November 20, 2012

Memo to: Cindy Heil, ADEC

From: Tom Carlson and Bob Dulla 

Subject: Summary of Inventory Revisions to the 2008 Fairbanks CO 

Maintenance Plan

Since the development of the 2008 Fairbanks CO Maintenance Plan (MP), several 

methodological revisions have been applied and updated activity data were obtained that 

supersede elements of the CO inventory reflected in that earlier plan. These are 

summarized briefly in this memorandum. 

The revisions/updates to the CO inventory in the 2008 Plan are listed below and grouped 

by inventory sector: on-road mobile, non-road mobile, area, and point.

On-Road Mobile

Vehicle emissions were estimated for the Fairbanks modeling area using EPA’s MOVES 

(Motor Vehicle Emission Simulator). The analysis was based on the MOVES2010b

version released in June 2012. MOVES is the successor to EPA’s MOBILE series of onroad vehicle emissions models. It can be used to estimate exhaust and evaporative 

emissions as well as brake and tire wear emissions from all types of on-road vehicles. 

Compared to MOBILE6.2, MOVES incorporates substantial new emissions test data and 

accounts for changes in vehicle technology and regulations as well as an improved 

understanding of in-use emission levels and the factors that influence them. 

Modeling Approach – The basic approach in applying MOVES to calculate vehicle 

emissions for the nonattainment area was based on MOVES technical modeling guidance 

developed by EPA1 for use in SIP and regional conformity analyses. In accordance with 

that guidance, MOVES was executed for the four-month (November through February) 

winter CO season that corresponds to the period in which violations of the ambient 

standard may occur in Fairbanks. Per EPA’s guidance, MOVES was also executed on an 

hourly time-scale to more accurately reflect diurnal variations in travel and ambient 

conditions that can affect vehicle emissions.

1 “Technical Guidance on the Use of MOVES2010 for Emission Inventory Preparation in State 

Implementation Plans and Transportation Conformity,” U.S. Environmental Protection Agency, Office of 

Transportation and Air Quality, EPA-420-B-10-023, April 2010.

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Cindy Heil -2- November 20, 2012

For SIP and conformity analysis, MOVES must be executed using the County 

Domain/Scale option. (MOVES can also be executed in National Scale and Project Scale 

modes.) For regional conformity analyses using MOVES County Scale option, EPA’s 

guidance essentially directs users to input a detailed series of data that replace 

nationwide-based default values with vehicle fleet, travel activity, and other parameters 

that represent the county or region being modeled. 

MOVES was executed for the Fairbanks, Alaska geographic area to produce estimates of 

CO emissions. Discussions of the development of the detailed MOVES inputs in 

accordance with EPA’s MOVES SIP development guidance are presented below. 

Vehicle Populations (Source Type Population & Age Distribution) − Vehicle 

registrations from the Alaska Division of Motor Vehicles (DMV) and recent Alaska 

Parking Lot Survey data conducted by ADEC provided the basis for the vehicle fleet 

populations and age distributions used to model the Fairbanks vehicle fleet with MOVES. 

The DMV data were obtained through ADEC from a “dump” of the statewide registration 

database as of May 2010. The DMV database includes vehicle make, model, model year, 

Vehicle Identification Number (VIN), vehicle class code, body style, registration status,

and expiration date.

Using a VIN decoding tool licensed by ADEC, supplemental information such as vehicle 

class, gross vehicle weight, vehicle type, body type, and fuel type (e.g., gasoline vs. 

diesel) were also determined in order to help classify each vehicle into one of the 13 

MOVES Source Types. Key vehicle attribute fields from the DMV database and VIN 

decoder outputs were used to categorize each vehicle record into one of the 13 usagebased “Source Type” categories as defined in MOVES to characterize the vehicle fleet. 

Gasoline vs. Diesel-Fueled Vehicle Fractions (AVFT Strategies) – MOVES provides 

users the ability to override its default nationwide-based travel splits between different 

fuels and technologies. These Alternative Vehicle Fuel and Technology (AVFT) inputs 

are supplied to MOVES2010b through the County Data Manager.

In order to account for differences in splits between gasoline- and diesel-fuel vehicles in 

the Fairbanks fleet compared to the U.S. as a whole, fuel fraction tables by source type 

and model year were also constructed using the DMV VIN decoded data described 

earlier. Not surprisingly, the MOVES default splits between gasoline and diesel vehicles 

were not representative of the Fairbanks fleet. Generally speaking, gasoline fractions 

were found to be lower in Fairbanks than the nationwide-based MOVES defaults (and 

diesel fractions were commensurately higher).

Travel Activity (Vehicle Type VMT) – Estimates of VMT over the expanded 

transportation modeling network (covering the entire CO nonattainment area) from the 

TransCAD travel model link output files were processed and input to MOVES through 

the “Vehicle Type VMT” input within the County Data Manager. The Vehicle Type 

VMT input must be in units of VMT per year, not VMT per day. The annual VMT must 

also be supplied by “HPMS Vehicle Type,” which is essentially an aggregated version of 

the 13-category MOVES Source Type scheme. Since states are required to provide 

periodic travel (i.e., VMT) estimates to FHWA via the Highway Performance Monitoring 

System (HPMS), EPA has designed MOVES to accept VMT input by these HPMS 
Cindy Heil -3- November 20, 2012

Vehicle Type categories. Link-level TransCAD model output files from the 

transportation modeling performed by FMATS for a 2010 base year and a 2035 forecast

were processed to prepare these MOVES inputs for each analysis year. The 2010 

TransCAD outputs were used directly to represent VMT for the 2010 analysis year. For 

analysis years 2011 through 2015, VMT was linearly interpolated from the 2010 and 

2035 TransCAD outputs (which exhibited an annual VMT growth rate of roughly 1.0%). 

For analysis years 2005 through 2009, total VMT was back-casted from the 2010 

TransCAD outputs based on historically developed regional VMT estimates supplied by 

ADOT&PF.

The TransCAD outputs encompasses a modeling domain that extends beyond the CO 

nonattainment area. Spatial processing performed during the development of the 

TransCAD outputs was used to identify whether each link was within or outside the 

smaller CO nonattainment area. The VMT estimates for this analysis were based on the

subset of links within the CO nonattainment Area.

Annual mileage per vehicle estimates by HPMS Vehicle Type were extracted from 

MOVES2010b nationwide default model runs and were used in conjunction with travel 

model VMT splits between Passenger and Truck VMT to apportion total VMT output by 

TransCAD into the six HPMS Vehicle Type categories required by MOVES.

Other MOVES Inputs – The remaining MOVES modeling inputs representing the 

Fairbanks CO nonattainment area included seasonal, daily, and diurnal travel fractions; 

travel activity by speed range (or bin) and roadway type; freeway ramp fractions; ambient 

temperature profiles; I/M program inputs; and fuel specifications. Each of these inputs 

was supplied to MOVES to represent Fairbanks-specific conditions through the model’s 

County Data Manager Importer and is discussed separately below.

Monthly, Day-of-Week, and Hourly VMT Fractions – In conjunction with annual VMT 

by HPMS Vehicle Type, MOVES also requires inputs of monthly, weekday/weekend, 

and hourly travel fractions. Based on data assembled by ADOT&PF from 2009 seasonal 

traffic counts, traffic within the CO nonattainment area portion of the FMATS modeling 

area exhibits a seasonal variation such that roughly 93% of annual average daily travel 

occurs on average winter days (with 107% occurring on average summer days). These 

seasonal variations were incorporated into the MonthVMTFraction input table. 

Day-of-week fractions were set to assume that travel levels are the same on weekends as 

weekdays. In the absence of a weekend or seven-day travel model, this is a reasonable 

assumption.

Hourly VMT fractions were defined based on diurnal trip percentages used to support the 

travel model development and validation that are listed in Appendix C.

Travel by Speed Bin and Roadway Type (Average Speed Distribution & Road Type 

Distribution) – The link-level TransCAD model output files described earlier were 

processed to develop average speed and road type distribution inputs, respectively.
Cindy Heil -4- November 20, 2012

The roadway type classification scheme employed in MOVES consists of the following 

five categories:

1. Off-Network;

2. Rural, Restricted Access;

3. Rural, Unrestricted Access;

4. Urban, Restricted Access; and

5. Urban, Unrestricted Access.

The “Off-Network” category is used by MOVES to represent engine-off evaporative or 

starting emissions that occur off of the travel network. For SIP and regional conformity 

analysis, EPA’s MOVES guidance indicated that the user must supply Average Speed 

Distribution and Road Type Distribution inputs for the remaining on-network road types 

(2 through 5), but direct MOVES to calculate emissions over all five road types. In this 

manner, starting and evaporative emissions are properly calculated and output.

The first of the two sets of inputs, Average Speed Distributions, consists of time-based2

(not distance-based) tabulations of the fractions of travel within each of MOVES’ 16 

speed bins (at 5 mph-wide intervals) by road type and hour of the day. These inputs were 

calculated from the TransCAD link outputs by time of day. The TransCAD outputs 

consisted of travel times, average speeds, and vehicle volumes for each link in the 

expanded modeling network for each of three daily periods:

1. AM Peak (7-9 AM); 

2. PM Peak (3-6 PM); and 

3. Off-Peak (9 AM-3 PM, plus 6 PM-7 AM).

Spreadsheet calculations were performed on the TransCAD link outputs to calculate 

time-based travel (multiplying link travel time by vehicle volume to get vehicle hours 

traveled or VHT) across all links. The link VHT was then allocated by MOVES road 

type and average speed bin. (The link classification scheme employed in the TransCAD 

modeling could easily be translated to the MOVES Rural/Urban and Limited/Unlimited 

Access road types.) Normalized speed distributions (across all 16 bins) were then 

calculated for each road type and time of day period and formatted for input into 

MOVES.

These distributions were very similar for the 2010 and 2035 TransCAD outputs. 

Distributions for each analysis year (2005-2015) were developed by straight-line 

interpolation/extrapolation of the nominal trends in the 2010 and 2035 TransCAD-based 

distributions.

MOVES allows the Average Speed Distribution inputs to be specified separately by 

Source Type (i.e., vehicle category). Thus, individual distributions were developed from 

Passenger VHT and Truck VHT tabulations of the TransCAD outputs. The Passenger 

VHT was available for each of the three modeling periods. Truck VMT was only 

available on a single daily basis.

2 MOVES requires Average Speed Distribution inputs on a time-weighted basis and Road Type 

Distribution inputs on a distance-weighted basis.

 
Cindy Heil -5- November 20, 2012

Freeway Ramp Fractions (Ramp Fraction) – MOVES uses default values of 8% (or 0.08) 

to represent the fraction of time-based limited access roadway travel (Road Types 2 and 

4) that occurs on freeway ramps. Fairbanks-specific ramp fraction values were tabulated 

from the TransCAD link level outputs and were supplied to MOVES in the Ramp 

Fraction input section of the County Data Manager to override the nationwide-based 

defaults. The Fairbanks ramp fractions in urbanized areas are higher than the default 

values in MOVES, reflecting the fact that shorter freeway lengths (with resulting higher 

ramp fractions) are driven in Fairbanks compared to the nationwide-based defaults.

Ambient Temperature Profiles (Meteorology Data) – Monthly average diurnal (i.e., hourby-hour) ambient temperature and humidity profiles compiled by EPA for each county in 

the U.S. and contained in MOVES’ default database were used for the emission modeling 

runs. According to EPA guidance, these ambient meteorology data profiles were 

compiled from 30 years (1971-2000) of daily temperature and humidity data. The 

profiles for Fairbanks (ZoneID=20900) are based on the station at the Fairbanks 

International Airport. The ambient temperatures range from +11.7°F in November (Hour 

16) down to -16.1°F in January (Hour 5). Relative humidity ranged from 48% to 82%.

Profiles for each of the winter months modeled were exported from the MOVES database 

and input via the County Data Manager. 

I/M Program Data (I/M Programs) – Since the Fairbanks I/M program was terminated at 

the end of 2009, the “Use I/M Program” input element to MOVES for the 2010-2015 

analysis years was set from “Yes” to “No” to account for the elimination of the program. 

A compliance rate of 96% was modeled based on the latest parking lot survey data.

Fuel Specifications (Fuel Supply) – EPA has developed detailed fuel specifications (e.g., 

RVP, oxygen content, sulfur content, etc.) for different gasoline and diesel fuel blends 

used in each county of the U.S. and has loaded these specifications into the 

FuelFormulation and FuelSupply tables in the MOVES default database. (The first of 

these tables identifies the detailed properties of a specific fuel blend; the second table 

identifies the state and county of the U.S. and the calendar year to which it applies.) 

Semi-annual fuel survey data collected by the Alliance of Automobile Manufacturers 

(AAM) were reviewed to confirm whether the default fuel properties for Fairbanks 

defined in MOVES were correct. Retail gasoline data for the 2008 winter for Fairbanks 

from the AAM surveys indicated that sulfur and oxygen contents in MOVES reasonably 

matched measured levels. 

However, Fairbanks diesel blends are not included in the AAM surveys. MOVES 

assumed diesel fuel sulfur content of 43 ppm in 2008 through 2011 and 11 ppm in 2012 

and later years. These sulfur levels are believed to be reasonably representative of those 

required under Alaska’s Ultra Low-Sulfur Diesel (ULSD) regulation.

Thus, MOVES default gasoline and diesel fuel specifications for Fairbanks were used in 

the analysis.
Cindy Heil -6- November 20, 2012

Non-Road Mobile

The non-road inventory was based on updated modeling with EPA’s NONROAD model

for recently developed “Big 3” criteria pollutant inventories that were generated for 

Anchorage, Fairbanks, and Juneau. Key revisions included a substantial increase in 

snowmobile emissions based on locally collected snowmobile population estimates, 

rather than NONROAD model defaults. Base year estimates from that effort were 

combined with updated aircraft inventory estimates and railroad emission estimates 

developed in support of the Fairbanks PM2.5 SIP. 

Area

Area source estimates were also updated based on emissions compiled for the Fairbanks 

PM2.5 SIP. Key revisions were focused within the space heating sector (primarily woodburning emissions) based on locally collected activity data and heating device emission 

testing data supporting the PM2.5 SIP development. Historical and forecasted population 

trends from that effort were also used to develop the updated area source CO estimates.

Point

Point source estimates were updated on a facility-specific basis where data were available 

from the PM2.5 SIP development. Similar population-based trends applied to the area 

sources were also used to project base year 2008 point source emissions obtained for the 

PM2.5 SIP.

Summary

Table 1 summarizes the emission changes described above, comparing each of the source 

categories in 2005, 2010, and 2015. Adjustments for additional control measures 

included in each MP are also incorporated so that the final inventory values can be 

contrasted. The table shows that emission estimates for all of the source categories 

changed between the two inventories. As described above, the changes are the result of 

new insights from surveys, updated activity forecasts, and model revisions. The most 

significant of these are as follows:

• Use of MOVES2010b (which has higher per-vehicle emission rates than 

MOBILE6 at cold temperatures);

• Higher residential wood burning emissions in the area source sector based on 

emission testing and updated activity data collected in support of the Fairbanks 

PM2.5 SIP; and

• Higher nonroad emissions based on an upwardly adjusted snowmobile population 

reflected in Alaska’s latest criteria pollutant inventories for Fairbanks (the earlier 

estimates had been based on default populations estimated for Fairbanks in an 

earlier version of EPA’s NONROAD model).
Cindy Heil -7- November 20, 2012

Table 1

Comparison of Source Category Emissions 

Between 2008 and Current CO Maintenance Plans

(Tons/Day) 

Source

Category

2008 Maintenance Plan Current Maintenance Plan

2005 2010 2015 2005 2010 2015

On-Road 24.98 21.25 19.15 45.48 43.48 45.19

Nonroad 3.04 3.40 3.62 14.80 15.97 16.79

Area 0.58 0.62 0.65 19.69 21.28 22.38

Point 3.08 3.29 3.44 3.09 3.34 3.51

Total 31.69 28.56 26.87 83.06 84.08 87.87

If you have any questions about the information presented above, please do not hesitate 

to contact us.