Passenger Cab Car Grade Crossing

Impact Test Report

Rail Passenger Equipment

Impact Tests

U.S. Department of

Transportation

Federal Railroad

Administration

Office of Research

and Development

Washington, DC 20590

DOT/FRA/ORD-07/24 Final Report

October 2007

This document is available to the

public through the National Technical

Information Service, Springfield, VA 22161.

This document is also available on the FRA

Web site at www.fra.gov.
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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 

October 2007 

3. REPORT TYPE AND DATES COVERED 

Final Report 

June 2002 

4. TITLE AND SUBTITLE 

Passenger Cab Car Grade Crossing Impact Test Report 

5. FUNDING NUMBERS 

RR28/EB035 6. AUTHOR(S) 

Tyrell, David; Martinez, Eloy; Jacobsen, Karina; Perlman, Benjamin 

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

U.S. Department of Transportation 

Research and Innovative Technology Administration 

John A. Volpe National Transportation Systems Center 

55 Broadway 

Cambridge, MA 02142-1093 

8. PERFORMING ORGANIZATION 

REPORT NUMBER 

DOT-VNTSC-FRA-08-01 

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

U.S. Department of Transportation 

Federal Railroad Administration 

Office of Research and Development 

1120 Vermont Avenue, NW–Mail Stop 20 

Washington, DC 20590 

10. SPONSORING/MONITORING 

AGENCY REPORT NUMBER 

DOT/FRA/ORD-07/24 

11. SUPPLEMENTARY NOTES 

12a. DISTRIBUTION/AVAILABILITY STATEMENT 

This document is available to the public through the National Technical Information Service, 

Springfield, VA 22161. This document is also available on the FRA Web site at 

www.fra.dot.gov. 

12b. DISTRIBUTION CODE 

13. ABSTRACT (Maximum 200 words) 

Two full-scale oblique grade crossing impact tests were conducted in June 2002 to compare the crashworthiness performance of 

alternative corner post designs on rail passenger cab cars. On June 4, 2002, a cab car fitted with an end frame built to pre-1999 

requirements impacted a steel coil at approximately 14 mph (22.5 km/h). Following on June 7, 2002, a cab car fitted with an end 

frame built to current requirements also impacted a steel coil at approximately 14 mph (22.5 km/h). 

The tests were conducted in response to a recommendation from the American Public Transportation Association’s Passenger 

Rail Equipment Safety Standards Committee to measure the crashworthiness performance of alternative cab car end frame 

designs. During the test of the 1990s design, the corner post failed, eliminating the survival space for the operator. During the test 

of the state-of-the-art (SOA) design cab car, the corner post remained attached and deformed less than 9 in (228 mm), preserving 

space for the operator. 

The crush of the cars was analyzed using detailed finite element models. The impact end of each car was modeled, including 

approximately one quarter of the length of the car. The back end of the cab car model was fixed, and its end structure was 

impacted by an initially moving cylinder with the same mass and dimensions as the steel coil used in the tests. 

The results from the full-scale grade crossing impact tests validated the preliminary results of the three-dimensional lumped 

parameter computer model of the collision dynamics. 

14. SUBJECT TERMS 

Transportation, safety, crashworthiness, passenger rail vehicles, cab car end structure, grade 

crossing, impact test 

15. NUMBER OF PAGES 

72 

16. PRICE CODE 

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(cm2

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(km2

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) 

AREA (APPROXIMATE) 

1 square centimeter (cm2

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1 square meter (m2

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10,000 square meters (m2

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1 ounce (oz) = 28 grams (gm) 

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MASS - WEIGHT (APPROXIMATE) 

1 gram (gm) = 0.036 ounce (oz) 

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= 

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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 yard (cu yd, yd3

) = 0.76 cubic meter (m3) 

VOLUME (APPROXIMATE) 

1 milliliter (ml) = 0.03 fluid ounce (fl oz) 

1 liter (l) = 2.1 pints (pt) 

1 liter (l) = 1.06 quarts (qt) 

1 liter (l) = 0.26 gallon (gal) 

1 cubic meter (m3

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1 cubic meter (m3

) = 1.3 cubic yards (cu yd, yd3) 

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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 

ii 

13
 

Preface 

The grade crossing impact tests were conducted under the sponsorship of the Federal 

Railroad Administration’s Office of Research and Development, as part of the ongoing 

study called the Equipment Safety Research Program. The grade crossing impact tests 

mark completion of the first stage of testing conventional equipment, while concurrently 

beginning the second stage of testing improved equipment designs. 

The authors would like to thank Dr. Tom Tsai, Program Manager, and Claire Orth, 

Division Chief, Equipment and Operating Practices Research Division, Office of 

Research and Development, Federal Railroad Administration, for their support. The 

authors would also like to thank Gunars Spons, Federal Railroad Administration Resident 

Manager at the Transportation Technology Center, for managing the full-scale test effort. 

Dr. Barrie Brickle, Senior Engineer, Transportation Technology Center, Inc. (now 

retired), was the test engineer who implemented the grade crossing tests. Kent Johnson, 

President, Premier Engineering, and Dr. Ron Mayville, President, R.A. Mayville and 

Associates, LLC, designed the state-of-the-art and 1990s end frames. Dr. Richard 

Stringfellow, Senior Engineer, and Patricia Llana, Mechanical Engineer, TIAX, LLC, 

developed the finite element models of the state-of-the-art and 1990s end frames. David 

Tyrell, Eloy Martinez, Karina Jacobsen, John Zolock, Volpe Center, and Professor 

Benjamin Perlman, Tufts University, designed the grade crossing tests and analyzed the 

test measurements. 

The design of the tests was developed in coordination with the Construction/Structural 

Subcommittee of the American Public Transportation Association’s (APTA’s) Passenger 

Rail Equipment Safety Standards Committee. The authors would like to thank Ken 

Barnish, Assistant Chief Mechanical Officer, Metro-North Railroad, Chair of the 

Subcommittee, and Tom Peacock, Manager, Technical Services, APTA, for their efforts 

to coordinate the activities. Ed Murphy, Chief Mechanical Officer, Southeastern 

Pennsylvania Transit Authority, arranged for the donation of the cars used in the test. 

Gordon Campbell, LTK Engineering, consulting with Bombardier, provided structural 

drawings of the cars used in the test. 

iii 

Table of Contents 

List of Figures................................................................................................................................ vi 
 

List of Tables ................................................................................................................................. vi 
 

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


1. Background.................................................................................................................................3 
 

2. Introduction.................................................................................................................................7 
 

3. Overview of Cab Car End Structures..........................................................................................9 
 

3.1. Cab Car End Frame Designs..............................................................................................10
 


3.2. Overview of 1990s and SOA End Frame Design Requirements.......................................11 
 

3.3. Evaluation of Severe Deformation.....................................................................................14 
 

4. Test Conditions .........................................................................................................................17 
 

5. Comparison of Crashworthiness...............................................................................................19 
 

6. Discussion.................................................................................................................................21 
 

Appendix A. Summary of Pre- and Post-Test Analyses Results..................................................23 
 

Appendix B. Test Requirements...................................................................................................53 
 

References......................................................................................................................................61 
 

Acronyms.......................................................................................................................................63 
 

v 
 

List of Figures 

Figure 1. Post-Accident Photographs of Portage, IN, Grade Crossing Collision.............. 7 
 

Figure 2. Schematic of Key Structural Components of the Cab Car End Frame Designs 9 
 

Figure 3. Photographs of 1990s (Left) and SOA (Right) End Frames ............................ 10 
 

Figure 4. Schematics Contrasting 1990s and SOA End Frame Designs; Collision and

 Corner Posts as Tested...................................................................................... 11 
 

Figure 5. Corner Post Mode of Deformation at 7.75 in (197 mm) of Crush; Load 
 

Applied 18 in (457 mm) Above Floor ............................................................. 14 
 

Figure 6. Force on the Corner Post Structure Over the Crush Distance.......................... 15 
 

Figure 7. Schematic of In-Line Collision Scenario ......................................................... 17 
 

Figure 8. Setup of 1990s Design Test.............................................................................. 18 
 

Figure 9. Photographs Comparing the Corner Post Crush of the 1990s (Left) and SOA 

 (Right) End Frame Designs .............................................................................. 19 
 

Figure 10. Comparison of Crush Estimation versus Initial Collision Speed ................... 20 
 

List of Tables 

Table 1. Summary of Cab Car End Structure Crashworthiness Standards and 

 Requirements ..................................................................................................... 13 
 

vi 
Executive Summary 

Two full-scale oblique grade crossing impact tests were conducted in June 2002 to 

compare the crashworthiness performance of alternative corner post designs on rail 

passenger cab cars. On June 4, 2002, a cab car fitted with an end structure built to pre1999 requirements impacted a steel coil at approximately 14 mph (22.5 km/h). 

Following on June 7, 2002, a cab car fitted with an end structure built to current 

requirements underwent the same test. Each car was equipped with strain gauges, string 

potentiometers, and accelerometers to measure the deformation of specific structural 

elements, as well as the longitudinal, lateral, and vertical displacements of the carbody. 

The gross motions of the cars and steel coil, the force-crush behavior of the end 

structures, and the deformation of major elements in the end structures were measured 

during the tests. 

The tests themselves were conducted in response to a recommendation from the 

American Public Transportation Association’s (APTA) Passenger Rail Equipment Safety 

Standards/Construction-Structural (PRESS C&S) Subcommittee to measure the 

crashworthiness performance of alternative cab car end structures. During the test of the 

1990s design, the corner post failed, eliminating the survival space for the operator. 

During the test of the state-of-the-art (SOA) design cab car, the corner post remained 

attached and deformed less than 9 in (229 mm), preserving space for the operator. 

Before the tests, the crush behaviors of the cars and their dynamic responses were 

simulated with car crush and collision dynamics (CD) models. The car crush model was 

used to determine the force-crush characteristics of the corner posts, as well as their 

modes of deformation. The CD model was used to predict the extent of crush of the 

corner posts as functions of impact velocity, as well as the three-dimensional 

accelerations, velocities, and displacements of the cars and coil. Pre-test analyses of the 

models were used in determining the initial test conditions, instrumentation, and 

locations. 

The crush of the cars was analyzed using detailed finite element (FE) models. The 

impact end of each car was modeled, including approximately one quarter of the length 

of the car. The back end of the cab car model was fixed, and its end structure was 

impacted by an initially moving cylinder with the same mass and dimensions as the steel 

coil used in the tests. 

Before the tests, runs were made with the models with and without material failure. This 

approach allowed calculation of an upper bound and a lower bound on the force-crush 

characteristics. The pre-test predictions of the analysis of the SOA design car, including 

material failure, very closely match the results of the test for the force-crush 

characteristic, strains at the measured locations, the geometry of the deformed structure, 

and the locations and extent of material failure. The pre-test predictions of the analysis of 

the 1990s design also closely match the test measurements; however, the extent of 

material failure predicted was slightly less than observed in the test. Failure of the corner 

1 
 
post was predicted to occur at a speed of 1.6 mph (2.57 km/h), approximately 10 percent 

greater than the test speed. A more sophisticated implementation of the material failure 

modeling helped bring the model results into very close agreement with the test 

measurements. 

The CD was analyzed using a lumped parameter model, with nonlinear stiffness 

characteristics. The suspension of the car is included in the model in sufficient detail to 

predict derailment. The model uses the force-crush characteristic developed in the car 

crush analysis as input and includes the lateral force that develops as the corner post is 

loaded longitudinally. 

The results from the full-scale grade crossing impact tests agree with and confirm the 

preliminary results of the three-dimensional lumped parameter computer model of the 

CD. The predictions of the three-dimensional accelerations, velocities, and 

displacements of the car and the coil are in very close agreement with the measurements 

made in the tests of both cars, up to the time of failure of the corner post. The cars 

remained on the track in both tests, as predicted with the model. 

2 
 
1. Background 

In January 2000, the APTA Commuter Rail Chief Executive Office (CEO) Executive 

Committee requested the FRA Office of Research and Development to develop 

information on the effectiveness of APTA’s recently introduced Manual of Standards 

and Recommended Practices for Passenger Rail Equipment [1] and FRA’s recently 

established regulations [2]. APTA was particularly interested in the increase in 

crashworthiness associated with the additional and revised cab car end frame standards 

and regulations. These standards and regulations are intended to provide crashworthiness 

in the event of a grade crossing collision, train-to-train collision, or impact with an object 

fouling the right-of-way. 

FRA included full-scale impact tests and associated planning and analysis activities in its 

overall research plans to develop the information requested. The details of the tests were 

developed in conjunction with the APTA/PRESS C&S Subcommittee. 

FRA developed the information on cab car crashworthiness requested by APTA in four 

steps: 

•	 Step 1: Design Development of Test Articles 

•	 Step 2: Development of Test Conditions 

•	 Step 3: Implement Tests 

•	 Step 4: Compare Performance 

These steps were carried out in close coordination with the APTA/PRESS C&S 

Subcommittee, as follows. 

On November 1, 2000, at the Drake Hotel in Chicago, the specific objectives of the test 

and alternative test conditions were discussed during a meeting of a steering group 

formed by the APTA/PRESS C&S Subcommittee. At that meeting, the working group 

agreed that the corner post—the vertical structural member located where the sidewall 

meets the end wall—would be the focus of the tests, that the comparison would be with a 

cab car end structure design meeting the then-current standards and a design meeting 

typical practice immediately prior to the development of the standards and regulations, 

and that the test approach would be a cab car impacting a free-standing coil of steel. The 

corner post was chosen to address longstanding FRA concerns about the corner structure 

of cab cars. The end structure designs were chosen to address the APTA CEO’s request 

to clarify “how much the new standards had bought them.” 

Alternative test approaches considered by the working group included: 

1.	 A quasistatic large deformation test 

2.	 A dynamic test of a car into a fixture mounted on a fixed wall 

3.	 A dynamic test of a car into a fixture mounted on a rail car 

4.	 A dynamic test of a car into a steel coil test article mounted on a highway flatbedtractor trailer 

5.	 A dynamic test of a car into a free-standing steel coil 

3 
 
The working group eliminated the quasistatic test approach because of the difficulty in 

assuring that the support conditions for the rail car structure during such a test would 

simulate or closely approximate the support conditions for the structure under dynamic 

(accident) conditions. The working group, because of the low-test speeds required to 

cause significant structural damage, eliminated the approach of mounting a fixture to a 

wall. The group eliminated the approach of mounting the test article to the flat car due to 

the relative complexity of the test. The group also eliminated the approach of recreating 

an accident because of the difficulties associated with analyzing the behavior of more 

than two impacting objects [3]. The complex interactions of multiple deformable bodies 

make it a practical impossibility to design a repeatable test. In addition, such an approach 

requires detailed modeling of the highway vehicle. The group agreed that resources 

would be better employed by further analyzing the rail car structure. The group selected 

the approach of the cab car impacting a freestanding coil. This approach has the 

advantages of being relatively simple to set up; it is repeatable with careful setup; and the 

impact speeds and loading conditions closely approximate accident conditions. Section 3 

of this report provides an overview of the test, and Appendix B includes the detailed test 

requirements. 

At the January 17, 2001, meeting of the APTA/PRESS C&S Subcommittee, held at 

APTA’s headquarters in Washington, DC, the decisions of the working group were 

presented and discussed. The stated objective of the test was to compare the 

crashworthiness performance of pre- and post-1999 corner post designs for cab cars, as 

well as show the required loads in the then-current APTA Standards (post-1999 

requirement), that the cab car end structure must withstand. A grade crossing test 

approach was proposed using a 40,000 lbm (18,144 kg) steel coil on a frangible support 

run twice: once with a cab car compliant with pre-1999 regulations and once with a cab 

car compliant with post-1999 regulations. An overview of the pre-1999 regulations was 

discussed along with the following cautions: 

•	 The specifications prescribed the static loads that the structure must support. 

•	 The specifications do not fully prescribe how the structure should behave under 

those static loads. 

•	 The test results will likely be related to the amount of energy absorbed. 

•	 A design compliant with pre-1999 practice may potentially have greater 
 

crashworthiness if it absorbs more energy. 
 

Preliminary test predictions of various cab car end frame design concepts were presented 

according to the maximum safe speed for operators and passengers in a crash. 

Overview of the designs of the cab car end frames to be tested was presented at the July 

19, 2001, meeting of the C&S Subcommittee, held in Washington, DC. Examples of two 

designs were to be tested: a 1990s design, compliant with typical practice of the 1990s, 

and an SOA design, compliant with all of the FRA regulations and APTA standards then 

in place. These designs were developed to be retrofitted to Budd Pioneer cars. The 

1990s design is characterized by a stepwell and a relatively light corner post. In contrast, 

the cross-section of the SOA design corner post is larger, and the side sill is continuous 

4 
 
(i.e., no stepwell exists). A recent purchase by New Jersey Transit indicated a 

willingness to eliminate a stepwell. In addition, modifications to the draft sill would have 

been required if the stepwell had been retained, while no modifications were necessary 

with a continuous side sill. The differences in the designs were principally driven by the 

then-current APTA standard requiring severe deformation of the corner and collision 

posts before failure of the attachments. Section 2 presents a more extensive overview of 

the designs, and another cab car end structure report [4] includes detailed descriptions of 

the designs. 

A cab car with an end frame built to the 1990s design was impact tested on June 4, 2002, 

and a cab car with an end frame built to the SOA design was tested on June 7, 2002. 

Both tests were conducted at the Transportation Technology Center (TTC) in Pueblo, 

CO. The impact speed in both tests was approximately 14 mph (22.5 km/h). In the test 

of the 1990s design, the corner post failed, eliminating the operator’s survival space. In 

the test of the SOA design, the corner post deformed by 9 in (228 mm). The corner post 

did not fail, thereby preserving the operator’s survival space. The 1990s design has a 

maximum safe speed—the maximum speed for which the operator’s space will be 

preserved—of 11 mph (17.7 km/h). The SOA design has a maximum safe speed of 16 

mph (25.7 km/h), an increase of nearly 50 percent. Sections 3 and 4 present a more 

extensive overview of the test results, and Appendix A includes detailed descriptions of 

the results. 

Preliminary results of these tests were presented at the APTA/PRESS C&S 

Subcommittee Meeting held October 29, 2002, at Southeastern Pennsylvania 

Transportation Authority (SEPTA) in Philadelphia, PA. Detailed results were presented 

at the APTA/PRESS C&S Subcommittee Meeting, March 4, 2003, held in Washington, 

DC. An overview of the development of the 1990s and SOA designs, development of the 

test conditions, implementation of the tests, and the test results were presented at the 

APTA/PRESS Committee Meeting, May 22, 2003, Newark, NJ. Two technical papers 

on the preliminary results of these tests were presented and published in April 2003 

[5][6]. 

In spite of the results of the effort, which showed a significant increase in 

crashworthiness resulting from the then-current APTA standards, the APTA/PRESS 

Committee voted to accept significant changes to their standards for cab car end 

structures. The standards requiring that the corner and collision post sustain severe 

deformation before failure of the post attachments were replaced with a recommended 

practice that these attachments be able to sustain minimum prescribed loads with 

negligible deformation. 

5 
 

2. Introduction 

The goals of this crashworthiness research program are to provide a survivable volume 

for the operator to safely ride out the collision and to minimize the forces imparted to the 

operator during the ride down phase of the collision. The safe allowable crush distance 

for the end frame is defined as 12 in (305 mm). Any crush in excess of this distance may 

result in the bulk crushing of the operator. 

Several collisions have occurred in recent accident history during which the end frame 

structure was engaged above the underframe and a subsequent loss of operator survivable 

volume occurred. Two recent examples of such collisions include the Yardley, PA, 

collision between a cab car-led commuter train and a tractor semitrailer carrying coils of 

steel [7] and the Portage, IN, grade crossing collisions between a cab car-led commuter 

train and a tractor-tandem trailer carrying coils of steel [8]. 

Figure 1 is a series of photographs taken from the collision that occurred in Portage, IN, 

on June 18, 1998, where a cab car-led passenger train collided with the flatbed loaded 

with steel coils of a semitrailer stuck at a grade crossing. When the train impacted the 

flatbed, one of the restraining straps snapped, causing a 40,000 lbm (18,100 kg) steel coil 

to penetrate the bulkhead and collision post and proceed to roll through the passenger 

compartment. This collision resulted in five minor injuries and three fatalities. The left 

picture is the impacted end of the lead cab car, the middle is an interior shot of the broken 

collision post, and the right is the steel coil after the accident. 

Figure 1. Post-Accident Photographs of Portage, IN, Grade Crossing Collision 

The purpose of such testing is to establish the minimum level of crashworthiness 

enhancement by modifying current designs using increased strength-based requirements. 

The motivation for such testing comes about as a result of the danger posed to operators 

of cab cars when operating a consist in the push mode. Under these operational 

conditions little space exists between the operator and any object that the cab car may 

strike during a grade crossing collision or a collision with an obstruction fouling the 

right-of-way of the consist. 

7 
 

Cant 

R ail

Body Bolster

Anti-telescoping

Plate

Corner Post

C ollision

Post

End

Beam

Lateral 

ber/Shelf

Bulkhead Extended Side Sill

3. Overview of Cab Car End Structures 

The purpose of the end frame structure is to provide protection for the operator and 

passengers of a cab car in the event of a collision with the superstructure of the vehicle. 

This structure is composed of several structural elements that act together to protect the 

occupants. The base of the end frame structure is composed of the end/buffer beam, 

which is directly connected to the draft sill of the vehicle. For cars that include stepwells, 

the side sills of the underframe generally do not directly connect to the end/buffer beam. 

Four major vertical members are connected to the end/buffer beam: two collision posts 

located at roughly one-third points along the length of the end/buffer beam and two 

corner posts located at the outermost width of the vehicle. These structural elements are 

also connected together through two additional lateral members, a lateral member/shelf 

located just below the window frame structure and at the top by an anti-telescoping (AT) 

plate. The attachment of the end frame structure typically occurs at three locations to the 

rest of the vehicle. The first location is at the draft sill at the level of the underframe. 

This is the main connection where a majority of any longitudinal load applied to the end 

frame is transferred into the underframe of the vehicle. Two other connections at the 

cant/roof rail are located at either side of the car just below the level of the roof. When a 

longitudinal load is applied to the end frame, it is reacted by the draft sill and the cant 

rails into the main carbody structure. Figure 2 depicts a schematic of a typical 

arrangement. 

D raft Sill

M em

(SO A only)

C a n t 

R a il 

B o d y B o ls te r 

A n ti-T e le sc o p in g 

P la te 

C o r n e r P o st 

D r a ft S ill 

C o llisio n 

P o st 

E n d 

B e a m 

L a te r a l 

M e m b e r /S h e lf 

B u lk h e a d 

(S O A o n ly ) E x te n d e d S id e S ill 

(S O A o n ly ) 

Figure 2. Schematic of Key Structural Components of the Cab Car End Frame 

Designs 

9 
 
3.1. Cab Car End Frame Designs 

Two end frame designs were developed for the grade crossing testing program. The first 

end frame design is representative of typical designs of passenger rail vehicles before 

1999. The second end frame design incorporated all the enhanced requirements passed in 

1999 from the Federal regulations in 49 CFR Parts 238 and APTA SS-C&S-034-99 

Standard for the Design and Construction of Passenger Railroad Rolling Stock. The 

second end frame design is referred to as the SOA design. The two end frame designs 

developed were then retrofitted onto two Budd Pioneer passenger rail cars for testing. 

Two Budd Pioneer cars [9] were modified with the end frame designs. The draft sill, 

body bolster, and cant rail from the Pioneer car were retained, while the AT plate, end 

beam, collision posts, corner posts, and lateral member/shelf were replaced with updated 

designs. Many of the elements are similar for the 1990s and the SOA designs, including 

the end/buffer beams and AT plates. 

The principal differences between the two designs are the size of the corner posts, the 

presence of a bulkhead sheet attached from the lateral member/shelf to the collision post 

to the corner post and to the end beam on the SOA design, and the length of the side sill 

on the SOA design which extends past the rear operator compartment to the end beam 

removing the presence of the stepwell. Figure 3 and Figure 4 show the design 

comparisons. In addition to changes in the cross-sectional sizes and thickness of some 

structural members, another change is associated with the connection details for the 

corner posts. The collision posts of both designs penetrate the top and bottom flanges of 

the end/buffer beam and the AT plate. This is based upon typical practice in the early 

1990s for the 1990s design and a requirement in the APTA standard for the SOA design. 

The corner posts differ, because the corner posts for the 1990s design do not penetrate 

both top and bottom flanges of the end/buffer and AT beams while the posts of the SOA 

design do. The SOA design therefore has a significantly stiffer connection that is better 

able to resist torsional loads transferred to the AT plate. 

Figure 3. Photographs of 1990s (Left) and SOA (Right) End Frames 

10 
 
1990s Design 0.25-in lug 

0.25 in 0.25-in lug 

0.375 in 	 7.75 
 

in 4.5 in 
 

6.5 in 4.5 in 

Collision Corner 

SOA Design 0.375-in lug 

0.3125-in lug 0.3125 in 

0.375 in 	 7.75 6 in 

in 

6 in 6.5 in 

Collision Corner 

Figure 4. Schematics Contrasting 1990s and SOA End Frame Designs; Collision 

and Corner Posts as Tested 

Both end frame designs were constructed primarily with A710 steel. A710 is becoming 

popular for use in the rail industry because of the higher nominal material properties and 

the increased ductility. Such properties allow for construction of individual structural 

elements of smaller cross-section and thinner thickness. Higher ductility and thinner 

thicknesses increase the permanent deformation that a structure can sustain before 

material failure starts to occur. 

3.2. Overview of 1990s and SOA End Frame Design Requirements 

As part of the development of the two end frame designs, a survey of existing cab car end 

frame designs was conducted, and detailed design requirements were developed for each 

design. The survey helped define the range of cross-sectional geometries for the end 

frame members and the approaches used in connecting these members. The design 

requirements describe in detail the functions and constraints of the designs, including the 

geometric (space) requirements, the service load requirements, the collision load 

requirements, and the fabrications requirements. Appendix A includes a more detailed 

overview of the design requirements and the evolution of the collision requirements. The 

results of the survey and all of the design requirements for both end frame designs are 

described in reference [4]. 

The design requirements for the 1990s end frame design are based upon the strength 

requirements from the industry standard, as well as typical industry practice. The 

11 
 
Association of American Railroads (AAR) discontinued maintenance of the AAR S-034 

in 1983. Subsequently, APTA developed an enhanced version of the standard and 

released a revised standard entitled, “APTA SS-C&S-034-99 Standard for the Design and 

Construction of Passenger Railroad Rolling Stock,” in 1999. The SOA end frame design 

developed for this testing program included all requirements listed in the 1999 APTA 

standard, as well as those required by 49 CFR Part 238 regulations, also passed in 1999. 

Differences in the requirements for the 1990s design and the SOA design were higher 

values for the static load requirements for key end frame members, as well as a 

requirement on the performance of the collision and corner posts when overloaded. The 

1999 APTA requirements for cab car end structures included the following statement: 

....post and its supporting structure shall be designed so that when it is 
 

overloaded ... failure shall begin as bending or buckling in the post. 
 

The connections of the post to the supporting structure, and the 
 

supporting car body structure, shall support the post up to its ultimate 
 

capacity. The ultimate shear and tensile strength of the connecting
 


fasteners or welds shall be sufficient to resist the forces causing the 
 

deformation, so that shear and tensile failure of the fasteners or welds 
 

shall not occur, even with severe deformation of the post and its 
 

connecting and supporting structural elements. 
 

The term severe deformation is ambiguous, but after discussions with APTA technical 

staff, the severe deformation requirement was defined as a horizontal crush of the post a 

distance equal to its depth. Some failure of the parent material was allowed in the post 

but no failure was allowed in the welded connections. 

An additional difference in the requirements was the exclusion of the stepwells to allow 

for extended side sills from the body bolster to the end/buffer beam. Recent car orders— 

notably the New Jersey Arrow 7 procurement—allowed elimination of the stepwells on 

the car end of the car. By bringing the side sills forward to support the end/buffer beam 

directly at the corners, the size of the end/buffer beam could be maintained to a similar 

size as the one developed for the 1990s design. 

Table 1 shows a summary of the design requirements developed for both the 1990s and 

the SOA end frame designs. 

12 
 
 

 

 

 

Table 1. Summary of Cab Car End Structure Crashworthiness Standards and 
 

Requirements 
 

Standard/Requirement 

Component 1990s Design SOA Design 

Collision Post • 300x103 lbf (1,334 kN) at the floor 

without exceeding the ultimate shear 

• 500x103

 lbf (2,224 kN) at the floor without 

exceeding the ultimate shear strength 

(must be present strength • 200x103

 lbf (890 kN) at 30 in (762 mm) 

at the 1/3 points • 300x103 lbf (1,334 kN) at 18 in (457 mm) without exceeding the ultimate strength 

along the width of above the floor without exceeding the • 60x103

 lbf (267 kN) applied anywhere 

the vehicle) ultimate strength 

• Both requirements apply for loads 

applied ±15 degrees inward from the 

longitudinal 

• If reinforcement is used to achieve the 

strength, it must extend fully to 18 in 

(457 mm) and then taper to 30 in (762 

mm) above the underframe 

without yield 

• All requirements apply for loads applied ±15 

degrees inward from the longitudinal 

• Strengths must be achieved without failing 

connections 

• The post must be able to deform 

substantially without failing the connections 

Corner Post •150x103

 lbf (667 kN) at the floor without 

exceeding the ultimate shear strength 

•300x103 lbf (1,334 kN) at the floor without 

exceeding the ultimate shear strength 

(must be present • 30x103

 lbf (134 kN) at 18 in (457 mm) •100x103 lbf (445 kN) at 18 in (460 mm) 

at the extreme above the floor without exceeding the above the floor without exceeding the yield 

corners of the material yield strength strength

vehicle) •Both requirements apply for loads applied 

anywhere between longitudinal to 

transverse inward 

•45x103

 lbf (200 kN) applied anywhere along 

the post without yield 

•All requirements apply for loads applied 

anywhere between longitudinal inward to 

transverse inward 

Lateral Member 

(must be present 

between the 

corner and 

collision posts just 

below the cab 

window) 

•15x103

 lbf (66.7 kN) applied in the 

longitudinal direction anywhere between 

the corner and collision post without 

yield 

• 15x103

 lbf (66.7 kN) applied in the 

longitudinal direction anywhere between the 

corner and collision post without yield 

•Include a bulkhead in the opening below the 

shelf 

The FRA regulation and APTA standards do not fully prescribe all the requirements that 

a functional cab car end structure must meet; that is, they are necessary but not sufficient 

to fully describe the design. Many alternative designs can potentially meet the 

regulations and standards, and each may be expected to behave somewhat differently 

under dynamic loading conditions. In addition to the static loads prescribed by FRA 

regulations and APTA standards, the SOA design was also developed against 

requirements for post-yield behavior (i.e., the structure was designed to deform 

gracefully). A draft report that is currently being reviewed for publication describes the 

full set of design requirements, the static load tests performed to demonstrate compliance 

of the designs to the appropriate regulations and standards, and the details of the designs 

themselves. 

13 
 
3.3. Evaluation of Severe Deformation 

Figure 5 shows representative results from a large deformation quasistatic analysis of the 

corner post subjected to an overload. The load is applied at a height of 18 in (457 mm) 

above the corner post to the end/buffer beam connection. The load is supported by the 

corner post and the following support members: the lateral shelf, the bulkhead sheet, the 

corner post-cant rail-AT plate connection, and the corner post-end/buffer beam-extended 

side sill connection. The lateral shelf and the bulkhead sheet are very effective in 

shedding load into the rest of the end frame structure. A plastic hinge has formed at the 

corner post-end/buffer beam-extended side sill connection. The corner post-cant rail-AT 

plate connection experienced torsional deformations. These deformations result in plastic 

hinges forming at both the cant rail-AT plate connection and the connection of the 

collision post to the AT plate. 

Figure 5. Corner Post Mode of Deformation at 7.75 in (197 mm) of Crush; Load 
 

Applied 18 in (457 mm) Above Floor 
 

The contour plot of effective plastic strain for the corner post shows some areas of the 

post exhibiting strains in excess of the elongation strain on the material certification 

sheets for the A710 plate stock used to construct the corner post. The bulkhead sheet has 

been removed for clarity. The deformation state shown is for the corner post at 7.75 in 

(197 mm) of inward longitudinal deformation. The areas where the strains are highest 

are where failure of the post would be expected. 

Figure 6 shows a plot of the force-deflection characteristic of the SOA end frame under 

this loading condition. The shape of the curve has an initial linear portion of the curve 

associated with the linear elastic behavior of the post; then once the peak load is reached 

at approximately 235,000 lbf (517,000 kg), the curve plateaus over the next 6 in (152 

mm). The fact that no failure is included in the model results in the force plateau 

continuing out past 12 in (305 mm) of crush. The actual characteristic would instead 

reach a peak value and then gradually drop off until failure at the base of the post. At that 

point the load would drop off significantly. From the contour plot of effective plastic 

strain shown in Figure 5, the results after 7.75 in (197 mm) of inward deformation 

become questionable. Up to a crush distance equal to the depth of the corner post, 

14 
 
 

200 

Force (10 3 lbf) 

however, no excessive strains are predicted, and the corner post is compliant with the 

severe deformation requirement. 

250 

150 

Depth of 

Corner Post 

100 

50 

0 

0 2 4 6 8 10 12 14 

Load Point Displacement (inches) 

Figure 6. Force on the Corner Post Structure Over the Crush Distance 

Current Federal regulations and the 1999 APTA standards for passenger car end frames 

prescribe minimum static loads that the structure must support without failure. While 

static loads prescribe minimum levels of strength requirements, such specifications do not 

fully account for the structural behavior of an end frame under dynamic conditions. In a 

dynamic test, the crush of the end frame can be characterized in terms of energy absorbed 

over the distance crushed. An end frame with posts that can deform significantly before 

failing will absorb more energy. A design consistent with pre-1999 practice may 

potentially provide greater crashworthiness protection if it absorbs more energy than a 

design compliant with the current Federal regulations and the 1999 APTA standard. 

15 
 

4. Test Conditions 

Figure 7 is a schematic of the grade crossing test. The two full-scale tests conducted 

involve modified Budd Pioneer cab cars impacting a steel coil supported on a frangible 

table. The coil, weighing approximately 40,000 lbm (88,000 kg), was positioned with the 

bottom of the coil just above the height of the cab car floor and centered on the corner 

post in plain view. The test’s objective was to measure the effectiveness of the corner 

post in preserving the occupant volume. Examples of such a collision scenario are 

discussed earlier and include the Yardley, PA [7], collision and the Portage, IN [8], 

collision involving steel coils penetrating the end structure of cab car-led passenger 

trains. 

Two different end frames were tested, one typical of practice in the 1990s and one 

compliant with current FRA regulations and APTA recommended practices. In both 

tests, the coil was impacted at approximately 14 mph (22.5 km/h). This speed was 

chosen so that excessive intrusion (more than 12 in or 305 mm) into the operator’s 

survival volume would occur in the test of the 1990s design and limited intrusion (less 

than 12 in or 305 mm) in the test of the SOA design. 

Top View
 


V 

Elevation View 

Figure 7. Schematic of In-Line Collision Scenario 

Figure 8 shows a photograph of the test setup for the 1990s design. The car was 

instrumented to measure the accelerations of the carbody, the displacements of the 

suspensions, the displacements of the corner posts, and the strains in selected structural 

members. The coil was instrumented to measure its three-dimensional acceleration, 

17 
 
including yaw, pitch, and roll. Onboard and wayside high-speed film and video cameras 

were used to record the impact. Appendix B details the instrumentation and test 

requirements. The same instrumentation setup was used in the test of the SOA design. In 

both tests, a locomotive was used to push the cab car up to speed; the cab car was then 

released and impacted the coil. 

Figure 8. Setup of 1990s Design Test 

18 
 
5. Comparison of Crashworthiness 

During the full-scale test, the force on the 1990s end frame exceeded the corner post’s 

predicted failure point, and the corner post separated from its upper attachment. Upon 

impact, the corner post began to hinge near the contact point with the coil; tearing at the 

upper connection subsequently occurred. The intensity of the impact ultimately caused 

the upper connection of the corner post and AT plate to fail. More than 30 in (762 mm) 

of deformation occurred. The SOA design performed very closely to pre-test predictions 

made by the FE and CD models. The SOA design crushed approximately 9 in (229 mm) 

in the longitudinal direction. Figure 9 shows post-collision photographs. 

Figure 9. Photographs Comparing the Corner Post Crush of the 1990s (Left) and 

SOA (Right) End Frame Designs 

In planning the grade crossing test, extensive pre- and post-test analyses were conducted 

to determine the impact speed and the measurement requirements; Appendix A describes 

the results of these analyses in detail. The results from these analyses allowed for the 

design of the tests such that the operator’s survival space was substantially reduced for 

the 1990s design cab car and preserved for the SOA design cab car. 

Figure 10 shows a plot of the cab car maximum crush as a function of the impact speed. 

The black horizontal line indicates the crush at which intrusion into the occupant 

compartment occurs. These analyses results were used in developing the test 

requirements, to determine the desired impact speed of 15 mph (24.1 km/h). A single 

19 
 
Closing Speed (mph)

0 5 10 15 20

Cr

us

h 

(in

ch

es)

0

4

8

12

16

20

24

1990's without Material Failure

SOA without Material Failure

1990's with Material Failure

SOA with Material Failure

Operator's Volume Lost

Pr

es

cri

be

d 

Te

Sp

ee

d 

SOA

1990's

collision speed was chosen in order to cause significant deformation of the corner post 

during the tests, with the expectation that the operator’s survival volume would be 

preserved in the test of the SOA design, i.e., that the intrusion into the occupant volume 

would be less than 12 in (305 mm). For the test of the 1990s design, the deformation of 

the corner post was expected to exceed 12 in (305 mm) and consequently intrude into the 

operator’s survival volume. Before the tests, the 1990s design corner post was predicted 

to fail for an impact speed greater than 16 mph (25.7 km/h). During its test, the corner 

post of the 1990s design cab car end structure failed at the tested impact speed of 14.4 

mph (23.2 km/h), a speed approximately 10 percent slower than predicted. The graph in 

Figure 10 shows that the increased standards for the corner posts prove more effective in 

crashworthiness protection. 

Closing Speed (mph) 

0 5 10 15 20 

Crush (inches) 

0 

4 

8 

12 

16 

20 

24 

1990s without Material Failure 

SOA without Material Failure 

1990s with Material Failure 

SOA with Material Failure 

Operator’s Volume Lost 

Prescribed Test

Speed 

SOA 

1990s 

Figure 10. Comparison of Crush Estimation versus Initial Collision Speed 

The above plot shows the increased level of crashworthiness performance of the SOA 

design over the 1990s design. Post-test results demonstrate that the 1990s design will fail 

at a closing speed about 5 mph (8.05 km/h) less than the SOA design. APTA’s improved 

design standards for corner posts allow an increased ability for preserving the operator’s 

survival volume. 

20 
 
6. Discussion 

The grade crossing collision tests were conducted to measure the effectiveness of 

alternative cab car end structures in preventing intrusion during a grade crossing 

collision. The test conditions developed were based in part on the Portage, IN, collision 

[8] between a cab car-led commuter train and a tractor-tandem trailer carrying steel coils, 

and the Yardley, PA, collision [7] between a cab car-led commuter train with a 

semitrailer carrying steel coils. The results of the test of the 1990s design show that this 

corner post is not sufficient to preserve the operator’s survival volume in such an impact. 

During the SOA test, the corner post remained attached, and intrusion was kept below 12 

in (305 mm) of crush, thus preserving occupied volume for the conductor to ride out the 

collision. 

The pre-test analyses are close (within 10 percent for key variables) to the test 

measurements taken from the 1990s end frame design test. Revision of the model to 

include late changes in the design and minor changes to the material failure modeling 

bring the model results into very close (within 5 percent) agreement with the test 

predictions. The pre-test analysis predictions nearly overlay the test results for the forcecrush characteristic for the SOA design. Both sets of analyses are capable of predicting 

the correct modes of deformation and the total amount of energy consumed during the 

collision well. Careful application of FE modeling allowed accurate prediction of the 

crush behavior of rail car structures. 

The 1990s end frame design was developed using practices typical of that time period. 

While severe deformation was qualitatively considered in developing the design, it was 

not quantitatively considered; the negligible deformation requirements were evaluated 

quantitatively to develop this design. The SOA end frame design was developed to 

comply with APTA’s then-current severe deformation requirement. Nonlinear quasistatic 

FE analyses were performed to demonstrate compliance with these requirements. 

The methodologies used to design the cab car end frames and the results of the tests show 

that significant increases in rail passenger equipment crashworthiness can be achieved if 

the deformation of the structure when overloaded is taken into consideration. Modern 

analyses methods can accurately predict the structural crush (severe deformation) and 

consequently can be used with confidence to develop structures that collapse gracefully. 

Modern testing techniques allow the verification of the crush behavior of such structures. 

21 
 


 

 

Appendix A. 
 

Summary of Pre- and Post-Test Analyses Results 
 

A.1. General Approach 

The general approach used to study the crashworthiness performance of alternative 

designs and compare the results against conventional equipment follows several 

interrelated steps (see Figure A-1). An FE model is used to estimate the structural modes 

of deformation of the impacting bodies, as well as the areas where failure is expected to 

initiate and propagate. The forces absorbed by the impacting bodies are proportional to 

longitudinal deformation. These force-crush characteristics are then used as input into a 

CD model. The CD model predicts the relative displacements, the gross motions, and the 

secondary impact environment. The interior occupant models use the secondary impact 

environment information to predict the kinematics of occupants as they ride down the 

event and are used to predict the likelihood of injury or fatality. The results from the 

three models are used to design the initial and boundary conditions for the full-scale tests. 

They are also used to determine the types of instrumentation to be used, as well as the 

placements and range. The fidelity of the models is established by comparison against 

the full-scale test results. 

MODEL: Finite MODEL: CollisioCollision MODEL: Interior 

Element Analysis Dynamics Analysis Occupant Analysis 

OUTPUT: OUTPUT: Gross OUPUT: 

Force/Crush orce- 	 Motions Secondary Impact 

Behavior Motions 

Validate Models with 

Tests 

Figure A-1. Modeling Process Flowchart 

In preparation for the full-scale grade crossing tests, a subset of the analyses was 

conducted to determine the conditions of the test, including the impact speed, and to 

determine the quantities to be measured. The tests were analyzed in two steps: 

•	 Step 1: Car Crush Behavior. Detailed dynamic, nonlinear, large displacement FE 

models of the 1990s and SOA cab car structures were developed. An 

approximation to the loading condition in the test was used in these models. The 

principal purpose of these models was to develop the force-crush behaviors and 

the modes of deformation for the cab car designs. These models have been 

implemented in ABAQUS/Explicit [10], and all include the influence of material 

failure. 

•	 Step 2: Train Collision Dynamics. Three-dimensional lumped-mass CD models 

were used to determine the trajectories of the cab car and coil. Impact elements 

23 
 
were used in these CD models, with the parameters for these elements taken from 

the results of the FE analyses of car crush behavior. The CD models were used to 

evaluate the extent of crush as a function of impact speed. These models have 

been implemented in ADAMS [11]. 

A.2. Structural Modeling and Analysis 

Crush Model 

Figure A-2 shows the FE model of the 1990s design integrated onto an existing cab car. 

The first 20 ft (6.1 m) of the car are modeled. For most of the model, the characteristic 

element length is about 3 in (76.2 mm). For the corner post and the area around its 

attachments, the characteristic element length is typically less than 0.5 in (12.7 mm) and 

in some cases less than 0.25 in (6.4 mm). In the model, the translations of the rear-most 

elements of the cab car are fixed. The rigid coil is initially given a longitudinal velocity 

and is then free to translate and rotate during the simulated impact. In order to bound the 

range of response, the model was run with and without material failure. The FE car crush 

model for the SOA design is similar to the model of the 1990s design. 

Figure A-2. FE Car Crush Model, 1990s Design 

The following sections provide a detailed description of the results predicted before 

conducting the tests in order to develop the instrumentation requirements. Test 

measurements are contrasted to the pre-test predictions. The 1990s design crush model 

was modified after the tests were conducted to capture a failure mode not predicted 

beforehand but observed at the test, and these results are compared against the test 

measurements. 

Circa 1990s Design 

Figure A-3 shows the force-crush characteristic developed for the 1990s design as 

predicted with the model and as measured during the test. The plot shows pre-test and 

post-test predictions. The pre-test predictions from the analysis, including material 

failure and the test measurements, are in close agreement up to approximately 12 in (305 

mm) of crush. After 12 in (305 mm) of crush, the pre-test predictions show the force 

24 
 
increasing, while the test measurements show the force decreasing. A source of the 

discrepancy could have resulted from late changes in the attachment of the AT plate to 

the cant rail that were not incorporated in the model before the test and from limitations 

of the current approach to modeling material failure in FE solvers. As a result, failure of 

the upper attachment of the corner post occurred sooner in the test than predicted. 

300 Test Data 

Post-Test Analysis 

Pre-Test, W/O Failure 250 Pre-Test W/Failure 

200 

150 

100 

50 

0 

Crush (inches) 

Figure A-3. Measured and Predicted Force-Crush Characteristic, 1990s Design 

Instead of attaching the AT plate to the cant rails with several short gussets, as initially 

designed, doublers were used over the cant rails up to the bulkhead wall. In addition, 

several gussets were used where the doublers met the bulkhead wall. The model was 

revised after the test to include these changes. These changes increased the stiffness of 

the AT plate support, which in turn increased the stiffness of the upper attachment of the 

corner post. 

Figure A-4 shows the force time post-test FE results, as well as the derived force time 

curve, taken from test measurements. A nine-accelerometer array was used on the steel 

coil for the test, and the force presented is the resolved acceleration times the mass of the 

steel coil. The results from the simulation and those derived from the test are very close 

for the first 0.03 second (s). Between 0.03 s and 0.05 s the measurements show 

somewhat elevated force levels compared to the analysis (approximately 25 percent). 

The results overlay one another again between 0.05 s and 0.06 s. The key difference 

occurs after 0.06 s where the measurements indicate softening behavior due to the failure 

of the lateral member/shelf and pull out of the corner post from the AT plate over 

approximately 0.015 s. The model is predicting a peeling/tearing failure of the lateral 

member/shelf from the corner post, thereby losing a source of load transfer. This resulted 

in a decreased load in the FE results between 0.02 s and 0.05 s. The pull out failure of 

the corner post from the AT plate occurs in the FE model around 0.1 s. The softening 

behavior occurs over a much shorter time frame at approximately 0.004 s. The 

differences in predicted failure response in time is not surprising given the current SOA 

in ductile material failure modeling. Force (kips) 

0 6 12 18 24 30 36 

25 
 
Force (kips) 

300 

250 

200 

150 

100 

50
 

0 

Test Measurement 

Post-Test Analysis 

0.00 0.05 0.10 0.15 0.20 0.25 0.30 

Time (seconds) 

Figure A-4. Measured and Predicted Force-Time History, 1990s Design 

Currently, material failure is modeled in many FE analysis packages using a simple 

strain-to-failure criterion. When the total strain on an element reaches a prescribed value, 

that element is removed from the mesh. This approach works well when the principal 

cause of material failure is tension and the extent of material failure is limited. An 

additional concern in modeling failure using this approach is the dependence of predicted 

strain and hence failure with mesh size. The finer the mesh, the greater the accuracy in 

capturing higher strain gradients and higher strain levels. The post-test model used a 

much finer mesh than the original model, and the failure criterion was adjusted based 

upon the stress state and mode of failure. A lower strain-to-failure criterion was used in 

the area where the corner post pulled out of the AT plate. The combination of the finer 

mesh and lower strain-to-failure criterion coupled with the stiffer connection caused the 

post-test model to fail in a manner similar to what was observed in the test. A small 

discrepancy exists in the results; the test measurements show pull out occurring sooner 

and lasting longer than what is predicted in the post-test simulation. 

Figure A-5 shows a comparison of the post-test FE results taken from corresponding 

positions on the corner post and the measured longitudinal displacements taken from 

selected string potentiometers. String potentiometer position varies from bottom to top, 

starting at position 1 and ending at position 5 with the lead letter differentiating the test 

measurement (T) from the analysis result (A). The string potentiometers are 

symmetrically placed to equally divide the corner post between the end beam and the AT 

plate. 

26 
 
20 

15 

10 

ASP3 

TSP3 

ASP4 5 TSP 4 

ASP5 

TSP5 

0 

Time (seconds) 

Figure A-5. Measured and Predicted Longitudinal Displacement-Time Histories on 

the 1990s Design Corner Post 

A detailed discussion of the information presented by TSP3 is given that represents the 

mechanisms occurring for all the string potentiometers. The first slope occurs between 

initial impact and 0.01 s, which corresponds to approximately 2.75 in (69.9 mm) of 

displacement. The second slope range occurs between 0.01 s and 0.09 s and corresponds 

to failure of the lateral member/shelf, as well as pull down of the AT plate. Finally, 

between 0.07 s and 0.09 s, the last slope corresponds to pull out of the corner post from 

the AT plate. This shows the lag time in response from the position of TSP3, TSP4, and 

TSP5. The nearest string potentiometer to the AT plate, TSP5, shows disturbances from 

the AT plate before the further removed string potentiometer, TSP3, shows disturbances. 

The test data has only been plotted to just after failure of the AT plate attachment; data 

past that time is unreliable due to failure of the gauges. 

The maximum measured displacement of the corner post near the point of impact before 

separation of the AT plate attachment, taken from Figure A-5, is approximately 19 in 

(483 mm). Upon pull out, some elastic recovery and post-test measurement show that the 

corner post was permanently deformed by 18.5 in (470 mm). Displacement (inches) 

0.00 0.05 0.10 0.15 0.20 

27 
 
 

Right Side Gauges 

(Left Side) Gauges Near 

Body Bolster 

Figure A-6. Gauge Locations at the End Structure and Under Structure of a 1990s 

Design Carbody 

Measured strain provides information about the load transfer and timing of events. 

Figures A-6 through A-17 show the locations of strain gauges and the measurements 

recorded at these locations. Figure A-6 is a series of photographs of the 1990s design end 

structure and understructure, with squares representing the approximate strain gauge 

locations. 

Figures A-7 and A-8 show the combined results from the strain gauges placed at the base 

as well as at the top of the corner post. The accompanying photograph shows the 

approximate locations of these gauges on the corner post. After initial contact of the coil 

with the corner post, the load built up, reaching a peak around 0.02 s. After that time, the 

central hinge fully forms, and the secondary hinge at the base of the post grows. The 

28 
 
corner post completely pulls out of the AT plate at 0.07 s. After that time frame the post 

is allowed to fully rotate at the corner post—buffer/end beam connection until the coil 

forces the corner post into the back partition wall. The strain gauge information at the 

base of the corner post experienced an initial offset, but the shape of the strain time curve 

is consistent with that obtained from the top of the corner post. Strain (με) 

cortfl cortfr cortrl cortrr 

3000 

2000 

1000 

0 

-1000 

-2000 

-3000 

0.00 0.02 0.04 0.06 0.08 0.1 0 

Time (seconds) 

Figure A-7. 1990s Design Corner Post Strain Gauge Measurements—Top Strain (με) 

corbfl corbfr corbrl corbrr 

3000 

2000 

1000 

0 

-1000 

-2000 

-3000 

0.00	 0.02 0.04 0.06 0.08 0.10 

Time (seconds) 

Figure A-8. 1990s Design Corner Post Strain Gauge Measurements—Bottom 

29 
 
Figures A-9 through A-11 show the information obtained using the strain gauges placed 

on the AT plate. Impact is registered with a slight delay in timing. The first set of peak 

strains occur between 0.01 s and 0.02 s. It is during this time frame that only the post 

deforms. At 0.04 s the AT plate starts to form a hinge at the connection with the 

collision post. The photometric analysis also shows that this time also corresponds with 

the frangible box structure upon which the steel coil rested strikes the buffer/end beam. 

The plastic hinge continues to evolve until the corner post pulls out of the AT plate 

between 0.07 and 0.08 s. The smallest strains measured occurred in the middle of the AT 

plate. 

atprfb atprft atprrb atprrt 

3000 

2000 

1000 

0 

-1000 

-2000 

-3000 

Figure A-9. 1990s Design AT Plate Strain Gauge Measurements—Right Strain (με) 

0.00 0.02 0.04 0.06 0.08 0.10 

Time (seconds) 

30 
 
Strain (με) 3000 

2000 

1000 

0 

-1000 

-2000 

-3000 

atpmfb atpmft atpmrb atpmrt 

0.00 0.02 0.04 0.06 0.08 0.10 

Time (seconds) 

Figure A-10. 1990s Design AT Plate Strain Gauge Measurements—Center Strain (με) 3000 

2000 

1000 

0 

-1000 

-2000 

-3000 

atplfb atplft atplrb atplrt 

0.00 0.02 0.04 0.06 0.08 0.10 

Time (seconds) 

Figure A-11. 1990s Design AT Plate Strain Gauge Measurements—Left 

Figures A-12 through A-14 show the strains measured at the top, middle, and base of the 

collision post. Strains build up upon initial contact with the load first being transferred 

from the lateral member/shelf to the middle of the collision post, then proceeding through 

the AT plate, and finally through the end beam. The end beam is very stiff and acts like a 

31 
 
fixed boundary condition on the corner post, while the AT plate acts more like a 

longitudinally pinned connection with a rotational spring. Between 0.02 and 0.05 s, the 

lateral member shelf experiences a combined tensile and shear load as it tears out of its 

connection to the collision post. The lateral member/shelf completely fails at 0.05 s. 

Load is then only transferred through the AT plate and the buffer/end beam into the 

collision post. The strains are greatest at the base of the collision post due to the long 

moment arm through which the longitudinal load is transferred from the top of the 

collision post through the AT plate. Pull out of the corner post is very apparent in all 

measurements due to the rapid change in slope of the strain between 0.07 and 0.08 s. 

coltfl coltfr coltrl coltrr 

3000
 


2000
 


1000
 


0
 


-1000
 


-2000
 


-3000
 


Figure A-12. 1990s Design Collision Post Strain Gauge Measurements—Top Strain (με) 

0.00 0.02 0.04 0.06 0.08 0.10 

Time (seconds) 

32 
 
Strain (με) 3000 

2000 

1000 

0 

-1000 

-2000 

-3000 

colmfl colmfr colmrl colmrr 

0.00 0.02 0.04 0.06 0.08 0.10 

Time (seconds) 

Figure A-13. 1990s Design Collision Post Strain Gauge Measurements—Middle 

3000 

2000 

1000 

0 

-1000 

-2000 

-3000 

colbfl colbfr colbrl colbrr 

Strain (με) 

0.00 0.02 0.04 0.06 0.08 0.10 

Time (seconds) 

Figure A-14. 1990s Design Collision Post Strain Gauge Measurements—Bottom 

33 
 
Figures A-15 through A-17 show the strain gauge measurements taken on the draft sill 

for the 1990s design. The magnitudes of strains are largest near the point of loading and 

progressively decrease further back into the car structure. The load goes into the draft sill 

as a bending load with compressive strains measured on the side closest to the loading 

point and tensile strains on the opposite side of the draft sill. The load builds up 

gradually to a peak in the first 0.02 s. Pull out of the corner post is again apparent 

because of the rapid change in strain in the same time period as discussed previously. Strain (με) 3000 

2000 

1000 

0 

-1000 

-2000 

-3000 

Right Side Gauges 

(Left Side symmetric) 

dsblf dsbrf dstlf dstrf 

0.00 0.02 0.04 0.06 0.08 0.10 

Time (seconds) 

Figure A-15. 1990s Design Draft Sill Strain Gauge Measurements—Front 

3000 

2000 

1000 

0 

-1000 

-2000 

-3000 

RightSideGauges

(LeftSidesymmetric)

dsblm dsbrm dstlm dstrm 

Strain (με) 

0.00 0.02 0.04 0.06 0.08 0.10 

Time (seconds) 

Figure A-16. 1990s Design Draft Sill Strain Gauge Measurements—Middle 

34 
 
 

3000 

2000 

1000 

0 

-1000 

-2000 

-3000 

Figure A-17. 1990s Design Draft Sill Strain Gauge Measurements—Rear 

Figure A-18 shows three still photographs taken from a high-speed movie film of the 

1990s design grade crossing test. The first frame shows the coil and corner post at the 

instant of impact. The second frame shows the coil and cab car just before complete 

failure by pull out of the corner post from the AT plate at approximately 0.08 s. At this 

time the post has displaced inwards 18 in (457 mm). The third frame shows the coil and 

cab car after 0.09 s and 19 in (483 mm) of displacement of the corner post. Just below 

those three frames are results from the pre-test analysis with material failure for the mode 

shape of the cab car end structure at the same times and nearly the same displacements. 

Gauges Near 

Body Bolster 

dsblr dsbrr dstlr dstrr 

0.00 0.02 0.04 0.06 0.08 0.10 

Time (seconds) 

Strain (με) 

35 
 
 

Figure A-18. Measured and Pre-Test Predicted Mode of Deformation, 1990s 
 

Design, Up to Corner Post Upper Attachment Failure 
 

The predicted deformation mode shape matches that observed in the test but for one 

detail. In the third frame, the frame from the test shows only a small amount of vertical 

distortion of the roof above the upper rear corner of the near-side doorway, while the 

frame from the model predictions shows more distortion of the top of this doorframe. 

This difference in mode may result from the changes in the attachment of the end frame 

to the original car structure, as well as the strain-to-failure criterion used. In addition, the 

difference in length of roof material is not present on the test vehicle. The original model 

integrally attached roof sheeting to the AT plate, which experiences a counterclockwise 

torque as the AT plate is pulled downwards. To maintain compatible deformations, this 

load is reacted above the doorframe where a plastic hinge is formed in the cant rail, the 

roof sheeting, and the hat sections on top of the roof. 

Despite the minor differences discussed between the pre-test, post-test, and test 

measurements, very good agreement exists overall in terms of total energy consumed 

through plastic deformations, as well as modes of deformation and failure. This 

information is then provided as input into the CD models discussed in the next section. 

Further work is currently underway to develop a better engineering failure algorithm that 

can be incorporated into the FE solver. The goal of this work is to be able to account for 

failure in a component by combining not only strain states but the stress states as well 

[11][12]. 

Figure A-19 shows a still photograph taken from the high-speed film. This frame shows 

the failed upper attachment of the corner post. The photograph on the right is a plot of 

the deformed mesh from the revised FE analysis. The coil has been removed for clarity. 

The results of the revised analysis are in close agreement with the test observations. The 

pull out mode of failure has been captured using the model with a refined mesh. A shift 

has occurred in the time it takes for the pull out failure to occur as noted in the string 

potentiometer discussion. 

36 
 
Figure A-19. Measured and Post-Test Predicted Mode of Deformation, 1990s 
 

Design, Corner Post Upper Attachment Failure 
 

SOA Design 

Figure A-20 shows the pre-test predictions for the force-crush characteristic for the SOA 

design. The model was exercised with and without material failure. The model 

predictions with material failure nearly overlay the test results. Similar to the results 

discussed with the 1990s design, a small phase shift occurred in the timing of events. 

The peak load caused by the initial contact occurs almost instantaneously for the FE 

model and is higher than what occurs in the test measurements. As seen from the test 

measurements, a finite rise time occurs for the initial load, and the peak load is smaller. 

In the test measurements and the crush model results, the initial peak is associated with 

the formation of the central plastic hinge on the corner post. The second and third peaks 

with their associated load plateaus correspond to the formation of the plastic hinges at the 

corner post/end beam connection and the corner post/AT plate connection respectively. 

The difference between the crush models with and without failure is apparent after 4 in 

(102 mm) of crush. The model without failure considerably overpredicts the load after 6 

in (152 mm) of crush, but has a similar unloading slope as observed in the test. The 

model with failure predicts slightly higher loads after 7 in (178 mm) of crush, but the 

same maximum crush distance as observed in the test. The rate of unloading predicted 

with the no failure model, however, is slower than observed in the test. 

37 
 
Force (kips) 

300 

250 

200 

150 

100 

50 

0 

Pre-Test W/Failure 

Test Data 

Pre-Test, W/O Failure 

0 6 12 18 24 30 36
 

Crush (inches) 

Figure A-20. Measured and Predicted Force-Crush Characteristic, SOA Design 

Figure A-21 shows the force-time comparison of the test measurements and the crush 

model with failure. The force-time trace from the test was derived using the resultant 

deceleration taken from the nine-accelerometer array on the coil multiplied by the coil 

mass. These results are unfiltered. Despite the minor inconsistencies between the test 

measurements and the crush model results, very good agreement exists. The phase shift 

experienced in the model is not surprising given the simplicity of the failure criterion 

used. In the FE model, when elements fail they are removed from the calculation. When 

too much material is removed, the predicted response in the FE model is softer than the 

response seen in the test. 

300 

Force (kips) 

250
 

200
 

150
 

100
 

50
 

0
 

Test 

Pre-Test Analysis 

Measurement 

0.00 0.05 0.10 0.15 0.20 

Time (seconds) 

Figure A-21. Measured and Predicted Force-Time Histories, SOA Design 

Figure A-22 shows a comparison of the measured string potentiometer longitudinal 

displacement (solid line) with that predicted before the test (dashed line). The crush 

model results reflect the average displacement taken at the centroid of the center element 

at the appropriate height on the corner post. The results presented are for the same string 

potentiometers as discussed in the 1990s design discussion above. Initially, the 

displacements predicted in the crush model are less than those measured in the test at a 

given point in time, which means the response predicted is stiffer. However, when 

failure is predicted to start in the model, the structural stiffness decreases as a result of 

38 
 
too much material being removed during element removal. While the peak predicted 

displacements are larger in the model than predicted by the tests, the unloaded final 

displacements are close. The flat lines at the end of each test result plotted show the final 

position of the post after rebound of the coil has occurred. The test measurement taken at 

the point closest to the point of initial contact is 8 in (203 mm) while that predicted by the 

model is 8.5 in (215 mm). 

20 

TSP3 

ASP3 

TSP4 

15 ASP4 

TSP5 

ASP5 

10 

5 

0 

Time (seconds) 

Figure A-22. Measured and Predicted Longitudinal Displacement-Time Histories 

on SOA Corner Post 

Figure A-23 shows three still photographs taken from a high-speed movie film of the test 

of the SOA design. The first frame shows the coil and corner post at the instant of 

impact; the second frame shows the coil and the cab car after approximately 0.03 s and 

5.25 in (133 mm) rearward displacement of the corner post. The third frame shows the 

coil and the cab car after approximately 0.08 s and 9 in (229 mm) of displacement of the 

corner post. Just below those three frames are results from the pre-test analysis with 

material failure for the mode shape of the cab car end structure at the same times and 

nearly the same displacements. The predicted mode shape closely matches the mode 

shape observed in the test. Slightly more vertical distortion of the roof occurs above the 

upper trailing corner near-side doorway predicted by the model than seen in the test 

result. Similar late changes in the attachment of the end frame to the original car 

structure were made in the SOA design as in the 1990s design; however, the SOA design 

is not as sensitive to these changes, since the corner post was attached to the top and 

bottom plates of the AT plate. The additional strength of the attachment in the SOA 

design forced the AT plate to deform downward, rather than allowing the attachment to 

fail, as it did in the 1990s design. Displacement (inches) 

0.00 0.05 0.10 0.15 0.20 

39 
 
Figure A-23. Measured and Pre-Test Predicted Mode of Deformation, SOA Design 

Despite the minor differences discussed between the pre-test and test measurements, 

overall very good agreement exists in terms of total energy consumed through plastic 

deformations, as well as modes of deformation and failure. This information is then 

provided as input into the CD models discussed in a later section. The next section 

discusses in greater detail the areas that experienced material failure for both sets of tests. 

Material Failure 

As shown in the force-crush characteristics in Figures A-3 and A-20, modeling of 

material failure was necessary for accurate prediction of the force-crush characteristic. 

Material failure occurred at multiple locations in both tests and under a range of stress 

states. Material failure was sufficiently extensive in the test of the 1990s design to allow 

separation of the top of the corner post from its attachment to the AT plate and separation 

of the lateral member/shelf from the corner post. 

In both tests the corner post acted largely as a fixed-pinned beam that is overloaded. A 

plastic hinge formed early in the test near the center of impact. As the test progressed, 

the corner post bent into a V, which put a significant tension load on the corner post. 

Both the upper and lower attachment of the corner post had to support the shear load 

from the coil and the tension load due to the bending of the beam. The end beam did not 

visibly plastically deform, and the floor attachment acted as a fixed connection. The AT 

plate and the cant rail did deform downward, and consequently the roof connection of the 

corner post acted as a pinned connection. Figure 9 in Section 5 shows a post-test 

photograph of the deformed shape of the corner post. 

Material failure occurred in the 1990s end frame design test at the attachment of the 

corner post to the end beam, at the attachment of the corner post to the AT plate, and at 

the attachment of the lateral member/shelf to the corner post. Figure A-24 shows closeups of the material failures at these locations. The left-hand photograph shows the failure 

that occurred at the base of the corner post/end beam connection. As the central hinge in 

the corner post rotated and pushed inwards, large bending and tensile stresses developed 

40 
 
on the top plate of the end beam on the impact side, while large bending and compressive 

stresses devolved on the aft side of the connection. The failure of the top plate is in the 

parent material of the sheet just outside the weld, effectively in the heat-affected zone. 

The photograph in the center shows the top of the corner post, which pulled out of the AT 

plate during the collision. The stress state to cause this failure mode was almost a pure 

state of shear. The right side photograph shows the attachment of the lateral 

member/shelf to the collision post. This connection failed due to the combination of 

bending and shear. 

Figure A-24. Post-Test Photographs of Material Failure in 1990s Design, Corner 
 

Post Connection to End Beam, Failed Connection at Top of Corner Post, and Failed 
 

Connection to Shelf on Collision Post 
 

Material failure occurred in the SOA end frame design test at the connection of the corner 

post to the end beam, at the attachment of the AT plate to the cant rail, and at the 

attachment of the lateral member/shelf to the corner post. Figure A-25 shows 

photographs of the material failure at these locations. As the central plastic hinge rotated 

and displaced inwards, large tensile and bending stresses developed on the impacting side 

of the corner post at its connection with the end beam, while large bending and 

compressive stresses developed on the aft side of the corner post. Unlike the failure 

mode experienced by the 1990s end frame design, this time the parent material in the 

corner post, rather than the end beam failed. The failure progressed nearly the full depth 

of the post. No upward bending in the end beam occurred in the upper flange because 

this design had the corner post penetrating through both the upper and lower flanges of 

the end beam, and the end beam was reinforced by the closed side sill that extended all 

the way forward from the aft operator’s compartment wall. The necking/cup-cone 

deformations present on the pulled-out post and the in-situ post are indicative of a tensile 

failure that then proceeded to open further as a result of the combined tension and 

bending. The material failure that occurred at the AT connection with the cant rail was in 

the region of a weld. This failure mode was caused by the rotation of the AT plate as the 

central hinge displaced inwards, and a prying load ensued between the AT pad 

connection point and the cant rail. Finally, the last area with material failure is at the 

connection point of the bulkhead sheet with the lateral member/shelf and the collision 

post. As the coil penetrated inwards during the collision, the bulkhead sheet and the 

lateral member/shelf transmitted load to the collision post. Large tensile and shear 

stresses developed at this connection point. The failure proceeded from the outside 

inwards and downwards between the collision post and bulkhead sheet weld. 

41 
 
Figure A-25. Post-Test Photographs of Material Failure in SOA Design, Corner 
 

Post Connection to End Beam, AT Plate Connection to Roof Plate, and Shelf 
 

Connection to Collision Post 
 

As described earlier, currently material failure is modeled in many FE analysis packages 

using a simple strain-to-failure criterion. When the total strain on an element reaches an 

input value, that element is removed from the mesh. This approach works well when the 

principal cause of material failure is tension and the extent of material failure is limited. 

Limitations of the current approach to modeling material failure include that materials 

fail at different strains in tension, compression, and shear [11], and that once material 

failure has initiated, lower strain is needed to propagate the failure [13]. 

Sophisticated application of current FE analysis packages allow these limitations to be 

overcome to some degree. By first running the model without material failure, the areas 

of high strain and potential material failure can be found. The model can then be run 

again with the parameters associated with material failure adjusted to account for the 

stress state of the high-strain areas. If the three-dimensional stress state of two or more 

high-strain areas substantially differs (for example, one in tension and one in 

compression), then the model can be substructured and different material-failure 

parameters applied to each substructure. An effort is currently underway to better 

understand material failure under a wide range of strain states and to develop algorithms 

that more accurately predict material failure [12]. 

A.3. Collision Dynamics Model 

CD models were created using ADAMS software [11] to evaluate the collision results. 

This three-dimensional model predicts the crush of the cab car and the three-dimensional 

motions of the coil and the cab car. 

The CD model is a lumped-mass representation of the cab car and the steel coil. As 

shown in Figure A-26, the model consists of a series of masses connected by nonlinear 

springs. The longitudinal springs use the force-crush characteristic obtained from an FE 

model, which simulates the crush behavior of the end structure. Set with the appropriate 

initial conditions, the CD model provides the gross motions of the cab car and the coil 

and the amount of deformation at the impacting end of the cab car. The lateral deflection 

of the coil is modeled in a similar manner as the CD model, developed for analyzing an 

42 
 
oblique collision of a locomotive with a container, which in turn evolved from the CD 

model developed for analyzing an oblique collision of a locomotive-led consist with a 

cab car-led consist [14]. 

V
 

Figure A-26. Schematic of Lumped-Mass CD Model 

Modeling Parameters 

As shown in Figure A-26, the impacting end of the passenger car is joined to the main 

body by two springs, each representing half the symmetric structural behavior of the 

carbody end. These characteristics are defined by nonlinear characteristics that are 

derived from the FE model. 

In the model, a spherical rigid body represents the steel coil. When the colliding bodies 

try to penetrate each other, the contact force is modeled by an impact element that uses a 

compression-only, nonlinear spring-damper function to calculate the resultant collision 

force. The impact stiffness and damping coefficients are 1.0E+06 lb/ft and 2.0E+04 lb-s/ft, 

respectively. 

The truck elements account for the wheel to rail interaction. They allow for both vertical 

and lateral forces with the ground. Accordingly, spring-damper elements are used 

between the truck and carbody to represent the secondary suspension. 

The mass properties for the carbody and coil in the model are defined as shown in Tables 

A-1 and A-2. 

Table A-1. Vehicle Mass Properties 

Property 1990s 

Carbody 

SOA 

Carbody 

Truck Corner 

Post 

Mass (lbm) 33,800 35,018 12,000 250 

Centroidal Roll 

(lbm-ft2

) 

9.68E+05 9.68E+05 3.55E+04 8.16E+02 

Centroidal Pitch 

(lbm-ft2

) 

2.22E+07 2.22E+07 1.08E+05 8.16E+02 

Centroidal Yaw 

(lbm-ft2

) 

2.25E+07 2.25E+07 9.28E+04 8.16E+02 

Table A-2. Steel Coil Mass Properties 

Property Coil 

Mass (lbm) 41,300 

Axial Inertia (lbm-ft2

) 2.25E+05 

Transverse Inertia (lbm-ft2

) 1.60E+05 

43 
 
Force-Crush Behavior 

The combined results of the FE and CD models provide the predictions necessary to 

create a focused full-scale test. The FE model established the limits within which the 

collision must occur. The CD model used the force-crush curves from the FE model 

before the test to estimate the corresponding collision speeds bounded by the desired 

deformation. The curves were entered into the CD model as the non-linear force-crush 

characteristics of the specific end structures. The CD model was used to estimate the 

extent of crush of the cab car as a function of the impact velocity. 

Following the full-scale test, the force-crush characteristics input into the CD model can 

be updated with the test measurements. The pre-test prediction for the 1990s cab car 

force-crush characteristic proved accurate up to about 12 in (305 mm). After this point in 

the full-scale test, the corner post pulled out of its upper attachment at the AT plate. 

After the test, the input for the 1990s CD model was updated with force-crush from the 

processed test data. With this one change, the 1990s model results compare closely with 

the test results for the amount of cab car crush and for the gross motions of the cab car 

and coil. The SOA cab car test went nearly exactly as simulated, with approximately 9 in 

(229 mm) of longitudinal deformation occurring in the corner post. Consequently, the 

input to the SOA CD model did not require post-test changes. Figures A-27 and A-28 

show the pre-test and post-test force-crush curves. 

300 

Without Material Failure 

With Material Failure 

250 Post-Test 

200 

150 

100 

50 

0 

Crush (inches) 

Figure A-27. 1990s Force-Crush Characteristics Force (kips) 

0 6 12 18 24 30 36
 


44 
 
300 Without Material Failure 

With Material Failure 

250 

200 

150 

100 

50 

0 

Crush (inches) 

Figure A-28. SOA Force-Crush Characteristics 

Gross Motions 

During both tests, the cab cars impacted the heavy object, demolished the frangible table, 

and continued along the track at a decreasing velocity. In the 1990s cab car impact test, 

the impact of the heavy object broke through the corner post. The steel coil became 

momentarily embedded in the end structure and then fell beside the cab car. During the 

SOA cab car collision, the impact of the steel coil caused about 9 in (229 mm) of 

longitudinal deformation in the corner post, after which the coil fell from the cab car onto 

the track. During the impacts, when the coil and the car were in contact, the lateral and 

vertical displacements of the coil and the car were small—less than 1 in (25.4 mm). The 

yaw displacements of the coil, as it deflected from the cab car, were significant in both 

tests—approximately 19 degrees for the 1990s cab car test and 4 degrees for the SOA cab 

car test. With the revised input force-crush characteristic, the predictions of the CD 

model with the 1990s design end structure are in close agreement with the test 

measurements, including the yaw of the coil. The predictions of the CD model of the test 

of the cab car with the SOA end frame are also in close agreement with the test 

measurements. 

The deceleration records for the two impact tests are displayed in Figures A-29 and A-30, 

plotted with corresponding data from the CD model. While in contact, the coil and the 

carbody acceleration histories are essentially mirrors of each other, scaled according to 

weight. 

Force (kips) 

0 6 12 18 24 30 36 

45 
 
Acceleration (Gs) -8 

-6 

-4 

-2 

0 

2 

4 

6 

8 Coil Measurement 

Coil Analysis 

Cab Car Measurement 

Cab Car Analysis Coil 

Cab Car 

0.00 0.05 0.10 0.15 0.20 0.25 0.30 

Figure A-29. Longitudinal Decelerations of 1990s Cab Car 

8 

Acceleration (Gs) 6 

4 

2 

0 

-2 

-4 

-6 

-8 

Coil 

Coil Coil 

Cab Car 

Cab Car 

Cab Car 

0.00	 0.05 0.10 0.15 0.20 0.25 0.30 

Time 

Figure A-30. Longitudinal Decelerations of SOA Cab Car 

The cab car that had been modified with the 1990s end structure had previously been 
 

used in the single car full-scale test [15], and the cab car that had been modified with the 
 

SOA end frame had been the lead car in the two-car full-scale impact test [16]. Since the 
 

back ends of both cars were open during the grade crossing tests, the body shells were 
 

relatively free to vibrate. As a result, the cab car data had to be filtered with a lower 
 

bandwidth filter. The cab car data was filtered with a CFC 15 filter, while the coil data 
 

was filtered with a CFC 60 filter [17]. The CFC 15 filtering resulted in less than 1 
 

percent error in the displacement of the cab car as integrated from the accelerometer data, 
 

for both tests [18]. 
 

The CD model reproduces the test longitudinal carbody accelerations very closely. It 

captures the initial peak deceleration due to impact followed by a reasonable estimate of 

the carbody motions. From Figures A-21 and A-22 above, it is apparent that the data 

extracted from the coil instrumentation has significantly less noise than the carbody 

46 
 
bodies come to a constant velocity. 

16 

Coil Measurement 

14 

Cab Car Coil Analysis 

Cab Car Measurement 

12 Cab Car Analysis 

10

(mph) 

8 

6

Velocity 

4 

2 Coil 

0 

instrumentation. Consequently, the coil acts effectively as a force transducer for 

comparison and revision of test data with the model results. 

The difference between the 1990s and SOA designs is evident in these results. The SOA 

design displays higher accelerations due to the increased strength of the end structure 

required by the revised 1999 APTA standards. The 1990s design receives lower 

accelerations over a longer time period, indicative of the prolonged deformation. The 

failure is seen in the drop off of acceleration at around 0.1 s, as the corner post gives way 

and briefly looses contact with the coil. 

The raw accelerometer data was integrated to produce the velocity-time histories. 

Figures A-31 and A-32 show the comparison of the model results to the test data. The 

CD models accurately predict the gradient of speed and final time at which the colliding 

Time (seconds) 

Figure A-31. Velocity-Time History of 1990s Cab Car 

0.00 0.05 0.10 0.15 0.20 0.25 0.30 

47 
 
Velocity (mph) 

16 

14 

12 

10 

8 

6 

4 

2
 

0 

Coil Measurement 

Cab Car Cab 

Coil Analysis 

 Car Measurement 

Cab Car Analysis 

Coil 

0.00 0.05 0.10 0.15 0.20 0.25 0.30 

Time (seconds) 

Figure A-32. Velocity-Time History of SOA Cab Car 

In both collisions the trains arrive at a post-impact velocity of about 8 mph (12.8 km/h). 

The SOA cab car impact takes approximately half the time of the 1990s cab car impact to 

reach this constant velocity due to the increased stiffness of the SOA design. 

Accelerometers measuring lateral and vertical carbody motions were analyzed, and these 

motions were found to be negligible. The lateral and vertical displacements of the cab 

car and coil were all less than 1 in (25 mm) while they were in contact, for both tests. 

Peak lateral carbody accelerations ranged from 2-3 Gs in the first 0.03 s and are primarily 

attributed to the initial impact of the heavy object at the corner, causing a slight moment 

about the train’s center of mass. While these lateral forces were identified to be of a 

characteristic pattern seen in larger scale collisions in which derailment occurred, the 

magnitude of the lateral forces was well below a state of concern [19]. After initial 

impact, lateral accelerations were less than 1 G. 

The CD model also accurately predicts the yaw of the coil. Figures A-33 and A-34 show 

comparisons of the coil’s rotational acceleration about the vertical axis. The coil yaw 

acceleration is reflective of the pattern of the contact force. In the 1990s cab car test, the 

coil shows a peak rotational acceleration of about 22 radians per second squared. The 

CD model predicts a yaw acceleration of about 20 radians per second squared. The 

second significant peak, occurring at about 0.2 s, shows when the coil breaks through the 

corner post and impacts the passenger compartment wall. This second peak in the yaw 

acceleration occurs because the contact point on the coil is different for the rear of the 

doorframe than it is for the corner post. The CD model currently does not account for 

this shift, although it could be modified. The SOA cab car comparison shows that the CD 

model follows the slope of the test data very precisely. Double integrating the test data 

produces a final rotational displacement of about 20 degrees. The still shots shown in 

Figure A-35 depict general visual agreement with the position of the rotated coil. 

48 
 
Yaw Accelerations (radians/second ) 2 

-50 

0 

50 

100 

150 

Analysis 

Test 

0.00	 0.05 0.10 0.15 0.20 0.25 0.30 

Time (seconds) 

Figure A-33. Comparison of Coil Yaw Acceleration, 1990s Cab Car Impact, Test 
 

Data, and Analysis Results 
 

Yaw Accelerations (radians/second ) 2 

-50 

0 

50 

100 

150 

Test 

Analysis 

0.00	 0.05 0.10 0.15 0.20 0.25 0.30 

Time (seconds) 

Figure A-34. Comparison of Coil Yaw Acceleration, SOA Cab Car Impact, Test 
 

Data, and Analysis Results 
 

49 
 
Figure A-35. Still Photographs of CD Simulation and 1990s Full-Scale Test 

The CD models estimated the gross motions of the objects with relative accuracy. Figure 

A-35 shows still shots from an overhead view of the CD simulation in comparison with 

the high-speed camera of the 1990s full-scale collision. The pictures show the position at 

which the coil: 

•	 Initially impacts the train (indicated by the flash of lights on the side of the 

passenger car) 

•	 Breaks through the corner post 

•	 Impacts the cab wall 

A.4. Processing of Test Data 

All post-processing of test data follows the recommendations of SAE J211-1, 

Instrumentation for Impact Tests [17]. The objective of post-processing the data is to 

correct time relative to initial collision impact, scale, and filter data, and to perform 

mathematical operations required to produce the results needed to compare test 

measurements to model predictions. 

The raw data collected from the accelerometers is processed in multiple ways to provide 

the most useful comparisons. The sum of the mass times the acceleration-time histories 

of the colliding bodies yields the active collision force. This gives a reasonable estimate 

of the contact force predicted by the CD models. 

The accelerometer data is also used directly to analyze the gross motions of the colliding 

bodies. The acceleration-time histories are integrated to acquire the velocity and 

50 
 
 

 

 

 

 

 

 

 

displacement records. The impacting force-time history can then be plotted against the 

displacement, showing the force required to crush the end structure. 

The raw accelerometer data recorded a noisy signal of the carbody’s motion. To make 

reasonable comparisons of acceleration-time histories, the data is filtered to extricate 

some of the high frequency content caused by the suspension, structural connections, and 

accelerometer attachments. The filtered data shows the motion of the train as a rigid 

body. This data is compared to the motions produced by the CD models. Figure A-36 

shows the filtering process implemented. 

Acceleration 

Data 

Butterworth 

4-Pole Phaseless 
 

Digital Filter at 
 

180 Hz 
 

(from SAE J211-1)
 


Butterworth
 

4-Pole Phaseless 
 

Digital Filter at 
 

180 Hz 
 

(from SAE J211-1) 
 

Integration of 

Acceleration 

to Velocity Using 

Trapezoidal Integration 

Integration of 

Velocity to 

Displacement Using 

Trapezoidal Integration 

Acceleration 

Time-Trace 

Force 

Time-Trace 

Occupant 

Environment 

Velocity 

Time-Trace 

Displacement 

Time-Trace 

Figure A-36. Post-Processing Flowchart 

The filtering process was guided by the recommendations of SAE J211-1, as well as the 

post-processing practices exercised in previous full-scale rail vehicle experiments. SAE 

J211-1 recommends frequency response classes for recording various components of fullscale data. A CFC 60 Butterworth 4-pole phaseless digital filter was used on the coil 

accelerometer data, and a CFC 15 filter was used on the carbody accelerometer data. 

A representative accelerometer was determined to be located at the front side of impact 

on the draft sill. This location provided the most useful data because it was at the front of 

the train near the impact but behind the end structure and area of crush. Accelerometers 

located towards the rear of the train not only have a time delay in their signal but 

provided noisier data because of the greater influence of the rear end of the carbody, 

which did not have an end structure. 

51 
 
Post-processing of strain gauges and string potentiometers includes filtering and plotting 

for comparisons and checks of valid results. Post-test analysis of the high-speed film is 

valuable to document vehicle displacements for comparison with integrated 

accelerometer data and with model results. 

52 
 
Appendix B. 
 

Test Requirements 
 

B.1. Test Requirements 

The following is taken from the draft specifications for a Cab Car End Structure, Volpe: 

Development of Conventional Passenger Cab Car End Structure Designs for Full-Scale 

Testing, 74431-S-001a, 20 June 2001. 

•	 General. The vehicle ends designed and built to this specification 
 

will be used for full-scale testing. Therefore, it is important that
 


the design facilitate measurements and observations to be made
 


during the tests. The types of tests envisioned include: a) a single 
 

vehicle colliding with an object representing a grade crossing
 


obstacle; b) a multiple vehicle consist colliding with the rigid 
 

surface; and c) a multiple vehicle consist colliding with a grade
 


crossing obstacle. The tests will be conducted at TTC in Pueblo,
 


Colorado. 
 

•	 Visibility. The vehicle end shall be designed in such a way that it 
 

will be possible to view the collision and corner posts during crush
 


deformation in the test. For example, parts of the roof and sides 
 

must remain open to facilitate viewing by cameras mounted on the 
 

ground or on the vehicle. 
 

B.2. Test Instrumentation 

The primary objectives of the grade crossing impact test instrumentation are to record the 

gross motions of the colliding bodies with sufficient accuracy to analyze and compare the 

data with model predictions. This is accomplished by instrumenting the cab car and coil 

with accelerometers, string potentiometers, and strain gauges, to record, respectively, 

structural accelerations, corner post and suspension displacements, and material strains to 

define the load path. 

SAE J211-1 provides general guidelines for all data acquisition [17]. For the 1990s test, 

120 data channels were required for the instrumentation. There were 52 accelerometers, 

9 string potentiometers, and 80 strain gauges. For the SOA design, 132 channels were 

required for the instrumentation. There were 52 total accelerometers, 9 string 

potentiometers, and 92 strain gauges. Data was recorded at a sampling rate of 

approximately 8000 Hz. There was 1 second of pre-trigger data collection and 7 s of 

post-trigger data collection. A closure switch, located on the front of the impacting car, 

marked all the data with a reference point indicating the point of impact in each record. 

53 
 
Accelerometers are used to measure the carbody gross motions in three dimensions, as 

well as the pitch, yaw, and roll. Figure B-1 shows accelerometer locations. 

Accelerometers placed throughout the carbody also capture the bending and twisting 

about the carbody axis. All longitudinal accelerometers had a range of 200-1000 Gs, 

vertical accelerometers had a range of 100-400 Gs, and most lateral accelerometers were 

200 Gs. 

Roof AcceleroAccelerometers

TR-4 TR-3 TR-2 TR-1 

TL4- TL-3 TL-2 TL-1 

Floor Accele Floor Accelerometers

R-4 R-3 R 2- R-1 

C C 2- -4 C-3 

L-1 

L-4 L-3 -L 2

Three- -Axis Accelerometer

Single- -Axis (vertical) 

Single- -Axis (longitudinal) 

Figure B-1. Accelerometer Locations on Cab Car 

Nine accelerometers were placed on the steel coil as shown in Figure B-2. All 

accelerometers had a range of 400 Gs. The following nine-array accelerometer 

configuration is used to provide a collection of data based on the local coordinate system 

of the coil [20]. This allows for the translational and rotational motions to be precisely 

measured. 

54 
 
Vertical

Lateral Lateral

AZ2

AX2

AY1

AZ1

A AY3 X3

AY0 AX0

AZ0

Lateral Lateral

AZ2

AX2

AY1

AZ1

A AY3 X3

AY0 AX0 

AZ0

Longitudinal

Two-Axis Accelerometer 

Three-Axis Accelerometer 

Figure B-2. Accelerometer Locations on Heavy Object 

Nine string potentiometers were used in each test. Four string potentiometers were 

located on the passenger car between the body bolster and truck bolster to measure the 

relative vertical displacement of the suspension. Five string potentiometers were located 

on the corner post to measure its longitudinal deflection. Figures B-3 and B-4 show the 

locations and lengths of these displacement transducers relative to the corner post and the 

cab wall. 

13 1⁄4”

30 1⁄4”

30 3/16”

30 7/16”

31 1/8”

31 1⁄4”

121 1⁄4”

103 1⁄2”

85 3⁄4”

68 1⁄4”

51”

Vert Dist to TOR

47 5/8”

13 1⁄4” 

30 1⁄4” 

30 3/16” 

30 7/16” 

31 1/8” 

31 1⁄4” 

121 1⁄4” 

103 1⁄2” 

85 3⁄4” 

68 1⁄4” 

51” 

Vert Dist to TOR 

47 5/8” 

Figure B-3. String Potentiometer Locations of 1990s Design 

55 
 
13 3/8”

30 7/8”

31 3/16”

31”

31 1/2”

31”

120 1/2”

102 3/4”

85”

67”

49 3/4”

Vert Dist to TOR

13 3/8” 

30 7/8” 

31 3/16” 

31” 

31 1/2” 

31” 

120 1/2” 

102 3/4” 

85” 

67” 

49 3/4” 

Vert Dist to TOR 

Figure B-4. String Potentiometer Locations of SOA Design 

Strain gauges were used to determine the load path into the structure and to ascertain the 

timing of events for failure of components. The 1990s end frame design was 

instrumented with 80 uniaxial strain gauges, while the SOA end frame was instrumented 

with 92 uniaxial strain gauges. The structural elements of interest and the number of 

strain gauges placed on each component follow: 

•	 The cant rail at the impact end of the cab car (12 uniaxial strain gauges). 

•	 The draft/center sill at the impact end of the cab car (12 uniaxial strain gauges). 

•	 The corner post (12 uniaxial strain gauges). 

•	 The collision post (12 uniaxial strain gauges). 

•	 The buffer/end beam (8 uniaxial strain gauges). 

•	 The AT plate (12 uniaxial strain gauges). 

•	 The lateral member/shelf below the window frame (12 uniaxial strain gauges). 

•	 For the SOA design, 12 extra strain gauges will be required on the side sill that 

extends from the body bolster and connects with the buffer beam. 

Figure B-5 shows schematically the locations of the strain gauges placed on the SOA 

design, which was retrofitted onto a Budd Pioneer cab car. Figure B-6 shows 

schematically the locations of the strain gauges placed on the 1990s design, which was 

also retrofitted onto a Budd Pioneer cab car. As the two figures show, the strain gauges 

were placed similarly on both the 1990s and SOA end frames to compare the way the 

load transfers through the end frame back into the rest of the vehicle. 

Figure B-7 shows a photograph with the locations of strain gauges used on the 1990s end 

frame design. Two sets of strain gauges were used, and they are displayed in different 

colors in the photograph. All strain gauges shown were used for a series of quasistatic 

tests conducted to verify compliance of the end frame designs and supporting structure 

against the design requirements discussed in [4]. Only gauges shown by rectangles in the 

photograph were used for the dynamics impact test. 

56 
 
SOA End Frame SOA End Frame 

Figure B-5. Schematic of Strain Gauge Placement on SOA End Frame Design 

57 
 
Circa 1990s Design
 


Figure B-6. Schematic of Strain Gauge Placement on 1990s End Frame Design 

58 
 
Figure B-7. Strain Gauges on 1990s End Frame Design 

Eight high-speed cameras and four video cameras were used to record the impact from 

the following different angles: side-of-impact view of entire train, two side views 

focused on impact zone, head-on view, opposite side-of-impact angled view of front end, 

overhead view (camera located on a boom), and two onboard cameras (did not survive 

collisions). Figure B-8 shows placement of these cameras. The exterior high-speed 

cameras filmed at 300 frames per second, and the interior cameras filmed at 500 frames 

per second. Upon impact, contact switches, located on the coil and corner post, triggered 

flashes of light. 

59 
 
Figure B-8. Schematic Layout of High-Speed Camera Locations 

Reflective 4-in diameter targets, placed on the end structure, facilitate photometric 

analysis of the film. The longitudinal and vertical coordinates of each target are 

identified with frame-by-frame grid analysis, and the speeds and location of the specific 

elements are then calculated. 

60 
 
References 

1.	 American Public Transportation Association, Member Services Department, Manual 

of Standards and Recommended Practices for Passenger Rail Equipment, Issue of 

July 1, 1999. 

2.	 U.S. Department of Transportation, Federal Railroad Administration, “49 CFR Part 
 

216 et al., Passenger Equipment Safety Standards; Final Rule,” Federal Register, 
 

May 12, 1999. 
 

3.	 Penrose, R., The Emperor’s New Mind: Concerning Computers, Minds, and the 
 

Laws of Physics (New York: Penguin Books, 1991). 
 

4.	 Mayville, R., Stringfellow, R., and Martinez, E., “Development of Conventional Cab 

Car End Structure Designs For Full Scale Testing,” U.S. Department of 

Transportation, to be published. 

5.	 Martinez, E., Tyrell, D., and Zolock, J., “Rail-Car Impact Tests with Steel Coil: Car 

Crush,” American Society of Mechanical Engineers, Paper No. JRC2003-1656, April 

2003. 

6.	 Jacobsen, K., Tyrell, D., and Perlman, A.B., “Rail-Car Impact Tests with Steel Coil: 

Collision Dynamics” American Society of Mechanical Engineers, Paper No. 

JRC2003-1655, April 2003. 

7.	 National Transportation Safety Board, “Collision of Reading Company Commuter 
 

Train and Tractor-Semitrailer, Near Yardley Pennsylvania, June 5, 1975,” RAR-76-

4, March 3, 1976. 
 

8.	 National Transportation Safety Board, “Collision of Northern Indiana Commuter 
 

Transportation District Train 102 with a Tractor-Trailer Portage, Indiana June 18, 
 

1998,”RAR-99-03, July 26, 1999. 
 

9.	 White, J.H., Jr., The American Railroad Passenger Car (Baltimore: The Johns 
 

Hopkins University Press, 1978). 
 

10.	 ABAQUS/Explicit Users Manual, Version 5.8, 1998, Hibbitt, Karlsson and Sorenson, 

Inc. 

11.	 ADAMS, Version 12.0.0, Mechanical Dynamics, Inc. Ann Arbor, Michigan. 

12. Bao, Y., and Wierzbicki, T., “Determination of Fracture Locus for the 2024T351 

Aluminum,” Impact and Crashworthiness Laboratory, Report No. 81, May 2002. 

13. Bao, Y., and Wierzbicki, T., “Comparative Study of Fracture Criteria: Part II–Finite 

Element Analysis,” Impact and Crashworthiness Laboratory, Report No. 67, 

November 2001. 

14. Tyrell, D., Severson, K., Marquis, B., and Perlman, A.B., “Simulation of an Oblique 

Collision of a Locomotive and an Intermodal Container,” Crashworthiness, 

Occupant Protection and Biomechanics in Transportation Systems, American 

Society of Mechanical Engineers, AMD Vol. 237/BED Vol. 45, 1999. 

61 
 
15. Tyrell, D., Severson, K., and Perlman, A.B., “Single Passenger Rail Car Impact Test 

Volume I: Overview and Selected Results,” U.S. Department of Transportation, 

DOT/FRA/ORD-00/02.1, March 2000. 

16. Tyrell, D., Severson, K., and Perlman, A.B., “Passenger Rail Two-Car Impact Test 

Volume I: Overview and Selected Results,” U.S. Department of Transportation, 

DOT/FRA/ORD-01/22.I, January 2002. 

17. Society of Automotive Engineers, “Surface Vehicle Recommended Practices– 

Instrumentation for Impact Test,” SAE J211-1, March 1995. 

18. Severson, K., Tyrell, D., and Perlman, A.B., “Rail Passenger Equipment Collision 

Tests: Analysis of Structural Measurements,” Rail Transportation, American Society 

of Mechanical Engineers, RTD-Vol. 19, 2000. 

19. Blader, F.B., 1989, “A Review of Literature and Methodologies in the Study of 

Derailments Caused by Excessive Forces at the Wheel/Rail Interface,” Association 

of American Railroads, Research and Test Department, Report No. R-717. 

20. Lee, H., Plank, G., Weinstock, H., and Coltman, M., Methodology for the 

Calibration of the Data Acquisition with a Six Degree-of-Freedom Acceleration 

Measurement Device, DOT-TSC-NHTSA-88-03, U.S. Department of 

Transportation, Transportation Systems Center, 1989. 

62 
 
Acronyms 

AAR Association of American Railroads 

APTA American Public Transportation Association 

AT anti-telescoping 

C&S Construction and Structural 

CD collision dynamics 

CEO Corporate Executive Officer 

CFC Collision Frequency Class 

FE finite element 

FRA Federal Railroad Administration 

PRESS Passenger Rail Equipment Safety Standards 

SAE Society of Automotive Engineers 

SOA state-of-the-art 

TTC Transportation Technology Center 

63