DOT/FRA/ORD-13/50 Final Report

December 2013

U.S. Department of 

Transportation

Federal Railroad 

Administration

Using Wheel Temperature Detector Technology 

to Monitor Railcar Brake System Effectiveness

Office of Research

and Development

Washington, DC 20590
NOTICE

This document is disseminated under the sponsorship of the 

Department of Transportation in the interest of information 

exchange. The United States Government assumes no liability for 

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conclusions, or recommendations expressed in this material do not 

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products, or organizations imply endorsement by the United States 

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The United States Government does not endorse products or 

manufacturers. Trade or manufacturers’ names appear herein 

solely because they are considered essential to the objective of this 

report.
i

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

December 2013

3. REPORT TYPE AND DATES COVERED

Technical Report

4. TITLE AND SUBTITLE

Using Wheel Temperature Detector Technology to Monitor Railcar Brake System 

Effectiveness

5. FUNDING NUMBERS

DTFR53-00-C-00012

6. AUTHOR(S) Task Order 252

Jim Robeda, Devin Sammon, and Benjamin Madrill

7. PERFORMING ORGANIZATION 

Transportation Technology Center, Inc.

P. O. Box 11130

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 Research and Development 

Washington, DC 20590

10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

DOT/FRA/ORD-13/50

11. SUPPLEMENTARY NOTES

COTR: Monique Stewart

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)

Wheel temperature detector technology has been used extensively in the railroad industry for the past several decades. The 

technology has traditionally been used to identify wheels with elevated temperatures. There is currently a movement in the 

industry to detect railcars with ineffective brakes by using the technology to identify wheels that have lower than expected 

temperatures when a train is in a braking mode or condition. This report documents a study to determine the effectiveness of the 

technology in distinguishing between applied and nonapplied brakes when a train passes a wheel temperature detector with train 

brakes applied. The study used controlled testing as well as data from revenue service operations to investigate the effectiveness

of the technology and to compare its capabilities with the current manual inspection process.

14. SUBJECT TERMS

Wheel temperature detector, ineffective brake, air cut out, bad order, cold wheel 

15. NUMBER OF PAGES

32

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)] = y C [(9/5) y + 32] = x F

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 CONVERSIO

 -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°

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
iii

Contents

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

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

1.1 Background......................................................................................................................... 3

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

1.3 Overall Approach................................................................................................................ 3

1.4 Scope................................................................................................................................... 4

1.5 Organization of the Report.................................................................................................. 4

2. Methodology............................................................................................................................. 5

2.1 Benchmarking Manual Inspection Results......................................................................... 5

2.2 Compiling Wheel Temperature Detector Data ................................................................... 6

2.3 Demonstrating the Effectiveness of the Technology.......................................................... 7

2.4 Investigating Piston Travel versus Force............................................................................ 7

2.5 Comparing Methodologies (manual inspection versus technology detection)................... 7

3. Results....................................................................................................................................... 8

3.1 Benchmarking Manual Inspection Results......................................................................... 8

3.2 Compiling Wheel Temperature Detector Data ................................................................... 9

3.3 Demonstrating the Effectiveness of the Technology.......................................................... 9

3.3.1 Proof-of-Concept Testing ......................................................................................... 10

3.3.2 Controlled Fully Loaded Test Train Operating at Track Speeds.............................. 12

3.4 Investigating Piston Travel versus Force.......................................................................... 19

3.5 Comparing Methodologies (manual inspection versus technology detection)................. 20

4. Conclusions and Recommendations....................................................................................... 23

5. References............................................................................................................................... 24

Abbreviations and Acronyms ....................................................................................................... 25
iv

Illustrations

Figure 1. Braking Tank Car with Proper Piston Travel................................................................. 2

Figure 2. UP Route Map Highlighting Loading, Unloading, and Inspection Locations............... 5

Figure 3. Wheel Temperature Detector Data Sample.................................................................... 6

Figure 4. Wheel Temperature Detector Installation at FAST...................................................... 10

Figure 5. Proof-of-Concept Test Data — Day 1 Results............................................................. 11

Figure 6. Proof-of-Concept Test Data — Day 2 Results............................................................. 12

Figure 7. Loaded Test Train 1 — Day 1 Results......................................................................... 14

Figure 8. Loaded Test Train 2 — Day 1 Results......................................................................... 14

Figure 9. Loaded Test Train 3 — Day 1 Results......................................................................... 15

Figure 10. Loaded Test Train 4 — Day 1 Results......................................................15

Figure 11. Loaded Test Train 5 — Day 2 Results....................................................................... 16

Figure 12. Loaded Test Train 6 — Day 2 Results....................................................................... 16

Figure 13. Loaded Test Train 7 — Day 2 Results....................................................................... 17

Figure 14. Loaded Test Train 8 — Day 2 Results....................................................................... 17

Figure 15. Loaded Test Train 9 — Day 3 Results....................................................................... 18

Figure 16. Loaded Test Train 10 — Day 3 Results..................................................................... 18

Figure 17. Body-Mounted Brakes — Rigging Condition Comparison (7-inch piston 

travel w/ 20-psi brake pipe reduction) .................................................................. 19

Figure 18. Truck-Mounted Brakes — Rigging Condition Comparison (nominal piston 

travel w/ 20-psi brake pipe reduction) .................................................................. 20
v

Tables

Table 1. Brake Repair Categorization by Job Code (Field Manual of the A.A.R. 

Interchange Rules)....................................................................................................... 9

Table 2. Manual and Controlled Full Train Test Results for Defective Cars.............................. 21

Table 3. Results of Single-Car Air-Brake Test............................................................................ 21
1

Executive Summary

The primary objective of this research project was to demonstrate the capability of wheel 

temperature detector technology to evaluate brake effectiveness by comparing relative wheel 

temperatures within a train. A properly working brake system is defined by its ability to produce 

at least the minimum designed amount of force to slow the train while maintaining piston travel 

distance to less than the proposed maximum for that car. 

Proof-of-concept testing demonstrated the ability of wheel temperature detectors to distinguish 

between applied and nonapplied brakes for known braking conditions. This implies that it is also 

possible to make this distinction for unknown braking conditions when sound statistical methods 

are applied. 

In an attempt to more closely replicate revenue service conditions, testing was conducted over 

several days with a fully loaded test train operating at track speeds at the Facility for Accelerated 

Service Testing (FAST) of the Transportation Technology Center (TTC). This testing allowed 

the consist wheels to reach a steady-state temperature prior to brake application. Data collected 

during this controlled fully loaded train testing were independently analyzed by two engineers 

using different methodologies. The cars identified as having ineffective brakes were the same in 

both cases. This implies that there may be multiple ways to analyze the data to produce reliable 

results. 

The controlled testing helps validate the revenue service detector results that show a brakerelated defect detection rate of approximately four times that of the manual inspection defect 

detection rate. Revenue service detector results that show several cars with a repeated “coldwheel” condition over the course of multiple trips past the detector indicate a failure of the 

manual test to properly identify “ineffective” brakes. The failure of the manual test to identify 

these ineffective brakes may be due to the fact that the manual test only verifies brake 

application and has no way of measuring brake effectiveness. Additionally, the manual test is 

conducted under static conditions that do not account for possible vibration-induced control 

valve failures during dynamic operation. Finally, the manual test requires that the brake remain 

applied for only three minutes. In revenue service, train brakes are often applied and must hold

for much longer periods. 

Testing to examine the correlation between piston travel and applied shoe force shows that force 

can vary for constant piston travel when the brake rigging configuration is altered. This variation 

can be attributed to the action of the automatic slack adjuster common to modern railcars. The 

slack adjuster maintains constant piston travel as brake rigging changes occur. Brake rigging 

changes, such as lever angularity and brake rod lengths, while not affecting piston travel 

(because of the action of the automatic slack adjuster), have a definite effect on shoe force. 

Therefore, proper piston travel does not ensure adequate shoe force. 
2

1. Introduction

The Code of Federal Regulations, Title 49 Part 232.103, requires that every car in a departing 

train have an effective brake. CFR 49 Part 232.5 gives the following definition of effective and 

properly functioning brakes:

Effective means a brake that is capable of producing its nominally designed 

retarding force on the train. A car’s air brake is not considered effective if it is not 

capable of producing its nominally designed retarding force or if its piston travel 

exceeds: 

(1) 10.5 inches for cars equipped with nominal 12-inch stroke brake cylinders; or 

(2) The piston travel limit indicated on the stencil, sticker, or badge plate for that 

brake cylinder. 

Brake effectiveness is normally evaluated by railroads during the Class 1 (initial terminal) and 

subsequent Class 1A (1,000-mile) brake inspections. This routine inspection and evaluation is 

based on a visual check of the brake rigging and piston travel as prescribed above. Figure 1 

shows an example of proper piston travel. In addition, the nominally designed retarding force 

has a hold-time component that is currently accounted for by the 3-minute allowance for a Class 

1 or Class 1A retest. However, there is no measurement of brake force. By using wheel 

temperature detector technology to assess wheel temperatures as a train with applied brakes

passes a sensor, Transportation Technology Center, Inc. (TTCI) submits that an indirect 

measurement of brake force can be made, thus providing a better indication of brake 

effectiveness that also accounts for true revenue service hold-time.

Figure 1. Braking Tank Car with Proper Piston Travel
3

1.1 Background

Wheel temperature detector technology has been used extensively by North American freight 

railroads for several decades to monitor the mechanical condition of passing trains. Railroad 

experience with the technology in revenue service applications has shown the capability to

identify problems associated with wheels, bearings, and brake systems, along with giving 

railroad personnel timely notification before a potentially catastrophic failure occurs. TTCI 

conducted a test program to study the value of this technology for use in determining train brake 

system effectiveness. This project was jointly funded by the Federal Railroad Administration’s

(FRA), Office of Research and Development, Office of Railroad Policy and Development, and 

the Association of American Railroads’ (AAR) Strategic Research Initiatives Program.

In traditional applications, wheel temperature detectors are generally set to alarm for elevated

wheel temperatures above a predetermined threshold. Such elevated temperatures may result 

from defective brake rigging or brake control valves, applied hand brakes, or various other brake 

system defects. In recent years, railroads have begun looking for temperatures considerably 

lower than the average and using existing technology to monitor wheel temperatures on trains 

that have the brakes applied since low wheel temperature would give an indication of an 

inoperative or ineffective brake. When used for this purpose, the wheel temperature detectors 

are generally placed at a stationary, wayside location where train brakes would typically be 

applied, such as on a long, descending grade. Thus, using the technology to identify wheels in a 

train that are measurably colder than the expected temperature threshold as they pass the detector 

provides a method of detecting a possible brake system defect.

The hypothesis behind this study is that wheel temperature measurements on moving trains are

an indirect measure of the applied brake system retarding force and that this methodology 

exceeds the ability of an inspector to manually objectively determine brake effectiveness using 

piston travel as the sole indicator.

It should be noted that individual wheel temperatures (for braking and nonbraking conditions) 

are affected by several variables such as rim thickness, amount of flange to rail contact, track 

lubrication, track curvature, truck condition, etc. This variation is generally normally distributed 

and can be normalized by using sound statistical methods. The idea is to look for obvious 

outliers when trying to determine brake effectiveness. 

1.2 Objectives

The primary objective of this research project was to demonstrate the capability of wheel 

temperature detector technology in evaluating brake effectiveness by comparing relative wheel 

temperatures within a train. In addition, tests were conducted to investigate the correlation 

between piston travel and brake shoe force.

1.3 Overall Approach

The project attempted to meet its objectives by concentrating on the following five major tasks:

Task 1: Benchmarking wheel failure rates found with manual inspection practices

Task 2: Compiling data from wheel temperature detectors to determine failure rates through 

use of this technology

Task 3: Demonstrating the ability and effectiveness of the technology in distinguishing

between applied and released brakes 
4

Task 4: Investigating the correlation between piston travel and brake shoe force

Task 5: A direct comparison of the two methodologies

These tasks were accomplished through controlled testing as well as limited monitoring of 

revenue service train operations.

1.4 Scope

The scope of this project included benchmarking manual inspection results, as well as reviewing 

wheel temperature detector data results provided by a Class 1 railroad over a 1-year period. In 

addition, several controlled tests were conducted at TTC in Pueblo, CO, to evaluate and 

demonstrate the capabilities of the technology in effectively monitoring railcar brake systems 

and to investigate the correlation between piston travel and brake shoe force.

1.5 Organization of the Report

This report is organized into four major sections: Section 1—the project’s background, 

objectives, overall approach, and scope; Section 2—the methodology used to accomplish the 

project objectives; Section 3—the results from each of the project tasks and applicable data; and 

Section 4—the results, conclusions, and recommendations. 
5

2. Methodology

As part of a cooperative research effort between FRA and AAR, TTCI was tasked to investigate 

the feasibility of using wheel temperature detector technology to evaluate brake effectiveness.

2.1 Benchmarking Manual Inspection Results

Data on manual inspection results were collected by Union Pacific (UP) Railroad for two series 

of coal cars that are operated by UP from the Powder River Basin through North Platte, NE, to 

unloading facilities in Illinois, Arkansas, and Wisconsin. One series was relatively new with a

history of very few problems. The second series was older with a history of more problems. Data 

were collected from October 2010 through September 2011. Figure 2 shows the UP route map 

highlighting loading, unloading, and inspection locations.

Figure 2. UP Route Map Highlighting Loading, Unloading, and Inspection Locations

Loading Facilities

Unloading Facilities
6

2.3 Compiling Wheel Temperature Detector Data

UP also provided detector data results for the period October 2010 through September 2011.

Wheel temperature detector data were collected for the same equipment sets that were monitored 

for manual inspection results. Only trains that passed the detector site were compared with 

manual inspection results.

The detector site that was used is located at Sheep Creek, WY (Powder River Subdivision, 

Milepost 198.20), which is approximately midway between North Platte, NE, and the loading 

facilities of the Powder River Basin. This section of track is a descending grade of slightly more 

than 1 percent. Braking trains make an average brake pipe reduction of 7 pounds per square inch 

(psi), and brakes are applied for an average of 4.9 minutes ahead of the detector. 

Using a specialized filtering algorithm, UP uses the wheel detector data to calculate a “filtered 

temperature” from the running average of the train. Comparison of the raw data and the filtered 

data is made to classify the train into one of three categories: clearly braking, clearly 

nonbraking, or unclassified braking. Once a train is determined to be clearly braking, a 

normalized value for each wheel is calculated. This value is the ratio of the actual wheel 

temperature over the filtered temperature. A normalized value of less than 0.3 for any given 

truck indicates a cold-wheel condition that implies an ineffective brake that has a temperature (F) 

less than 30 percent of the running average.

UP provided the calculated results that show if a car had a cold- or hot-wheel condition. 

Figure 3 shows an example of the raw detector data with the filtered temperatures, as well as 

the normalized values for a sample train.

Figure 3. Wheel Temperature Detector Data Sample

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0

50

100

150

200

250

300

350

1

55

109163217271325379433487541

3185

139193247301355409463517

WHL_TEMP

WHL_FLTR_TEMP

WHL_FLTR_VAR_VALU

WHL_TEMP_NORM_VALU
7

2.5 Demonstrating the Effectiveness of the Technology

Several different demonstration tests were performed using the wheel temperature detector 

located on track at FAST. FAST is a 2.7-mile closed loop consisting of short tangent sections 

connecting 5- and 6-degree curves. The test train consist at FAST is made up of aluminum coal 

gondolas loaded to 315,000 pounds. These cars all have truck-mounted brake arrangements. 

Initial testing used a short train of one locomotive and 13 cars. This was primarily a proof-ofconcept test to demonstrate the basic premise of using the technology to distinguish between 

known applied and released brakes. Subsequent testing used a train of approximately 105

aluminum coal gondolas and 4 locomotives. These tests were meant to more closely replicate

revenue service conditions.

2.6 Investigating Piston Travel versus Force

The correlation between piston travel and brake shoe force was investigated using the JIM 

SHOE® Brand Brake Force Measurement System. Brake rigging configurations were 

manipulated to create conditions that could possibly affect piston travel and/or brake shoe force 

at the wheel tread interface (e.g., lever angularity, binding rigging, and/or malfunctioning slack 

adjuster).

2.7 Comparing Methodologies (manual inspection versus technology detection)

Data collected for task one (see Section 2.1) and task two (see Section 2.2) were used to compare 

the results of the current manual inspection process with wheel detector technology detection 

capabilities. 
8

3. Results

3.1 Benchmarking Manual Inspection Results

Results of manual inspections from 49 of the newer equipment trains, as well as inspection 

results from 270 of the older equipment trains were provided by UP for a total of 319 trains. 

All of the newer equipment trains underwent Class 1 initial terminal air brake testing performed 

by train crew personnel in accordance with CFR 49 Part 232.205 at either the loading or 

unloading facilities. Approximately half of these trains (51 percent) also underwent Class 1A, 

1,000-mile air-brake testing performed by mechanical department personnel at North Platte, NE,

in accordance with CFR 49 Part 232.207. 

No defects were reported for any of the newer equipment trains at any location during the test 

period.

The majority of the older equipment trains also underwent Class 1 initial terminal air-brake 

testing performed by train crew personnel in accordance with CFR 49 Part 232.205 at either the 

loading or unloading facilities. Approximately two-thirds of these trains (67 percent) also 

underwent Class 1A, 1,000-mile air-brake testing performed by mechanical department 

personnel at North Platte, NE, or Parsons, KS, in accordance with CFR 49 Part 232.207.

Defects were reported for a total of 44 cars. Of these, 37 were reported at North Platte, NE, 5 

were reported at Parsons, KS, 1 at Coffeyville, KS, and 1 at Lexington, NE. Only 18 of the 44 

cars show car repair billing records for brake-related defects (see Table 1). Of these, 15 were 

repaired at North Platte, NE, 2 were repaired at Parsons, KS, and 1 was repaired at Coffeyville, 

KS.

Car repair billing records indicate that only two cars had repairs coded Test Repair or Valve 

Repair (see Table 1). The remaining repairs were coded as Shoe/Key or General Repair (see 

Table 1).

Brake repairs were generalized into four groups based on Job Codes listed in the 2011 Field 

Manual of the A.A.R. Interchange Rules, as Table 1 shows.
9

Table 1. Brake Repair Categorization by Job Code

(Field Manual of the A.A.R. Interchange Rules)

Test Repair Valve Repair Shoe/Key Repair

1139 1277 1830 1116 1403 1452 1450 1212 1658 1592

1140 1279 1838 1268 1404 1454 1612 1216 1660 1594

1145 1281 1840 1270 1405 1456 1160 1220 1662 1596

1146 1283 1842 1272 1406 1476 1162 1224 1670 1598

1147 1285 1843 1276 1408 1480 1164 1227 1672 1600

1150 1287 1844 1303 1411 1484 1165 1228 1680 1601

1151 1289 1845 1313 1413 1488 1172 1232 1696 1768

1152 1291 1846 1316 1414 1490 1180 1236 1697 1770

1155 1293 1852 1318 1415 1496 1184 1244 1698 1792

1157 1296 1999 ** 1320 1416 1498 1188 1260 1742 1794

1159 1298 1340 1417 1500 1192 1264 1556 1796

 1301 1356 1418 1502 1194 1492 1574 1800

 1304 1360 1419 1504 1196 1628 1576 1802

 1308 1386 1422 1505 1197 1629 1578 1804

1311 1388 1424 1506 1198 1630 1580 1808

1321 1392 1428 1516 1200 1650 1584 1812

1323 1400 1440 1520 1204 1652 1586 1814

1325 1401 1444 1524 1208 1654 1588 1816

1999 * 1402 1448 1532 1210 1656 1590 1999 ***

* with qualifiers AC, AK

** with qualifiers BE, BF

*** with qualifiers AA-BV, CR-DX, EB-EG excluding BE, BF, AC, AK

General Repair

3.2 Compiling Wheel Temperature Detector Data

Detector results were provided by UP for the 319 trains documented above. The results show 

only one cold-wheel and one hot-wheel indication by the detector located at Sheep Creek for the 

49 newer equipment trains. Neither of these cars shows a car repair billing record. A total of

76 cold-wheel indications and 2 hot-wheel indications were reported by the detector at Sheep 

Creek for the 270 older equipment trains. 

A total of 43 different cars accounted for the 76 cold-wheel indications. Of these, 27 had a 

single indication of cold wheels, 7 had two indications, 2 had three indications, 6 had four 

indications, and 1 had five indications. The two cars with hot-wheel indications were unique. 

Car repair billing records show repairs on 10 of the 43 cars with cold-wheel indications. 

However, these repairs are coded as Shoe/Key or General Repair (see Table 1). There are no 

records of brake valve replacement or single-car air-brake tests for any of these cars.

3.3 Demonstrating the Effectiveness of the Technology

A wheel temperature wayside detector previously installed at FAST was used for this 

demonstration test. The wheel temperature detector was provided by the Inspection and 

Information Systems Division of Progress Rail Services. Figure 4 shows the wheel temperature 

detector in track at FAST.
10

Figure 4. Wheel Temperature Detector Installation at FAST

3.3.1 Proof-of-Concept Testing

The initial proof-of-concept testing was conducted for 2 days in November 2010. The test was 

conducted in two separate stages. For the first stage, a test train of 13 cars and 1 locomotive was 

used. The test train was composed of cars with effective brakes as well as select cars with 

disabled brakes. The test train made several laps without a brake application. A minimum brake 

application was then made, and a sufficient number of laps were run to raise the wheel 

temperatures on the braking cars to a level not to exceed 350  ̊F. 

For the second stage, the approach was to operate the test train with a hand brake applied on one 

car. The test train made several laps past the detector with the brakes released. The temperature 

of the consist wheels was then monitored to determine the ability of the technology to detect 

stuck brakes. 

Before the start of the test, a manual inspection of the train bakes was performed. This manual 

inspection was done in accordance with CFR Part 49 Section 232.207 Class 1A—1,000-mile Air 

Brake Test. The inspectors walked the length of the train with the brakes applied and noted the 

brake rigging condition, piston travel, and position and condition of the brake shoes. The brakes 

were then released, and the inspectors rewalked the test train to ensure that the brakes were 

effectively released. The manual inspection determined that the brake system was in compliance 

with CFR 49 Part 232.207.

Once the inspection was completed and before the start of the test, the brake system was cut out 

on the 4th and 13th cars of the consist. The test started with a low-speed safety track 

conditioning run (TCR) to determine whether the track was in suitable condition for higher speed 

runs. Once the track was deemed safe, the train made five laps under normal operating 

conditions at 40 mph. On the sixth lap, a 10-pound per square inch brake-pipe reduction was 

made to apply the brakes, and the train maintained the 40-mile per hour speed while continuing 
11

laps. The wheel temperature was monitored with each pass. After three laps at 40 mph with 

brakes set, wheel temperature detector data indicated that the wheels had reached the 

predetermined safe temperature limit. The brakes were released, and the first day of the test was 

concluded. The test train was stored overnight so that the wheels in the consist could cool for the 

second day of testing. Figure 5 shows the results from the first day of testing.

Figure 5. Proof-of-Concept Test Data—Day 1 Results

The data shows an increase in wheel temperatures once a brake application was made and for 

each subsequent lap for the cars with known operating brakes. Little or no wheel temperature 

increase is seen for the cars with known inoperative brakes. 

For the second day of the test, all of the brakes were cut in and operative. Before testing began,

a hand brake was set on the fifth car of the test train. The train was then taken through a TCR 

and operated at 40 mph for several laps past the wheel temperature detector. Wheel temperatures 

were closely monitored. When wheel temperatures on the sixth car reached the predetermined 

safe temperature limit, the train was stopped, and the hand brake was released. The train was 

started again and completed two more laps past the detector. Figure 6 shows the results from the 

second day of testing.
12

Figure 6. Proof-of-Concept Test Data—Day 2 Results

The data shows increasing wheel temperatures for the car with the applied hand brake on each 

subsequent lap until the hand brake is released. Wheel temperatures decrease on this car on each 

subsequent lap once the hand brake is released. Wheel temperatures for the remaining cars in the 

consist increase somewhat during the course of the test. These results prompted the idea to 

conduct a test that would let the wheels reach a steady-state operating temperature before making 

a brake application.

3.3.2 Controlled Fully Loaded Test Train Operating at Track Speeds

In an attempt to more closely replicate revenue service conditions, testing was conducted over 

several days with a fully loaded test train operating at track speeds. This testing allowed the 

consist wheels to reach a steady-state temperature prior to a brake application. Previous proofof-concept testing did not do this, and the temperature differential between braking and 

nonbraking wheels may have been more pronounced. This testing was conducted in October and 

November 2011. The testing took place on three different days over a 3-week period.

Normal operations at FAST were conducted during the test period with the exception of periodic 

brake applications to generate wheel temperature detector data for the braking condition over the 

course of testing. The test train varied from 102 to 106 cars with 4 locomotives during the 3 tests

running under normal operational conditions. A brake-pipe reduction of 6 psi was used for the 

brake applications on 2 of the test days, and a 10-pound per square inch reduction was used on 

the final day of testing.
13

Once a steady-state wheel temperature was reached, a brake application was made and held for 

two laps past the detector (approximately 5 miles), and then the brakes were released. This was 

done twice on the first and second day of testing. Only one brake application was made on the 

final day of testing because of operational problems not associated with the test. After the first 

day of testing, one car in the test train (FAST car number 286, shown as the control car on the 

graphs) had the air brakes cut out so that data for that car could be used to compare operating and 

nonoperating brakes under known conditions.

To determine the steady-state nonbraking condition, wheel temperature detector data was used to 

compute an average wheel temperature for the entire train, as well as an average wheel 

temperature for each car prior to the brake application. Once the brakes were applied, data from 

the second pass by the detector was used to compute train and car averages for the braking 

condition. 

The average wheel temperature for each car was compared with the train average. A lower limit 

was established at two average deviations below the train average. Temperatures that fell below 

the lower limit were considered a cold-wheel condition, indicating a car with an ineffective 

brake. Figures 7 through 10 show the results of the train runs from the first day of testing.
14

Figure 7. Loaded Test Train 1—Day 1 Results

Figure 8. Loaded Test Train 2—Day 1 Results

Data for Train 2 shows that six cars fall below the lower limit threshold indicating possible 

ineffective brake conditions.

1

10

100

1000

0 10 20 30 40 50 60 70 80 90 100 110

Temperature above Ambient  ̊F

Car Number

Train 1 (Non-Braking)

Car average

Train Average

1

10

100

1000

0 10 20 30 40 50 60 70 80 90 100 110

Temperature above Ambient  ̊F

Car Number

Train 2 (Braking)

Car Average

Train Average

Lower Limit

Train 2 (Braking)

Control car

Train 1 (Nonbraking)
15

Figure 9. Loaded Test Train 3—Day 1 Results

Figure 10. Loaded Test Train 4—Day 1 Results

The data for Train 4 show that the same six cars that fell below the lower limit threshold during 

the first brake application were again below the threshold.

The test was repeated with some changes to the train due to normal operational conditions. On 

the second day of testing, one car in the consist (FAST car number 286, shown as the control car 

on the graphs) had its brake system cut out to facilitate comparison of a car with a known 

ineffective brake with the train average. Figures 11 through 14 show the results from the second 

day of testing.

1

10

100

1000

0 10 20 30 40 50 60 70 80 90 100 110

Temperature above Ambient  ̊F

Car Number

Train 3 (Non-Braking)

Car Average

Train Average

1

10

100

1000

0 10 20 30 40 50 60 70 80 90 100 110

Temperature above Ambient  ̊F

Car Number

Train 4 (Braking)

Car Average

Train Average

Lower Limit

 Train 3 (Nonbraking)

Train 4 (Braking)

Control car
16

Figure 11. Loaded Test Train 5—Day 2 Results

Figure 12. Loaded Test Train 6—Day 2 Results

Data for Train 6 again shows that six cars fall below the lower limit threshold, indicating 

possible ineffective brake conditions. Four of these six cars also showed an ineffective brake 

condition on both trains in the previous tests. Of the remaining two cars, one is the car that was 

purposely cut out for the test, and one is a car that was not in the test train during the previous 

test. The two additional cars that fell below the threshold in the previous tests were still in the 

consist but did not fall below the threshold during this test. 

1

10

100

1000

0 10 20 30 40 50 60 70 80 90 100 110

Temperature above Ambient  ̊F

Car Number

Train 5 (Nonbraking)

Car Average

Train Average

1

10

100

1000

0 10 20 30 40 50 60 70 80 90 100 110

Temperature above Ambient  ̊F

Car Number

Train 6 (Braking)

Car Average

Train Average

Lower limit

Control Car
17

Figure 13. Loaded Test Train 7—Day 2 Results

Figure 14. Loaded Test Train 8—Day 2 Results

The data for Train 8 shows seven cars below the threshold. The same six cars that fell below the 

lower limit threshold during the first brake application were again below the threshold. One 

additional car also fell below the threshold during this brake application. This is one of the two 

cars that fell below the threshold during the first day of testing that were subsequently above the 

threshold during the first brake application.

For the final day of testing, the train position was again slightly changed because of normal 

operational considerations. The car that had been cut out for the previous test was left in the 

consist, and the air was still cut out. A brake pipe reduction of 10 psi was used to make the 

brake application on the final day of testing. Figure 15 and Figure 16 show the results from the 

third and final day of testing.

1

10

100

1000

0 10 20 30 40 50 60 70 80 90 100 110

Temperature above Ambient  ̊F

Car Number

Train 7 (Non-Braking)

Car Average

Train Average

1

10

100

1000

0 10 20 30 40 50 60 70 80 90 100 110

Temperature above Ambient  ̊F

Car Number

Train 8 (Braking)

Car Average

Train Average

Lower Limit

Train 7 (Nonbraking)

Control Car
18

Figure 15. Loaded Test Train 9—Day 3 Results

Data for Train 10 shows seven cars that fall below the threshold. These are the same seven cars 

that were below the threshold for Train 8 during the second day of testing.

Figure 16. Loaded Test Train 10—Day 3 Results

1

10

100

1000

0 10 20 30 40 50 60 70 80 90 100 110

Temperature above Ambient  ̊F

Car Number

Train 9 (Non-Braking)

Car Average

Train Average

1

10

100

1000

0 10 20 30 40 50 60 70 80 90 100 110

Temperature above Ambient  ̊F

Car Number

Train 10 (Braking)

Car Average

Train Average

Lower Limit

Train 10 (Braking)

Control car

Train 9 (Nonbraking)
19

3.4 Investigating Piston Travel versus Force

Current manual brake inspections use piston travel as an indicator of brake effectiveness. 

Several tests were conducted to determine the relationship between piston travel and brake shoe 

force. Two cars, one with body-mounted brakes and one with truck-mounted brakes, were 

tested. The JIM SHOE® Brand Brake Force Measurement System was used during these tests. 

Force measurements were taken and recorded for the car with body-mounted brakes in the 

nominal condition, with a brake lever disconnected and a bound brake beam. Several

20-pound per square inch brake pipe reductions were used to allow the automatic slack adjuster 

to adjust piston travel to 7 inches. Figure 17 shows the results.

Figure 17. Body-Mounted Brakes—Rigging Condition Comparison 

(7-inch piston travel with 20-psi brake pipe reduction)

Applied shoe force is reduced by approximately 39 percent for the manipulated rigging 

conditions with constant piston travel of 7 inches.

Force measurements were taken and recorded for the car with truck-mounted brakes in the 

nominal condition and with a bound brake beam. The piston travel indicator was within range 

for both of the brake applications. Figure 18 shows the results.

0

500

1000

1500

2000

2500

Nominal Truck lever

disconnected

#1 beam bound

2019

1261 1349

Average applied shoe force in pounds

Rigging Condition

Body Mounted Brakes

Rigging Condition Comparison

(7" Piston Travel)
20

Figure 18. Truck-Mounted Brakes—Rigging Condition Comparison 

(nominal piston travel with 20-psi brake pipe reduction)

Bound rigging reduced brake shoe force by approximately 25 percent, whereas the piston travel 

indicator stayed within the acceptable range.

3.5 Comparing Methodologies (manual inspection versus technology 

detection)

Results of the revenue service manual inspection benchmarking study show that brake-related 

defects were found at the rate of 0.06 defects per train. 

Revenue service wheel temperature detector results show that possible brake-related defects 

were found at the rate of 0.24 defects per train.

One car that was identified with a cold-wheel condition by the detector on May 26, 2011, was 

subsequently found defective at North Platte, NE, during a manual inspection on June 1, 2011. 

Car repair billing records indicate that the car was repaired at North Platte on June 3, 2011, and 

the repair was coded General Repair (see Table 1). There were no more defect indications for 

this car by either manual inspection methods or the detector.

None of the air-brake defects found by the manual inspections were identified as possible defects 

by the technology. Therefore, the true defect rate may lie somewhere between 0.06 and 0.24 

defects per train.

The technology identified seven cars with possible ineffective brakes during controlled fully 

loaded train testing at FAST. After the test was completed, qualified inspectors performed a 

Class 1A 1,000-mile air-brake test. Five cars did not meet the Class 1A inspection criteria. Only 

one car was found defective by both the detector and the manual inspection. It should also be 

noted that one of the cars that failed the manual test was not in the consist during controlled fully 

0

200

400

600

800

1000

1200

Nominal Bound rigging

1103

821

Average applied shoe force in pounds

Rigging Condition

Truck Mounted Brakes

Rigging Condition Comparison

(Piston Travel within Indicator)
21

loaded train testing. Manual and controlled fully loaded train test results for these 11 cars are 

shown in Table 2.

Table 2. Manual and Controlled Full Train Test Results for Defective Cars

FAST 

Car 

No.

Manual 

Test

(Class 1A)

WTD 

Test

Temperature above or below(-) lower control 

limit (F ̊) (WTD Test) Remarks

Train 2 Train 4 Train 6 Train 8 Train 

10

260 Fail Pass 50.5 52.2 62.1 55.5 54.5

317 Fail Pass 90.2 90.8 81.1 96.2 50.0

269 Fail Pass 19.7 17.2 24.3 28.1 16.0

272 Fail N/A N/A N/A N/A N/A N/A

Not in consist for WTD 

test

 117 Fail Fail -9.9 -9.7 19.6 12.7 17.2

Failed WTD test 1st

night only

360 Pass Fail -14.3 -17.0 8.4 -17.4 -1.9

367 Pass Fail -12.4 -8.5 -7.9 -12.7 -7.6

395 Pass Fail -21.8 -20.7 -22.1 -22.0 -3.9

249 Pass Fail -6.2 -2.2 -22.1 -17.4 -13.3

217 Pass Fail -9.3 -12.6 -9.9 -6.7 -6.6

143 Pass Fail N/A N/A -11.7 -11.7 -5.1

Not in consist 1st night 

WTD test

286 Control Control 96.0 74.4 -22.1 -21.2 -15.1

Air cut out after 1st night 

WTD test 

The control car (FAST car number 286) had the air cut out after the first night of testing. The 

defective cars were each given a manual single-car air-brake test. Table 3 shows the test results.

Table 3. Results of Single-Car Air-Brake Test

Defects

FAST 

Car 

No.

Manual 

Test

(Class 

1A)

WTD 

Test

Single 

Car AirBrake 

Test

Pressure 

Tap 

Gasket 

Leaking

Train 

Line 

Leaking

Auxiliary

Reservoir

Pipe 

Broken

Cylinder 

Pipe 

Leaking

Cylinder 

Packing 

Cup 

Leaking

Service 

Portion 

Defective

Emergency 

Portion 

Defective

260 Fail Pass Pass No defects found

317 Fail Pass Fail X

269 Fail Pass Fail X

272 Fail N/A Fail X X X

117 Fail Fail Pass No defects found

360 Pass Fail Fail X X

367 Pass Fail Fail X

395 Pass Fail Fail X X

249 Pass Fail Fail X

217 Pass Fail Fail X X X

143 Pass Fail Fail X
22

Two of the five cars (Fast car numbers 260 and 117) found defective by the manual test method 

passed the single-car air-brake test with no problems. This included the car (FAST car number 

117) that failed both the manual and the controlled fully loaded train testing. It should be noted 

that this car failed the controlled fully loaded train testing only on the first night of testing, but 

passed on the second and third nights. One of the five cars (FAST car number 317) found 

defective by the manual test method required a service portion valve change in order to pass the 

single-car air-brake test. One (FAST car number 272) required a service and emergency portion 

valve change, as well as a broken auxiliary reservoir pipe that required welding (this car was not 

in the consist during controlled fully loaded train testing). A final one (FAST car number 269) 

required only minor leak repairs to pass the single-car air-brake test. 

Of the six remaining cars that were identified with possible ineffective brakes during controlled 

fully loaded train testing at FAST, one (FAST car number 249) required only minor leak repairs 

to pass the single-car air-brake test, one (FAST car number 360) had to have a brake cylinder 

packing cup replaced (truck mounted brakes), one (FAST car number 217) had to have a cylinder 

pipe gasket replaced, and three (FAST car numbers 367, 395, and 143) had broken auxiliary 

reservoir pipes that required welding. One of these (FAST car number 395) also required a 

service portion valve change to pass the single-car air-brake test.
23

4. Conclusions and Recommendations

Both the proof-of-concept testing and the controlled fully loaded train testing demonstrated the 

ability of technology to distinguish between applied and nonapplied brakes for known braking 

conditions. This implies that it is also possible to make this distinction for unknown braking 

conditions when sound statistical methods are applied. 

The data collected during the controlled fully loaded train testing was independently analyzed by 

two engineers using different methodologies. The cars identified as having ineffective brakes 

were the same in both cases. This implies that there may be multiple ways to analyze the data to 

produce reliable results. 

The controlled testing helps validate the revenue service detector results that show a brakerelated defect detection rate of approximately four times that of the manual inspection defect 

detection rate is possible using wheel temperature detectors. However, both methodologies 

indicate that a very small percentage of brake-related defects were actually present in the test 

fleet. Revenue service detector results that show several cars with a repeated cold-wheel 

condition over the course of multiple passes indicate a failure of the manual test to properly 

identify ineffective brakes. This could possibly be the result of testing the train in a static 

condition (manual inspection) as opposed to a dynamic condition (detector), as well as the 

possibility that the true revenue service hold-time of the brake system is not sufficient to provide 

an effective brake. 

Another consideration when comparing results of the two methodologies is the fact that the 

manual test is performed with a 20-pound per square inch brake pipe reduction. When train 

brakes are used for train handling purposes in revenue service, brake pipes are reduced typically 

by 6–10 psi. This is what was seen in the revenue service testing and replicated in the controlled 

fully loaded train testing.

Results of single-car air-brake testing on the failed cars at FAST indicate that testing brakes in 

the dynamic condition may exacerbate problems that do not fully manifest themselves in a static 

environment. For example, small leaks in brake cylinder packing cups, piping, and fittings that 

may not affect piston travel and/or hold-times during the manual test may be amplified during 

dynamic testing. The effects of the small leaks during dynamic testing may negatively impact 

the nominally designed retarding force of the car’s braking system. Results also indicate the 

possibility of differences in brake valve function during static and dynamic operations. 

Testing to examine the correlation between piston travel and applied shoe force shows that force 

can vary for constant piston travel when the brake rigging configuration is altered. This can be 

attributed to the action of the automatic slack adjuster common to modern railcars. The slack 

adjuster maintains constant piston travel as brake rigging changes occur. Brake rigging changes 

such as lever angularity and brake rod lengths, while not affecting piston travel (due to the action 

of the automatic slack adjuster), have a definite effect on shoe force. Therefore, proper piston 

travel does not ensure adequate shoe force. 

Results from this limited testing indicate that wheel temperature detector technology has the 

capability to distinguish between effective and noneffective brakes. However, it is 

recommended that additional testing be conducted to further investigate the cause-and-effect 

relationship between brake system defects and relative wheel temperature. 
24

5. References

Federal Railroad Administration, Department of Transportation, Code of Federal Regulations,

Title 49 Part 200 – Part 299, Washington, DC.
25

Abbreviations and Acronyms

AAR Association of American Railroads

CFR Code of Federal Regulations

FAST Facility for Accelerated Service Testing

TCR track conditioning run

TTC Transportation Technology Center (the site)

TTCI Transportation Technology Center, Inc. (the company)

UP Union Pacific Railroad