U.S. Department 

of Transportation

Federal Railroad 

Administration

Preview Information in Cab Displays for 

High-Speed Locomotives

Office of Research 

and Development 

Washington, DC 20590

U.S. Department of Transportation 

Research and Special Programs Administration 

John A. Volpe National Transportation Systems Center 

Cambridge, MA 02142

Human Factors in Railroad Operations

DOT/FRA/ORD-04/12 Final Report 

July 2005 

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public through the National Technical 

 Information Service, Springfield, VA 22161 

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4. TITLE AND SUBTITLE

Preview Information in Cab Displays for High-Speed Locomotives

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6. AUTHOR(S)

Jay Einhorn, Thomas Sheridan, and Jordan Multer 

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

U.S. Department of Transportation 

Research and Special Programs Administration 

John A. Volpe National Transportation Systems Center 

Cambridge, MA 02142-1093 

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Safety of High-Speed Ground Transportation Systems series 

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13. ABSTRACT (Maximum 200 words) 

This research examined the usefulness of preview information in the control of high-speed trains. Experiments were run on a 

human-in-the-loop locomotive simulator. The primary goal was to examine whether the proposed information-aiding displays 

improved safety and efficiency of train operation over an existing display. Safety was measured by monitoring speed control, signal 

adherence, and reaction time. Efficiency was measured by monitoring stopping accuracy and schedule deviation. 

Locomotive engineers and student participants performed similarly with respect to signal adherence and speed control. Preview 

information was useful in both cases; Longer preview and variable preview displays provided the best results. The preview displays 

were detrimental to accurate station-stopping, as the displays provided an inadequate level of resolution to stop accurately. 

Although the locomotive engineers responded favorably to the preview displays, further work is needed to determine how the 

engineer allocates attention between information in the cab and information outside the cab.

14. SUBJECT TERMS

attention allocation, automation, high-speed trains, human-in-the-loop simulation, intelligent 

railroad systems, situation awareness, supervisory control 

15. NUMBER OF PAGES

60 

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ABSTRACT
METRIC/ENGLISH CONVERSION FACTORS 

ENGLISH TO METRIC METRIC TO ENGLISH

LENGTH (APPROXIMATE) LENGTH (APPROXIMATE) 

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

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

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

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

1 kilometer (km) = 0.6 mile (mi)

AREA (APPROXIMATE) AREA (APPROXIMATE) 

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

(cm2

) 

1 square centimeter (cm2

) = 0.16 square inch (sq in, in2) 

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

yd2

) 

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

1 square mile (sq mi, mi2) = 2.6 square kilometers 

(km2

) 

10,000 square meters (m2

) = 1 hectare (ha) = 2.5 acres 

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

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

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

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

1 short ton = 2,000 pounds 

(lb) 

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

=

1,000 kilograms (kg) 

1.1 short tons

VOLUME (APPROXIMATE) VOLUME (APPROXIMATE) 

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

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

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

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

1 pint (pt) = 0.47 liter (l) 

 1 quart (qt) = 0.96 liter (l) 

1 gallon (gal) = 3.8 liters (l) 

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

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

TEMPERATURE (EXACT) TEMPERATURE (EXACT) 

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

QUICK INCH - CENTIMETER LENGTH CONVERSION

0 1 2 3 4

Inches

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

5

3

QUICK FAHRENHEIT - CELSIUS TEMPERATURE CONVERSION

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

 

°F

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

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

ii
PREFACE 

This research was performed as part of an ongoing program at the U. S. Department of 

Transportation's John A. Volpe National Transportation Systems Center (Volpe Center) in 

collaboration with the Human-Machine Systems Laboratory (HMSL) of the Massachusetts 

Institute of Technology (MIT). The Federal Railroad Administration’s (FRA) Office of Research 

and Development sponsored this study as part of its effort to support the safe and efficient 

operation of high-speed ground transportation. 

As vehicle speed increases, the limits of human information processing remains fixed. High 

speeds increase the processing demand per unit time on the locomotive engineer, while also 

decreasing the available response time. One approach to this dilemma is to give the locomotive 

engineer information about the status of the upcoming track earlier in time. This report addresses 

whether preview information is helpful with regard to safe and efficient train operations. 

iii
ACKNOWLEDGMENTS 

This report is the result of many people’s labor. We would like to thank Kari Kulaszewicz for 

her help and good nature; Steven Villareal for his help with the sound generation and the 

building of the locomotive cab; John Pollard for his help with many different aspects of the 

simulation, and Frank Sheelen for his technical expertise. Dr. Ed Lanzilotta wrote much of the 

code that the MIT/Volpe locomotive simulator is based on, and his guidance and effort will serve 

as a reminder of how people of faith and wisdom should act. 

Many people from the railroads and locomotive manufacturers shared their knowledge and frank 

opinions with us. We thank Masahiko Horiuchi of East Japan Railway Company; Dick Bruss, 

Ron Berben, and Pat Kelley of Amtrak; Daniel Metaut and Philippe Mingasson of Alsthom; 

Bengt Lindwall of AdTranz; Howard Moody of the Association of American Railroads; and 

George Kuehn of the Illinois Institute of Technology Research Institute. 

I would particularly like to acknowledge Steven Jones and Joe Arcuri of Amtrak for their help in 

finding locomotive engineers to participate. The participants themselves are owed a deep debt of 

gratitude for giving up their days off to help us with our work. 

The Federal Railroad Administration sponsored this work as part of its activities to develop 

Intelligent Railroad Systems (Federal Railroad Administration, 2002). 

iv
LIST OF ACRONYMS 

AAR – Association of American Railroads 

ARES – Advanced Railroad Electronics System

ATC – Automatic Train Control 

ATCS – Advanced Train Control System

ATP – Automatic Train Protection 

BN – Burlington Northern Railroad (predecessor to BNSF) 

BNSF – Burlington Northern Santa Fe Railroad 

CIR – Computer Integrated Railroading 

DB – Deutsche Bahn (German Railways) 

FRA – Federal Railroad Administration 

GE – General Electric 

GM – General Motors 

HMSL – Human-Machine Systems Laboratory 

ICE – Inter-City Express 

ITCS – Incremental Train Control System

JR – Japan Rail 

MIT – Massachusetts Institute of Technology 

OTW – Out-The-Window 

PSI – Pounds per Square Inch 

PTS – Positive Train Separation 

RAC – Railway Association of Canada 

SJ – Statens Jarnvager (Swedish State Railways) 

SNCF – Société Nationale des Chemins de Fer Français (French National Railways) 

TGV – Train à Grande Vitesse 

UP – United Pacific Railroad 

Volpe Center – John A. Volpe National Transportation Systems Center 

v

TABLE OF CONTENTS 

Section Page

EXECUTIVE SUMMARY ......................................................................................................... ix

1. INTRODUCTION..................................................................................................................1

1.1 RESEARCH GOALS ............................................................................................................2 

2. LOCOMOTIVE CAB DISPLAYS IN HIGH-SPEED OPERATIONS............................3

2.1 SWEDEN............................................................................................................................3 

2.2 JAPAN ...............................................................................................................................5 

2.3 FRANCE.............................................................................................................................7 

2.4 GERMANY.........................................................................................................................8 

2.5 NORTH AMERICAN RAILROADS ........................................................................................9 

2.6 AMTRAK .........................................................................................................................11 

2.7 SUMMARY.......................................................................................................................12 

3. SIMULATOR EXPERIMENT...........................................................................................15

3.1 OVERVIEW......................................................................................................................15 

3.2 LOCOMOTIVE SIMULATOR ..............................................................................................15 

3.3 EXPERIMENTAL DESIGN..................................................................................................16 

3.4 TASK...............................................................................................................................20 

3.5 PARTICIPANTS.................................................................................................................21 

3.6 TRAINING........................................................................................................................21 

4. RESULTS AND DISCUSSION ..........................................................................................23

4.1 SPEED CONTROL .............................................................................................................23 

4.2 SIGNAL ADHERENCE.......................................................................................................23 

4.3 BRAKE RESPONSE LATENCY...........................................................................................25 

4.4 SCHEDULE DEVIATION....................................................................................................25 

4.5 STATION-STOPPING ACCURACY......................................................................................26 

4.6 COMPARISON BETWEEN ENGINEERS AND STUDENTS......................................................27 

5. SUMMARY ..........................................................................................................................29

APPENDIX A: TRAIN SCHEDULE.........................................................................................33

APPENDIX B: EXIT QUESTIONNAIRE................................................................................35

APPENDIX C: FUTURE LOCOMOTIVE SIMULATOR CONSIDERATIONS................37

GLOSSARY..................................................................................................................................43

REFERENCES.............................................................................................................................45

vii
LIST OF FIGURES 

Figure Page

1. X2000 Instrument Panel ..............................................................................................................4 

2. X2000 Fault Indication Panel ......................................................................................................4 

3. Shinkansen MON4 Display .........................................................................................................6 

4. Shinkansen MON10 Display .......................................................................................................6 

5. Interior of a TGV-PBKA Cab......................................................................................................7 

6. ASTREE Cab Display (de Curzon, 1994) ...................................................................................8 

7. Interior of an ICE Cab .................................................................................................................9 

8. AAR LSI (Train Control) Display .............................................................................................10 

9. AAR ATCS (Track/Authority) Display.....................................................................................11 

10. GE/Amtrak Genesis II Gauge Display.....................................................................................12 

11. Simulated Locomotive Cab......................................................................................................16 

12. Genesis II Locomotive Display ...............................................................................................17 

13. Preview Display.......................................................................................................................18 

LIST OF TABLES 

Table Page

Table 1. Askey's Display-Aiding Levels .........................................................................................1 

Table 2. Shinkansen Power Car Characteristics..............................................................................5 

Table 3. Independent Variables.....................................................................................................19 

Table 4. Operating Disturbances....................................................................................................20 

Table 5. Frequency of Speed Violations by Display Condition ....................................................23 

Table 6. Signal Adherence by Preview Condition.........................................................................24 

Table 7. Stop Signal Overruns.......................................................................................................25 

Table 8. Mean Braking Response Latency(s) to Restricted Signal ...............................................25 

Table 9. Schedule Deviation by Display Number for Trips without a Signal Change..................26 

Table 10. Mean Station-Stopping Accuracy (ft) by Group ...........................................................27 

Table 11. Mean Brake Response Time (s) by Group ....................................................................28 

viii
EXECUTIVE SUMMARY

INTRODUCTION 

High speeds increase the processing demand per unit time on the locomotive engineer, while also 

decreasing the available response time. Increasing train speed reduces the time available for the 

engineer to adjust train speed in anticipation of the upcoming track conditions. As trains travel 

faster, locomotive engineers must process more information in less time. Providing information far 

enough in advance to process and take action may enable the locomotive engineer to more safely 

operate the train at speeds above 79 mph. Traditionally, the locomotive engineer obtained visual 

information for making train control decisions by looking out the window. When available, wayside 

signals indicate whether the train can enter a block and indicate whether the train can operate at 

maximum speed authorized for that track section or whether it must operate at lower speed. When 

operating at high speeds, the locomotive engineer may not have sufficient time to brake after 

identifying the signal. One answer is to display this information in the locomotive cab. In the 

United States, trains traveling above 79 mph must display signals in the cab. 

Information about the status of the track some distance ahead of the train is expected to aid 

locomotive engineers by partially compensating for the decreased signal processing time 

imposed by higher train speeds (above 79 mph). Such preview information may include the 

signal speed, the civil speed, track occupancy, and braking characteristics. Both Kuehn (1992) 

and Askey (1995) demonstrated that displays incorporating preview information increased safety 

and efficiency of train operation. The Advanced Train Control System (ATCS) guideline for 

preview information was based upon discussions with engineers. The current study seeks to 

answer the question, “How does preview distance affect locomotive engineer train handling 

performance?” 

The current research seeks to build on this knowledge regarding “preview information” by 

specifically examining the length of preview on locomotive engineer performance. This 

information was included in an experimental display. This display was compared to the 

Genesis II display used in Amtrak locomotives. The Genesis II display shows in-cab signals, but 

does not provide preview information. 

Prior to the development of a preview display, the development of train control systems and 

locomotive cab displays in countries with high-speed operations were reviewed. Based on this 

information, along with interviews with locomotive engineers, locomotive manufacturers, and 

railroads, a preview decision aid was developed and tested. 

The literature review uncovered a wide variety of cab display paradigms used in the countries 

operating high-speed trains. The differences that exist include many important aspects of train 

control and cab display design. For instance, Japanese engineers favor linear speedometers, 

while American engineers favor circular speedometers. Each country has its own convention 

regarding how train control information (speed, traction and braking) is displayed. This raises 

the question, “To what extent does the way train control information is displayed (e.g., 

horizontal versus vertical, linear versus circular, etc.) affect how the engineer operates the 

train?” There also seems to be consensus among the railroads in the various countries operating 

trains at high speeds that the engineer needs information over and above the current block signal. 

ix
This experiment examined the differences in safety and efficiency of train operation that might 

arise by using displays with and without preview information. Information that is helpful to the 

engineer may include upcoming speed restrictions, location and velocity of nearby traffic, and 

upcoming distance cues (such as mileposts). This information was included in an experimental 

display. This display was compared to the Genesis II display used in Amtrak locomotives, a 

display that offers no preview information. The Genesis II display shows signals in the cab, but 

does not provide preview information. 

To investigate these questions, an experiment was run on a human-in-the-loop locomotive 

simulator, using locomotive engineers and students. A second goal of the research was to 

compare the performance of engineers and non-engineers. Previous studies using the locomotive 

simulator were conducted using only students as participants. Can the results of these studies be 

applied to locomotive engineers? Evaluating performance for both groups allowed us to better 

understand the benefits and limitations of using students in a job that requires a high level of 

training to become proficient. 

METHOD 

The independent variables manipulated were preview distance and participant type. Two 

displays were used to show the different preview distances. This baseline display showed only 

the current block signal (no preview information) in the form of a location-coded signal and 

digital readouts of the civil and signal speed limits. There were three preview conditions: 1.4 

mile, 3.4 mile, and variable preview. The preview display conditions were all variations of one 

experimental display that showed the same brake, traction, and warning information as the 

Genesis II display, but also contains speed-by-distance and traffic preview information. 

The large window in the middle of the preview display showed the upcoming speed restrictions. 

If the white horizontal bar indicating the train’s current location was above the red line, the train 

was violating the effective speed limit. Mileposts, switches, and stations were indicated just 

below the speed preview window, above the track preview display (described below). The 

preview displays also displayed predictive full-service and emergency braking curves. 

The following dependent measures were used to evaluate operator performance: speed control, 

signal adherence, brake reaction time latency, schedule deviation, and station-stopping accuracy. 

Speed control was monitored by collecting data on the train speed relative to the allowed speed. 

Locomotive engineers were expected to keep their trains within a certain range of acceptable 

values. Signal adherence was measured by recording whether the participant violated a signal 

(i.e., running past a red “stop” signal or passing a signal at a speed higher than permitted). Brake 

reaction time latency to failure scenarios (i.e., a car stuck in a grade crossing or a dropped signal) 

was monitored by recording reaction times to take action in response to a “failure” event (i.e., 

the distance between the train and the event, such as a signal or a car stuck in a crossing). 

Schedule deviation was measured by the difference between the expected arrival time at each 

station and the actual arrival time at each station. Station-stopping accuracy was measured by 

comparing the participant’s actual stopping location at each station relative to a pre-defined mark 

(the end of each station platform). 

x
Three Amtrak locomotive engineers and six MIT students participated in this experiment. Each 

participant operated the locomotive simulator on a section of track modeled after a trip from

South Station in Boston, Massachusetts to Attleboro, Massachusetts. The participant’s task was 

to operate the train, given the schedule constraints and operating conditions. The participant 

encountered a variety of disturbances such as unexpected signals, speed restrictions, and moving 

to a siding to allow another train to pass. 

RESULTS AND DISCUSSION 

In this study, the preview displays improved performance on tasks where the locomotive 

engineer’s train control actions were made in advance of the visual information needed to 

support those actions. Routine speed control improved with the preview displays, although it was 

unclear whether this difference would exist for the locomotive engineers if they were more 

familiar with the territory and the train’s dynamics. The largest number of speed violations 

occurred in the no-preview display condition. 

The number of signal overruns decreased with preview information compared to the no-preview 

condition. Among the preview displays, participants demonstrated an easier time making control 

decisions in the variable preview condition. They exhibited the best braking performance using 

the variable preview display, when exposed to an expected (static) or unexpected (dynamic) 

signal. Participants using the 1.4-mile fixed preview display performed better when faced with 

an expected signal than when using the 3.4-mile fixed preview display. When faced with an 

unexpected signal, the opposite result occurred. Participants performed better using the 3.4-mile 

preview display than the 1.4-mile preview display. 

Braking response time also improved with the preview information, particularly with the 

variable preview display. Response latencies were shorter with the preview displays than the nopreview condition. Participants performed best with the variable preview display followed by the 

1.4-mile display and the 3.4-mile display. The response latency was considerably shorter for the 

variable display and the 1.4-mile display conditions. 

Preview information did not seem to support station-stopping accuracy. However, participants 

also reported more problems using the preview displays for station-stopping, particularly the 

variable preview display. 

Qualitative data from this study supports the quantitative data that long preview or preview that 

scales with speed (offering greater resolution at lower speeds) is preferable. When asked what 

preview distance would make the job easiest, most of the participants responded “as much as 

possible” or referred to either the 3.4-mile fixed preview or the variable preview, while one 

engineer responded “5 to 10 miles.” 

The Amtrak engineers reacted favorably to the preview displays, particularly since they “helped 

learn the territory.” It is unclear whether the engineers would have found the preview displays as 

useful if they already knew the territory and the train’s dynamics. In low visibility conditions 

where locomotive engineers cannot rely on the normal visual cues, a preview display may prove 

beneficial. One engineer responded, “No preview is needed if you know the physical 

characteristics [of the train and track].” 

xi
In designing such information aids, particular attention needs to be paid to the engineer’s 

strategies for allocating attention. The engineers who operated the locomotive simulator liked the 

preview displays and performed well with them. One engineer indicated that the preview 

displays aided navigation in unfamiliar territory and was useful to see the rate of deceleration 

relative to distance. 

However, two of the engineers stressed their need to focus attention out the window. One 

engineer complained about the amount of “electronic harassment” in modern locomotive cabs 

precluding engineers from focusing their attention out the window. That engineer said that the 

engineer’s attention is not necessarily needed to brake in time for a potential emergency, but 

rather to be able to blow the horn in time in such a case, or to accurately control the train when 

approaching a station platform. In fact, this participant related that many engineers “cut out” 

(turn off) the cab signaling and Automatic Train Protection (ATP) in low-speed territory to 

remove the “distraction” of the warnings and focus their attention on very fine control of the 

train’s speed. However, the danger is that they forget to cut it back in when they return to highspeed territory. 

With regard to station stopping accuracy, there was evidence that the preview displays adversely 

affected performance, due to the lack of resolution at lower speeds. The best information to 

support station stopping is to look out the window. To aid station stopping, the preview display 

needs to show enough detail for a locomotive engineer to properly judge stopping distance. 

Research is needed with regard to how this change of resolution should take place (e.g., 

continuously or discretely). One way to investigate this question is to allow the engineer to 

control the preview distance and record what is chosen as a function of speed. Future work 

should focus on how locomotive engineers allocate their attention, and on how to effectively 

incorporate decision aids and training for those aids into that attention allocation scheme. 

The data indicate that the student and engineer groups exhibited similar behavior in a relatively 

limited range of conditions. The two groups exhibited similar behavior towards signal adherence 

and speed control. However, the engineers appeared to focus their attention outside the cab, 

which kept them from making full use of the preview display. This was supported by the 

engineers’ assertions that they need to focus their attention out the window. This data suggests 

that previous experiments using students as participants may give similar results using 

locomotive engineers under two conditions: When locomotive engineers are inexperienced and 

when the visual information engineers rely upon to make decisions is impoverished. Otherwise, 

the training and operating experience of experienced locomotive engineers results in behavior 

that differs from those of students and others who lack this experience. 

xii
1. INTRODUCTION 

Trains, like ships, possess a considerable amount of inertia. There is a relatively long lag 

between when a locomotive engineer initiates a change in speed and that change affects the 

speed of the locomotive, compared to motor vehicles and airplanes. An engineer must respond to 

visual cues in the environment far in advance to safely operate a locomotive. These visual cues 

include a variety of track conditions such as grade, curvature, and track classification. Some of 

these cues are permanent features of the environment; others are temporary. Locomotive 

engineers spend considerable time learning the features of the territory over which they will 

operate before they are certified to operate on that territory. Increasing train speed reduces the 

time available for the engineer to adjust train speed in anticipation of the upcoming track 

conditions. In some territories, signals along the track indicate that a train may move at the 

maximum authorized speed over that section. 

As trains travel faster, locomotive engineers must process more information in less time. At 

some point, the rate at which information needs to be processed exceeds the engineer’s abilities 

to respond in time. This limitation is reached sooner if information is displayed in a way that is 

difficult to access or understand. Providing information far enough in advance to process and 

take action may enable the locomotive engineer to more safely operate the train at speeds above 

79 mph. Traditionally, the locomotive engineer obtained visual information for making train 

control decisions by looking out the window. From many years of operating experience, the 

engineer used landmarks along the territory to determine braking points. When available, 

wayside signals indicate whether the train can enter a block and indicate the speed limit. When 

operating at high speeds, the locomotive engineer may not have sufficient time to brake after 

identifying the signal. One answer is to display this information in the locomotive cab. In the 

United States, trains traveling above 79 mph must display signals in the cab. 

Askey (1995) examined the effects of providing varying levels of information to the locomotive 

engineer on operator awareness, safety, and efficiency. This study examined whether this 

information overloads the operator to the point where the operator cannot react to an unexpected 

scenario or perform a secondary task in an acceptable manner. Askey created three decision aids 

that varied in the level of information, as described in Table 1. Performance improved with 

increasing levels of display aiding for the following measures: station-stopping accuracy, 

schedule adherence, and reaction time to unexpected signal changes. Moreover, the participants 

rated the most complex display as imposing the lowest overall workload and preferred it to any 

of the lower-level aiding displays. 

Table 1. Askey’s Display-Aiding Levels

Basic Preview Predictor Advisor

Current- and 

next-block 

signals 

Effective speed limit 

information for a 

certain, multi-block 

preview distance 

Maximum service and 

emergency braking curves, 

along with a future location 

prediction 

Advises on the optimal speed 

trajectory to satisfy all speed and 

schedule constraints with the 

minimum fuel expenditure 

1
Askey’s proposed decision aids were motivated by a desire to compensate for human limitations 

in signal detection and information processing. Kuehn (1992) examined the efficacy of the 

Advanced Train Control System (ATCS) displays with respect to safety and efficiency of 

operation in light of these same limitations. He concluded that the ATCS display, which 

incorporated a gradient, authority, and speed restriction preview for five miles ahead of the train, 

resulted in increased safety (as measured by the number of speed violations and red signal 

overruns). Participants in the ATCS group produced significant reduction in fuel consumption 

over the conventional paper warrant group. 

Information about the status of the track some distance ahead of the train is expected to aid 

locomotive engineers by partially compensating for the decreased signal processing time 

imposed by higher train speeds (above 79 mph). Such preview information may include the 

signal speed, the civil speed, track occupancy, and braking characteristics. Providing the 

engineer with this information far enough in advance may allow the engineer to make better (i.e., 

safer and more efficient) decisions in the time available. 

Both Kuehn (1992) and Askey (1995) demonstrated that displays incorporating preview 

information increased safety and efficiency of train operation. However, neither study focused 

on the amount of preview as a variable. The ATCS guideline for preview information was based 

upon discussions with engineers. The current study seeks to answer the question "How does 

preview distance affect locomotive engineer train handling performance." 

1.1 RESEARCH GOALS 

1. This research was performed to examine whether preview information is useful, and if so, 

how far down the track should the engineer be able to “see.” These questions were 

investigated by measuring performance in a human-in-the-loop locomotive simulator. 

2. This study represents the first time locomotive engineers were used as participants in the 

locomotive simulator. Previous experiments were conducted using students. A second goal 

compared the performance of locomotive to students. 

3. A third goal was to solicit locomotive engineers’ feedback on the realism of the part-task 

simulator after making extensive upgrades. The simulator upgrades included adding a cabin 

environment; track, engine and alarm sounds; and more realistic control inputs. 

2
2. LOCOMOTIVE CAB DISPLAYS IN HIGH-SPEED OPERATIONS 

This section reviews the development of train control systems and locomotive cab displays in 

countries with high-speed operations. Based on this information, along with interviews with 

locomotive engineers, locomotive manufacturers, and railroads, a preview decision aid was 

developed and tested. 

In North America, the railroads developed specifications for modern train control systems 

suitable for high-speed operations. The Association of American Railroads (AAR) and the 

Railway Association of Canada (RAC) cooperatively developed specifications for the 

development of positive train control systems. Individually, railroads developed their own 

requirements for train operation, driven internal needs. These railroads included Amtrak, 

Burlington Northern Railroad (BN), Swedish State Railways, the Japan Rail (JR) companies, 

Société Nationale des Chemins de Fer Français (SNCF, the French National Railways), and 

Deutsche Bahn AG (DB, German Railways). The manufacturers most directly involved in the 

development of the high-speed train control technology included: AdTranz (acquired by 

Bombardier); Bombardier; Alstom; General Electric (GE); and General Motors (GM). 

2.1 SWEDEN 

AdTranz manufactured Sweden’s high-speed trains, the X2000, the first of which was put into 

operation in 1990. Sweden’s rail network is characterized by numerous curves. The curves limit 

operating speeds due to tremendous lateral forces that degrade passenger comfort. Sweden’s 

sparse population made it uneconomical to construct dedicated high-speed guideways. 

Consequently, Statens Jarnvagar (SJ, also called Swedish State Railways) put its effort into 

redesigning the passenger car characteristics to increase speeds by up to 35 percent in curves (to 125 

mph) and over 50 percent on straight track with no decrement in ride quality. The X2000 achieves 

these goals with two improvements over traditional railroad cars: A mechanism that tilts the cars 

inwards in curves (thereby decreasing centrifugal forces on passengers in the cars) and the 

improved running characteristics of the “soft” bogies (which allow the front and rear axles of 

each bogie to pivot, thereby decreasing rolling resistance around curves. The resulting smooth 

ride received good reviews (Wilner, 1994). 

SJ implemented an incremental transponder-based automatic train control (ATC) system in 

operation over its entire network. This system displays the current and next block signals in the 

cab as shown in Figure 1. If the train’s speed exceeds 6 mph (10 km/hr) above the permitted 

speed, the on-board ATC computer will stop the train. The computer will also stop the train if

the operator fails to reset the alerter at least once each minute, if the gates at a grade crossing are 

not lowered in time, or if the automated induction loop system detects a motor vehicle stuck in a 

grade crossing (FRA, 1991a). As all trains operated in Sweden are required to be compatible 

with SJ’s ATC system, the X2000 is differentiated from other locomotives with respect to cab 

displays only by its fault indication panel, which is designed to aid the engineer in understanding 

errors and avoiding unnecessary stops for minor faults.

3
Figure 1. X2000 Instrument Panel

The X2000 cab displays include a combination of digital and analog formats. The brake pressure 

and current speed (the two largest displays on the instrument panel) are displayed on circular 

analog dials. The tractive effort and line voltage, displayed to the right of the speedometer and 

brake pressure gauge, are displayed on vertical linear gauges. For the ATC system to make its 

calculations properly, the engineer must enter the train’s length, maximum speed, braking 

capacity and brake delay via the thumbwheels located above and to the right of the line voltage 

gauge. The system indication panel to the left of the train control panel, shown in Figure 2, 

consists of twenty backlit, color-coded lamps, some of which must be interpreted in combination 

with information shown in the fault indication panel above the windscreen. The combination of 

display paradigms gives the impression of a system pieced together over time, and recent 

photographs of the X2000 cab look much like SJ cabs from the early 1980s. 

Figure 2. X2000 Fault Indication Panel 

The item that stands out in comparison to other countries is the digital display of both the current 

and next block signal, in the upper left-hand portion of the display panel. Providing the next 

block’s signal allows the engineer more time to react to an upcoming signal change. However, 

the operator is still required to know the distance and time to the beginning of the upcoming 

block. The ATC system relies on engineer input of train characteristics, like the German system. 

4
2.2 JAPAN 

In Japan, high-speed trains (the Shinkansen) operate throughout the country on dedicated rightsof-way. There are five types of Shinkansen power cars in use and three different types of cab 

displays as shown in Table 2. The MON4 and MON10 displays are software-generated displays 

that give information regarding train location and speed, as well as a graphical representation of 

consist and brake status (see Figure 3 and Figure 4). The current speed limit is indicated by a 

lighted dot at the perimeter of the speedometer.1

 Currently, the operator is given no information 

regarding braking distance, distance to the next block, grade, or other trains’ locations. 

Table 2. Shinkansen Power Car Characteristics 

Power Car Production Date Cab Display 

 200 1981 MON1 

 400 1990 MON4 

 E1 1993 MON4 

 E2 1994 MON10 

 E3 1994 MON10 

There has been a strong push for standardization of cab displays to improve the design and 

reduce operator confusion.2

 Shinkansen guideways lack wayside signals. Instead, the current 

block signal is displayed on the dashboard. In 1995, JR East looked at how to best display the 

next block’s signal as well. JR East conducted extensive testing using surveys, simulations, and 

overlays of information in cabs in actual operation. JR East felt that giving the engineer more 

than two blocks of information was too much, as the engineer would not be able to use this 

information (Horiuchi, 1996). Consequently, they focused their efforts on how best to display the 

current and next block information. 

 

1

 The earlier displays (series 200) used a linear speedometer display. At the engineers’ request, the next generation 

of displays (the MON4 in the series 400 and E1) contained circular speedometers. When the most recent displays 

were developed (the MON10 in the series E2 and E3), the engineers requested a return to a linear speedometer 

display. Amtrak experienced the opposite situation with the Genesis cab. The Genesis locomotive built by GE 

contained a linear speedometer. When the locomotive was purchased from GE for operation beginning in the fall of 

1996, the engineers requested a return to a circular speedometer display like the ones used in the older control

stand-style locomotive cabs. 

2

 Except for engineers operating Shinkansen trains, engineers are certified by track, not by locomotive. This means 

that engineers may be presented with an unfamiliar cab on any trip. 

5
Figure 3. Shinkansen MON4 Display

Figure 4. Shinkansen MON10 Display

Their preferred design does not show any block signals at all. Instead, the display contains a 

circular speedometer with a triangle around the perimeter that indicates the maximum speed for a 

given movement authority. The maximum speed will allow the operator to stop or decelerate so 

that the train remains within the limits of its authority for the next block. If the actual speed of

the train is within a certain buffer range of this indicator, the signal turns yellow. If the actual 

6
speed exceeds the maximum safe speed, the signal becomes red and a penalty brake application 

is made. JR East also proposed a distance gauge that would show the distance between the 

operating train and the next train down the track. 

2.3 FRANCE 

In France, the Train à Grande Vitesse (TGV) high-speed trains operate partially on dedicated 

rights-of-way and partially on mixed-use guideways. The manufacturer of the TGV locomotives, 

Alstom, makes TGV-type locomotives for use in France and surrounding countries. Due to the 

differing operating environments, there are a several different cab environments on the TGV 

locomotives. The original TGV locomotives have a left-hand side operator’s position, while 

newer TGV locomotives have a central operator’s position originally designed to accommodate 

travel on foreign tracks where the traffic and signals may be either on the right-hand (e.g., 

Germany) or the left-hand (e.g., France and Belgium) side as shown in Figure 5. The SNCF 

locomotives use a wheel to control power output from the motors, while the locomotives for all 

other operators use a more conventional traction lever. The newer cabs with the central 

operator’s position have a much wider instrument panel area to accommodate the variety of 

signaling systems in use by the European railroads. 

Figure 5. Interior of a TGV-PBKA Cab

Beginning with the TGV-A in 1988, TGV locomotives were equipped with an on-board data 

processing system for conducting train start-up tests, displaying equipment status, 

troubleshooting, or assisting with repairs. The data processing system interface consists of a 

recessed monitor and keyboard located to the right of and behind the traction control lever or 

wheel. Cab signals are displayed instead of wayside signals on the dedicated high-speed 

guideways. The cab signaling provides ten aspects. The engineer’s control task is made 

somewhat simpler by the fact that each block is of a uniform length (11

/3 miles or 2.1 km). 

SNCF experimented with a “moving-block” train control system, named ASTREE, in which the 

train’s speed and location were calculated on-board and relayed to a central control area where 

the data is combined with those of other trains to calculate maximum safe (current) speeds. This 

project was halted and the data gathered were used, in part, to develop the European Train 

7
Control System (Jane’s World Railways, 1996). The ASTREE experiment focused more on the 

central control of the trains, rather than on the cab display of information to the operator. When 

it was developed, it represented one of the more complete implementations of advanced train 

control and data link communications. It included such items as a target speed, an updated 

schedule, and suggestions for energy savings (see Figure 6). 

Figure 6. ASTREE Cab Display (de Curzon, 1994)

2.4 GERMANY 

The German high-speed train system, the Inter-City Express (ICE), boasts the highest level of 

computer-aided support of any rail network, allowing manual control, partial computer-assisted 

speed control, and fully computer-assisted speed control (FRA, 1991b). During manual control, 

the train control system operates in the background. If the train reaches the nominal speed curve, 

a warning is given to the engineer. If the train reaches the monitored speed curve (i.e., that speed 

above which the train could not decelerate or stop in time), the emergency brakes are applied. 

Before each trip, the engineer must key in the train identification number, train length, and the 

status of the braking systems. During the trip, the engineer must input any changes in the braking 

capability of the train to allow the ATC system to make the necessary calculations accurately. 

The cab displays consist of two analog circular gauges for speed and power in the middle of the 

dashboard with an angled software-generated display on either side (see Figure 7). One monitor 

provides braking information, while the other displays general diagnostic information. 

8
Figure 7. Interior of an ICE Cab

In 1991, DB instituted a new signaling scheme wherein the trackside signal displayed the aspect, 

the effective speed limit (in multiples of 10 km/hr), and the direction of divergence if

approaching an interlocking. The signal indicated the status two blocks ahead of the train 

(Jane’s, 1996). Thus, the engineer was given greater time in which to react without transmitting 

any more information. 

In 1995, DB began testing a high-capacity train control scheme based on fixed-block track. 

Computer Integrated Railroading (CIR) utilized shorter block lengths than used previously. 

Based on current train positions and speeds, a computer calculated minimum acceptable 

headways, which were then relayed to the cab of each respective train. No wayside signals were 

used. 

2.5 NORTH AMERICAN RAILROADS 

The AAR and RAC developed a comprehensive set of guidelines outlining their vision of

positive train control called ATCS. ATCS used digital data communications and computers to 

manage and control the elements of the railroad. These elements included locomotives, track 

forces, field devices, the dispatch office, and railroad management systems (Moody, 1993). The 

goal of this system was to improve safety, efficiency, and customer service. These specifications 

were revised several times and several railroads implemented test beds of ATCS-style systems in 

various forms (Moody, 1990; Progressive Railroading, 1991). 

One of the earliest examples was the Advanced Railroad Electronic System (ARES) developed 

by Burlington Northern Railroad (BN) in conjunction with Rockwell International and tested on 

the Minnesota Iron Range from 1987 to 1993. ARES was an ambitious train control project, 

encompassing automated traffic planning and assessment, computerized dispatching and record 

keeping, cab command and control, improved data links, automatic location and speed 

monitoring, and locomotive health and status monitoring (Ditmeyer and Smith, 1993; Moody, 

1990). The ARES cab display, called the Train Situation Indicator, displayed route profile and 

9
alignment, grade crossing locations, sidings and other physical structures, and train movement 

authorities. 

The FRA, Amtrak, the State of Michigan, and GE Harris-Harmon Electronics developed a 

system called Incremental Train Control System (ITCS) on a passenger corridor between Detroit 

and Chicago. The AAR, FRA, and the State of Illinois joined together to develop the North 

American Joint Positive Train Control System (NAJPTCP) for the Chicago – St. Louis, Illinois 

corridor. Lockheed Martin served as the contractor for this PTC system. 

The ATCS guidelines provide for computer-assisted support of train control. While the 

locomotive engineer is nominally in control of the train, the computer-based train control system

can override any engineer actions that would result in an unsafe situation. The ATCS 

specifications outline two types of cab displays. One display emphasizes train control parameters 

and the other displays track and movement authority information. These displays are shown in 

Figure 8 and Figure 9, respectively. 

Figure 8. LSI (Train Control) Display

These guidelines designate what types of information are required and what information is 

optional. The guidelines discuss how these pieces of information should appear on the screen 

(see Figure 8 and Figure 9). The train control display indicates where each piece of information 

should appear on the screen and delineates an area for “optional” information, such as train 

control notices. The track authority display can be either graphical or text based. The suggested 

graphical track display incorporates many of the same concepts encompassed by Askey’s (1995) 

preview, predictor, and advisor displays. 

10
Figure 9. AAR ATCS (Track/Authority) Display 

Tests performed at IITRI demonstrated increased safety and efficiency of train operation when 

the ATCS display was compared to the traditional paper warrants (Kuehn, 1992). These results 

show the promise of such decision aids. 

2.6 AMTRAK 

Since the national 79 mph speed limit was instituted in 1947 (Wilner, 1994), the migration to 

higher speeds in the United States has been slow, consisting of incremental increases in 

maximum safe operating speeds. To travel above 79 mph, a train must be equipped with cab 

signaling or automatic train protection (ATP). Train control systems with ATP initiate a penalty 

brake application if the speed limit or movement authority is violated. 

The Genesis Series II cabs, put into revenue service in 1995, marked the first use of softwaregenerated displays used by Amtrak. The Genesis cab used a desktop style control stand and 

included three computer display screens (two for the engineer, and one for the conductor). The 

auxiliary function display is complex, with several menu-driven levels that can be selected using 

function keys. Figure 10 shows the primary display the engineers used in routine train control. 

11
The general response to both the cab and the display was positive. However, some engineers felt 

that the Series II displays were too “busy,” and that a circular speedometer (like the traditional 

circular analog gauges) was better than the linear version. 

Figure 10. GE/Amtrak Genesis II Gauge Display 

2.7 SUMMARY 

A wide variety of cab display paradigms were used in the countries operating high-speed trains. 

The differences that exist include many important aspects of train control and cab display design. 

The differences in information displayed include, but are not limited to: the kind of information 

provided (e.g., fault indication lights), the level or amount of information provided (e.g., one 

block or two blocks of signals), and the presentation of this information. For instance, Japanese 

engineers favor linear speedometers, while American engineers favor circular speedometers. 

Sweden presents the operator with the current and next block signals, while Japan and the United 

States only display the current block signal. Japanese and French railroads do not have wayside 

signals on high-speed corridors, while the United States and Swedish railroads do have wayside 

signals. 

The variety of cab display conventions suggests a number of different avenues for research. Each 

country has its own convention regarding how train control information (speed, traction and 

braking) is displayed. This raises the question: to what extent does the way train control 

information is displayed (e.g., horizontal versus vertical, linear versus circular, etc.) affect how 

the engineer operates the train? Within a railroad, there is also variation within individual 

operators’ territory, with respect to signaling paradigms and display regimes. This variation has 

the potential to cause confusion among engineers who may have to operate a different 

locomotive (with different displays) on any given day. A uniform signaling system and as 

uniform a cab environment as possible would increase safety by reducing confusion and 

minimizing operator errors. 

12
There also seems to be consensus among the railroads in the various countries operating trains at 

high speeds that the engineer needs information over and above the current block signal. 

However, nowhere is an engineer given any information about distance further ahead than the 

next block. The results of Kuehn (1992) suggests that preview information may be helpful not 

only for safety, but for efficiency as well. However, it remains unclear what level of preview, or 

how far down the track that information is provided, is most useful. The current research seeks to 

build on this knowledge regarding “preview information” by specifically examining the length of 

preview on locomotive engineer performance. 

13

3. SIMULATOR EXPERIMENT 

3.1 OVERVIEW 

This experiment examined the differences in safety and efficiency of train operation that might 

arise by using displays with and without preview information. Information that is helpful to the 

engineer may include upcoming speed restrictions, location and velocity of nearby traffic, and 

upcoming distance cues (such as mileposts). This information was included in an experimental 

display. This display was compared to the Genesis II display used in Amtrak locomotives. The 

Genesis II display shows in-cab signals, but does not provide preview information.3

 

To investigate these questions, an experiment was run on a human-in-the-loop locomotive 

simulator, using locomotive engineers and students. A second goal of the research was to 

compare the performance of engineers and non-engineers. Previous studies using the locomotive 

simulator were conducted using only students as participants. Can the results of these studies be 

applied to locomotive engineers? Evaluating performance for both groups allows better 

understanding of the benefits and limitations of using students in a job that requires a high level 

of training to become proficient. 

3.2 LOCOMOTIVE SIMULATOR 

The simulator consists of three networked Silicon Graphics computers and one Windows-based 

computer. When operating the train, the participant sat in a simulated locomotive cab, which 

included a 17-inch display monitor (showing the computer-generated instrument panel), one 

control box on either side of the monitor, and a window through which the participant viewed a 

computer-generated image of the out-the-window (OTW) view on a 6-by 4-foot screen. The 

participant communicated with the dispatcher by two-way radio. Track and engine noises tied to 

the simulation were broadcast via speakers in the cab. Figure 11 shows a photograph of the cab 

environment. The two control boxes on either side of the monitor governed the emergency brake, 

doors, cruise control, alerter, overspeed warnings, bell, horn, and circuit breakers. A separate 

workstation functioned as the dispatcher’s workstation, allowing the dispatcher to control all the 

switches and authorities. In these experiments, the experimenter performed the duties of the 

dispatcher. See (Lanzilotta, 1996) and (Askey, 1995) for further descriptions of the locomotive 

simulator. 

 

3

 The Genesis II display contained a 60-second speed predictor; however, observations of its use indicated that its

function was not smooth. Engineers interviewed as part of this study indicated that they did not trust it or 

understand it, and did not use it. The speed predictor was not included in the experiment. 

15
Figure 11. Simulated Locomotive Cab 

3.3 EXPERIMENTAL DESIGN 

3.3.1 Independent Variables 

The independent variables manipulated were preview distance and participant type. Two 

displays were used to show the different preview distances. The baseline display was a mock-up 

of the Genesis II display, shown in Figure 12. This display showed only the current block signal 

(no preview information) in the form of a location-coded signal and digital readouts of the civil 

and signal speed limits. The other display conditions were all variations of one experimental 

display that showed the same brake, traction and warning information as the Genesis II display, 

but also contains speed-by-distance and traffic preview information as shown in Figure 13. 

The large window in the middle of the preview display showed the upcoming speed restrictions. 

The horizontal axis scaled with distance, while the vertical axis scaled with speed. The vertical 

white line in this portion of the display indicated the current train position, while the short 

horizontal white line emanating from the vertical white line indicated the train’s length as well as 

its speed. The horizontal and vertical red lines indicated the maximum allowable speed at that 

location. 

If the white horizontal bar indicating the train’s current location was above the red line, the train 

was violating the effective speed limit. Mileposts, switches, and stations were indicated just 

below the speed preview window, above the track preview display (described on the next page). 

16
The preview displays also displayed predictive full-service and emergency braking curves. The 

yellow curve indicated the speed profile for a full-service brake application. The red curve 

indicated the speed profile for an emergency brake application. The green curve indicated the 

speed profile for the coming 25 seconds given current grades and control input. As the amount of 

power or braking changed, the predicted trajectory changed accordingly. 

Figure 12. Genesis II Locomotive Display

17
Figure 13. Preview Display 

The smaller window below the speed preview window shows the upcoming track structure and 

authorities. Green indicated authority to move in that portion of track, while red indicated a lack 

of authority. The horizontal (distance) axis is on the same scale as the speed preview subdisplay, and the same milepost, switch, and station indications apply. 

Preview distance was controlled by varying the resolution of the horizontal (distance) axis on the 

speed and traffic preview sub-displays to control how far down the track the operator can “see.” 

One hypothesis was that the stopping distance is the most influential factor when considering 

how far down the track the engineer needs to be able to see. Thus, one preview condition 

(variable preview) was a function of stopping distance at full-service braking and “reaction plus 

decision” distance (approximately reaction time plus “decision time” multiplied by current 

speed, ignoring acceleration during that same time period). As the train’s speed increased, the 

preview distance provided to the engineer increased accordingly. The variable preview display 

always provided the status of the track at least some distance ahead of the end of the full-service 

braking predictive curve (i.e., the resolution of the horizontal axis decreased, as the display 

provided information about the status of the track further ahead of the train’s current location). 

This “variable preview” display had 1,640 feet as the minimum preview offered at low speeds. 

18
The other (fixed) preview distances (see Table 3) were zero, 1.4 miles (approximately two 

blocks, mimicking the level of information now available in Sweden), and 3.4 miles (which is 

higher than the longest variable preview distance expected at the top speed of 150 mph). Each 

preview display shows the track about 0.3 miles (1,640 feet) behind the train as well. 

Table 3. Independent Variables 

Participant Preview Condition

Engineer Current block only

(no preview) 

1.4 miles 

(2.24 km) 

3.4 miles 

(5.6 km) 

Variable 

Student Current block only

(no preview) 

1.4 miles 

(2.24 km) 

3.4 miles 

(5.6 km) 

Variable 

3.3.2 Dependent Variables 

Speed Control 

Speed control was defined here as the ability to maintain or stay below the permitted speed, once 

that speed has been reached. A violation of this requirement could take place during a clear 

signal, when the civil limit must be obeyed, or it could take place during a restricted signal, once 

the speed required by that limit had been achieved. 

Speed control was monitored by collecting data on the train speed relative to the allowed speed. 

Locomotive engineers were expected to keep their trains within a certain range of acceptable 

values. The operator was allowed to drive up to 4 mph above the speed limit without penalty. If 

the train operated more than 4 mph over the limit longer than 5 seconds, a penalty brake 

application (full-service brake application) was initiated by the train’s ATP system. Control of

the train was not returned to the participant until the train’s speed was brought below the speed 

limit. The simulator automatically recorded the duration of any overspeed, as well as the number 

of penalty brake applications. 

Signal Adherence 

A task similar to speed control was signal adherence. Violating a movement authority (i.e., 

running past a red “stop” signal) or a missed signal (i.e., passing a signal at a speed higher than 

indicated by the signal) is also speed violation (i.e., the train speed is greater than the speed 

limit). Although the outputs (engineer actions) of these two control tasks were similar, the inputs 

and decision processes were different. When controlling the speed under a constant speed limit, 

the engineer must decide (based on the operating conditions) whether to apply the throttle or the 

brake. When adhering to an (upcoming) signal change, the engineer must decide at what point to 

apply the brakes. In the former (i.e., speed control) case, the engineer risks overshooting or 

undershooting the target speed. At most, the initial overshoot will be just greater than zero, as the 

train must first cross the speed limit before surpassing it. In the latter (i.e., signal adherence) 

case, the engineer is at risk of severely overshooting the upcoming signal if the brakes are not 

applied in time. The initial overspeed could be significant relative to the new speed limit. 

19
Signal adherence was measured by the number of signal violations (i.e., entering a block with a 

speed greater than that block’s limit) and the magnitude of each violation. 

Brake Reaction Time Latency 

Brake reaction time latency to failure scenarios (i.e., a car stuck in a grade crossing or a dropped 

signal) was monitored by recording reaction times to take action in response to a “failure” event 

(i.e., the distance between the train and the event, such as a signal or a car stuck in a crossing). 

The time of the event was automatically recorded in the data log. If the response fell within the 

domain of predictable actions, it too was recorded. The reaction time was measured from the 

time between the event and the initiation of the participant’s response. 

Schedule Deviation 

Schedule deviation was measured by the difference between the expected arrival time at each 

station and the actual arrival time at each station. 

Station-Stopping Accuracy 

Station-stopping accuracy was measured by comparing the participant’s actual stopping 

location at each station relative to a pre-defined mark (the end of each station platform). In 

passenger operations, station-stopping accuracy is an important part of the engineer’s job. An 

inaccurate stop may require the conductors to perform extra work and may force the passengers 

to lug their bags to different exits. 

3.4 TASK 

Each participant operated the locomotive simulator on a section of track modeled after a trip 

from South Station in Boston, Massachusetts to Attleboro, Massachusetts. The trip included two 

intermediate stations (Sharon and Foxboro). The time between each station averaged 12 minutes, 

bringing the total travel time to approximately 37 minutes. The participant’s task was to operate 

the train, given the schedule constraints and operating conditions. The participant encountered a 

variety of disturbances, as described in Table 4. The trip between Boston and Attleboro was 

divided into three legs (from Boston to Sharon, from Sharon to Foxboro, and from Foxboro to 

Attleboro). The participant encountered disturbances in two of these three legs. 

Table 4. Operating Disturbances 

Disturbance Description

1 Take a siding or crossover to a parallel track due to an unexpected train moving in the 

opposite direction. 

2 Respond to an unexpected change to a restricted signal (i.e., a “stop” signal). 

3 Respond to an unexpected change to a restricted signal (i.e., a stop signal due to a relay

failure). 

4 Respond to a temporary speed restriction. 

20
With four different values for the independent variable (no preview, variable preview, 1.4 miles, 

and 3.4 miles) and two disturbances per trip, each participant ran one trip with each display and 

saw eight disturbances: two on each display. With four different types of disturbances, each 

participant encountered each type of disturbance twice. Thus, each participant experienced four 

Boston-Attleboro trips (two round-trips), making each trip with a different cab display. After 

completing both trips, each participant completed a questionnaire and answered questions to 

collect opinions about the effectiveness of each display. 

3.5 PARTICIPANTS 

Three Amtrak locomotive engineers and six MIT students participated in this experiment. The 

locomotive engineers were three males with between 10 and 29 years of service as engineers. All 

engineers worked as passenger train engineers, with some freight experience mixed in. The 

youngest engineer was 45 years old. The six students consisted of four current MIT students and 

two recent graduates. The students were males between 19 and 23 years old. None of the 

students had any experience operating trains. 

The presentation order of the displays and the disturbances was counterbalanced across 

participants. The experiment was originally designed to use an equal number of locomotive 

engineers and students. However, only three of the proposed six Amtrak engineers were able to 

participate in the time allotted to running experiments, due to scheduling difficulties. Therefore, 

the counterbalanced design was incomplete for the locomotive engineers. 

3.6 TRAINING 

Due to the two groups’ varying experience with train control (greater for the engineers) and 

working with computers (greater for the students), the training regimens were different for the 

two groups. Training procedures for students were developed during the previous two 

experiments using the locomotive simulator (Askey, 1995; Lanzilotta, 1996). 

3.6.1 Student Training 

Each participant was given a written tutorial of train control and simulator operation issues to 

read before arriving for the first session. After reviewing the material, the participant answered 

25 multiple-choice questions. After reviewing incorrect answers with the participant and 

answering any questions, the experimenter led the participant through one trip between South 

Station and Attleboro (lasting approximately one hour). The participant saw each of the displays 

to be used during the experiment. The experimenter demonstrated all train control modes, how to 

communicate with the dispatcher, and the meaning of each piece of information displayed on the 

monitor. After answering all questions, the participant practiced operating the train on five trips 

(lasting approximately 4 hours) between Boston and Attleboro. During the first leg, there were 

no disturbances. The next four legs had at least one of the disturbances. 

The student’s performance with respect to schedule adherence, station-stopping, signal 

adherence and speed control was measured. If a student consistently performed at an acceptable 

level by the end of the second full round-trip, the training was terminated at the end of that trip 

and the experimental trials began. Four of the six student participants completed the training by 

21
the end of the second full round trip. If the student performed at an unacceptable level by the 

final training trip, the student’s participation ended. All students completed the training 

successfully. 

3.6.2 Engineers 

Although the locomotive engineers had extensive experience operating locomotives, they still 

needed a significant amount of time to learn how to operate the locomotive simulator and 

become familiar with the operator interface. The locomotive engineers were given a short 

version of the tutorial to read. The locomotive engineers were given an opportunity to review the 

material with the experimenter and ask questions. 

Each engineer’s participation lasted one full day. The engineers’ training sessions consisted of 

an instructional portion and a test portion. During the instructional portion, the participant saw 

each of the displays and each of the disturbances while being talked through the operation of the 

train by the instructor. The instructional portion lasted 1 hour. The engineer practiced operating 

the train on three trips with disturbances (lasting approximately 2 1/2 hours) to become familiar 

with train operation. 

22
4. RESULTS AND DISCUSSION 

4.1 SPEED CONTROL 

Table 5 shows the frequency of speed violations by display condition. The student group 

averaged 1.66 instances of speeding (ten events), while the engineer group averaged 1.33 

instances of speeding (four events). The largest number of speed violations occurred in the nopreview display condition. The number of speed violations in the no-preview condition was 

greater than with all preview displays, combined. This result suggests that speed control was 

more difficult using the no-preview display. 

The minimum overspeed using three of the four displays was just over four mph. The ATP 

system in the locomotive simulator allowed a “buffer” zone of four mph over the effective speed 

limit before any warning or punishment was given. 

Table 5. Frequency of Speed Violations by Display Condition 

Preview Condition

None 1.4 Mile 3.4 Mile Variable 

Speed Violation Frequency 8 2 3 1 

In five of the six speed violations in the preview conditions, students were approaching the point 

where the civil speed limit increased and were accelerating before entering the block with the 

higher speed limit. These five violations lasted from 0.1 to 5.1 seconds, and the maximum speed 

violation reached as high as 12.7 mph above the speed limit. One possible conclusion to draw 

from this behavior is that they were anticipating the speed limit increase shown on the preview 

display. Participants may not have built up enough knowledge of the territory to know exactly 

how far away the point was from where the civil limit increases, whereas (in real train operation) 

locomotive engineers know that information readily. 

The other eight instances of speeding occurred with the no-preview display. Routine speed 

control may be harder with the no-preview display than with the preview displays. Despite their 

practice runs, all of the engineers expressed difficultly in controlling the train without any 

previous knowledge of the train’s braking and acceleration characteristics. This difficulty was 

exacerbated when using the no-preview display. 

4.2 SIGNAL ADHERENCE 

Signal adherence here refers to the operator’s ability to control the train’s speed in response to 

unexpected signal changes. Table 6 shows the speed adherence performance of the two groups 

by display condition. Students and locomotive engineers performed similarly, with the most 

signal overruns in each group occurring in the no-preview display condition. Performance with 

regard to red (“stop”) signals, however, was nearly identical between the two groups and across 

the different display conditions. 

23
Table 6. Signal Adherence by Preview Condition

Preview Condition 

None 1.4-

mile 

3.4-

mile 

Variable 

Students Average Number of Signal 

Violations 6.3 4.2 2.8 3.5

Average Length of Signal 

Overrun (ft)4

1943 1890 2318 1890

Average Initial Speed 

Deviation (mph) 44.8 57.7 70.1 70.2

Locomotive 

Engineers 

Average Number of Signal 

Violations 7.3 5 4.6 1.66

Average Length of Signal 

Overrun (ft) 1890 1352 2466 2091

Average Initial Speed 

Deviation (mph) 32.4 48.5 59.1 68.1

The data indicated similar performance for the two groups with respect to signal adherence. 

Students violated an average of 16.8 signals while engineers violated an average of 18.6 signals. 

Both groups violated the most signals in the no-preview display condition. 

The average speed of the signal violation was lowest with the no-preview display and the 1.4 

mile fixed preview display. This result was surprising given the hypothesis that greater preview 

distance should give the operator time to respond to a signal change. One explanation is that the 

participants braked less aggressively with the longer preview displays because they could see the 

distance in which they had to slow down, whereas with the no-preview display, they did not 

know when the next more restrictive signal would come. Locomotive engineers knew what each 

signal indicated about the possible signal levels for the next block and adjusted their speed 

accordingly. For instance, if the signal for the current block was 45 mph (approach medium) for 

the current block and 30 mph (approach) for the next block, the engineer may not slow the train 

down immediately saving some trip time. However, the participants were not familiar enough 

with the block and signal locations in the simulation to exhibit this behavior. 

One of the most dangerous situations in operating a train occurs when passing a red signal. Table 

7 shows the average overrun by display condition. There were 17 red signal violations between 

both groups. The results were similar for the two groups. In every case, the signal turned red 

within the participant’s visual range. In every case, the participant was unable to stop the 

 

4

 Data excluded eight speed violations (three by engineers, five by students) in a crossover section, as these sections 

were only 50 feet. 

24
train in time to comply with the signal. Overall, there was little difference between the preview 

and no preview displays. 

Table 7. Stop Signal Overruns 

Preview Condition

None 1.4 Mile 3.4 Mile Variable 

Mean Red Signal Overrun (ft) 3623 3400 3487 3274 

During the experiment, it became clear that the engineers did not treat signal limits as absolute. 

Railroad operating rules provide a margin for error so that the engineer could operate a few miles 

above the posted speed limit without being in violation of a movement authority. Operating a 

train at speeds greater than indicated by the signaling system was not viewed as a safety hazard 

or as a poor reflection of the operator’s abilities. 

4.3 BRAKE RESPONSE LATENCY 

Table 8 shows the time between the first restricted signal passed and initiation of braking for two 

signal conditions. In the static signal condition, the red signal was set from the beginning of the 

trip. In the dynamic signal condition, the signal was set when the train was within a few miles of 

the signal. Negative numbers indicate that braking was initiated before passing the signal while 

positive numbers indicate that braking was initiated after passing the signal. The more negative 

the number, the greater the “cushion” between the act of braking and the more restrictive speed 

required by the non-clear signal. Performance was not a function of preview distance. Response 

latencies were shortest with the preview displays than the no-preview condition. 

Table 8. Mean Brake Response Latency (s) to Restricted Signal

Preview Condition

Signal Type None 1.4-mile 3.4-mile Variable 

Static 1.7 -18.3 -5.7 -23.4

Dynamic 1.87 1.32 .03 -2.51

Participants performed best with the variable preview display followed by the 1.4-mile display 

and the 3.4-mile display. Although the trend was the same for both static and dynamic signals, 

the preview displays offered fewer benefits in the dynamic signal condition. The response 

latency was considerably smaller for the variable display and 1.4-mile display conditions. 

4.4 SCHEDULE DEVIATION 

Schedule adherence is one of the measures by which passengers judge railroad service. Table 9 

shows the schedule deviations by display condition. Very few schedule delays occurred for trips 

25
that lacked signal changes. Each participant arrived early at the next station almost every time. 

The early arrival was related to the time given to get to the next station. As the time given to get 

to the next station increased, the size of the early arrival increased. Although the participants 

knew that they would be penalized for arriving at a station too early, almost every trip without a 

signal change resulted in an early arrival. When a participant encountered a signal change, time 

was invariably lost, and the schedule could no longer be met, so those situations were not 

considered. The experimenter asked each participant to try to maintain the time differential 

between stations set by the schedule (e.g., “Always leave 13 minutes to get from Sharon to 

Foxboro, even if you are behind schedule.”) However, participants consistently did not follow 

this instruction. The participants may have misunderstood this instruction, forgot the instruction, 

or tried to make up for lost time. 

The data were inconclusive with respect to the impact of preview information on schedule 

adherence. 

Table 9. Schedule Deviation by Display Number for Trips without a Signal 

Change

Schedule Deviation (s) 

Preview Condition 

Track Segment Schedule (s) None 1.4-mile 3.4-mile Variable 

S. Station to Sharon 420 28.2 66.6 9.0 31.2 

Sharon to Foxboro 780 25.2 -3.0 

Foxboro to Attleboro 960 46.2 56.4 67.8 

Loop 90 18.0 21.0 17.4 19.8

Attleboro to Foxboro 960 58.2 69.6 

Foxboro to Sharon 780 -0.6 0.6 

Sharon to S. Station 480 31.8 34.8 

Mean Absolute Deviation 31.1 34.3 26.0 38.4 

4.5 STATION-STOPPING ACCURACY 

The locomotive engineer must be able to accurately stop at a particular point in the station to 

allow passengers to get out at the correct door. The inability to achieve such a stop smoothly and 

on the first attempt may result in excess fuel consumption, passenger discomfort, aggravation, or 

all of above which reflects negatively on an engineer’s performance. The participants were 

instructed that deviations between –32.8 ft and +19.7 ft were acceptable, and that overshoots 

were penalized more than undershoots (the engineer can always inch the train forward, but 

backing up is much more difficult and sometimes prohibited). The locomotive engineers 

experienced more trouble stopping accurately at the stations than the students. They indicated 

that this was due to a lack of experience with the train handling characteristics (i.e., the braking 

and acceleration of the train) and the territory. Variation in performance between the displays 

26
was low, as shown in Table 10. There was qualitative data both in favor of and against the 

preview displays regarding this task. 

Table 10. Mean Station-Stopping Accuracy (ft) by Group

Preview Condition 

Group None 1.4-mile 3.4-mile Variable

Student 11.5 15.7 10.5 11.8

Engineer 21.3 21.3 16.1 13.5

The data presented in Table 10 indicate that preview information has little or no effect on 

stopping accuracy. Some participants reported trouble stopping accurately with the preview 

displays. One locomotive engineer misjudged the braking distance to the end of a station 

platform by looking at the display and used the emergency brake. An emergency brake 

application in a non safety-critical situation would be considered poor operating practice. The 

participant was using the 3.4-mile fixed preview display, which offered poor resolution for 

accurate stopping at low speeds. Several other participants, both students and engineers, also 

reported trouble using the fixed-preview displays for accurate station stopping. These comments 

support the assertion that the preview displays were poorly suited for aiding accurate station 

stops. The variable preview display was also considered difficult to use. Several participants 

expressed their dislike for the constant recalculation of the scale on the variable-preview display. 

This observation suggests a display in which the display scale continually changes may be 

difficult to use. 

One possible solution is to change the scale of the preview displays at lower speeds to show a 

smaller portion of the track in greater detail. Simply looking out the window may provide the 

best source of information to stop or control the train at very low speeds. 

4.6 COMPARISON BETWEEN ENGINEERS AND STUDENTS 

The performance between the students and locomotive engineers showed mixed results. The two 

groups performed similarly on speed control and signal adherence and differently on initiating a 

braking response to a restricted signal and station-stopping accuracy. 

The students performed consistently better than the engineers with regard to station-stopping 

accuracy. The engineers said that their lack of experience with the train’s dynamics and the track 

features adversely affected their performance. The simulator’s train dynamics were modeled 

after the TGV, a locomotive with which the engineers were unfamiliar. The engineers operated 

locomotives like the General Motors SD40 that had braking and acceleration characteristics that 

were considerably different from the TGV locomotive. Locomotive engineers learn the 

characteristics of the territory over which they will operate over a considerable period. This 

knowledge is critical to successfully stopping a train at a station. However, the locomotive 

engineers had only an hour or two to become familiar with the train handling characteristics and 

the territory. The students received more training time to learn to operate the train and become

familiar with the territory. These difficulties could be addressed by modeling the dynamics of a 

27
train with which the engineers were familiar and displaying features in the out-the-window view 

that exist on the territory over which the engineers operate. 

The engineers and students also differed in their initiation of braking in response to a restricted 

signal. Table 11 shows mean braking response latency for both groups. Negative numbers 

indicate that braking was initiated before passing the signal. Positive numbers indicate that 

braking was initiated after passing the signal. The more negative the number, the greater the 

“cushion” between the act of braking and the onset of the more restrictive speed. The students 

began braking earlier than the engineers in all of the preview display conditions and later in the

no-preview condition. 

Table 11. Mean Brake Response Time (s) by Group

Preview Condition 

Group None 1.4-mile 3.4-mile Variable

Expected (Static) Signal 

Engineers 1.4 -15.7 -4.5 -19.1

Students 1.8 -20.0 -6.2 -27.7

Unexpected (Dynamic) Signal 

Engineers 1.6 1.5 1.2 -0.3

Students 1.9 1.2 -0.7 -3.4

These differences may reflect differences in the attention allocation strategies between the two 

groups. The engineers obtain information by looking out the window to determine when to 

brake. Focusing their attention out the window is also important to look out for hazards such as 

trespassers and motor vehicles in grade crossings. With less experience operating trains, the 

students may have had more difficulty determining when to initiate braking in the no-preview 

condition. In the preview conditions, the students may have relied more heavily on the braking 

information supplied by the preview displays to determine when to brake. 

The difference in the engineers’ reaction times between the no-preview and preview displays 

makes sense in light of the engineers’ expressed need to focus attention out the window, thus 

keeping their attention away from the tool that would allow them to react sooner. The students 

were not trained to focus their attention out the window and were able to more quickly respond 

to events in the cab. 

28
5. SUMMARY

As trains travel faster, locomotive engineers must process more information in less time. 

Providing information far enough in advance to process and take action may enable the 

locomotive engineer to more safely operate the train at high speeds. 

In this study, the preview displays improved performance on tasks where the locomotive 

engineer’s train control actions were made in advance of the visual information needed to 

support those actions. Preview information may prove most valuable to engineers learning to 

operate in an unfamiliar territory or in conditions such as poor weather where the visual 

information that the engineer normally relies upon is unavailable. One engineer said that, while 

he liked the preview display, the extra information provided would not have been necessary had 

he better known the “physical characteristics” of the train and territory. 

More specific results include: 

• Routine speed control under a static signal was improved with the preview displays, though 

again, it is unclear whether this difference would exist for the locomotive engineers if they 

were more familiar with the territory and train’s dynamics. 

• The number of signal overruns decreased with preview information. 

• Braking response time improved with the preview information, particularly with the variable 

preview display. 

• Preview information did not seem to influence station-stopping accuracy, though the 1.4-mile 

(shorter) fixed preview display resulted in station stops that were more deviant than with the 

other displays. There was qualitative data supporting each of the types of display with 

respect to station stopping. All of the preview displays received high marks for providing 

good information regarding stopping distance from higher speeds, while the variable preview 

display also received praise for increasing the resolution at lower speeds, thereby allowing 

more accurate stops. 

• Among the preview displays, performance with respect to signal overruns was poorest with 

the 3.4-mile fixed preview display. 

• Participants demonstrated an easier time making control decisions in the variable preview 

condition. They exhibited the best braking performance using the variable preview display, 

when exposed to an expected (static) or unexpected (dynamic) signal. Participants using the 

1.4-mile fixed preview display performed better when faced with an expected signal than 

when using the 3.4-mile fixed preview display. When faced with an unexpected signal, the 

opposite result occurred. Participants performed better using the 3.4-mile preview display 

than the 1.4-mile preview display. 

Qualitative data from this study supports the quantitative data described above that long preview 

or preview that scales with speed (offering greater resolution at lower speeds) is preferable. As 

one participant put it: 

The 3.4-mile preview display made control easiest. The reason I felt variable 

preview was a little less effective is because you (the operator) [sic] had to scale 

distances as a part of the interpretation. It took some getting used to. The 1.4-mile 

29
display was my least favorite of the preview displays because you could not see 

the entire predicted braking curves at high speeds. 

When asked what preview distance would make the job easiest, most of the participants 

responded “as much as possible” or referred to either the 3.4-mile fixed preview or the variable 

preview, while one engineer responded “5 to 10 miles.” Another engineer responded, “No 

preview is needed if you know the physical characteristics [of the train and track],” though a 

much higher processing burden is then placed on the engineer, particularly in critical situations. 

In general, preview distance should be at least the minimum stopping distance plus some buffer 

distance to account for reaction time. 

The Amtrak engineers reacted favorably to the preview displays, particularly since they “helped 

learn the territory.” It is unclear whether the engineers would have found the preview displays as 

useful if they already knew the territory and the train’s dynamics. In low visibility conditions 

where locomotive engineers cannot rely on the normal visual cues, a preview display may prove 

beneficial. 

In designing such information aids, particular attention needs to be paid to how engineers 

allocate their attention. The engineers who operated the locomotive simulator liked the preview 

displays and performed well with them. One engineer indicated that the preview displays aided 

navigation in unfamiliar territory and were useful to see the rate of deceleration relative to 

distance. 

However, two of the engineers stressed their need to focus attention out the window. One 

engineer complained about the amount of “electronic harassment” in modern locomotive cabs 

precluding engineers from focusing their attention out the window. That engineer said that the 

engineer’s attention is not necessarily needed to brake in time for a potential emergency, but 

rather to be able to blow the horn in time in such a case, or to accurately control the train when 

approaching a station platform. In fact, this participant related that many engineers “cut out” 

(turn off) the cab signaling and ATP in low-speed territory to remove the “distraction” of the 

warnings and focus their attention on very fine control of the train’s speed. However, the danger 

is that they forget to cut it back in when they return to high-speed territory. 

With regard to station stopping accuracy, there was evidence that the preview displays adversely 

affected performance, due to the lack of resolution at lower speeds. The best information to 

support station stopping is to look out the window. To aid station stopping, the preview display 

needs to show enough detail for a locomotive engineer to properly judge stopping distance. 

Research is needed with regard to how this change of resolution should take place (e.g., 

continuously or discretely). One way to investigate this question is to allow the engineer to 

control the preview distance and record what is chosen as a function of speed. Future work 

should focus on how locomotive engineers allocate their attention, and on how to effectively 

incorporate decision aids and training for those aids into that attention allocation scheme. 

The data indicate that the student and engineer groups exhibited similar behavior in a relatively 

limited range of conditions. The two groups exhibited similar behavior towards signal adherence 

and speed control. This data suggests that previous experiments using students as participants 

may give similar results using locomotive engineers under two conditions: When locomotive 

engineers are inexperienced and when the visual information engineers rely upon to make 

decisions is impoverished. Otherwise, the training and operating experience of experienced 

30
locomotive engineers results in behavior that differs from those of students and others who lack 

this experience. 

31

APPENDIX A: TRAIN SCHEDULE 

The following page lists the train schedule used by the subjects in the preview display 

experiment. 

Train Schedule 

Time Station

00:05:00 Depart South Station 

00:12:00 Arrive Sharon

00:12:30 Depart Sharon

00:25:30 Arrive Foxboro

00:26:00 Depart Foxboro

00:42:00 Arrive Attleboro (southbound) 

00:42:30 Depart Attleboro (to loop) 

00:44:00 Arrive Attleboro (northbound) 

00:44:30 Depart Attleboro (for South Station) 

01:00:30 Arrive Foxboro

01:01:00 Depart Foxboro

01:14:00 Arrive Sharon

01:14:30 Depart Sharon

01:22:30 Arrive South Station 

Note: If you are behind schedule, you still must keep the train doors open for at least 30 seconds 

at each stop. 

33

APPENDIX B: EXIT QUESTIONNAIRE 

The questionnaire on the following page was given to the experimental subjects after the test 

sessions had been completed. The answers provided on this questionnaire were used to 

determine the subjective evaluation of the instrument panels. 

Exit Questionnaire 

1. Rate the displays in order of preference by placing a mark in the appropriate box: 

Liked

very much

Liked Neutral (didn’t

like or dislike) 

Didn’t like 

very much 

Didn’t like at 

all 

no preview 

1.4 miles (fixed) preview 

3.4 miles (fixed) preview 

variable preview 

2. Rate the displays according to how difficult/easy it was to control the train: 

Controlling

train was 

very easy 

Controlling 

train was 

easy 

Controlling 

train was 

not easy or 

hard 

Controlling 

train was 

difficult

Controlling 

train was 

very 

difficult

no preview

1.4 miles (fixed) preview 

3.4 miles (fixed) preview 

variable preview

3. Do you feel that the training process provided adequate preparation for the test task?

____ adequate training 

____ too little training Explain: 

____ too much training Explain: 

4. How much preview distance (if any) would make the task of train control easiest?

5. Any other comments? (Critical comments are appreciated. Feel free to make comments on the 

attached pictures.) 

35

APPENDIX C: FUTURE LOCOMOTIVE SIMULATOR 

CONSIDERATIONS 

One of the goals of this research project was to obtain feedback from Amtrak locomotive 

engineers about the realism of the locomotive simulator. Previous research with the simulator 

was done using MIT students as participants. Consequently, previous versions of the simulator 

utilized simplistic track networks and unrealistic control paradigms, such as an alerter whose 

time interval was independent of speed, fictitious signal systems, and penalty applications of the 

emergency brake. 

Throughout the course of this study, two employees from the Volpe National Transportation 

Systems Center with prior rail experience and four Amtrak locomotive engineers operated the 

locomotive simulator. During and after each of these sessions, the participants’ reactions to 

various aspects of the simulation were collected. Some of these comments were acted upon 

immediately to improve the simulator’s realism. A plethora of comments, suggestions, and 

critiques resulting from these experiments, however, have not yet been acted upon. Many of 

these suggestions would significantly enhance future simulations by making them as realistic as 

possible. 

In general, creating a track structure that more closely represents an actual environment in which 

locomotive engineers operate offers several benefits. First, less training would be required for 

the engineers. The engineers would need the same amount of time to learn the operation of the 

simulation itself, but would not have to learn braking points and other reference cues. Second, 

the closer the simulation is to an actual rail environment (with respect to both the physical 

fidelity as well as to the system response to control inputs) the closer a locomotive engineer’s 

actions will be to what they would be in the actual rail environment. One of the engineers 

indicated that he would have driven differently had he known the territory better (e.g., he would 

not have been focusing on the display, but rather on the out-the-window cues). Two engineers 

indicated that they preferred the preview displays over the no-preview display because it helped 

them better learn the unfamiliar territory. 

CHANGES NEEDED TO IMPROVE THE PHYSICAL FIDELITY 

According to one engineer, trains coast at idle, maintaining a constant speed, whereas the 

simulator loses a couple of miles per hour per second at top speeds, due to drag and (track) 

friction. Maintaining constant speed at idle does not seem probable, and it is likely that the 

engineer simply needs better feedback regarding acceleration and deceleration. Each of the 

engineers also said that the acceleration of the simulator was too slow. The train dynamics in the 

simulation were based on the TGV short train set. The acceleration and deceleration 

characteristics were tweaked after feedback from the first engineer, but the next two participants 

also indicated that these trains were still “sluggish.” Future simulations should use acceleration 

and braking rates based on one of the locomotives Amtrak uses, preferably those that will be put 

into service at 150 mph in the coming years. 

37
As the engineers use landmarks for remembering braking and speed reference points, the 

wayside objects should be more distinctive. Furthermore, if the sponsors hope to mimic a 

particular portion of track, the actual reference point from that portion of track should be used. 

This includes not only the wayside objects, but also the block lengths and signals. 

There are several discrepancies related to the wayside signaling system that need to be resolved: 

• Signal boards with numbers on them indicate a “distant” signal (i.e., that the train is 

approaching an interlocking). 

• A “stop” signal on such a board indicates “stop and proceed” (with no further instruction). 

• When there is a number on a signal, the number should be associated with a milepost (to 0.1 

of a mile), not a block number. 

• The supervisor of the engineers expressed that most Amtrak divisions are using “color” 

signals rather than “location” signals (though he said that all engineers should know the 

location signals). 

At a switch, the signal needs to be placed before the switch, not after it. Also, at any crossover, 

the signal for the block going in the same direction on the parallel track (i.e., the block coming 

into the section of parallel track into which the engineer’s train is crossing) needs to be set to 

“stop,” indicating that no train on the parallel track can proceed into the section of track that the 

participant is about to enter. Also, the track itself needs to be drawn differently at the crossover, 

depending on which way the “frog” (the section of track that allows the crossover to occur) is 

attached. At 30 mph or so, the engineer will visually recognize which way the switch is attached 

to determine which direction the train will go in. 

Signals should be spaced more like those in the mimicked track; or, at the very least, they should 

be spaced farther apart than they are currently. To change the locations of the signals in the 

simulation, which now are based on where road segments begin and end, would be difficult. The 

only way to alter signal locations presently is to change the minimum block length for a signal to 

be drawn, and this would only change the number of signals drawn, not the signals’ locations. 

The signal locations could be read in from a file, similar to the mileposts, and if there is no file, 

they could default to the way they are drawn now. However, then the signal locations would not 

coincide with road segment ends, which is how authorities are calculated. A new paradigm for 

calculating and enforcing signal territories will likely be quite time-consuming. 

Two engineers said that the “clickety-clack” sounded like “flat” (i.e., worn) wheels, though they 

admitted that they sounded somewhat like jointed rail. Welded rail apparently does not make that 

type of noise. This should be investigated and, if need be, re-recorded. 

The equalizing reservoir pressure should read the same as the brake pipe during release. The 

brake pipe should “follow” the equalizing reservoir. 

One engineer mentioned that it was “strange” that there were no other trains in the system, but 

none mentioned the lack of cars at the grade crossings. 

38
CHANGES NEEDED TO IMPROVE FIDELITY OF TRAIN CONTROL 

During the course of the experiments, we uncovered many ways in which the train control 

paradigm of our simulator diverged significantly from what the engineers were used to: 

When encountering a signal that is more restrictive than the previous signal, the engineer needs 

to acknowledge that signal by depressing a button (either a dedicated “signal acknowledge” 

button, or the alerter), regardless of the train’s speed; if the train’s speed is above that of the new 

signal, the brake system must be suppressed (i.e., a certain minimum amount of brake pressure 

must be applied) to avoid a penalty application of the full-service brakes. This suppression level 

may vary from one train to the next between 14 and 26 psi reduction. This is an easy change to 

implement in the software and would be a good first task for someone trying to learn the 

simulation. 

The engineer normally is required to wait until the rear of the train has cleared a less restrictive 

signal before accelerating beyond the old (more restrictive) signal limit. The train “length” needs 

to be defined, and the piece of code that checks the train’s speed against the effective limit 

should take this into account. 

The engineer must wait some period of time after stopping to allow the brake system to 

“recharge,” or recompress adequate pressure in the brake pipe to stop the train. This recharging 

time may be less than a minute after a full-service application of the brakes, or more than a 

couple of minutes if an emergency application is given. 

A train is not allowed to approach a bunker (the obstructing “pylon” at the end of a line) at more 

than 15 mph (civil limit). If there is no signal next to or above the bunker, the block approaching 

the bunker must be set to “restrict,” as the bunker represents an obstruction in the track. If there 

is a signal next to or above the bunker, the signal for the last block approaching the bunker can 

be set to either “restrict” or “approach,” either of which indicates that the engineer needs to be 

prepared to bring the train to a stop before the next signal. (The engineer who ran past the bunker 

may not have been helped by these restrictions, as he entered a 70 mph speed zone at 118 mph.) 

These changes should be made in the permanent road databases and in the dispatcher software, 

which controls the signals of all trains attached to it. 

The cruise speed should be controllable by the participant. That is, the participant should be able 

to key in, or dictate in some other way, a speed to which the system would then accelerate or 

decelerate. This is already implemented in the software, but needs to be activated and explained 

in the tutorial. There are several other changes (e.g., the alerter penalizing with a full-service 

application of the brakes instead of a penalty application, the ATP giving a buffer zone above the 

limit and penalizing with a full-service application only until the effective limit is achieved, etc.) 

that were made to make the simulator mimic, as close as possible, what the Amtrak engineers are 

used to. In general, these changes were implemented with command-line software switches, 

leaving the previous options intact as well. Though this system allows maximum flexibility when 

running the software, the proper command-line options need to be learned. Refer to the simulator 

training manual (at the Volpe Center) for more details. 

39
WAYS THE ENGINEERS’ BEHAVIOR DIFFERED FROM EXPECTATIONS 

The Amtrak engineers’ control decisions based on signal levels were quite different than what 

had been expected. The engineers expressed that they might not give any application of the 

brakes right away (or at least not a very heavy application) when encountering a more restrictive 

signal. They generally know the distance (and thus the time) to the next signal as well as how 

restrictive that next signal could possibly be (i.e., the worst-case scenario) and can set their speed 

accordingly. Thus, the engineer might purposefully put the train in an overspeed situation (to 

save time, or to keep some brake pressure in reserve) when encountering a more restrictive 

signal. Though the speed and control input are recorded at regular intervals and later can be 

reviewed, the locomotive foreman explained that such control behavior did not reflect poorly in 

any way on the engineers. In an overspeed situation such as the one described above 

(approaching a more restrictive signal at a speed above the speed indicated by the signal), the 

engineer has five seconds to apply the brakes (at any level) before a penalty full-service 

application of the brakes is given. If the engineer applies the brakes before the penalty is applied, 

the penalty is averted. Some of the engineers seemed to operate the train in this way (i.e., 

braking slowly despite being above the speed limit indicated by the signal), though others did not 

(i.e., they observed the speed limit indicated by the signal). 

If a light “drops in your face” (i.e., turns to red when the signal is already in your range of 

visibility), it most likely indicates a failure of the track circuitry, and is thus not necessarily 

treated as a complete emergency. If the operator can see the track ahead of him for a distance 

equal to or greater than the train’s full-service stopping distance, he might just go to full-service 

braking, even if that would mean passing the red signal. However, if there is a siding or any 

other portion of the track that he cannot see, the engineer will go to emergency braking just to be 

sure. 

As mentioned before, several of the engineers expressed that they tend not to use full-service 

braking unless the situation requires it, as they like to keep some pressure in reserve in case of an 

emergency. Thus, the engineer would begin decelerating farther in advance than a full-service 

application would allow, but at a lower rate (maybe 13 to 16 pounds of reduction5

). A couple of 

the participants had trouble stopping at the stations accurately at first, due to this aversion to 

providing a full-service application of the brakes, but two of the three engineers performed 

satisfactorily by the end of the training (i.e., after being instructed that the system was designed 

to require a full-service application of the brakes). One engineer suggested that having the fullservice braking curve on the preview display would encourage risk-taking, and suggested having 

a “14-pound reduction” curve instead. The engineer who did not perform satisfactorily had to 

resort to the emergency brakes for three of the station stops, and actually crashed through the 

bunker at South Station at 20 mph. 

 

5

 Engineers talk about the amount of braking force applied to the wheels in terms of “pounds.” They are referring to

the pounds per square inch, or psi, of brake pressure that is exhausted from the brake pipe during a brake 

application. A pressure equal to this “reduction” is applied to the brake shoes. The maximum possible service 

application of brakes varies between 24 and 29 pounds, depending on the train, with zero pounds (or “no 

reduction”) corresponding to no application of the brakes. 

40
The locomotive foreman suggested that we gather data on the acceleration and deceleration 

forces exerted on the train (as the IITRI simulator does) and penalize the participants 

accordingly, as this constitutes a major part of their training. In particular, the engineers are 

trained to avoid using full-service brakes when stopping at a station, to avoid jolting the 

passengers. Collecting this data is a straightforward task, but conveying the forces generated in 

braking and acceleration may be difficult if these characteristics are not what the engineers are 

used to. 

GENERAL SUGGESTIONS 

Several participants requested an indication of the “cruise set speed” on the preview displays 

when cruise control is active. 

Participants’ performance might benefit from an audible indication of a change in the preview 

display status. The engineers are used to allocating their attention out the window (usually the 

side window), looking for reference points and thus need a cue to check the preview display 

more frequently. However, at least one of the engineers also expressed that he relies heavily on 

the cab signals and thus checks the cab displays relatively frequently. 

41

GLOSSARY

Automatic continuous braking systems: Provide full-service braking power to each car in the 

event of a loss of power or a break-in-two. 

Automatic train protection: Protects the train from over-speed or signal restriction violations by 

automatically applying the brakes when the speed limit is surpassed by a specified amount for 

a specified period of time, or when a signal restriction is not acknowledged. 

Cab signaling: In-cab display of the wayside signals for the current block. 

Consist: The combination of rail cars and locomotives that make up the train. 

Interlocking: Protect areas around switches, railroad grade crossings, and crossovers by linking 

the signal aspect with the interlocking state and preventing unsafe routings. 

Nominal speed curve: The speed above which a train cannot decelerate or stop in time for the 

next signal, using a full service brake application. 

43

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