Appendix B-6

Development of 2011 Railroad Component for 

National Emissions Inventory 

 
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MEMORANDUM 

TO: Laurel Driver/US EPA 

FROM: Heather Perez, Susan McClutchey, and Richard Billings/ERG 

DATE: September 5, 2012 

SUBJECT: Development of 2011 Railroad Component for National Emissions Inventory

1.0 Introduction 

As part of Work Assignment 5-07 under EPA Contract EP-D-07-097, entitled “Mobile 

Source Emission Inventories – FY12,” ERG developed growth factors for Class I and Class II 

and III railroads that were applied to the 2008 emission values developed for the National 

Emission Inventory (NEI) to approximate emission levels in 2011. The emissions were allocated 

to line haul shape IDs and yard locations based on 2008 allocations. ERG provided the EPA with 

the 2011 estimated railroad emissions as an Access database for inclusion into EIS staging tables 

by the EPA WAM. 

This report documents the development of the growth factors (Section 2), application of 

these growth factors to 2008 data are discussed in Section 3 along with a summary of the 2001 

emissions estimates. Lastly A listing of references used in this study are presented in Section 4. 

2.0 2008/2011 Railroad Growth Factors 

Railroad freight traffic data were obtained from a variety of sources including the

Department of Transportation’s Bureau of Transportation Statistics (BTS) and Surface 

Transportation Board, The Department of Energy’s Annual Energy Outlook (AEO), the 

American Association of Railroads (AAR), and the American Short Lines and Regional Railroad 

Association. 

Initially growth rates were reviewed as reported for the AEO’s 2012 reference case. 

These rates were developed relative to billions of ton miles traveled. Data that specifically 

covered the period from 2008 to 2011 were not included in the data table, so earlier reports 

(2008-2011) were compiled and reviewed. When the separate reports were evaluated together, 

the actual and projected annual growth rates were inconsistent. This observation suggested that 

the commercial rail freight market had a high degree of uncertainty associated with it for the 

study period. 
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This observation about the volatility of the market was substantiated when aggregated 

quarterly rail traffic data from the BTS were reviewed. Their data showed a peak in 2008 

followed by a significant decline in activity for multimodal rail traffic. Gradually the rail freight 

market was returning to the 2008 activity level, though the 2011 data point suggests that 

activities were slightly under the 2008 peak. Note that the rail traffic data presented in Figure 1 is 

for intermodal freight traffic and is only provided as a general indicator of rail activities. 

Figure 1. Intermodal Rail Traffic 2002 to 2012 

ERG compiled railroad freight traffic data from the 2008 and 2011 R-1 reports submitted 

by all Class I rail lines to the Surface Transportation Board. The R-1 data are more 

comprehensive than the BTS’s intermodal study as it includes all freight shipped by Class I 

railways. For the most part, the R-1 data follow the Trends noted in Figure 1 with one exception: 

the Soo Line saw an increase in traffic of over 45%. The Soo Lines business activities were 

investigated to understand the anomaly in their freight traffic data. The Soo Line acquired the 

Dakota, Minnesota and Eastern Railroad and the Iowa, Chicago & Eastern Railroad in late 2008. 

It is believed that this merger is the cause of the increased activity reported by the Soo line. 

When all the rail traffic data are aggregated, the Soo line’s freight traffic has a relatively 

small impact on the overall trend as it is the smallest of the Class I railways. The percent change 

from 2008 to 2011 for total ton-miles (including the Soo line) is -2.479. 

 
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Table 1. Class I Railroad Ton Miles Activity for 2008 and 2011 

Total Revenue Ton-miles 

of Freight (thousands)

Total non-Revenue 

Ton-miles of Freight 

(thousands)

Total Revenue and nonRevenue Ton-miles of 

Freight (thousands)

% change 

from 2008 

to 2011

 2008 2011 2008 2011 2008 2011

BNSF 664,384,072 648,431,637 5,997,398 6,117,197 670,381,470 654,548,834 -2.362

CSXT 248,121,469 228,394,651 347,234 1,216,165 248,468,703 229,610,816 -7.590

GTC 53,452,403 51,253,084 624,848 518,201 54,077,251 51,771,285 -4.264

KCSR 29,624,261 30,485,863 6,077 1,338,343 29,630,338 31,824,206 7.404

NS 195,343,113 191,712,562 273,331 1,267,931 195,616,444 192,980,493 -1.348

Soo 23,681,180 34,581,354 241,414 333,090 23,922,594 34,914,444 45.948

UP 562,629,694 544,397,317 5,187,410 5,485,720 567,817,104 549,883,037 -3.158

Total 1,789,913,904 1,745,533,115 -2.479 

ERG also tried to obtain rail freight trend data from the Association of American 

Railroads (AAR), but their current posted data only extend back to 2009. It was noted that the 

AAR data are used in the in the BTS’s National Transportation Statistics and are similar to the 

data in Table 1. 

Because Class II and III rail operations are often affected differently by changes in the 

economy than Class I railways, data were obtained from the American Short Lines and Regional 

Railroad Association to assess their growth rate for the study period. Unfortunately, freight 

traffic data in terms of ton-miles was not available, so information regarding employee hours for 

2008 and 2011 were evaluated, quantifying a decline in activity of 8.37 percent. It is possible 

that this decline overstates the actual change in Class II and III rail traffic, as employee 

efficiency may also change during periods of economic uncertainty. 

Lastly, it should be noted that growing the 2008 data using these measures does not 

account for improved locomotive efficiency. Because the price of railroad fuel increased over the 

study period and because fuel usage is such a large component of rail finances; when demand 

declines, railways often use their newer, more efficient locomotives and retire the older engines 

to reduce their system-wide fuel consumption. Under these conditions, less fuel would be needed 

to move cargo, suggesting that actual 2011 emissions may be slightly less than those estimated 

for this project. 

3.0 Emissions Estimate Summary 

The railroad component of the 2008 NEI was provided by ERTAC. ERTAC revised their 

data since the 2008 NEI was posted. Prior to scaling the 2008 data to represent 2011, the 2008 

NEI data set was amended to include the updates in the latest version of the ERTAC data. Note 

there were no changes to the Class I line haul operations which represent the largest rail emission 

source. The latest 2008 ERTAC data set for Class II/III line haul operations contained additional 

state and railroad provided data as well as an updated fuel use factor. These revisions were re 

applied to the county level and re-aggregated to match the latest ERTAC data set. The yard 
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engine data also had slightly different emissions and record counts. The new yard emissions 

were summed and reallocated to new yards which were assigned unique IDs and EIS/GIS point 

locations. 

The growth factors developed in Section 2 were applied to the updated 2008 railroad 

emission estimates using the following equation to approximate 2011 emissions: 

EE2011ij = EE2008ij × (1+ GFi /100) 

Where: 

EE2011ij = 2011 railroad emission estimate for operation type i and pollutant j 

 (Tons/Yr) 

EE2008ij = 2008 railroad emission estimate for operation type i and pollutant j 

 (Tons/Yr) 

GFi = 2011/2008 growth factor for operation type i (Class 1 railroad and all 

 yard operations = -2.475percent and Class 2 and 3 operations = 

 -8.37 percent) 

i = Rail operation type (Class 1 line haul, Class 2 and 3 line haul, and yard 

 operations) 

j = criteria pollutant and regulated HAPs. 

The 2011 emissions using the above approach are presented in Table 2 along with the 

updated 2008 values for each locomotive category. HAP emissions for each locomotive category 

are presented in the Appendix of this report. 

Table 2. 2008 and 2011 Annual Emission Estimates by Locomotive Category (Tons) 

Pollutant

Class I Class II/III Switch Total

2008 2011 2008 2011 2008 2011 2008 2011

CO 110,969 108,218 4,631 4,244 9,231 9,002 124,830 121,463

NH3 347 339 14 13 28 27 389 379

NOX 754,433 735,731 47,035 43,100 74,431 72,586 875,899 851,417

PM10 25,477 24,846 1,158 1,061 2,105 2,053 28,740 27,960

PM25 23,439 22,858 1,065 976 2,042 1,991 26,546 25,826

SO2 7,836 7,642 327 300 624 608 8,787 8,550

VOC 39,952 37,000 1,829 1,676 5,125 4,998 46,905 43,674

 
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4.0 References 

U.S. Environmental Protection Agency, Documentation for Locomotive Component of the 

National Emissions Inventory Methodology (NEI), May 3, 2011, 

http://www.epa.gov/ttn/chief/net/2008inventory.html. 

Department of Transportation / Bureau of Transportation Statistics (BTS), Multimodal 

Transportation Indicators, February 2012. 

http://www.bts.gov/publications/multimodal_transportation_indicators/february_2012/html/rail_r

evenue_ton_miles.html

Surface Transportation Board, Complete Annual R1 forms (2008-2011). 

http://www.stb.dot.gov/econdata.nsf/f039526076cc0f8e8525660b006870c9?OpenView

The Department of Energy, Annual Energy Outlook (AEO), June 2012. 

http://www.eia.gov/forecasts/aeo/data.cfm

American Association of Railroads (AAR), Class I Railroad Statistics, May 10, 2012. 

http://www.aar.org/~/media/aar/Industry%20Info/AAR-Stats-2012-05-10.ashx

Timmons, Richard; American Short Lines and Regional Railroad Association. Short Lines 

Today-Employee Hours (2006-2011), February 22, 2012. 

http://www.aslrra.org/images/news_file/AASHTO_SCORT_Feb_22_2012.pdf. 
Appendix A – 2011 HAP Emissions by Locomotive Category 
A-1 

Table A-1. 2011 HAP Emissions by Locomotive Category (Tons per year)

Pollutant

Class I 

Emissions Class II/III Switch Total

1,3-Butadiene 113.899 4.866 9.186 127.950 

2,2,4-Trimethylpentane 82.974 3.758 11.208 97.940 

Acenaphthene 0.738 0.032 0.060 0.830 

Acenaphthylene 10.413 0.445 0.850 11.708 

Acetaldehyde 659.298 28.164 53.178 740.640 

Acrolein 109.648 4.684 8.845 123.176 

Ammonia 338.587 13.276 26.958 378.820 

Anthracene 2.461 0.105 0.201 2.767 

Arsenic 0.009 0.000 0.001 0.010 

Benz[a]Anthracene 0.395 0.017 0.032 0.444 

Benzene 90.721 3.875 7.317 101.913 

Benzo[a]Pyrene 0.070 0.003 0.006 0.079 

Benzo[b]Fluoranthene 0.157 0.007 0.013 0.176 

Benzo[g,h,i,]Perylene 0.078 0.003 0.006 0.088 

Benzo[k]Fluoranthene 0.128 0.005 0.011 0.144 

Beryllium 0.696 0.030 0.058 0.783 

Cadmium 0.696 0.030 0.058 0.783 

Carbon Dioxide -- 1,617,263.311 3,283,729.797 4,900,993.109 

Carbon Monoxide 108,217.732 4,243.692 9,001.821 121,463.245 

Chromium (VI) 0.049 0.002 0.004 0.056 

Chromium III 0.096 0.004 0.008 0.108 

Chrysene 0.292 0.012 0.024 0.329 

Ethyl Benzene 74.000 3.351 9.996 87.348 

Fluoranthene 1.840 0.079 0.151 2.070 

Fluorene 3.417 0.146 0.279 3.842 

Formaldehyde 1,519.044 64.891 122.519 1,706.454 

Hexane 203.501 9.216 27.490 240.207 

Indeno[1,2,3-c,d]Pyrene 0.067 0.003 0.006 0.075 

Lead 2.088 0.089 0.173 2.350 

Manganese 0.051 0.002 0.004 0.057 

Mercury 0.696 0.030 0.058 0.783 

Naphthalene 63.268 2.702 5.193 71.163 

Nickel 0.163 0.007 0.013 0.183 

Nitrogen Oxides 735,730.789 43,099.979 72,586.140 851,416.909 

Phenanthrene 13.805 0.590 1.127 15.521 

PM10 Primary (Filt + Cond) 24,845.831 1,060.928 2,052.942 27,959.702 

PM2.5 Primary (Filt + Cond) 22,858.165 976.001 1,991.354 25,825.519 
A-2 

Table A-1. 2011 HAP Emissions by Locomotive Category (Tons per year)

Pollutant

Class I 

Emissions Class II/III Switch Total

Propionaldehyde 225.701 10.222 30.489 266.411 

Pyrene 2.591 0.111 0.213 2.914 

Styrene 77.700 3.519 10.496 91.715 

Sulfur Dioxide 7,641.578 299.635 608.406 8,549.619 

Toluene 118.400 5.362 15.994 139.757 

Volatile Organic Compounds 37,000.155 1,675.721 4,998.128 43,674.003 

Xylenes (Mixed Isomers) 177.601 8.043 23.991 209.635