U.S. Department of 

Transportation

Federal Railroad 

Administration

Assessment of Rail Seat Abrasion Patterns 

and Environment 

Office of Railroad

Policy and Development

Washington, DC 20590

DOT/FRA/ORD-12/07 Final Report

May 2012
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report.
i

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503.

1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE

May 2012

3. REPORT TYPE AND DATES COVERED

Technical Report

4. TITLE AND SUBTITLE

Assessment of Rail Seat Abrasion Patterns and Environment

5. FUNDING NUMBERS

DTFR53-00-C-00012

Task Order 246 6. AUTHOR(S) and FRA COTR

Richard Reiff, Russell Walker, Patricia Schreiber, Nicholas Wilson, and Hugh Thompson

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

Transportation Technology Center, Inc.

55500 DOT Road 

Pueblo, CO 81001

8. PERFORMING ORGANIZATION 

REPORT NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

U.S. Department of Transportation 

Federal Railroad Administration

Office of Railroad Policy and Development

Washington, DC 20590

10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

DOT/FRA/ORD-12/07

11. SUPPLEMENTARY NOTES

Program Manager: Hugh Thompson

12a. DISTRIBUTION/AVAILABILITY STATEMENT

This document is available to the public through the FRA Web site at http://www.fra.dot.gov.

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

Rail seat abrasion (RSA) of concrete ties is manifested by the loss of material under the rail seat area and, in extreme cases, results 

in loss of rail clip holding power, reverse rail cant, and gauge widening. RSA was measured in several curves on two railroads. 

The measurements encompass a range of environmental conditions and track curvature. The RSA measurements, track geometry 

measurements, and wheel/rail forces predicted with NUCARS® were compared to identify a correlation between wheel/rail forces 

and deep, wedge-shaped abrasion. RSA and wheel/rail forces were found to be related to curvature, but no clear examples were 

found where rail forces and RSA could be correlated to a local track geometry deviation. Comparisons were hampered by cases 

where RSA was measured in locations where previous repairs had been made and by other cases where very little RSA was 

present at the sites measured.

14. SUBJECT TERMS

Rail seat abrasion, concrete ties

15. NUMBER OF PAGES

59

16. PRICE CODE

17. SECURITY CLASSIFICATION

OF REPORT

Unclassified

18. SECURITY CLASSIFICATION

OF THIS PAGE

Unclassified

19. SECURITY CLASSIFICATION

OF ABSTRACT

Unclassified

20. LIMITATION OF ABSTRACT

NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89)

Prescribed by ANSI Std. 239-18

298-102
ii

METRIC/ENGLISH CONVERSION FACTORS

ENGLISH TO METRIC METRIC TO ENGLISH

LENGTH (APPROXIMATE) LENGTH (APPROXIMATE)

1 inch (in) = 2.5 centimeters (cm) 1 millimeter (mm) = 0.04 inch (in)

1 foot (ft) = 30 centimeters (cm) 1 centimeter (cm) = 0.4 inch (in)

1 yard (yd) = 0.9 meter (m) 1 meter (m) = 3.3 feet (ft)

1 mile (mi) = 1.6 kilometers (km) 1 meter (m) = 1.1 yards (yd)

1 kilometer (km) = 0.6 mile (mi)

AREA (APPROXIMATE) AREA (APPROXIMATE)

1 square inch (sq in, in2) = 6.5 square centimeters (cm2) 1 square centimeter (cm2) = 0.16 square inch (sq in, in2)

1 square foot (sq ft, ft2) = 0.09 square meter (m2) 1 square meter (m2) = 1.2 square yards (sq yd, yd2)

1 square yard (sq yd, yd2) = 0.8 square meter (m2) 1 square kilometer (km2) = 0.4 square mile (sq mi, mi2)

1 square mile (sq mi, mi2) = 2.6 square kilometers (km2) 10,000 square meters (m2) = 1 hectare (ha) = 2.5 acres

1 acre = 0.4 hectare (he) = 4,000 square meters (m2)

MASS - WEIGHT (APPROXIMATE) MASS - WEIGHT (APPROXIMATE)

1 ounce (oz) = 28 grams (gm) 1 gram (gm) = 0.036 ounce (oz)

1 pound (lb) = 0.45 kilogram (kg) 1 kilogram (kg) = 2.2 pounds (lb)

1 short ton = 2,000 pounds 

(lb)

= 0.9 tonne (t) 1 tonne (t) =

=

1,000 kilograms (kg)

1.1 short tons

VOLUME (APPROXIMATE) VOLUME (APPROXIMATE)

1 teaspoon (tsp) = 5 milliliters (ml) 1 milliliter (ml) = 0.03 fluid ounce (fl oz)

1 tablespoon (tbsp) = 15 milliliters (ml) 1 liter (l) = 2.1 pints (pt)

1 fluid ounce (fl oz) = 30 milliliters (ml) 1 liter (l) = 1.06 quarts (qt)

1 cup (c) = 0.24 liter (l) 1 liter (l) = 0.26 gallon (gal)

1 pint (pt) = 0.47 liter (l)

1 quart (qt) = 0.96 liter (l)

1 gallon (gal) = 3.8 liters (l)

1 cubic foot (cu ft, ft3) = 0.03 cubic meter (m3) 1 cubic meter (m3) = 36 cubic feet (cu ft, ft3)

1 cubic yard (cu yd, yd3) = 0.76 cubic meter (m3) 1 cubic meter (m3) = 1.3 cubic yards (cu yd, yd3)

TEMPERATURE (EXACT) TEMPERATURE (EXACT)

[(x-32)(5/9)] °F = y °C [(9/5) y + 32] °C = x °F

For more exact and or other conversion factors, see NIST Miscellaneous Publication 286, Units of Weights and 

Measures. Price $2.50 SD Catalog No. C13 10286 Updated 6/17/98

QUICK INCH - CENTIMETER LENGTH CONVERSION

0 1 2 3 4 5

Inches

Centimeters 0 1 2 3 4 5 6 7 8 9 10 11 12 13

QUICK FAHRENHEIT - CELSIUS TEMPERATURE CONVERSION

 -40° -22° -4° 14° 32° 50° 68° 86° 104° 122° 140° 158° 176° 194° 212°

 

°F

 °C -40° -30° -20° -10° 0° 10° 20° 30° 40° 50° 60° 70° 80° 90° 100°
iii

Acknowledgments

TTCI would like to acknowledge the support provided by the following people for this project: 

Mike Coltman, John A. Volpe National Transportation Systems Center (Volpe Center); Brian 

Marquis, Volpe Center; John Choros, Volpe Center; Seth Ogan, BNSF Railway; Mark Austin, 

CSX; and Hugh Thompson, Federal Railroad Administration, Office of Railroad Policy and 

Development.
iv

Contents

Executive Summary........................................................................................................................ 1

1 Introduction ............................................................................................................................. 2

1.1 Background ....................................................................................................................... 2

1.2 Project Objectives.............................................................................................................. 3

2 Project Method ........................................................................................................................ 5

2.1 Field Survey and Measurement Approach ........................................................................ 5

2.2 Track Geometry Measurements ...................................................................................... 13

2.3 NUCARS Simulations..................................................................................................... 14

3 Survey Measurements and NUCARS Simulation Results.................................................... 18

3.1 Site 1 – CSX Coal River Subdivision near St. Albans, WV ........................................... 18

3.2 Site 2 – BNSF near Needles, CA .................................................................................... 31

3.3 Site 3 – BNSF near Alliance, NE.................................................................................... 42

4 Conclusions and Recommendations...................................................................................... 47

4.1 Conclusions..................................................................................................................... 47

4.2 Recommendations........................................................................................................... 48

5 References............................................................................................................................. 49

Abbreviations and Acronyms ....................................................................................................... 50
v

Illustrations

Figure 1. Example of Severe RSA.................................................................................................. 2

Figure 2. Example of Ties Reported to Have RSA, but with Rail in Place It Is not Feasible to 

Measure RSA Depth ........................................................................................................ 5

Figure 3. Another View of the Same General Location as Shown in Figure 2; Ties Reported to 

Have RSA, but with Rail in Place It Is not Feasible to Measure RSA Depth ................. 6

Figure 4. Example of Ties Shown in Figures 2 and 3 with Rail Removed, Showing Depth 

of RSA ............................................................................................................................. 6

Figure 6. Bottom Side of the Template Used in Manual RSA Measurements............................... 9

Figure 7. Typical Maintenance Gang Conducting a Rail Change and RSA Repair..................... 10

Figure 8. Following the Rail Removal (Figure 7), Old Pads Are Removed and the Rail Seat Is 

Scraped Clean ................................................................................................................ 11

Figure 9. After Old Pads Have Been Removed, the Rail Seats Are Exposed .............................. 11

Figure 10. View from Figure 9 Looking Back to the Machine Repairing Rail Seats and Placing 

Pads in Position........................................................................................................... 12

Figure 11. Example Comparison of Truck Side L/V Ratios from NUCARS Simulations Using 

Different Combinations of Wheel Profile Measurements .......................................... 15

Figure 12. Example of Two-Layer Track Model in NUCARS .................................................... 16

Figure 13. Low Rail MP 16.78–16.68; This Curve Shows a Very Clear Relationship between 

Track Curvature and RSA Depth................................................................................ 20

Figure 14. High Rail MP 17.49–17.3, although Less Distinct Than the Curve at MP 16; This 

Curve Shows a Correlation between Curvature and RSA Depth .............................. 20

Figure 15. High Rail MP 19.7....................................................................................................... 21

Figure 16. Curve Data for MP 16; Distance along Curve Measurements and Predicted Car 

Performance of a Loaded Hopper............................................................................... 23

Figure 17. Rail Seat Vertical Forces and Roll Moments for MP 16 at Tie Located at 3,596 ft ... 25

Figure 18. Rail Seat Vertical Forces and Roll Moments for MP 16 at Tie Located at 3,478 ft ... 25

Figure 19. Wheel/Rail Contact Geometry for Axle 1 at 3,478 ft along the Track for MP 16 with 

Corresponding Left and Right Wheel L/V Ratios, Showing Hard Flange Contact on 

High Rail..................................................................................................................... 26

Figure 20. Wheel/Rail Contact Geometry for Axle 2 at 3,478 ft along the Track for MP 16 

with Corresponding Left and Right Wheel L/V Ratios, with High Rail Wheel 

Contacting in the Flange Root .................................................................................... 27

Figure 21. Curve Data for MP 17; Distance along Curve Measurements and Predicted Car 

Performance of a Loaded Hopper............................................................................... 28

Figure 22. Rail Seat Vertical Forces and Roll Moments for MP 17 at Tie Located at 2,154 ft ... 29
vi

Figure 23. Curve 17, Typical Rail Seat Conditions near Tie 205................................................. 30

Figure 24. Curve 17, View of Rail Seat Previously Repaired ...................................................... 30

Figure 25. Curve 16, Tie 104, Left Is Field Side, with More RSA Depth on the Field Side of the 

Rail Seat, and It Results in Outward Tilt (cant) of the Rail........................................ 31

Figure 26. High Rail MP 589 Average RSA and RSA Difference(cant); Shows Almost no 

RSA Depth.................................................................................................................. 33

Figure 27. Low Rail MP 588.5 Average RSA and RSA Difference (cant); Shows Almost no 

RSA Depth.................................................................................................................. 34

Figure 28. Low Rail MP 588.2 Average RSA and RSA Difference; Shows a Very Slight 

Tendency for Inward Cant (rail tilt) toward the End of Curve; Direction of 

Predominant Traffic Is Left to Right .......................................................................... 34

Figure 29. Low Rail MP 584.5 Average RSA and RSA Difference (cant); RSA Depth Is near 

Zero, Except in Full Body of Short Curve.................................................................. 35

Figure 30. Low Rail MP 583 Average RSA and RSA Difference (cant)..................................... 35

Figure 31. MP 584.5 Typical RSA in Curve, Tie 126, and Tie 157............................................. 36

Figure 32. Curve Data for MP 584.5; Distance along Curve Measurements and Predicted Car 

Performance of a Loaded Hopper............................................................................... 38

Figure 33. Rail Seat Vertical Forces and Roll Moments for MP 584.5 at Tie Located at 345 ft; 

Blue Lines Show Forces and Moments at 15 mph; Red Lines at 50 mph.................. 39

Figure 34. Wheel/Rail Contact Geometry for Axle 1 at 345 ft along the Track for MP 584.5, 

with Corresponding Left and Right Wheel L/V Ratios.............................................. 40

Figure 35. Wheel/Rail Contact Geometry for Axle 2 at 345 ft along the Track for MP 584.5, 

with Corresponding Left and Right Wheel L/V Ratios.............................................. 40

Figure 36. Effect of Rail Lubrication Conditions on Axles 1 and 2 Low Rail L/V Ratios and 

Low Rail Roll Moments for MP 584.5 at Tie Located at 345 ft................................. 42

Figure 37. Curve between MP 11.9 and MP 11.6, Average RSA and RSA Cant, High Rail ...... 43

Figure 38. Alliance Curve between MP 12.96 and MP 12.62, Average RSA and RSA Cant, 

High Rail..................................................................................................................... 44

Figure 39. Alliance Curve between MP 22.6 and MP 21.7, Average RSA and RSA Cant, 

Low Rail...................................................................................................................... 44

Figure 40. Alliance Curve between MP 26.3 and MP 25.95, Average RSA and RSA Cant, 

Low Rail...................................................................................................................... 45

Figure 42. High Rail Seat of Tie 396 on Curve at MP 12.8 ......................................................... 46

Figure 43. High Rail Seat of Tie 401 on Curve at MP 12.8 ......................................................... 46
vii

Tables

Table 1. Description of Measurement Sites at St. Albans, WV.................................................... 19

Table 2. Description of Measurement Sites at Needles, CA, Milepost (MP)............................... 32

Table 3. Description of Measurement Sites at Alliance, NE........................................................ 43
1

Executive Summary

Rail seat abrasion (RSA) of concrete ties is manifested by the loss of material under the rail seat 

area and, in extreme cases, results in loss of rail clip holding power, reverse rail cant, and gauge

widening. RSA was found to be related to the average forces created by track curvature. RSA 

could not be correlated to a localized track geometry feature in the measurements made as part of 

this research program.

The objective of this project was to identify the field conditions where RSA is occurring. Ideally,

the measurements would have identified localized areas of deep, wedge-shaped abrasions that 

contribute to loss of rail cant and gauge widening, and then, it would have documented the track 

geometry and wheel/rail force environment that led to such a condition. These results might have 

been used to design a modification to a short section of the Facility for Accelerated Service 

Testing (FAST) High Tonnage Loop at the Transportation Technology Center (TTC) near 

Pueblo, CO, to induce high wheel/rail forces for the purpose of monitoring RSA growth.

RSA was inspected and measured in 16 curves on two railroads, encompassing a range of 

environmental conditions and track curvature. For a few of the measured curves, RSA 

measurements were compared with measured track geometry and wheel/rail forces generated by 

NUCARS®1 simulations to correlate wheel/rail forces and abrasion depth. The NUCARS 

simulations confirmed the correlation of RSA with track curvature but could not identify local 

track geometry features associated with severe RSA. To more clearly differentiate specific 

features, more accurate input to the NUCARS simulations related to the specific site may be

required such as rail lubrication, types of vehicles running over the site, and variations in the rail 

fastener and support conditions. The St. Albans, WV, sites had the tightest curvature, the highest 

annual precipitation, and the deepest RSA. Many of the curves at this location had previous 

repairs. It was impossible to determine whether the measured abrasion was recent or present at 

the time of previous repair, because the previous repair material was often removed as part of the 

pad removal and seat cleaning process. 

The Needles, CA, sites had the next tightest curvature and the least annual precipitation. These 

curves had not been previously repaired. Only one of the curves measured had measureable 

RSA. This was just the onset of abrasion, and it was occurring along the gauge side of the 

rail seat.

The Alliance, NE, site had the lowest curvature, and its precipitation levels were between those 

of Needles and St. Albans, although much closer to Needles. Some of the curves had been 

repaired previously and some had not. The Alliance curves showed very little abrasion. 

RSA measurements required rail removal; therefore, the inspections were coordinated with the 

cooperating railroads’ rail replacement or rail seat repair schedules. Measurements were

contingent on not interfering with the repair teams and allowed very limited time for RSA

measurement. Most measurements were made with a steel template and a digital depth gauge, 

although a prototype automated measurement system was tried. For future work, an improved 

automated device is recommended to allow more measurements in the limited time available.

 

1 NUCARS® is a registered trademark of Transportation Technology Center, Inc.
2

1. Introduction

RSA of concrete ties is manifested by the loss of material under the rail seat area and reduction

of rail clip holding power. This condition, especially at its onset, is difficult to detect visually. 

Severe abrasion can result in loss of clip toe load, rail tipping (cant), and wide gauge and can 

cause derailment. Figure 1 shows an example of severe RSA. 

Figure 1. Example of Severe RSA

Several programs sponsored by the railroad industry, suppliers, and FRA are in place to develop 

RSA detection systems; however, to solve the problem, the root cause must be determined. RSA 

is known to occur in areas of high loads, sharp curves, and high precipitation. However, because

RSA does not occur everywhere, one theory suggests that selected combinations of track 

geometry track fastener and support conditions, and other local and environmental conditions

result in increased wheel/rail forces that are incipient to the damaging conditions that result 

in RSA. 

The work under this phase of the project assessed field conditions where RSA was reported to be 

occurring and produced comparisons of wheel/rail forces and track forces on the basis of

predicted vehicle dynamic response to track geometry inputs. These results are intended to 

provide input for developing a predictive model for RSA detection. 

1.1 Background

Detailed track inspection at the locations of two derailments attributed to RSA indicated concrete 

ties exhibited an excessively large wedge shaped loss of material on the field side of the rail seat 

area. At these locations, loss of material was present for a short portion of a curve corresponding 

to a track location that contained a “down and out” geometry irregularity on the outside rail of 

the curve. The John A. Volpe National Transportation Systems Center (Volpe) conducted 

analyses that estimated that the combination of the vertical and lateral wheel forces resulting 
3

from these types of track geometry irregularities can result in rail base field side stresses

exceeding the design compression capacity of concrete ties [1].

The objective of this research project was to explore the correlation between development of the 

wedge-shaped form of RSA and dynamic wheel/rail interaction loads resulting in field side 

pressures in excess of typical concrete strength and how these loads relate to initiation and 

growth of this type of RSA. 

Development of RSA has previously been studied at the FAST High Tonnage Loop at TTC, but 

did not focus on the effects of particular track geometry features [2, 3]. The previous research 

evaluated the performance of new and different rail fastener and rail seat components and 

materials for their effects on reducing rail RSA. Different methods for repairing RSA were also 

evaluated.

The scope of this project was divided into two major segments. The first segment (subject of this 

report) investigated RSA found in track under revenue service conditions and compared it to

measured track geometry to determine whether the hypothesized deviations suspected to result in 

high applied concrete surface stress correlated to field RSA measurements. The intent of this 

investigation was to characterize the types of RSA occurring in revenue service, and where 

located, to identify the conditions, which may contribute to the occurrence of wedge-shaped

abrasions.

The second, follow-on segment in 2012 is planned to develop experiments that, under a 

controlled environment, will produce conditions necessary for the initiation and growth of this 

type of RSA. The second segment is also expected to complete the development of the predictive 

model, which builds on field assessment results. This work would also include field validation of 

track segments where the model predictions show no occurrence of RSA. In addition, on the 

basis of predictive modeling and track test results, future deliverables would include 

development of best practices to reduce the tendency of RSA. Modeling development and 

associated efforts will be conducted primarily by the engineering staff from Volpe, while field 

assessment and activity coordination will be the primary responsibility of Transportation 

Technology Center, Inc. (TTCI).

1.2 Project Objectives

The first segment of the project had three main objectives:

• Measure RSA at selected revenue service sites to determine severity and extent of RSA,

depth and patterns of RSA, and track geometry. 

• Use the field measurements as input to NUCARS simulations to determine track features 

and locations where vehicle performance was expected to introduce high lateral loads

into the track. 

• Use the results of the measurements and NUCARS simulations to identify potential track 

geometry features for use in a future project for modifying a short segment of the FAST 

High Tonnage Loop to purposely induce high truck side lateral/vertical (L/V) ratios for 

monitoring the effect on developing RSA and/or track component damage. 

Concurrently, survey measurements and simulation results were provided to the Federal 

Railroad Administration (FRA) and Volpe to support their efforts in developing RSA 
4

predictive modeling tools. Using this information, Volpe engineering staff will lead the effort 

to determine whether common vehicle track interaction characteristics can be reliably used to 

accurately predict development, growth, and severity of RSA. 
5

2. Project Method

For the first segment of work, TTCI developed detailed test plans for field inspection and 

measurement. These were reviewed by Hugh Thompson (FRA Contracting Officer’s Technical 

Representative - COTR) and Volpe engineering staff to ensure that the data obtained, addressed

future requirements of the planned modeling effort. A technical advisory group (TAG) was 

established to coordinate the two participating railroads (CSX and BNSF Railway (BNSF)). To 

address their specific needs, each railroad assigned a track engineer to help coordinate field 

inspections and provide track geometry measurements for use in subsequent analyses. This 

included obtaining work plans, traffic history, track geometry history, and ensuring safe and 

legal track access to obtain measurements.

2.1 Field Survey and Measurement Approach

To obtain field data, a significant effort was required by personnel from the cooperating railroads 

to provide access to locations on track, track inspection data, and historical information. Because

no acceptable or validated means of measuring RSA depth and shape with rail in place currently

exists, the field measurements required access to rail seats during periods when the railroads

were changing rail and/or repairing rail seats. Examples of this situation are shown in Figure 2

and Figure 3 (ties reported to have RSA but with rail still attached). Figure 4 is the same 

approximate location but with the rail removed, showing variations in RSA over just a few ties. 

Note that the large tie plates shown in these photographs were installed to mitigate and control 

RSA at these particular locations.

Figure 2. Example of Ties Reported to Have RSA, but with Rail in Place It Is not 

Feasible to Measure RSA Depth

(New replacement rail pads are in ballast next to ties in preparation of RSA repair.)
6

Figure 3. Another View of the Same General Location as Shown in Figure 2; Ties Reported

to Have RSA, but with Rail in Place It Is not Feasible to Measure RSA Depth

Figure 4. Example of Ties Shown in Figures 2 and 3 with Rail Removed, 

Showing Depth of RSA

(Note that RSA depth is not uniform from tie to tie. The red arrows show that the two nearest ties have RSA 

undercutting the fastener clip, whereas the green arrow shows that the third tie has much less RSA 

and no undercutting.)
7

Because the rail blocks the ability to measure depth, locations where RSA data could be 

collected were contingent on when and where rail removal work was planned by the participating 

railroads. In many cases, last-minute issues and emerging conditions such as track time, 

equipment delays, and availability of railroad personnel limited the data that could be collected.

For each area or subdivision where RSA was suspected based on aging track conditions, the 

work plan for the host railroad was provided. Curves were compared to track chart data and a 

prework inspection conducted to assess site conditions. This included walking each curve, 

locating key curve points including points of tangent to spiral, spiral to curve, curve to spiral and 

spiral to tangent. A tie numbering system was established at each curve associated with a nearby 

feature such as a milepost (MP) marker. This method was selected over detailed distance 

measurements, because ties are on 2.0-foot centers, and by counting tie numbers an accurate 

distance could be determined for any specific location. Ties were numbered by marking every 

tenth tie in the planned direction of work (Ties 0, 10, 20, etc.) to facilitate correlating location

with RSA data collected during the maintenance activity. Where such inspections could be 

conducted well in advance of the actual track work, the cross section profiles on both rails were 

measured by using a MiniProfTM profilometer at the key curve points (above) and at several 

locations within the full body of the curve. Other notes were made on localized site variations 

and conditions that might contribute to variable loading, such as low spots, alignment kinks, etc. 

The speed and type of train traffic normally operated over the sites was observed, and details 

were provided by the host railroads. Any other parameters identified as being important to the 

formation of RSA were also noted. However, in the short windows of time allowed there was not 

sufficient time to collect detailed information about the condition of specific fastener 

components: clips, insulators, and pads.

Either before or after the inspection, the most recent track geometry data (prior to planned work) 

was obtained for comparison with the RSA data and for use in the NUCARS vehicle dynamic

performance predictions. 

To aid in RSA depth and shape measurements, TTCI fabricated a prototype laser trace fixture 

that measures the RSA depth around the edge of the rail seat, as Figure 5 shows.
8

Figure 5. Automated RSA Profile Data Collection System Prototype Used to Collect the 

Perimeter Depth and Pattern of RSA

The automated laser device was a prototype and was not sufficiently robust to withstand field 

test environments and handling. Rain or moisture easily damaged controls and electrical systems, 

and it was too cumbersome to rapidly collect data. In addition, the large size and relatively small 

triangular-shaped base of the machine led to problems, because it tipped during the measurement 

process and created data errors. To supplement the automated system, manual measurements 

were utilized by using a flat template and dial indicator gauge. Figure 6 shows the template used 

in the manual system. 
9

Figure 6. Bottom Side of the Template Used in Manual RSA Measurements

A dial indicator gauge was placed in predetermined numbered holes located around 

the template to obtain a profile of the abrasion depth. The “L” template was then 

turned 90 degrees to measure the other two sides of the rail seat area.)

The test plan was to measure RSA depth during the time rail seats were exposed when rail 

changes or rail seat repairs were conducted. The normal procedure followed by railroads includes 

the following major steps. Minor differences or additional steps are often followed but do not 

change the overall concept and time available to measure RSA:

1. Unclip fasteners from both sides of the rail being lifted

2. Lift and slide rail to one side or the other (Figure 7) 

3. Follow with a crew removing existing rail pads, then clean rail seats (Figure 8) 

a. NOTE: At this point, rail seats are exposed and could be measured for RSA depth 

and photographed (Figures 9, 10)

4. Apply repair epoxy when RSA is of sufficient depth

5. Install new rail seat pads

6. Reinstall rail (or if a rail change, install new rail)

7. Adjust rail for proper longitudinal stress and reclip 
10

The overall process from rail removal to reinstallation for a curve took several hours, but the 

“moving window” between steps 3 and 4 provided only a very short time, generally less than 

5 minutes, to measure rail seats. Because of safety issues (rail movement, passing trains on 

adjacent tracks, and nearby equipment), the window for measurements was usually less than 

5 minutes. A typical measurement of gauge and field side RSA depth and subsequent recording 

of the data required 45–50 seconds per tie; thus, collecting data at every tie to obtain a 

continuous tie-by-tie pattern of RSA through a full curve was not feasible. 

Figure 7. Typical Maintenance Gang Conducting a Rail Change and RSA Repair

(Existing, old rail is being removed and set to the field (outside, right) side of track. 

Note new rail has already been placed in the center of the track.)
11

Figure 8. Following the Rail Removal (Figure 7), Old Pads Are Removed and the Rail Seat 

Is Scraped Clean

(Note new pads, insulators, and clips have been distributed. At this stage, RSA cannot be measured due to logistics 

and work space conflicts.)

Figure 9. After Old Pads Have Been Removed, the Rail Seats Are Exposed

(The manual RSA measuring template and dial indicator are placed in position, and dial indicator readings are 

collected. In this photo the field (outside) of the rail seat is being measured.)
12

Figure 10. View from Figure 9 Looking Back to the Machine Repairing Rail Seats and 

Placing Pads in Position

(At this location, two RSA measurement groups are monitoring rail seat conditions, working in tandem. The “working window” 

for measuring RSA is from this site to about 30 feet (ft) toward the machine in this photo. Because the new rail in the center of 

the track is being placed into the rail seats directly behind the machine in the background, it is not safe to work more than 30 ft 

from this location.)

To speed up the RSA measurements as much as possible, TTCI fabricated two additional manual

gauges. This allowed two teams of two people each (one measuring, the other recording data) to 

measure three to four ties in a row and then “leap frog” ahead of the other team, as Figure 10

shows. In one instance, sufficient personnel were available to use all three manual gauges, plus 

one person to document visual conditions (photograph) of each measured rail seat. Whenever the 

tie pad replacement and rail seat repair crew caught up, the measurement teams skipped ahead 

10–15 ties and resumed measuring a batch of ties. Generally, the person photographing rail seats 

was positioned ahead of the measurement crews and would specify groups of ties to measure 

when RSA issues were noted. 

This measurement procedure was cumbersome, but it allowed the overall trends and patterns of 

RSA on each selected curve to be documented and measured. However, the wide spacing 

between measurements is likely to limit the ability to link or correlate RSA to short wavelength 

track geometry features. Because it was not possible to measure every tie, it is not possible to 

determine from the data whether a single measurement is a short wavelength peak, with either 

more or less RSA at intermediate locations, or whether RSA varies proportionately between 

measurement locations. However, the RSA illustrated in Figure 4 suggests that RSA can vary 

considerably from tie to tie and therefore can occur on a fairly short wavelength.

For example, at the CSX St. Albans measurement site at MP 16, 30 measurements were made at 

relatively even spacing over a length of 282 ties for approximately 562 ft or approximately 19 ft 

per measurement. This means that the shortest wavelength detectable in the RSA measurements

at that site is more than 40 ft, and accurate identification of the amplitudes is difficult for 
13

wavelengths less than 80 or 100 ft. This implies that short wavelength phenomena such as typical 

down-and-out perturbations may not be detectable in any of the measured RSA data. The 

situation on the BNSF Needles and Alliance sites where measurements were made in clusters is 

more complicated, because measurements were made on three or four adjacent ties, but the 

clusters were much more widely spaced, leading to the possibility of missing considerable short 

wavelength information between the clusters. 

To definitively identify short wavelength RSA, more frequent measurements over a longer 

distance are required. A faster, automated measurement system would have permitted more 

frequent measurements and would have been highly desirable; however, budget and time 

limitations prevented development and deployment of an alternative. The current project called 

for measuring RSA at only three railroad sites, with four to six curves selected at each site. With 

the cost to develop an automated system for this purpose deemed too high, to be cost-effective 

over manual methods, an automated measurement system would need to measure a rail seat 

every 10–15 seconds (or less). Should a future program in RSA evaluation need to collect data 

over many thousand ties, an automated (and fast) measurement device should be developed. 

2.2 Track Geometry Measurements

For each measurement site, track geometry measurements were obtained from either the host 

railroad or FRA for the sections of track that were inspected. This data was used for the 

following two purposes:

1. Compare with RSA data to determine whether RSA could be correlated to specific 

features in the track geometry such as down-and-out lateral alignment and cross-level 

perturbations

2. Input to the NUCARS simulations

For the purposes of this project, it was requested that the data be provided in “space curve” 

format, the ideal format for input to NUCARS. Space curve data is preferred, because normal 

midchord offset measurements can miss critical information that it is not possible to reconstruct 

from the data [4]. It was requested that at a minimum the following data be provided:

• Curvature

• Superelevation/Cross level

• Gauge

• Alignment (either track centerline or left and right rail alignment)

• Vertical profile (either track centerline or left and right rail vertical profiles)

BNSF provided space curve data in the requested format from the Needles site, and FRA 

provided the data for the Alliance site on BNSF by using the DOT 218 measurement car. 

However, CSX was not able to provide space curve data from the St. Albans site. 

The data available from CSX had been measured by using a form of midchord offset 

measurement. The midchord offset measurements for the profile and alignment data had an 

unusual measurement wavelength and was unsuitable for input to NUCARS. Therefore, for 

comparison to the RSA measurements on CSX and for input to NUCARS, the profile and 

alignment for CSX were reconstructed from the curvature, gauge, and superelevation data. 
14

However, because of the measurement wavelengths for the available data information, it is very 

likely that some short wavelength variations in the vertical profile and alignment were not 

included in the simulations, although the gauge and cross level were correctly represented in the 

simulations. The missing geometry data may have resulted in lower wheel forces from the 

simulations. 

2.3 NUCARS Simulations

A limited number of NUCARS simulations were conducted to estimate the vehicle dynamic 

response and wheel/rail forces that would be generated by typical freight cars running over the 

inspection sites. The results of the NUCARS modeling were then compared with the 

measurements of RSA from the sites and the measured track geometry from the sites to 

determine whether any correlations could be made between local track geometry features (such 

as down and out track perturbations), vehicle dynamic response, and RSA.

2.3.1 NUCARS Vehicle Model

The test different sites all have traffic from a mix of different rail vehicles. For example, the St.

Albans site has primarily coal gondolas and hopper cars, whereas the Needles site has primarily 

intermodal freight cars. However, at all sites it is expected that the cars that generate the largest 

forces will be loaded to a maximum axle load of 36 tons and use some form of three-piece 

freight car trucks. Therefore, for the limited number of simulations conducted for this segment of

the project, only one vehicle was simulated: a loaded, 286,000-pound (lb), four-axle coal 

gondola with standard three-piece freight car trucks with variable friction damping and constant 

contact side bearings. The basic dimensional information for this car was as follows:

Truck spacing: 486 inches (in) (40.5 ft)

Axle spacing in truck: 70 in

Total weight: 286,000 lb

Carbody weight: 266,500 lb

Carbody center of gravity height above rails: 83 in

In a future segment of this project, it is recommended that the operation of a few other vehicles,

such as loaded intermodal cars, be simulated to determine whether other car types generate 

similar responses and effects on RSA development.

Wheel profiles were measured on four typical coal hoppers that ran over the St. Albans site. 

Figure 11 shows the results of NUCARS trial simulations conducted with some of these different 

profiles. It can be seen that different wheel profiles can generate different levels of wheel/rail 

forces, although the trends of higher L/V ratios in the body of the curve are the same. From these 

trial simulations, the wheel profile that generated the largest truck side L/V ratios was selected 

for use in all further simulations. The truck side L/V ratio was selected as the primary 

performance parameter, because it represents the combined effect of two adjacent axles acting 

on the rails. 
15

Figure 11. Example Comparison of Truck Side L/V Ratios from NUCARS Simulations 

Using Different Combinations of Wheel Profile Measurements

(The blue line uses a single wheel profile with good steering characteristics; the red line uses a pair of asymmetric wheel profiles 

as measured on one axle; the green line uses a single wheel profile with poor steering characteristics.)

2.3.2 NUCARS Track Model

To accurately simulate the dynamic response of the rails on the ties and the consequent forces 

and moments in the rail seats, the track model capability in NUCARS was used to simulate the 

rails, fastening system, ties, and ballast. Figure 12 illustrates an example of a two-layer track 

model, similar to what was implemented for this project. Details of the track model were 

adjusted to meet the requirements of this project.
16

Figure 12. Example of Two-Layer Track Model in NUCARS

The NUCARS track model used for this project included the following basic assumptions:

• Flexible rails, with motions in the vertical (z), lateral (y), and roll (around x) directions, 

including vertical, lateral, and twist bending modes. Sufficient flexible modes were 

provided to include the pinned-pinned mode for each flexible direction, based on the tie 

spacing. 

• Flexible ties, with vertical (z), lateral (y), and roll (around x) motions, including the first 

seven modes of vertical bending. Ties were spaced 24 in apart. 
17

• Rail seats and fasteners were represented by two vertical and two lateral connections per 

rail seat, one on each side of the base of the rail.

• Ballast was represented as eight discrete vertical and lateral connections between each tie 

and the ground.

Because detailed measurements of fastener and pad characteristics and local ballast stiffnesses

were not available, representative values for these parameters were selected on the basis of

experience with previous measurements and model simulations of similar track. For this phase of 

work, the NUCARS simulations assumed ballast and track fastener conditions (stiffness, preload, 

etc.) to be identical at each tie. The track parameters were assumed to be the same for all the sites 

modeled. NUCARS permits input of different conditions for the ballast at each tie and different 

conditions for each fastener. For future phases of work, these parameters could be varied from tie 

to tie and site to site, as required or appropriate.

Rail profile measurements from each measurement simulated were used as inputs to the model. 

The NUCARS track model uses the wheel and rail profile measurements to calculate the 

wheel/rail contact geometry for each wheel at each simulation integration step as the vehicle 

moves along the track. The wheel/rail contact geometry calculations include the effects of the 

rail vertical, lateral, and roll motions at each wheel. The penetration contact model used in the

NUCARS track model permits calculation of up to 10 overlapping contact points per wheel.

NUCARS permits outputting the forces in the rail seats and fasteners at any selected tie. As 

noted above, two vertical and lateral connections were used per rail seat. These connection forces 

were converted to a single rail seat vertical force and rail seat roll moment to allow comparisons 

between ties and sites. 
18

3. Survey Measurements and NUCARS Simulation Results

TTCI developed detailed test plans for field inspection and measurements. These were reviewed 

by the FRA COTR and Volpe engineering staff to ensure data obtained satisfactorily addressed

future requirements of the planned modeling effort. 

Data collected included:

• Recent track geometry measurement outputs

• Field inspection photos and notes on RSA variation at the site

• Measurements of RSA depth, pattern, and appearance, at locations noted by the 

photographer as having more severe RSA

• MiniProf rail profiles collected at various locations around a curve

• Train operation characteristics—load, line density, traffic volume, speeds, direction, 

braking, etc.

Three survey sites were identified, one on CSX and two on the BNSF. Once the data at the CSX 

site was collected, the methods used to correlate track location with track geometry information 

and NUCARS simulation results went though several iterations to select a wheel profile for use 

in the simulations and to develop methods for displaying and comparing the NUCARS 

simulations with the track data. In addition, improved field measurement techniques and 

additional RSA templates were fabricated to further streamline future RSA depth collection 

efforts. These efforts required several months to complete, delaying the time frame when the 

BNSF sites could be inspected until early 2011. 

Survey measurements and corresponding NUCARS simulation results are presented for each of 

the three sites in the following three subsections.

3.1 Site 1 – CSX Coal River Subdivision near St. Albans, WV

The first location for measuring RSA on this project was offered by CSX on its Coal River 

Subdivision near St. Albans, WV. This is a single track line with virtually 100-percent coal 

traffic, with loaded unit trains traveling in one direction and empty returns in the opposite 

direction. A nearby large town, Charleston, WV, has an average of 43 in of precipitation per 

year, making it the wettest site surveyed. 

In early July 2010, six curves were selected for measurement on the basis of length, accessibility,

and visual indications, suggesting RSA was present. Track maintenance schedules and 

measurement resources allowed these curves to be inspected in detail and RSA measured during 

track work performed in August 2010. Table 1 lists the details of the actual measurement sites at 

St. Albans.
19

Table 1. Description of Measurement Sites at St. Albans, WV

Milepost

(MP)

Curvature 

(deg)

Superelevation 

(inch)

Balance 

Speed 

(mph)

Normal 

Operating 

Speed 

(mph)

Rail 

Measured 

(High/Low)

Comments, Notes, etc.

26.3 11 2.0 16 Low

22 2 1.0 27 25 Low Compound curve

20 15 1.0 10 25 High

Curvature ranges from 

14 to 16 degrees

Superelevation ranges from 

0 to 1 in

19 12 3.0 20 High

Wayside lubricators nearby, 

supplemented by Hy-Rail 

application

17 5 0.5 12 15–20 Low

Wayside lubricators nearby, 

supplemented by Hy-Rail 

application

16 8 2.0 20 Low

Wayside lubricators nearby, 

supplemented by Hy-Rail 

application

Figure 13 through Figure 15 show the abrasion data collected in the curves at MP 16, MP 17, and 

MP 19, respectively. These curves were measured with the more accurate manual gauge. The 

other three curves were measured with the automated system only. The first 208 ties of the curve 

at MP 19 were measured with the automatic machine until rain damaged the equipment. A large 

amount of scatter in that part of the plot is apparent (Figure 15). A similar amount of scatter was 

seen in the other three curves. Because of this, results from those curves are not shown. In 

Figure 13 through Figure 15, the Average is the aggregated value of the RSA depth 

measurements taken on the rail seat. Positive values indicate wear into the tie. The Difference is 

the average of the data from the field side of the rail seat minus the average of data from the 

gauge side of the rail seat. The abrasion measurements are referenced to the original cant of the 

rail seat. Therefore, a difference value of zero indicates no rail roll, but the rail will be canted to 

the angle that was built into the rail seat. A positive difference indicates abrasions that would 

tend to cause the rail to roll (cant) outward relative to the original rail seat and a negative 

difference would cause the rail to roll (cant) inward. 
20

Figure 13. Low Rail MP 16.78–16.68; This Curve Shows a Very Clear 

Relationship between Track Curvature and RSA Depth

Figure 14. High Rail MP 17.49–17.3, although Less Distinct Than the 

Curve at MP 16; This Curve Shows a Correlation between 

Curvature and RSA Depth

-1

0

1

2

3

4

5

6

7

8

-0.150

-0.100

-0.050

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0 50 100 150 200 250 300

Curvature (deg)

Rail Seat Abrasion Depth (in)

Tie Number

Avg

Difference

Curvature

-1

0

1

2

3

4

5

6

-0.150

0.000

0.150

0.300

0.450

0.600

0 100 200 300 400 500 600 700

Curvature (deg)

Rail Seat Abrasion Depth (in)

Tie Number

Avg

Difference

Curvature
21

Figure 15. High Rail MP 19.7

(The first 208 ties in the spiral and beginning of curve were measured with the laser trace machine before wet weather damaged 

it, and the rest of the ties were measured with the manual gauge. The larger scatter apparent in the laser trace machine data is 

thought to be to the result of the large machine tipping on its relatively small triangular base.)

On this line segment, track maintenance work was limited on these curves to one rail per curve, 

either the high or low rail, as shown above. 

Results from inspecting RSA on the Coal River Subdivision suggest the following: 

• Significant RSA depth at some locations but not a uniform depth on any curve

– RSA varied significantly from location to location around each curve.

– All ties had been previously repaired, some possibly twice.

– The prior repairs impacted the ability to accurately measure RSA, and it was 

impossible to differentiate current wear from older wear.

– RSA depth often increased within the limits and directly adjacent to dirt road 

crossings where moisture was trapped as the result of limited drainage.

• Data collected of RSA average depth and difference (cant) suggests

– As RSA depth increases, so does rail cant

– At the curves, all cant resulting from RSA was outward (more RSA depth on field 

side than gauge side) 

– A close correlation with position in curve and RSA depth

• More curvature results in more RSA depth and cant

• Typically, at the tangents there was little or no measured RSA

• RSA depth gradually increased through the spiral

0

2

4

6

8

10

12

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0 200 400 600 800 1000

Curvature (Deg)

Rail Seat Abrasion Depth (in)

Tie Number

Average RSA

Difference RSA

Curve
22

• RSA depth remained generally uniform through the body of

the curve (not including the spiral)

• A few isolated locations of deeper RSA did not correlate with 

variations in measured track geometry or predicted wheel/rail

forces. These locations tended to be near grade crossings or areas 

where previous rail seat repairs had failed maintaining track 

structure. It is suspected that the RSA near grade crossings is the 

result of poorer drainage and higher levels of moisture under the 

rail seats at these locations

• The scatter and large RSA values in the first 208 measurements at 

MP 19.7 shown in Figure 15 are probably suspect because of

problems encountered with the laser measurement device

Two curves were analyzed and summarized in data plots generated to show RSA depth and 

difference (cant angle) versus distance along the curve. RSA depth is based on the average of all 

readings (both field and gauge side) for each rail seat. RSA difference subtracts the average

gauge side RSA depth from the average field side RSA depth. Thus, a positive difference value 

indicates outward cant of the rail or deeper RSA on the gauge side compared with the field side. 

A difference of 0.1 in corresponds to approximately 0.95 degrees of rail cant.

Figure 16 compares measured RSA depth, RSA difference (RSA cant), to track geometry and 

NUCARS predictions of wheel/rail forces for MP 16, with direction of travel from right to left in 

the graph. 

The first graph in Figure 16 shows the measured track curvature and superelevation/cross level. 

The second graph shows the manual measurements of average RSA depth and RSA depth 

difference (field-gauge) for the right/low rail. The third graph shows the measured track gauge 

and alignment as well as the left/high and right/low rail cants as measured by the track geometry 

car. 

The track geometry data (curvature, superelevation, alignment, and gauge) was used as input to 

the NUCARS simulations. The fourth and fifth graphs show the NUCARS predictions of lead 

axle single wheel L/V ratios and lead truck side L/V ratios, which were performed with the 

assumption of dry rail (rail friction coefficient of μ = 0.4). In this graph, a positive L/V ratio on 

the right rail and a negative L/V ratio on the left rail represent gauge-spreading forces. Note that 

in actual practice the friction coefficients in this curve are probably different as a result of the 

presence of track lubricators in the vicinity, which would result in somewhat different forces and 

dynamic response. However, friction levels were not measured.
23

Figure 16. Curve Data for MP 16; Distance along Curve Measurements and Predicted Car Performance of a Loaded Hopper

(Top to bottom shows curvature and superelevation, measured RSA average depth and difference, track geometry data, predicted lead axle L/V, and predicted lead truck side L/V.)
24

Figure 17 shows the corresponding NUCARS predictions of rail seat vertical forces and roll 

moments. This graph shows the forces acting on the tie that is located near distance 3,596 ft in 

Figure 16. This is in the entry spiral nearest to the spiral to curve location at the beginning of the 

curve. At the left side of the plot, the vehicle has not yet arrived at the tie. Then, each axle 

approaches and travels over the tie, and the corresponding rail seat forces and moments are 

shown. Axle 1 arrives first, shown on the left side of the graph, and Axle 4 is last shown on the 

right side. 

Figure 18 shows the NUCARS predictions of rail seat vertical forces and roll moments for the tie 

that is located nearest to distance 3,478 ft in Figure 16. This is at the start of the exit spiral (curve 

to spiral location) at the end of the curve. 

In these two graphs, negative vertical forces indicate pressure downward on the rail seat, and 

positive roll moments indicate moments that would cause the rail to roll outward and apply 

greater pressure to the outside of the rail seat. 

The rail seat moment can be seen to vary considerably with location in the curve. At the entry

spiral (3,596 ft), the roll moments on the high (left) rail seat only reach 15,000 in-lb and undergo 

a reversal when the second axle of the truck passes over. On the low (right) rail, the moments are 

much higher and do not reverse. At the end of the curve near the exit spiral (3,478 ft), the 

moments on both rails are much higher, and they do not reverse on either rail, indicating that 

both rails have a tendency to roll outward, which is consistent with both the RSA measurements 

and rail cant measurement at this location.
25

Figure 17. Rail Seat Vertical Forces and Roll Moments for MP 16 at Tie Located at 3,596 ft

Figure 18. Rail Seat Vertical Forces and Roll Moments for MP 16 at Tie Located at 3,478 ft

Axle 1 Axle 2 Axle 3 Axle 4

Axle 1 Axle 2 Axle 3 Axle 4
26

The results show that although the curve is relatively sharp, the L/V ratios are not excessive, but 

they are applying gauge-spreading forces to the rails. The differences in roll moments as the 

leading and trailing axles of each truck pass over the tie are because the lead and trail axles 

contact the rails in different positions, with the leading axle in hard flange contact on the high 

rail generating higher L/V ratios on the right low rail (Figure 19) than the trailing axle

(Figure 20), as would normally be expected for operation on dry rails. The lateral positions of the 

contact affect how the lateral and vertical forces generate the roll moments seen at the rail base. 

However, the largest roll moments are consistent with rolling both of the rails outward, as was 

seen for the low rail RSA measurements.

Figure 19. Wheel/Rail Contact Geometry for Axle 1 at 3,478 ft along the Track for MP 16

with Corresponding Left and Right Wheel L/V Ratios, Showing Hard Flange Contact 

on High Rail
27

Figure 20. Wheel/Rail Contact Geometry for Axle 2 at 3,478 ft along the Track for MP 16 

with Corresponding Left and Right Wheel L/V Ratios, with High Rail Wheel Contacting in 

the Flange Root

Figure 21 shows the relationship of measured RSA, RSA field-gauge (RSA Cant) for MP 17, 

with direction of travel from right to left in the graph. RSA measurements are compared with the 

NUCARS predictions, which were performed with the assumption of dry rail (rail friction 

coefficient of μ = 0.4). In this graph, a positive L/V on the right rail and a negative L/V on the 

left rail represent gauge-spreading forces. Note that in actual practice, the friction coefficients in 

this curve are probably different because of the presence of track lubricators in the vicinity, 

which would result in somewhat different forces and dynamic response. However, friction levels 

were not measured.

Figure 22 shows the corresponding NUCARS predictions of rail seat vertical forces and roll 

moments, with Axle 1 on the left side of the graph and Axle 4 on the right. These forces are at 

the tie that is located near to distance 2,154 ft in Figure 21. L/V ratios, rail seat forces, and 

moments for MP 17 are slightly less than for MP 16, because the curve is less sharp. However,

the trends are very similar.
28

Figure 21. Curve Data for MP 17; Distance along Curve Measurements and Predicted Car Performance of a Loaded Hopper

(Top to bottom shows curvature, RSA depth and cant, track geometry data, predicted lead axle L/V ratio, and predicted lead truck side L/V ratio.)

.
29

Figure 22. Rail Seat Vertical Forces and Roll Moments for MP 17 at Tie Located at 2,154 ft

Data in Figure 16 and Figure 21 shows the trend of RSA depth increasing from nearly zero in 

tangent track to some measurable value in the curve, transitioning from zero to approximately 

0.2 in. in the spirals. RSA data in Figure 16 does not show any significant localized severity

while that shown in Figure 21 indicates localized short segments of deeper RSA at 

approximately 2,180 ft and a deeper pocket at approximately 2,460 ft. Minor variations in lateral 

vehicle curving forces are predicted near the 2,460 ft location, along with localized alignment 

deviations near that site. However, the changes in vehicle performance are noted after the 

variations in RSA, suggesting that the vehicles were responding to minor variations in rail cant 

or alignment and not directly causing RSA. 

Historical trends in track geometry measurement data would need to be evaluated to determine 

whether the alignment deviation has been in place for some time, and if so, is it the result of 

localized support conditions or the reaction to localized and long-term curving performance? 

Figure 23 to Figure 25 show examples of rail seat conditions noted during the inspection.

Axle 1 Axle 2 Axle 3 Axle 4
30

Figure 23. Curve 17, Typical Rail Seat Conditions near Tie 205

(Ties measured with Tie 0 at the beginning of the curve in direction of loaded traffic, located at approximately 2,150 ft.)

Figure 24. Curve 17, View of Rail Seat Previously Repaired

(Epoxy used in former repair was still in place and could not be removed; thus, impaired ability to measure actual RSA depth. 

Ties measured with Tie 0 at the beginning of the curve in direction of loaded traffic, located at approximately 1,750 ft.)
31

Figure 25. Curve 16, Tie 104, Left Is Field Side, with More RSA Depth on the Field Side of 

the Rail Seat, and It Results in Outward Tilt (cant) of the Rail

(Ties measured with Tie 0 at beginning of curve in direction of loaded traffic, located at approximately 3,580 ft.)

Data was collected on the six curves listed above, and to date, comparisons of RSA with 

measured track geometry and with NUCARS simulations have been performed only for the 

curves at MP 16 and MP 17 shown above. A review of RSA measurements from curves at

MP 16, MP 17, and MP 19 indicated that depth and rail roll (cant) follow curvature and 

superelevation with little or no deviations. The few isolated instances of deeper RSA did not 

correlate well with any localized track geometry anomalies or changes in predicted truck curving

performance. Because of the problems with the automated measuring device, the RSA 

measurements from the other three curves were too scattered to make a clear evaluation. 

3.2 Site 2 – BNSF near Needles, CA

The second location offered for RSA inspection was provided by BNSF near Needles, CA. Work 

crews were scheduled for early (first quarter) 2011; thus, preinspection of potential curves was 

conducted January 11–12, 2011, and rail replacement gangs were scheduled for the first week of 

February. The preinspection methods were identical to those followed on the CSX St. Albans 

site. Each potential curve on the work program was inspected and documented. To aid in 

correlating RSA measurements to track geometry data, the point of tangent to curve was located 

for each curve. Ties were then numbered, and every tenth tie was marked in the field in advance 

of track work. MiniProf rail profiles were also collected at all curve points and midcurve 

locations.

Because of changes in work schedules and priorities, some curves preinspected in January were 

not included in the final program, and other curves were substituted. Table 2 lists the details of 

the curves measured during the February 2011 work window at Needles.
32

Table 2. Description of Measurement Sites at Needles, CA

Milepost

(MP)

Curvature 

(deg)

Superelevation 

(inch)

Balance 

Speed 

(mph)

Normal 

Operating 

Speed 

(mph)

Rail 

Measured 

(High/Low)

Comments, Notes, Etc.

589 3.75 5 28 High

588.5 2.5 2 34 Low

588.2 3.75 2.5 31 Low

584.5 3.25 4 44

15–20 

uphill

25–55 

downhill 

depending 

on train 

type

Low

Block signal, insulated joints in both 

rails near mid-curve

Visual evidence of gauge face 

lubrication

583 3.75 Low

The Needles site differs significantly from the St. Albans site. The concrete ties at the Needles 

site had never been repaired since first installed in early 2000. Traffic over the Needles curves is

predominantly intermodal (mostly double-stack containers and piggyback traffic) with some 

mixed freight. No significant coal or unit trains operate over this line. This track segment is a 

double-track transcontinental main line, with frequent train passage. The line being worked for 

rail replacement was Main 1, which normally handles eastbound trains. Normal traffic patterns

and operation over these curves show train speeds of 50–55 miles per hour (mph), running 

downgrade. Because these trains are approaching a mandatory crew change at Needles

(MP 578), the curve closest to Needles (MP 583) may be subjected to slower or slowing trains, 

whereas all other curves measured normally have traffic at the full allowable track speed 

(50–55 mph). 

Of possibly greater influence on curving forces, occasionally traffic congestion or track work on 

Main 2 requires westbound trains to be routed to Main 1. These trains depart the Needles crew 

change from a complete stop and immediately encounter a continuous ascending 1 percent grade, 

usually limiting westbound trains to 15 mph over all curves in the RSA measurement area. Exact 

traffic mix was not determined; however, local BNSF staff estimated 80 percent of the trains 

over the five curves measured for RSA operate at or near 50 mph, with remaining traffic in the 

15-mile per hour range. 

Another major difference is climate. The St. Albans site is in an eastern area subjected to winter 

snow and year-round rain. The Needles location generally has less than 10 in of precipitation per

year and is considered a desert area. 

Of all five curves inspected at the Needles site, none had significant RSA. The deepest 

continuous RSA was in the 0.05-inch range, compared with approximately 0.20 in observed at

the St. Albans site. Overall observations of RSA conditions at the Needles site include:
33

• No deep RSA was noted at any location, deepest RSA recorded was approximately 

0.05 in

• All pads, clips, and insulators were replaced as part of rail work

• Only the curve at MP 584.5 showed any significant RSA, and it was in the 

initiation stages

• The RSA at MP 584.5 indicated the RSA would tend to roll the inside rail inward

Figure 26 to Figure 30 show RSA results for the five curves at Needles. Imposed on each figure 

are the suggested curvature locations based on track chart information only. For Figure 26 to 

Figure 30, the numbers shown along the central axis represent tie numbers to allow correlation 

with RSA data and photos. Because tie spacing is 2.0 ft, the distance in feet is simply twice the 

tie number. To aid comparison with all curves inspected at Needles, the RSA depth/cant scale 

has been made the same to emphasize that there was little RSA depth measured at all curves,

except at MP 584.5. Figure 31 shows typical RSA from the curve at MP 584.5.

Figure 26. High Rail MP 589 Average RSA and RSA Difference(cant);

Shows Almost no RSA Depth

0

0.5

1

1.5

2

2.5

3

3.5

4

-0.150

-0.100

-0.050

0.000

0.050

0.100

0.150

0 100 200 300 400 500 600 700

Curvature (deg)

Rail Seat Abrasion Depth (in)

Tie Number

Avg

Difference

Curvature
34

Figure 27. Low Rail MP 588.5 Average RSA and RSA Difference (cant);

Shows Almost no RSA Depth

Figure 28. Low Rail MP 588.2 Average RSA and RSA Difference;

Shows a Very Slight Tendency for Inward Cant (rail tilt) toward the 

End of Curve; Direction of Predominant Traffic Is Left to Right

0

0.5

1

1.5

2

2.5

3

-0.150

-0.100

-0.050

0.000

0.050

0.100

0.150

0 100 200 300 400 500 600 700

Curvature (deg)

Rail Seat Abrasion Depth (in)

Tie Number

Avg

Difference

Curvature

0

0.5

1

1.5

2

2.5

3

-0.150

-0.100

-0.050

0.000

0.050

0.100

0.150

0 100 200 300 400 500 600

Curvature (deg)

Rail Seat Abrasion Depth (in)

Tie Number

Avg

Difference

Curvature
35

Figure 29. Low Rail MP 584.5 Average RSA and RSA Difference (cant); RSA Depth Is 

near Zero, Except in Full Body of Short Curve

(RSA difference is negative in the curve, indicating inward cant (tilt). Photos (Figure 31) confirm this inward tilt. Note that there 

is a block signal, with insulated joints, both rails near midcurve, near Tie 205.)

Figure 30. Low Rail MP 583 Average RSA and RSA Difference (cant)

0

0.5

1

1.5

2

2.5

3

3.5

-0.150

-0.100

-0.050

0.000

0.050

0.100

0.150

0 50 100 150 200 250 300 350 400 450

Curvature (deg)

Rail Seat Abrasion Depth (in)

Tie Number

Avg

Difference

Curvature

0

0.5

1

1.5

2

2.5

3

3.5

4

-0.150

-0.100

-0.050

0.000

0.050

0.100

0.150

0 100 200 300 400 500 600 700

Curvature (deg)

Rail Seat Abrasion Depth (in)

Tie Number

Avg

Difference

Curvature
36

Figure 31. MP 584.5 Typical RSA in Curve, Tie 126, and Tie 157

(Gauge side is at top of photo and shows gauge side with deeper abrasion than field side, confirming inward tilt (cant).)
37

The only curve that showed a significant pattern of RSA was at MP 584.5. Figure 32 shows the 

RSA measurements compared with track geometry measurements and NUCARS simulation 

results from that curve. The first graph shows the measured track curvature and superelevation/

cross level. The second graph shows the manual measurements of average RSA depth and RSA 

depth difference (field gauge) for the right/low rail. The third graph shows the measured track 

gauge and alignment and the left/high and right/low rail cants as measured by the track geometry 

car. The track geometry data was used as input to the NUCARS simulations.

The track geometry data data was used as input to the NUCARS simulations. The fourth and 

fifth graphs show the NUCARS predictions of lead axle single wheel L/V ratios and lead truck 

side L/V ratios, which were performed with the assumption of dry rail (rail friction coefficient of 

μ = 0.4). In this graph, a positive L/V ratio on the right rail and a negative L/V ratio on the left 

rail represent gauge-spreading forces. Note that in actual practice the friction coefficients in this 

curve are probably different as a result of the presence of track lubricators in the vicinity, which 

would result in somewhat different forces and dynamic response. However, friction levels were 

again not measured. 

Figure 33 shows the corresponding NUCARS simulation results for rail seat vertical forces and 

moments at the tie located at 345 ft, with Axle 1 on the left side of the graph and Axle 4 on the 

right. Simulations were performed at 50 and 15 mph to represent the two common operating 

conditions and to demonstrate the effect of speed. A wheel/rail friction coefficient of μ = 0.4 was 

used to represent dry rail. To simplify the analyses and comparisons for this segment of the 

project, both the simulations were performed in the same direction, although normally the 

15-mile per hour operation would be expected to be in the opposite direction. 

Results show similar trends to those shown at the CSX St. Albans site: when the average force 

due to curvature increases, abrasion increases. No significant correlation between predicted 

vehicle-track forces and local track geometry features other than curvature are noticeable, and 

there are no areas with significantly more abrasion than is average for the curve. 
38

Figure 32. Curve Data for MP 584.5; Distance along Curve Measurements and Predicted Car Performance 

of a Loaded Hopper

(Top to bottom shows curvature and superelevation, RSA depth, track geometry data, predicted lead axle L/V ratio, and predicted lead truck side L/V ratio at 15 and 50 mph.)
39

Figure 33. Rail Seat Vertical Forces and Roll Moments for MP 584.5 at Tie Located at 

345 ft; Blue Lines Show Forces and Moments at 15 mph; Red Lines at 50 mph

The predicted roll moments on the low (right) rail imply forces that would tend to roll the low 

rail outward. This is contrary to the measured RSA patterns and track geometry car rail cant in 

this region of the curve, which show noticeable inward rail roll. Figure 34 and Figure 35 show 

the corresponding wheel/rail contact positions as well as low rail wheel and truck side L/V ratios 

at the tie at 345 ft for Axles 1 and 2 for the 50-mile per hour run. The gauge clearance between 

the wheels and rails can be seen to be somewhat less than at the St. Albans site shown in 

Figure 18 and Figure 19. The contact points for the wheels are shaded in red. Although both 

wheels are running in flange contact with the high (left) rail, Axle 2 is generating somewhat 

lower single wheel L/V ratios and is not pressing as hard against the flange, as demonstrated by 

its single point of flange contact.

The wheel/rail contact for Axle 2 is somewhat unusual, and it is probably affected by the 

asymmetric wear patterns of the wheel profiles used in the simulation, resulting in poor steering 

response. Normal expectations for a curve of this degree (2.75°) would be for the trailing axle of 

each truck to run closer to the center of the track without flange contact.

Axle 1 Axle 2 Axle 3 Axle 4
40

Figure 34. Wheel/Rail Contact Geometry for Axle 1 at 345 ft along the Track for MP 584.5,

with Corresponding Left and Right Wheel L/V Ratios

Figure 35. Wheel/Rail Contact Geometry for Axle 2 at 345 ft along the Track for MP 584.5,

with Corresponding Left and Right Wheel L/V Ratios
41

These results clearly imply that the NUCARS simulations do not replicate the conditions present 

at the actual Needles site. Some possible reasons for this include the following:

• Wheel/rail friction conditions used in the model (dry rail with friction coefficient μ = 0.4)

are not representative of actual conditions. The friction conditions on the track were not 

measured at the site, although evidence of some form of lubrication was found on the 

gauge faces and bases the rails, and many BNSF locomotives are equipped with onboard 

lubricators.

• One loaded hopper car model was used for all modeling to represent a severe loading 

condition. However, this car model may not reflect exactly the various types of 

intermodal cars (including articulated cars) and mixed traffic that dominate operation at 

this site. 

• Measured worn wheels from the CSX hopper car may not be representative of the wheels 

that normally run over the site.

• Track parameters (such as rail fastener and pad stiffness) used in simulation are not 

representative of those at the site. 

The first three reasons are expected to be the most likely causes. For example, Figure 36 shows

the effect on the low rail moments of simulating the following four different rail lubrication 

conditions:

• Dry rail (μ = 0.4)

• Gauge face lubrication (top of rail μ = 0.35, gauge face μ = 0.15)

• Top of rail (TOR) friction modifier (top of rail μ = 0.4, Kalker creep coefficients 

adjusted to 18 percent of nominal) [5]

• Gauge face lubrication and TOR friction modifier (top of rail μ = 0.35, gauge face 

μ = 0.15, Kalker creep coefficients adjusted to 18 percent of nominal) [5]

A considerable difference in low rail roll moments can be seen. Although none of the cases show 

rail moments that would tend to lead to RSA that cants the rail inward, the cases with TOR 

friction modifier show very low L/V ratios, and some reversal of roll moment as Axle 2 and 

Axle 4 pass over the tie. 

The above modeling was performed with the loaded hopper car model. Although the axle loads 

can be similar, the truck spacing, the articulation joints, and the details of the trucks used in other 

cars (including intermodal cars) can sometimes result in different dynamic response. In addition,

the wheel wear patterns may be different. In TTCI’s experience, these differences, in 

combination with some of the wheel/rail lubrication conditions discussed above, could cause 

negative rail seat roll moments. 
42

Figure 36. Effect of Rail Lubrication Conditions on Axles 1 and 2 Low Rail L/V Ratios and 

Low Rail Roll Moments for MP 584.5 at Tie Located at 345 ft

(Green lines show dry rails; red lines show gauge face lubrication; blue lines show TOR friction modifier; purple lines show 

gauge face lubrication and TOR friction modifier.)

3.3 Site 3 – BNSF near Alliance, NE

The final railroad site visited as part of this program was provided by BNSF near Alliance, NE. 

No preinspection trip was made for this site. Instead, part of the inspection team traveled to 

Alliance one day early to mark ties and measure rail profiles at the curves to be inspected over 

the next several days. The inspection was done the week of April 4, 2011. The location of 

tangent to spiral, spiral to curve, curve to spiral, and spiral to tangent was estimated for each 

curve, and the GPS location and tie number of key points were recorded to help when correlating 

the location to track geometry data. These curves are on Main 1 and carry mostly northbound 

traffic. The traffic is predominately unit coal trains, and it is a mix of empty and loaded trains. 

Alliance has an average of 16–17 in of precipitation per year, which is a little more than Needles 

(10 in per year), but considerably less than St. Albans (43 in per year). Unlike the St. Albans and 

Needles sites, there was no visual evidence of lubrication on the rails in the vicinity.

The original inspection plan called for inspection of several fairly tight curves close to the yard 

in Alliance, but as the result of changes in BNSF’s work schedule, the repair of these curves was 

postponed. Instead, some of the more shallow main line curves were repaired, and the inspection 

team was available to make measurements. Table 3 lists the details of the curves measured 

during the April 2011 work window.
43

Table 3. Description of Measurement Sites at Alliance, NE

Milepost

(MP)

Curvature 

(deg)

Superelevation 

(in)

Balance 

Speed 

(mph)

Normal 

Operating 

Speed 

(mph)

Rail Measured 

(high/low) Comments, Notes, Etc.

11.8 2 50 High

12.8 1 50 High

22.1 1.5 50 Low RSA previously repaired

26.1 0.5 45 Low

Figure 37 through Figure 40 show the RSA measurements from the four curves. All of these 

plots use the same scales as those at the Needles site. The data shows that no severe RSA is in 

any of the curves measured at the Alliance site.

Figure 37. Curve between MP 11.9 and MP 11.6, 

Average RSA and RSA Cant, High Rail

0

0.5

1

1.5

2

2.5

-0.150

-0.100

-0.050

0.000

0.050

0.100

0.150

0 100 200 300 400 500 600 700 800

Curvature (deg)

Rail Seat Abrasion Depth (in)

Tie Number

Avg

Difference

Curvature
44

Figure 38. Alliance Curve between MP 12.96 and MP 12.62, 

Average RSA and RSA Cant, High Rail

Figure 39. Alliance Curve between MP 22.6 and MP 21.7, 

Average RSA and RSA Cant, Low Rail

0

0.2

0.4

0.6

0.8

1

1.2

-0.150

-0.100

-0.050

0.000

0.050

0.100

0.150

0 200 400 600 800 1000 1200 1400 1600

Curvature (deg)

Rail Seat Abrasion Depth (in)

Tie Number

Avg

Difference

Curvature

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

-0.150

-0.100

-0.050

0.000

0.050

0.100

0.150

0.200

0 500 1000 1500 2000 2500

Curvature (deg)

Rail Seat Abrasion Depth (in)

Tie Number

Avg

Difference

Curvature
45

Figure 40. Alliance Curve between MP 26.3 and MP 25.95, 

Average RSA and RSA Cant, Low Rail

The Alliance curve at MP 12.8 seemed to have more abrasions than the other three curves 

measured. Good examples of abrasions are close to Tie 396. Figure 41 to Figure 43 show Ties 

395, 396, and 401, respectively. Although these ties do not have deep RSA, they do show the 

rough texture of the onset of abrasion, especially at the field side of the rail seat.

Figure 41. High Rail Seat of Tie 395 on Curve at MP 12.8

0

0.1

0.2

0.3

0.4

0.5

0.6

-0.150

-0.100

-0.050

0.000

0.050

0.100

0.150

0 100 200 300 400 500 600 700

Curvature (deg)

Rail Seat Abrasion Depth (in)

Tie Number

Avg

Difference

Curvature
46

Figure 42. High Rail Seat of Tie 396 on Curve at MP 12.8

Figure 43. High Rail Seat of Tie 401 on Curve at MP 12.8

Because little RSA was seen at the Alliance site, no NUCARS simulations were performed, and 

no attempt was made to correlate RSA measurements with measured track geometry. 
47

4. Conclusions and Recommendations

4.1 Conclusions

Sixteen curves on three different railroads were inspected and analyzed for RSA. Where RSA 

was found, the severity appeared to be generally related to track curvature. The one inspection 

location with the tightest curves and the highest annual rainfall had the most RSA. Where RSA 

was found, the depth of the abrasion seemed to be related to the position of the tie in the curve. 

Areas with deep abrasion were often associated with private road crossings. In these areas, the 

rail seat stayed damp longer, and the rail seats were more likely contaminated with dirt or sand 

that could act as an abrasive. However, none of these crossings appeared to be associated with 

track geometry features that were likely to induce vehicle dynamic response.

The NUCARS simulations of several of the sites with RSA confirm the general correlation 

between RSA and track curvature. The simulations also showed that the vehicle dynamic 

response, wheel/rail forces, and moments generated at the rail seats are very dependent on the 

details of the simulation input parameters. Therefore, NUCARS simulation results did not always 

exactly match the measured RSA patterns. Choice of wheel profile, train speed, and wheel/rail 

lubrication conditions were all shown to have noticeable effects on the results. It is expected that 

choice of vehicles being modeled would also have similarly large effects.

A hypothesis that a particular track geometry feature (such as down-and-out perturbations) is a 

trigger for the development of RSA could not be confirmed from the limited number of sites 

where RSA was found. No large down and out perturbations were identified in the measured 

track geometry for any of the sites. Because of the limited number and the spacing along the 

track between the RSA depth measurements, it is possible that a correlation between local track 

geometry features and RSA could have been missed. Also, the limited number of NUCARS 

simulations performed by using the measured track geometry did not show any strong dynamic 

response to local track features that could be correlated to the RSA measurements. 

Issues encountered during the inspection process that affected these outcomes include the 

following:

• Inspection sites were limited to locations where the host railroads were performing rail 

removal and replacement

• Host railroads’ track maintenance plans and schedules changed at the last minute

• Requirement for the inspection team to work within very tight access windows that 

limited time available to make RSA measurements

• Cumbersome and slow RSA depth measurement methods

Simplifications and other issues encountered that affected the NUCARS simulation results 

include the following:

• Use of a single vehicle (loaded hopper car) model for all modeling

• Assumption of dry rails (μ = 0.4) for the base case

• Use of single wheel profile pair for all modeling

• Track geometry data in mid chord offset format (CSX simulations)
48

4.2 Recommendations

An important objective could not be achieved from this segment of the project: a particular track 

geometry feature for installation at FAST for testing in subsequent project segments was not 

identified. Either more site inspections must be performed or an alternative selection method 

must be adopted to identify a track geometry feature. 

If more site inspections are performed, an alternative method for selecting sites for inspection 

could be adopted, such as prescreening the measured track geometry from proposed inspection 

sites to determine whether the locations of large rail cants are associated with other track 

geometry features.

If more site inspections are performed, the following improvements in measurements are 

recommended:

• Develop improved, automated RSA depth gauge to permit much faster and more frequent 

measurements; however, the speed of measurement should not compromise the reliability 

and repeatability of the measurements

• To capture short wavelength effects, measure RSA more frequently, at least every other 

tie to permit at least five measurements in 20 ft

• Document rail lubrication conditions for each site, preferably with a tribometer to 

measure friction coefficients; however, most available tribometers cannot accurately 

measure the effects of many TOR friction modifiers[5]

• Get all track geometry measurements in space-curve format 

• Measure pad thickness to estimate wear

• Measure insulator wear to estimate rail movement in rail seat

• Measure clip load to evaluate rail seat contact conditions

• Check the rail base for indications of wear or abrasion

Another alternative for selecting a perturbation to install at FAST would be to use the measured 

perturbation geometry from a previously inspected RSA site known to have severe perturbation 

geometry and/or to have contributed to derailment or other performance problems. 
49

5. References

1. Choros, J., Marquis, B., and Coltman, M. (2007). “Prevention of Derailments due to 

Concrete Tie Rail Seat Deterioration,” Proceedings of ASME/IEEE Join Rail & Internal 

Combustion Engine Spring Technical Conference, 13–16, March, Pueblo, CO 

2. Reiff, R., and Gage, S. (1995). “Concrete Tie Rail Seat Abrasion Test,” Proceedings of the 

First Annual AAR Research Review, Volume 1, FAST/HAL Test Summaries, Transportation 

Technology Center, Inc., 6–9 November, Pueblo, CO.

3. Reiff, R., and Gage, S. (1995 Aug.). “INTERIM Report: FAST Rail Seat Abrasion Test,” 

Technology Digest, TD-95-019, Association of American Railroads, Transportation 

Technology Center, Inc., Pueblo, CO.

4. Cohen, A., and Hutchens, W. A. (1970). “Methods for Reconstruction of Rail Geometry from 

Mid-Chord Offset Data,” The ASME Joint Transportation Engineering Conference, 11–14

October, Chicago, IL.

5. Fries, R., Urban, C., Wilson, N., and Witte, M. (2011). “Modeling of Friction Modifier and 

Lubricant Characteristics for Rail Vehicle Simulations,” Proceedings of the 22nd

International Symposium on the Dynamics of Vehicles on Roads and Tracks, 14–19 August,

Manchester, U.K.
50

Abbreviations and Acronyms

COTR Contracting Officer’s Technical Representative

FAST Facility for Accelerated Service Testing

FRA Federal Railroad Administration

L/V lateral/vertical ratio

MP milepost

RSA rail seat abrasion

TAG technical advisory group

TTC Transportation Technology Center (the site)

TTCI Transportation Technology Center, Inc. (the company)

TOR top of rail

Volpe John A. Volpe National Transportation Systems Center