mph ≤ speed <77.5 mph
  13. 57.5 mph ≤ speed <62.5 mph
  14. 62.5 mph ≤ speed <67.5 mph
  15. 67.5 mph ≤ speed <72.5 mph
  16. Equal to or greater than 72.5 mph

Factors by Month of Year—factors were developed for two months:

  1. January
  2. July

Factors by Time of Day—factors were developed for four time periods during the day:

  1. AM Period: 6:00 AM to 9:00 AM
  2. Midday Period: 9:00 AM to 3:00 PM
  3. PM Period: 3:00 PM to 6:00 PM
  4. Nighttime Period: 6:00 PM to 6:00 AM

Factors by Vehicle Type—factors were developed for two types of vehicles:

  1. Passenger Vehicles
  2. Commercial Vehicle

Factors by Roadway Type—factors were developed for four types of roadways:

  2. Rural Restricted Access

  3. Rural Unrestricted Access

  4. Urban Restricted Access

  5. Urban Unrestricted Access

Factors by Pollutant—factors were developed for seven pollutants:

  2 Carbon Monoxide

  3 Oxides of Nitrogen

 31   Sulfur Dioxide

 87  Volatile Organic Compounds

 90  Carbon Dioxide

100  Particulate Matter 10 micrometers or less in diameter

110  Particulate Matter 2.5 micrometers or less in diameter

 

Rates per Distance Factors (all factors are in kilograms per mile)

Rates per Profile

Each file includes the years 2019, 2020, 2025, 2030, 2040, and 2050, and includes total emissions in kilograms for Volatile Organic Compounds for a winter month in January, and a summer month in July for each time period during the day.

Rates per Vehicle

Each file includes the years 2019, 2020, 2025, 2030, 2040, and 2050, and includes total emissions in kilograms for each pollutant for a winter month in January, and a summer month in July for each time period during the day.

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