November 13 , 2012



### Tacoma

- Pierce County Nonattainment Area

Motor Vehicle Emissions Budget (MVEB)

Based on EPA’s final Transportation Conformity Rule Restructuring Amendments (77 FR 14979, March 14, 2012), the on

- road emissions for the most recent year of clean data, 2011, was selected as the motor

vehicle emissions budget to satisfy regional conformity test requirements for the Tacoma

- Pierce County

nonattainment area . The MVEB is based on a 2011 winter weekday inventory of onro ad mobile emissions of particulate matter less than 2.5 micrometers in diameter ( PM 2.5 ) and nitrogen oxides ( NO

x )

. This will be the first motor vehicle emissions budget in the State of Washing ton developed using EPA’s Motor Vehicle Emission simulator, or MOVES.

To create the MVEB, EPA's guidance for using MOVES for transportation conformity 1 was followed within

the constraints of local data availability. MOVES is significantly more complex than its predecessor,

MOBILE. The MVEB calculation method is design ed to be as simple as possible, yet without sacrificing

the accura cy of the emissions estimates. The basic calculation equation is shown below, followed by a

more detailed description o f the method and data sources.

Basic Calculation

E = ( M x F gmi ) + ( V x F gpveh )

where E = emissions in g rams
M = vehicle miles traveled ( VMT ) V = vehicle population

F gmi = emission factor in g rams /mi le

F gpveh = emission factor in g rams /vehicle

Vehicle Miles Traveled

PSRC estimate d 2011 average daily weekday VMT for the nonattainment area

. Per agreement with the consultation partners, t he 2011 estimate s were interpolated from 2008 and 2015 travel demand model
outputs.

VMT is estimated from PSRC’s travel demand model for individual roadway links for five time periods of the day:

• Morning = 6a m

- 9 a m;

• M idday = 9a m

- 3p m;

• Afternoon = 3p m

- 6p m;

• E vening = 6p m

- 10p m;

• N ighttime = 10p m

- 6a m

Data for each link and time period includes:

• Length

• Facility type

• Functional class ification (for most links)

• Congested speed

• VMT

1 Using MOVES to Prepare Emission Inventories in State Implementation Plans and Transportation Conformity: Technical Guidance for MOVES2010, 2010a and 2010b

. Transportation and Climate Division, Office of Transportation and Air Quality, U.S. Environmental Protection Agency. EPA

- 420

- B

- 12

- 028. April 2012November 13 , 2012

Emission Factors

EPA's MOVES model was used to generate emission factors for PM 2.5 and NO

x in grams per mile and grams per vehicle. The model was run at the county scale with local data for many of the inputs. Winter weekday conditions were estimated using the base year 2008 inventory median (50 th percentile) temperature profile for peak PM 2. 5 conditions. A detailed documentation of the MOVES inputs and methodology has been prepared by the Department of Ecology. This document includes explanations, instructions and information on the source of data used for the MOVES inputs, such as roadway classifications and travel distribution, meteorology, vehicle fleet data, fuel parameters, etc. This document will be used by PSRC as guidance for future conformity analyses.

The grams per mile emission factors were output by hour, road type, and speed b in. The grams per vehicle emission factors were output by hour. The grams per mile emission factors were averaged over each of the five time periods in PSRC’s travel demand model. This resulted in one emission factor per road type, time period, and spee d bin. The grams per vehicle emission factors were summed over each of the five time periods

, resulting in one emission factor per time period.

Emissions Estimation

Once the MOVES emission factors were prepared, the factors were applied to PSRC’s VMT data to

estimate total emissions

. The grams per mile emission factors represent emissions that occur while a vehicle is in regular operation. The grams per vehicle emission factors represent emissions that occur when a vehicle is stationary (for exa mple, start exhaust , extended idling, etc. ).

E ach roadway link from PSRC’s travel demand model was classified according to the MOVES road types:
Rural Restricted, Rural Unrestricted, Urban Restricted, or Urban Unrestricted. B ased on the congested speed

, each roadway link was assigned to the closest corresponding MOVES speed bin . The MOVES gram per mile emission factors by speed bin and road type were then applied to PSRC’s VMT by speed and road type , for each of the five time periods . T he emissions for each time period were then summed

for an estimate of total daily emissions.

The grams per vehicle emission factors were applied to the estimated vehicle population within the nonattainment area. This estimate was derived from the vehicle population within Pierce County, adjusted by the percentage of the human population in the nonattainment area. The estimated emissions for each time period were then summed for an estimat e of total daily emissions.

The two component emissions estimates were summed, and the resulting MVEB is identified below:

Pollutant Emissions (pounds per winter day)

PM 2.5 3,002

NO

x 71,598