Field Evaluation of a Wireless Handheld 

Computer for Railroad Roadway Workers U.S. Department 

of Transportation 

 Federal Railroad 

Administration

 

Office of Research 

and Development 

 

Washington, DC 20590 

Human Factors in Railroad Operations

DOT/FRA/ORD-09/02 Final Report This document is available to the 

January 2009 public through the National Technical 

 Information Service, Springfield, VA 22161 

This document is also available on 

 the FRA website at www.fra.dot.gov 
 

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

January 2009 

3. REPORT TYPE AND DATES COVERED 

Final Report 

September 2003-February 2005 

4. TITLE AND SUBTITLE

Field Evaluation of a Wireless Handheld Computer for Railroad Roadway Workers 

6. AUTHOR(S) 

Neslihan Doran and Jordan Multer 

5. FUNDING NUMBERS 

EB101/RR04 

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

U.S. Department of Transportation 

Research and Innovative Technology Administration 

John A. Volpe National Transportation Systems Center 

Cambridge, MA 02142-1093 

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REPORT NUMBER 

DOT-VNTSC-FRA-08-05 

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U.S. Department of Transportation 

Federal Railroad Administration 

Office of Research and Development

1200 New Jersey Ave. SE, MS 20 

Washington, DC. 20590 

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DOT/FRA/ORD-09/02 

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

Springfield, Virginia 22161. This document is also available on the FRA web site at 

www.fra.dot.gov. 

12b. DISTRIBUTION CODE 

13. ABSTRACT 

This report is the third in a series describing the development and evaluation of a software application to facilitate 

communications for railroad roadway workers using a wireless handheld computer. The current prototype operated on a cell 

phone integrated with a personal digital assistant (PDA). The roadway worker can perform two types of communication related 

tasks with the application: request information about train status and territory without assistance from the dispatcher and request 

track authority. 

This study documents a field evaluation of the application to identify the safety implications of digital wireless communications 

on roadway worker safety and performance. It compares performance using traditional voice radio and telephone 

communications to the use of an application that can display this information in a visual form. 

The software application was faster and more effective than the voice radio communication when used to convey long messages 

such as filling out Form Ds. Radio communication was faster than the visually based software application for simple 

communications that did not tax the operator’s memory. 

15. NUMBER OF PAGES

58 

14. SUBJECT TERMS

cognitive task analysis, data link, digital communications, decision-making, intelligent railroad 

systems, personal remote terminal, railroad dispatcher, roadway worker, track allocation, train 

routing, usability 16. PRICE CODE 

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NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std. 239-18298-102 
 

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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 

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

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 34

Inches

Centimeters 01 3 26 1 4 5 7 1 1098 1 12

5

3

QUICK FAHRENHEIT - CELSIUS TEMPERATURE CONVERSION

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

 

°F

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

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

ii
 

Acknowledgments 

This study is part of a research program to evaluate the human factors implications of computer 

and communications technology in railroad operations. The Federal Railroad Administration’s 

(FRA) Office of Research and Development sponsored the research, as part of its activities to 

develop Intelligent Railroad Systems (FRA, 2002). 

The authors would like to acknowledge several people who helped in the development of this 

work. John .K. Pollard, Amanda Difiore and Tony Iosifidis from Volpe National Transportation 

Systems Center were always ready to provide professional assistance and guidance with their 

experience with their technical expertise in hardware, software and methods for analyzing 

communications. We owe a debt of gratitude to John D. Ray, Deputy Director of Railroad 

Operations at the Massachusetts Bay Transportation Authority, Carl Senftleben, Superintendent 

of Train Operations and Ed O’Connell, Control Systems Dispatch Manager from Massachusetts 

Bay Commuter Railroad Company (MBCR) who opened their facility to us and worked with us 

to make the field test happen. We also thank MBCR employees, Robert Cashman and David 

West who participated in study as dispatcher and railroad engineer. They contributed their time 

and experience to complete this study. 

Finally, we would like to thank Thomas Raslear our sponsor, in the Federal Railroad 

Administration’s, Office of Research and Development for supporting this work. 

iii
 

iv
 

Table of Contents 

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

1. Introduction................................................................................................................................. 6 

1.1 Adapting Digital Communications Technology for Roadway Workers .............................. 6 

1.2 Research Goals ..................................................................................................................... 8 

2. Methodology...................................................................................................................... 10 

2.1 Overview............................................................................................................................. 10 

2.2 Current Radio System......................................................................................................... 10 

2.2.1 System Description ................................................................................................... 10 

2.2.2 Baseline Measurements ............................................................................................ 14 

2.3 Data Link System................................................................................................................ 14 

2.3.1 System Description ................................................................................................... 14 

2.3.2 Experimental Measurements..................................................................................... 18 

3. Results ............................................................................................................................... 20 

3.1 Current Voice Radio System .............................................................................................. 20 

3.1.1 Observations ............................................................................................................. 20 

3.1.2 Data Classification.................................................................................................... 20

3.1.3 Summary of Results.................................................................................................. 22 

3.2 Data Link Communications ................................................................................................ 25 

3.2.1 Summary of Results.................................................................................................. 25 

3.2.2 User Feedback........................................................................................................... 26 

3.3 Current Radio System vs. Data Link System ..................................................................... 28 

4. Conclusion......................................................................................................................... 30 

4.1 Use of Positioning Technologies ........................................................................................ 30 

4.2 Use of Handheld Device Printers........................................................................................ 30 

4.3 Custom Modifications......................................................................................................... 31 

Appendix A. NORAC Movement Permit Form D ....................................................................... 32 

Appendix B. Smartphone Screenshot ........................................................................................... 34 

Appendix C. Dispatcher Screenshots............................................................................................ 38 

Appendix D. NASA-TLX Scale Form.......................................................................................... 42 

Appendix E. Questionnaires ......................................................................................................... 44 

Glossary ........................................................................................................................................ 46 

References..................................................................................................................................... 49 

v
 

List of Figures 

Figure 1. Commuter Rail Map...................................................................................................... 11 

Figure 2. Dispatcher’s Work Environment................................................................................... 12 

Figure 3. Train Location Display Screen...................................................................................... 13

Figure 4. Kyocera Smartphone QCP6035 .................................................................................... 15 

Figure 5. Smartphone Menu ......................................................................................................... 16 

Figure 6. Train Schedule Sheet..................................................................................................... 16 

Figure 7. Network Setup at the Testing Facility........................................................................... 18 

Figure 8. Communication Content by Day................................................................................... 23 

Figure 9. Time to Request and Receive Form D by Data link...................................................... 25 

List of Tables 

Table 1. Track Display Color Coding Scheme ............................................................................. 12 

Table 2. Real-Time CDS Information Displayed On Smartphone............................................... 17 

Table 3. Voice Radio Classification Codes .................................................................................. 21 

Table 4. Error Identification Codes .............................................................................................. 21 

Table 5. Frequency of Voice Radio Railroad Communication..................................................... 22 

Table 6. Communication Errors by Occupation ........................................................................... 24 

Table 7. Errors Committed by Type ............................................................................................. 24 

Table 8. NASA-TLX Scale Rating Results .................................................................................. 27 

vi
 

Executive Summary 

Overview/Introduction 

Railroad operations rely on railroad dispatchers, train crews, and roadway workers to coordinate 

their activities. Railroad dispatchers allocate track for the safe movement of trains and 

maintenance. Train crews consisting of locomotive engineers and conductors operate trains, 

while roadway workers maintain the track infrastructure. Railroads depend upon 

communications technology to enable these employees to coordinate their activities and operate 

safely and productively. Analog communications technology as exemplified by voice radio while 

still the primary method for communications time critical information limit the ability to improve 

safety and productivity. 

The voice radio system presents two major problems. First, the available radio bandwidth is 

inadequate to support current communication needs (Federal Railroad Administration, 1994; 

Roth, Malsch, and Multer, 2001). Second, the information communicated using voice radio 

imposes a significant burden on operator’s memory when sending complex messages. 

The development of digital communication technology offers the potential to improve railroad 

safety and productivity. The use of digital communications has been proposed as a 

communication medium to supplement voice radio. Digital communications uses this bandwidth 

more efficiently than voice radio. Information transmitted digitally can be presented aurally or 

visually. Displaying messages visually can reduce radio frequency congestion by decreasing the 

number of messages communication by voice radio. These characteristics offer opportunities to 

address the limitations posed by voice radio. 

For digital communications to achieve their proposed benefits, all three parties, dispatchers, train 

crews, and roadway workers must have access to this technology. For the dispatcher working in 

an office environment and the train crew working in the protected space of a locomotive cab 

sufficient space exists to locate this equipment. However, adapting this technology for use by 

roadway workers represents a special challenge. Except for workers who operate equipment on 

the track, such as track inspectors, many roadway workers require a portable communication 

device with a sufficiently small form factor so that they can carry it along with other equipment 

needed to perform their job. 

A proposed railroad application of this technology involves a wireless handheld device such as a 

cell phone with integrated Personal Digital Assistant (PDA) to enable the information transfer 

between the roadway worker and the dispatcher. 

Oriol et al. (2004) identified the use of information technologies needed to fulfill the 

requirements of the railroad operations from the perspective of roadway workers. A prototype 

was designed to establish direct communication with the dispatching center to retrieve 

information, previously unavailable, without contacting the dispatcher by voice radio or cell 

phone. The testing for his work was done in a laboratory environment with three roadway 

workers and one smartphone. Oriol found that a data link device, able to receive real time 

information about train location, greatly improves situation awareness of roadway workers by 

letting them know about many of the potential hazards. Better knowledge of train location or 

higher situation awareness resulted in fewer requests for track authorization. 

1
 

Research Goals 

The goal of this project was to compare voice radio communications with a proposed data link 

communication system for the purpose of contrasting error rates and usability of these two 

communication media. As previous studies demonstrated that voice communication was better 

for short conversations, this study mainly focuses on the most time consuming communication 

type in railroad operations: authorizing train and equipment movements (i.e., Form D 

authorizations). 

The current project was aimed at testing the device in situ, with active dispatchers and track 

workers on the real routes. In this study, a handheld communication device combining a PDA 

and a cell phone was used for data link communications. Throughout the report the device is 

referred as a smartphone. This work presents the statistics related to both communication media, 

voice radio and data link, in the real-time field tests. The objective was to determine whether 

communication using data link improved compared to voice radio. 

Method 

The performance differences between data link and voice radio were measured separately at the 

Massachusetts Bay Transportation Authority’s (MBTA) north side commuter rail system 

dispatching center. In the voice radio condition, radio communications between the dispatcher 

and the train crews, roadway workers were recorded and then analyzed. 

Using the radio system, dispatcher receives many calls at the same time. The dispatcher decides 

which call to take based on the importance of the message. The communications between one 

dispatcher and the roadway workers in his territory were recorded for 5 consecutive days then 

coded to identify message content and error types. The average time required to complete a Form 

D (movement authorization) and/or a foul time was used as a measure to compare the radio 

system with the data link system. 

The dispatcher interacted with the roadway workers with the data link system using a computer 

monitor, keyboard and mouse. The experiment was conducted with one dispatcher and one 

roadway worker. The roadway worker contacted dispatcher using the smartphone. The device 

was used to request, fill out, and cancel Form D’s and to check the train status of the scheduled 

trains. Due to time restrictions and the security concerns of the dispatcher center supervisor, 

other features of the device such as territory information and detailed train location information 

were not available for testing. 

Results 

Voice Radio System 

The dispatcher environment was observed several times to get a better understanding of the daily 

work and issues. The communications included all interactions of one dispatcher: the 

communications with other dispatchers, train conductors and MOW crews. During the data 

collection period, the following remarks were observed: 

• Radio communication was subject to interference, background noise, fadeout, and sound 

distortion. The noise level in a locomotive cab made it difficult for the dispatcher and the 

train crew to hear each other. 

• From their experience, the dispatchers generally figure out the crew’s request. 

2
 

• As the voice radio link operated in a broadcast mode between a single dispatcher and all the 

trains and maintenance-of-way crews operating within the range of the radio under the 

dispatcher’s control, radio congestion is was a common occurrence when train traffic and 

maintenance activity were heavy. 

• In addition to the limitations imposed by the congestion, the radio communications have 

inherent human error issues: acoustic confusions, alphanumeric transpositions, and 

misinterpretation due to poor pronunciation are just some examples of the human induced 

errors. 

All these factors affected the dispatchers’ performance as well as the train crews and 

maintenance crews by causing delays in the issuance of the movement authorizations and track 

occupancy permits. 

Approximately 5 percent of the data were excluded from the analyses because the voice radio 

transmissions were inaudible to the analyst. More than half (58 percent) of the communications 

involved information requests. Movement authorizations (Form D) requests were the second 

most frequent type of communication activity followed by coordination activities and emergency 

activities. 

The analysis of five consecutive days of communications showed that the dispatchers were 

spending more time with Form D’s than with any other communications. The readback/hearback 

routine takes took the longest amount of time compared to the other types of communications. 

The analysis shows that filling out Form D’s via voice radio took twice as much time as the other 

types of communication. 

Analysis shows that the errors were mainly caused by the noisy radio communications. As 

mentioned earlier, the field environment, where the radios were used, was noisy because of loud 

train equipment. The presence of the dead spots, where the radio communication was inaudible, 

complicated the dispatcher’s work. On the basis of their experience, dispatchers frequently tried 

to guess the missing parts of the conversations. A common error took place when one of the 

parties transposed alphanumeric information such as train ID. Roadway workers committed 55 

percent of the transmission errors. Dispatchers accounted for one-third of transposition errors 

while train crews accounted for 11 percent of these errors. When identification errors or 

incorrect information occurred, dispatchers accounted for more than 80 percent. Rail workers 

were involved in approximately 17 percent. 

Comparison between voice radio and data link 

During each day of the test period, the field test crew (consisting of roadway workers) completed 

around 10 Form Ds. The study documented how long the maintenance employee took to request 

a Form D and for the dispatcher to fill out the form and to assign time effective. 

The major advantage of the new system was the decline in the number of communication errors. 

Since the cancellation of Form D’s was automated, the error for this particular task was 

eliminated. Once the foreman finished the job, he/she canceled the work permit without 

communicating by voice with the dispatcher. The dispatcher saw the form on the “cancelled” 

display window and acknowledged the termination of the work permit. 

3
 

The data, using the voice radio technology, shows that Form D’s were the most time consuming 

type of communication between the dispatcher and the crew on the tracks. On average, a 

dispatcher took 3 minutes 13 seconds to complete one Form D. This study shows that data link 

technology can decrease this time significantly. Using a smartphone this completion time was 

reduced to an average of 65 seconds. This result was different from Masquelier’s (2004) and 

Oriol’s (2004) laboratory experiment results. Their findings showed that the work permission 

processes were slower but more accurate with the device than with the radio. This study, 

conducted under conditions more closely approximating real world, showed that the work 

authorization processes were more accurate and faster with the handheld device. The study also 

shows that the new system, in providing the visual aid to users, eliminated alphanumeric 

transposition errors when requesting and issuing Form D movement authorities. 

The new system reduced errors attributable to auditory communications. As shown earlier, with 

the voice radio, some of the errors occurred because the radio transmissions were difficult to 

hear. They also minimized errors associated with memory lapses and numeric transpositions that 

are common with auditory-based communications. 

New error types emerged that were linked to the visual modality and usability issues such as 

tapping on the wrong part of the screen or navigation difficulties with the software. Usability 

errors should decrease with time as designers adapt the application to meet the needs of the users 

and the user adapts to the new user interface. 

Conclusions 

The current study supported the results of Malsch et al. (2001), Oriol et al., 2004, and 

Masquelier et al (2004) showing data link communications reduce voice radio-related errors and 

improve efficiency when communicating long and complex messages. The new system was 

faster and more effective than radio communication when used to convey long messages such as 

filling out Form Ds. Radio communication was faster than the data link for confirmation 

communications that only require yes/no answers. One reason for this difference appears to be 

the users’ lack of familiarity with the device. The time to convey short messages should improve 

as the users become more proficient with the new system. 

The users expressed many concerns about smartphones. Most of these concerns were related to 

its design. Users thought that the commercial smartphone used in this study was too small and 

delicate to be used in railroad operations. They expressed preference for a rugged device that 

would withstand being dropped and operating in a dusty environment. Another major issue was 

the screen resolution: the screen should be modified so that it is visible in direct sunlight. Other 

concerns were related to the unfamiliarity of the users with the PDA technology in general. 

Some users were unable to navigate within the menu and unable to go to the main menu once 

they were on a page that was not familiar to them. 

The data link system would reduce the dispatcher’s communication load by eliminating some 

incoming calls related to information requests like schedule updates and weather inquiries. The 

smartphone would receive updated data from the dispatch center, so the train schedule would be 

updated as soon as any change is entered at the control center. As the smartphone has access to 

the internet, the weather information could be checked by the roadway workers without 

contacting the dispatcher. The data link would also reduce the dispatcher’s workload by 

transferring long conversations to the digital medium. During long conversations, the dispatcher 

4
 

both receives and sends many messages. With the data link system, the dispatcher could send the 

same amount of information currently contained in multiple voice messages with only one digital 

message. 

5
 

1. Introduction 

1.1 Adapting Digital Communications Technology for Roadway Workers 

Railroad operations rely on railroad dispatchers, train crews, and roadway workers to coordinate 

their activities. Railroad dispatchers allocate track for the safe movement of trains and 

maintenance. Train crews, consisting of locomotive engineers and conductors, operate trains, 

while roadway workers maintain the track infrastructure. Railroads depend on communications 

technology to enable these employees to coordinate their activities and operate safely and 

productively. Analog communications technology, exemplified by voice radio while still the 

primary method for communications and time critical information, limits the ability to improve 

safety and productivity. 

The voice radio system presents two major problems. First, the available radio bandwidth is 

inadequate to support current communication needs (Federal Railroad Administration (FRA), 

1994; Roth, Malsch, and Multer, 2001). Within any geographic region, a much smaller number 

of radio channels are available for railroad operations than what the Federal Communications 

Commission has allocated. As each channel can only have a single user, other workers who want 

to use the same channel must wait until it is clear. Due to bandwidth limitations and high 

communication workload, voice radio communication channels are congested. 

Second, the information communicated using voice radio imposes a significant burden on 

operator’s memory when sending complex messages. To minimize the potential for errors on 

safety critical communications, railroad workers and dispatcher record important information on 

paper. They also engage in a readback/hearback procedure in which the receiver reads back the 

message from the sender, while the original sender listens to the message read back by the 

receiver to check that it was heard correctly. Although this process reduces the potential for 

error, it increases the time required to complete a transaction. This procedure also reduces the 

bandwidth available for communication. 

The development of digital communication technology offers the potential to improve railroad 

safety and productivity. The use of digital communications has been proposed as a 

communication medium to supplement voice radio. Digital communications uses this bandwidth 

more efficiently than voice radio. Information transmitted digitally can be presented aurally or 

visually. Displaying messages visually can reduce radio frequency congestion by lowering the 

number of messages communication by voice radio. These characteristics offer opportunities to 

address the limitations posed by voice radio. 

However, if the needs and limitations of operators are not clearly understood, new technology 

may adversely impact safety and productivity. Simply providing additional bandwidth could 

adversely impact the dispatcher’s performance, if the design of the system does not consider the 

communication load the dispatcher can handle safely. 

For digital communications to achieve their proposed benefits, all three parties, dispatchers, train 

crews, and roadway workers must have access to this technology. For the dispatcher working in 

an office environment and the train crew working in the protected space of a locomotive cab 

sufficient space exists to locate this equipment. However, adapting this technology for use by 

roadway workers represents a special challenge. Except for workers who operate equipment on 

the track such as track inspectors, many roadway workers require a portable communication 

6
 

device with a sufficiently small form factor so that they can carry it along with other equipment 

needed to perform their job. 

A proposed railroad application of this technology involves a wireless handheld device, such as a 

cell phone with integrated Personal Digital Assistant (PDA), to enable the information transfer 

between the roadway worker and the dispatcher. 

Previous studies (Malsch, Sheridan, and Multer, 2001; Basu, 1999; Oriol, Sheridan, and Multer, 

2004; and Masquelier, Sheridan, and Multer, 2004) analyzed the communication environment of 

the dispatcher to address questions based upon digital communications technology (also referred 

to as data link) as a means for sharing information in railroad operations. These studies 

examined what kind of information is appropriate for each medium (voice and visual), and by 

what criteria a dispatcher will select which communication medium. 

Earlier studies covered the dispatcher’s side (Malsch et al., 2001 and Basu, 1999) and the 

roadway worker’s side (Oriol et al., 2004 and Masquelier et al., 2004) of the issue separately. 

Malsch and Basu’s study evaluates the impact of using digital communication in place of the 

radio, on the dispatcher. Their findings and suggestions indicate: 

• Dispatchers like the idea of data link technologies. They liked the fact that they could receive 

requests from trains or work crews in an email-like fashion instead of radio calls that had to 

be answered in a first-come first-served basis. With this architecture, they could assign 

priorities to incoming messages and deal first with the most important ones. 

• They did not understand how the work crews in the field would send them digital messages. 

Not only did they not have the appropriate tool but some of them were unfamiliar with 

computers. 

• They found it valuable that they did not have to repeat a message many times with data link. 

• They welcomed a system that helped to solve the congestion problem affecting radio 

communications. 

Oriol et al. (2004) identified the use of information technologies needed to fulfill the 

requirements of the railroad operations from the perspective of roadway workers. A prototype 

was designed to establish direct communication with the dispatching center to retrieve 

information, previously unavailable, without contacting the dispatcher by voice radio or cell 

phone. The testing for his work was done in a laboratory environment with three roadway 

workers and one smartphone. Oriol found that a data link device able to receive real time 

information about train location greatly improves situation awareness of roadway workers by 

letting them know about many of the potential hazards. Better knowledge of train location or 

higher situation awareness resulted in fewer requests for track authorization. The experiment 

showed that roadway workers tended to remember slightly more information when they used the 

data link device. His work highlighted the following differences between radio and data link 

communications: 

• Data link device results in safer operations. 

• Data link device results in better knowledge of potential risks but in a reduced number of 

jobs completed. 

7
 

• Communication was slower but more accurate using the data link device. The workload 

remained the same. 

Masquelier et al. (2004) also conducted a laboratory study. Using the Massachusetts Institute of 

Technology (MIT)/Volpe National Transportation Center (Volpe) Railroad Dispatching 

Simulator, he studied the dispatcher’s perspective. Their work also showed that track 

authorization processes were slower but more accurate with the device than with the radio. His 

experiment found no error in location because of the Global Positioning Satellite (GPS) system, 

but trains tend to be more delayed with the device mainly due to the unfamiliarity of the 

participants with the system. Masquelier et al. (2004) suggested reducing the territory that each 

dispatcher controlled to compensate for the increase in workload due to the tracking display. 

The prototype communications system-based wireless data link device was intended to increase 

the safety of roadway workers while reducing the radio congestion. GPS has already been used 

to locate track cars. The data link device consisted of a handheld information appliance with 

wireless access to the internet, which is connected to a GPS receiver. 

Given that the previous studies were conducted in a laboratory setting, this study evaluated data 

link technology for railroad operations in a field environment. The intention is to assess the 

impact of this application on safety and productivity in actual field situations and compare them 

to the previous simulation-based studies. 

1.2 Research Goals 

The goal of this project was to compare voice radio communications with a proposed data link 

communication system for the purpose of contrasting error rates and usability of these two 

communication media. As previous studies demonstrated that voice communication was better 

for short conversations, this study mainly focuses on the most time consuming communication 

type in railroad operations: authorizing train and equipment movements (i.e., Form D 

authorizations). 

A wireless handheld device was tested earlier in an experiment, using simulators and scenarios 

for daily railroad operations. One group of roadway workers carried out assigned tasks using the 

smartphone and the other group used the radio in the conventional way. The laboratory research 

proved that the data link system represents a potential solution to supplement voice data. 

Previous results suggest that data link can improve communication efficiency, safety, and 

situation awareness. During the experiments, by providing information in a visual format, data 

link eliminated readback errors and hearback errors associated with the auditory modality. 

Previous experiments also suggest that data link is better suited for communications whose 

length or complexity impose a significant burden on memory. The current project was aimed at 

testing the device in situ, with active dispatchers and track workers on the real routes. 

In this study, a handheld communication device combining a PDA and a cell phone was used for 

data link communications. Throughout the report the device is referred as a smartphone. This 

work presents the statistics related to both communication media, voice radio and data link, in 

the real-time field tests. The objective was to determine if communication using data link 

improved compared to voice radio by: 

• Requiring fewer messages, 

8
 

• Requiring less time, 

• Reducing or eliminates certain types of messages, 

• Reducing or reduces imprecision and errors, and 

• Reducing communication delays. 

9
 

2. Methodology 

2.1 Overview 

The performance differences between data link and voice radio were measured separately at the 

Massachusetts Bay Transportation Authority (MBTA)’s north side commuter rail system 

dispatching center. In the voice radio condition, radio communications among the dispatcher, 

train crews, and roadway workers were recorded and then analyzed. 

Using the radio system, the dispatcher receives many calls at the same time. The dispatcher 

decides which call to take based on the importance of the message. The communications 

between one dispatcher and the roadway workers in his territory were recorded for 5 consecutive 

days then coded to identify message content and error types. The average time required to 

complete a Form D (movement authorization) and/or a foul time was used as a measure to 

compare the radio system with the data link system. 

The dispatcher interacted with the roadway workers with the data link system using a computer 

monitor, keyboard, and mouse. The experiment was conducted with one dispatcher and one 

roadway worker. The roadway worker contacted dispatcher using the smartphone. The device 

was used to request, fill out, and cancel Form Ds and to check the train status of the scheduled 

trains. Due to time restrictions and the security concerns of the dispatcher center supervisor, 

other features of the device such as territory information and detailed train location information 

were not available for testing. 

2.2 Current Radio System 

2.2.1 System Description 

The Commuter Rail Operations Control Center controlled the operations and the management of 

MBTA’s north side commuter rail system. The system was operated by employees from The 

Massachusetts Bay Commuter Railroad Company (MBCR). Dispatchers used the Centralized 

Dispatching System (CDS) to monitor and control train movements and maintenance activities. 

The dispatcher controlled train movements and maintenance within a defined geographic area 

called a territory. The area controlled by the PC based dispatching system was divided into five 

territories, represented by four branch lines and a terminal area. The top half of Figure 1 shows 

the four branches lines and Boston’s North Station terminal. 

10
 

Figure 1. Commuter Rail Map 

Figure 2, shows the layout of a typical dispatcher workstation. The workstations are located in a 

large room and the dispatchers can interact with each other. They can inform each other about 

the train delays, extra trains, and any malfunctions or ask whether a dispatcher is ready to receive 

a train. 

11
 

Figure 2. Dispatcher’s Work Environment 

Dispatchers monitor train movement and maintenance operations through several track displays, 

(see Figure 2). The physical characteristics of the track such as curves, grade crossings, and 

roads in the neighborhood are not shown. Figure 3 shows a close-up one of these screens. In 

Figure 2, six screens display the tracks, four screens display train timetables, one screen shows 

the movement authorization forms, and one screen shows other information related to control 

tasks. The track display used the following color coding scheme as shown in Table 1. 

Table 1. Track Display Color Coding Scheme 

White Track segment is available for routing trains or other uses 

Green Track segment has been cleared for train routing. 

Red Train or track vehicle occupies the track segment 

Blue Track segment is blocked for maintenance. 

12
 

Figure 3. Train Location Display Screen 

When a train occupied a track, its ID number and its movement direction were indicated on the 

track display. Train delays were also coded in red, below the train’s ID number indicating the 

length of the delay. The delay was updated as the train passed an interlocking. 

Each workstation was equipped with track display screens, a telephone, a radio and a computer. 

Dispatchers also kept paper records of the train schedules/timetables in case of system failure. 

Train conductors, locomotive engineers, and work crews conducted communications via radio or 

telephone. They received multiple requests at the same time over the radio. As a consequence, 

the dispatcher delayed responding to some requests. When the radio failed, they used the cell 

phone for one-to-one conversations with people in the field. Telephone and radio 

communications were integrated into a single communication system in the dispatch center to 

make it easier for dispatchers to handle all the communications. Dispatchers switched between 

radio and telephone using a foot pedal connected to the system. All such conversations were 

digitally recorded and archived for 90 days. 

13
 

Dispatchers used a computer to print the movement authorization forms for backup purposes to 

access the updated train schedules to view the passenger counts and train consist1

 information. 

Through their computers dispatchers obtained real-time weather information through the Internet 

and notified trains when delays were anticipated. 

2.2.2 Baseline Measurements 

Ninety three hr of voice communications, in the railroad environment were sampled over a 5-day 

period. Following data collection, each conversation was coded according to information 

content, error type, and duration. 

First, the conversations were recorded using a digital audio tape (DAT) recorder, a videocassette 

recorder (VCR), a lipstick video camera mounted on a microphone stand with a gooseneck, 

headphones, and a small monitor. Twenty-four hours of audio was captured on the VCR with 

low frame rate video of the display that showed the time and the date of the recorded material. 

Also, four hours of audio was recorded on the DAT machine which duplicated the first 4 hr on 

the video tape. Five consecutive days of conversations were recorded. 

The analog tape recordings were transferred to a digital medium using the software application: 

Sound Forge 5.0. This was a two-track digital audio editor with wide-ranging audio processing 

capabilities. For ease of data storage and processing speed, each audio file was limited to 2-hour 

period. The conversation time on the recordings was longer than the labeled messages because of 

the personal conversations that were discarded in the analysis. 

During the 5 days of data collection, dispatchers were observed several times to obtain an 

understanding of the work issues related to communication. 

2.3 Data Link System 

2.3.1 System Description 

Digital communications took place with the dispatcher using a desktop computer to send and 

receive communications while the roadway worker used a cell phone with an integrated PDA2

. 

A Kyocera Smartphone, Model 6035 was used in this study as shown in Figure 4. The 

information was transmitted through a wireless internet connection. A screen shot of the 

smartphone showing the main menu for the roadway worker communication application is 

illustrated in Figure 5. The device weighed 7 ounces and was nearly an inch thick. It contained 8 

megabytes of memory. 

The dispatcher communicated with the roadway worker using a desktop computer. A secure 

connection provided the updated train information to the worker in the field. The same 

connection enabled the information flow between the dispatcher and the crew member. The 

roadway worker filled out the Form D’s using the drop down menus on the smartphone. The 

updated display of the forms minimized the need to select individual alphanumeric characters to 

write messages. The crewmember interacted with the display using a stylus to select options 

 

1

 Consist: makeup or composition (as of coal sizes or a railroad train) by classes, types, or grades and arrangement 

2

 Since the completion of this research the railroad industry has begun evaluating the use of this technology. They 

refer to this application as a Personal Remote Terminal (PRT). 

14
 

from dropdown menus on each screen. Appendix B shows all the display screens for each of the 

possible menu selections. Upon completion, the crewmember sent the form to the dispatcher who 

confirmed the information by re-entering the same data and sent it back to the worker. The last 

step involved granting “time effective.” When the time effective was assigned, the Form D 

became active and the tracks were blocked. 

Figure 4. Kyocera Smartphone QCP6035 

The data link communications were observed at MBTA’s North Station Commuter Rail Center 

in Somerville, MA. The study required an internet interface that acted as a portal to send tabular 

train operations specialist (OS) data through a secured internet connection, located at MBTA 

control center. Figure 6 shows the tabular information displayed in the Train Schedule Sheet 

(Train OS). At the request of the MBTA, Aeronautical Radio, Inc. (known as ARINC), the 

software vendor for their computer dispatching system (CDS) provided the communication link 

15
 

to obtain real-time information from the CDS. The main challenge was to provide a secure oneway data feed from the CDS to Volpe’s server and a secure one way access from the smartphone 

to Volpe’s server. 

Train and territory information

Train status

Form D / Foul Time

Request Line 4

Request Lines 2,3 Request Foul Time

Cancel/Fulfill Clear 

My Form Ds My Foul Time

Figure 5. Smartphone Menu 

To maintain a secure network, MBCR requested that ARINC use encrypted data. The major 

problem was how the CDS data would be transferred to the Volpe server. The IT department of 

MBCR offered the following setup for the equipment. 

Figure 6. Train Schedule Sheet 

All connections were secured with firewalls. The CDS was connected to the internet via virtual 

private network (VPN), which provided a secure internet connection. VPN enabled a secure 

16
 

connection without using a private modem or phone line. The Volpe server only connected to 

one IP address, the site to access the smartphone. As a final security measure, the Volpe server 

was set up to prevent the use of web browsers on the server, itself. Table 2 shows the CDS data 

transmitted to the Volpe server and the smartphone. Figure 7 shows the path by which 

information flows between the CDS and the smartphone. 

Table 2. Real-Time CDS Information Displayed On Smartphone 

Train ID 

Milepost name 

Milepost ID 

Direction of train movement 

Updated schedule 

Prior to the data collection task, the software portion of the application was evaluated for 

usability by a track foreman and a dispatcher. During usability testing of the initial system, the 

users identified several problems with the interface. These problems described below were 

corrected prior to field testing: 

• The original time format on the smartphone was a 24-hour format and the one on the 

dispatcher screen was a 12-hour format. The time format on the smartphone was changed to 

a 12-hour format so that both users used the same time format. 

• The train schedule did not show the direction. East/West directions were added to the 

configuration. 

• The dispatcher requested three additional lines on the Form D where the foreman can enter 

necessary text information: 

o speed restriction, 

o crossing protection restored, and 

o signs removed. 

• An additional information box was added to the dispatcher’s computer screen to enter 

messages in text form. 

• When a request was denied by the dispatcher, the response was not visible on the smartphone 

screen. The display was changed to make this information clearly visible. 

17
 

MBTA Server 

MBTA Network MBCR Network 

Experiment Server 

Smartphone 

Figure 7. Network Setup at the Testing Facility 

2.3.2 Experimental Measurements 

The experimental equipment was placed next to the territory for the Boston East dispatcher and 

the smartphone was given to a track inspector. While the Boston East dispatcher was doing his 

daily job, another dispatcher employed the same procedures with the experimental devices. The 

procedures were first completed by the crew in charge, and once the blocking devices were in 

place, the procedures were repeated by the experiment crew. In some instances, the experiment 

crew had to wait until the crew in charge finished their job. The redundant procedures were 

implemented to maintain safety. 

Data was collected for 13 days according to the railroad employees’ availability. The data were 

collected between 8 a.m. and 3 p.m., during the regular shifts of the experiment crew. The data 

collection effort took place over 45 days. All measurements were collected at the dispatcher 

center. Since the program lacked a built-in chronometer, time measurements for Form D requests 

were recorded using a stopwatch. Due to limited space in the track inspection vehicle, it was not 

feasible to monitor the crew on the tracks. 

18
 

19
 

3. Results 

3.1 Current Voice Radio System 

3.1.1 Observations 

The dispatcher environment was observed several times to get a better understanding of the daily 

work and issues. The communications included all interactions of one dispatcher: the 

communications with other dispatchers, train conductors and maintenance-of-way (MOW) 

crews. During the data collection period the following remarks were observed: 

• Radio communication was subject to interference, background noise, fadeout and sound 

distortion. The noise level in a locomotive cab made it difficult for the dispatcher and the 

train crew to hear each other. 

• From their experience, the dispatchers generally figure out the crew’s request. 

• As the voice radio link operated in a broadcast mode between a single dispatcher and all the 

trains and MOW crews operating within the range of the radio under the dispatcher’s control, 

radio congestion was a common occurrence when train traffic and maintenance activity were 

heavy. 

• In addition to the limitations imposed by the congestion, the radio communications have 

inherent human error issues: acoustic confusions, alphanumeric transpositions, and 

misinterpretation due to poor pronunciation are just some examples of the human-induced 

errors. 

All these factors affected the dispatchers’ performance as well as the train crews and 

maintenance crews by causing delays in the issuance of the movement authorizations and track 

occupancy permits. 

3.1.2 Data Classification 

The data gathered using the current radio system was divided into messages where each message 

corresponded to one communication initiated by any party. Generally, more than one message 

constitutes a whole conversation between the roadway worker and the dispatcher. Each message 

was labeled with the following alphanumeric pattern: number-letter number (e.g. 21.I.0). The 

first number indicates the order of the message within a 2-hour section of the day. The letter 

stands for the categorization abbreviation, the last number indicates the error (if any) of the 

message. The categorizations and the abbreviations are shown in Table 3. 

The purpose of the categorization was to identify human errors, frequency of trains, message 

content and complexity of the interaction. One type of communication error was nonstandard 

phraseology, which was defined as noncompliance with the standardized wording or phrasing of 

railroad communications. When a dispatcher issued a Form D for track occupancy, the receiver 

was required to read back all instructions verbatim. After the readback, the dispatcher was 

required to state the effective time of the instruction and the receiver was also required to read 

back the effective time. 

20
 

Table 3. Voice Radio Classification Codes 

Symbol Definition Examples 

I Information request: Notification 

communications between the 

roadway workers and the 

dispatchers. 

Any schedule changes 

Explanations for the delays 

Information about other trains 

Report track, train, signal or equipment 

malfunction 

Report location 

Check whether there are any messages 

Report the crew and time on duty 

T Coordination: Communications 

between the dispatchers. 

Coordinate identifying tracks on which to put 

trains 

Train delays 

On what track to expect a train 

What trains are coming in and on what track 

Coordinate train movements in and out of 

yard 

D Request track occupancy such as 

Form D requests/issuance of Form 

D/foul time requests/issuance of 

foul time/cleared tracks, cancelled 

Form D, cancelled foul time 

Issuing Form D 

Issuing foul time 

Request Form D 

Request foul time 

Clear a track: cancel Form D/foul time 

E Emergency related 

communications 

Location of/direction to emergencies 

Contacting a passenger for emergency calls 

Report trespassers 

Report harassment to passing trains 

U Unidentified communications Inaudible messages due to the background 

noise or bad radio reception. 

For example, a communication error occurred when a dispatcher failed to state the effective time 

of a Form D following the readback (see Northeast Operating Rules Advisory Committee 

(NORAC) operating rules). Table 4 shows the numbers used for error identification. 

Table 4. Error Identification Codes 

Code Error Description 

0 Clear conversation 

1 Inaudible conversation 

2 Congestion over the radio 

3 Alphanumeric transposition 

4 Other errors 

21
 

Each message within a conversation was coded separately to eliminate the time spent before 

answering the calls. That means usually more than just one message correspond to a complete 

conversation. As mentioned earlier, the dispatcher receives multiple calls at the same time so 

he/she answers them on a priority basis. 

3.1.3 Summary of Results 

Approximately 5 percent of the data were excluded from the analyses because the voice radio 

transmissions were inaudible to the analyst. Table 5 shows the frequency of each voice radio 

communication type. More than half (58 percent) of the communications have involved 

information requests. One type of information request was from the train crew who asked the 

dispatcher if there were any new instructions before moving from point A to point B. Movement 

authorizations (Form D) requests were the second most frequent type of communication activity 

followed by coordination activities and emergency activities. 

Table 5. Frequency of Voice Radio Railroad Communication

Type Transmission 

Frequency 

Percent of 

Communications 

Information Requests 536 58.2 

Form D Request/Issuance 202 21.9 

Coordination 141 15.3 

Emergency 34 3.7 

Unidentified 9 1.0 

Total 922 100.0 

Figure 8 represents the counts of different types of communications. Each vertical line represents 

the minimum and maximum number of communication transmissions for each communication 

type per day. The points on the vertical lines represent the average (mean) values. The track 

workers and train crews are mostly calling the dispatchers to ask for new information. These 

information requests include schedule updates and speed restrictions. These conversations were 

usually of short duration. It is hypothesized that many of these information requests can be 

reduced or eliminated by providing real-time information directly to the train crews and MOW 

crews in the field. 

22
 

AMOUNT OF EACH COMMUNICATION TYPE

0

20

40

60

80

100

120

140

160

Information Request track

occupancy

Coordination Emergency

Communication Type

Communication Number

Figure 8. Communication Content by Day 

Table 6 represents the average time that each type of communication required and the associated 

standard error. The analysis of five consecutive days of communications showed that the 

dispatchers were spending more time with Form D’s than with any other communications. The 

readback/hearback routine took the longest amount of time compared to the other types of 

communications. The analysis shows that filling out Form D’s via voice radio took twice as 

much time as the other types of communication. Generally, a dispatcher completed his/her 

communications in less than 1 min. 26 seconds (s). When filling out Form D’s, the dispatcher 

required up to 3 min. 22 s to complete the task. 

Analysis shows that the errors were mainly caused by the noisy radio communications. As 

mentioned earlier, the field environment where the radios were used was noisy due to loud train 

equipment. The presence of the dead spots where the radio communication was inaudible 

complicated the dispatcher’s work. On the basis of their experience, dispatchers frequently tried 

to guess the missing parts of the conversations. A common error took place when one of the 

parties transposed alphanumeric information such as train ID. Roadway workers committed 55 

percent of the transmission errors. Dispatchers accounted for one-third of transposition errors 

while train crews accounted for 11 percent of these errors. When identification errors or 

incorrect information occurred, dispatchers accounted for more than 80 percent. Rail workers 

were involved in approximately 17 percent. 

Table 6. Communication Duration by Type

Communication Type Mean (s) Std Error (s) 

Request Track Occupancy 120 8.9 

Coordination 71 6.8 

Emergency 53 9.4 

Information 26 1.3 

23
 

Of the errors committed by the dispatcher, 38 percent caught their own mistakes. Another 

dispatcher caught the mistakes 38 percent of the time, while a railroad worker was responsible 

for error recovery 23 percent of the time. With respect to the errors committed by a railroad 

worker, two-thirds caught their own mistakes and the dispatcher corrected them on one-third of 

the occasions. The dispatcher always corrected errors committed by the train crew. 

Table 7 illustrates the following point. One would expect the train crew to account for a smaller 

portion of the total number of errors because they were involved in relatively fewer 

transmissions. The number of errors for maintenance workers is less than errors for dispatchers 

and they correspondingly are involved in fewer transmissions. Looking at the percentage of 

transmission of each party, one notices that there is a 1.4 percent error rate across the board for 

all three parties. 

Table 7. Communication Errors by Occupation 

Occupation Communication 

Frequency Errors 

Dispatcher 922 (100%) 13 (1.4%) 

Maintenance Crew 645 (70%) 9 (1.4%) 

Train Crew 74 (8%) 1 (1.4%) 

Total 922 23 

Errors involving number transpositions were the largest category of errors accounting for almost 

40 percent of the errors committed. Table 8 displays the frequency distribution for observed 

errors. Railroad workers committed 55 percent of number transmission errors. One-third of 

number transposition errors were committed by dispatchers with the train crew accounting for 11 

percent of these errors. 

When errors of identification or incorrect information were committed, dispatchers accounted for 

more than 80 percent. Rail workers were involved in approximately 17 percent of these errors. 

Two-thirds of time discrepancy errors were committed by railroad workers with the remaining 

third committed by the dispatcher. 

Table 8. Errors Committed by Type 

Type Error 

Frequency Errors (%) 

Number Transpositions 9 39 

Incorrect Information/Identification 6 26 

Incorrect Time of Day 3 13 

Memory Lapse 2 9 

Phraseology 2 9 

Directional Error 1 4 

Total 23 100 

24
 

Of the errors analyzed involving a memory lapse, both instances involved the dispatcher. Of the 

errors involving poor phraseology, one was committed by the dispatcher and the other by a 

railroad worker. The one instance of a directional error was committed by a dispatcher. 

Four percent of the transmissions resulted in a breakdown in communication due to equipmentrelated failures. Whereas this is not directly a human factors issue, it does speak to the issue of 

workload. If a party repeats a transmission or switches to a different communication mode (e.g., 

from radio to cell phone), workload increases. 

3.2 Data Link Communications 

3.2.1 Summary of Results 

During each day of the test period, the field test crew (consisting of roadway workers) completed 

around 10 Form Ds. The study documented how long the maintenance employee took to request 

a Form D and for the dispatcher to fill out the form, and to assign time effective. Charts were 

created using the average daily times, one including waiting time and one excluding that 

component. The charts also show the total time required to issue one Form D movement 

authority. 

Figure 9 shows the time to complete these activities by day. The chart shows some oscillations, 

but when the scale was taken into account, the data change is in the range of 10 s. The increase 

in time corresponding to day 10 can be explained by a 1-week interruption of the testing where 

the dispatcher working on the experiment went on vacation. On the first day after his time off, he 

needed some time to re-familiarize himself with the software. 

Assign Time 

Effective 

Request Form D 

Combined Form D 

Transactions 

0

20

40

60

80

100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Day

Mean Communication Time 

(sec.)

Figure 9. Time to Request and Receive Form D by Data link 

The major advantage of the new system was the decline in the number of communication errors. 

Since the cancellation of Form D’s was automated, the error for this particular task was 

eliminated. Once the foreman finished the job, he/she canceled the work permit without 

communicating by voice with the dispatcher. The dispatcher saw the form on the “cancelled” 

display window and acknowledged the termination of the work permit. 

25
 

3.2.2 User Feedback 

Most of the data obtained in the experiment was based on the feedback submitted by the field 

test crew. The railroad management also made comments about necessary modifications in the 

software so that the system would meet their needs. Based on these comments the following 

modifications need to be implemented before taking further steps: 

• The smartphone must have a larger screen than the approximately 2-inch by 4-inch display. 

The commercial smartphones have small screens to accommodate the demand of the business 

people. A device used for railroad operations needs to have a slightly larger screen where the 

fonts and the displays will be larger for better reading. 

• The screen should be visible in daylight and at night. One of the main issues with the 

smartphone was the visibility of the Liquid Crystal Display (LCD) screen in sunlight. 

According to the standards3

, the display screen on a sunlight readable/outdoor readable LCD 

should be bright enough so that the display is visible in direct or strong sunlight. Second, the 

display contrast ratio4

 must be maintained at 5 to 1 or higher. 

Although a display with less than 500 nits5

 screen brightness and a mere 2 to 1 contrast ratio 

can be read in outdoor environments, the quality of the display will be dreadfully poor and 

not get the desired information across effectively. A true sunlight readable display is 

normally considered to be an LCD with at least 1,000 nits of screen brightness and a contrast 

ratio greater than 5 to 1. In outdoor environments in the shade, such a display can provide an 

excellent image quality.

• The Form D number was generated by the system: the number must be assigned by the 

dispatcher according to railroad operating rules. This number not only serves to itemize the 

Form Ds but also to convey information about the dispatcher and the territory. 

• When canceling a Form D, the foreman did not receive a confirmation message. There 

should be a confirmation page before the form is actually cancelled. 

• Both ends of the system must have audio cues when a message is received. This way the user 

will be prompted of the incoming request preventing any delays that might occur if the user 

is not looking at the screen. For the Form D cancellation procedure, having an audio cue will 

notify the dispatcher immediately about the new status of tracks. 

• The foreman should be able to send a short message, such a short message service (SMS) to 

the dispatcher instead of directly calling him on the phone or the radio. This feature supports 

the main purpose of the system, which is to decrease the congestion on the phone/radio lines. 

 

3

 http://www.littlepc.com/faq_lcd_technology.htm#outdoorreadable 

4

 Contrast ratio (CR) is the ratio of luminance between the brightest “white” and the darkest “black” that can be 

produced on a display. A standard 200 nit LCD measured in a dark room has a 300 CR, but will have less than a 2.0 

CR under intense direct sunlight. 

5

 A NIT is a measurement of light in candelas per meter square (Cd/m2). For an LCD monitor it is brightness out of 

the front panel of the display. Most desktop LCD’s or Notebook LCD’s have a brightness of 200 to 250 Nits. The 

standard LCD’s are not readable in sunlight. 

26
 

• When the dispatcher rejects a request, the foreman should be able to go back to the incorrect 

form and make the necessary modifications instead of starting all over again. 

• The dispatcher and the foreman should view information on a Form D in the same format to 

help each other in case of a misunderstanding. (With the current setup, the displays are 

slightly different than each other because of the limited display area of the smartphone.) 

• The foreman should be able to enter his/her identification number when the smartphone is 

turned on: there should be a sign-in process. 

• Form Ds must include the dispatcher’s name, not just the territory name. 

• The system should make the distinction between canceling a Form D and fulfilling it. A 

cancelled Form D represents an unfinished work, whereas a fulfilled Form D indicates a 

completed work. 

• The current prototype did not allow additions to an existing Form D. The current procedures 

at the railroad where the testing took place permitted up to three additions to an existing 

Form D. 

The problems that occurred using the data link system were associated with: 

• Connection quality, 

• User ability to navigate within the menu, and 

• Tapping on the wrong parts of the screen (e.g., selecting wrong mileposts from the dropdown 

menus). 

Overall, the dispatcher and the roadway workers liked to use the device. They expressed their 

interest in using the communication application once the updates were completed. They were 

impressed with the fast communication and the reduced number of errors. The workload ratings 

using the NASA-TLX scale showed that the workload perception was different for the dispatcher 

and the track foreman. The scorings that they provided are shown in Table 9. The maximum 

score for all tasks is 20. An example of the form and the explanation of its futures can be found 

in Appendix D. 

Table 9. NASA-TLX Scale Rating Results 

Task Dispatche

r 

Track Foreman 

Mental demand 15 10 

Physical demand 3 2 

Temporal demand 14 5 

Effort 11 3 

Performance 12 19 

Frustration 15 2 

Overall 19 13 

One major feature that was requested by the superintendent of the dispatcher center was the use 

of handheld printers with the smartphone. This way, the roadway workers would also have a 

27
 

hard copy of the Form Ds that they requested. This feature becomes very important if the device 

stops working. Another reason for this request revolves around the computer literacy of the 

potential users. If implemented, the device may be used by roadway workers whose exposure to 

computer use has been limited. Once they have a problem with the device, it may be hard for 

them to access the main menu. In case they end up using a function that they are unfamiliar with 

and cannot go back to the main menu, having a hard copy of the work permit would prevent 

potential accidents. 

3.3 Current Radio System vs. Data Link System 

The data using the voice radio technology shows that Form D’s were the most time consuming 

type of communication between the dispatcher and the crew on the tracks. On average, a 

dispatcher took 3 minutes 13 seconds to complete one Form D. This study shows that data link 

technology can decrease this time significantly. Using a smartphone this completion time was 

reduced to an average of 65 seconds (see Table 10). This result was different from Masquelier et 

al’s (2004) and Oriol et al’s (2004) laboratory experiment results. Their findings showed that the 

work permission processes were slower but more accurate with the device than with the radio. 

This study, conducted under conditions more closely approximating real-world, showed that the 

work authorization processes were more accurate and faster with the handheld device. 

Table 10. Form D Completion Time by Communication 

Mode 

Mode 

Radio Data Link 

Form D Completion time (sec) 193 65 

The study also shows that the new system, in providing the visual aid to users, eliminated 

alphanumeric transposition errors when requesting and issuing Form D movement authorities. 

With voice radio, the dispatcher and the foreman check the information using the 

readback/hearback procedure. They do not have access to each other’s hard copy documents. If 

the dispatcher makes a mistake and the foreman does not realize it, there are no further checks. 

With the data link system, both users can see the same information which makes it easier to 

catch mistakes since both sides are checking the same source of information. 

As described in section 3.2.2, the problems that occurred with the data link system were mainly 

related to the design of the device or the software (usability). Users reported problems associated 

with navigating to the appropriate screen, selecting desired information with the stylus, and 

difficulty seeing the display under certain ambient lighting conditions. As the device and the 

associated software are updated to address these problems, user acceptance should improve. 

The new system reduced errors attributable to auditory communications. As shown earlier, with 

the voice radio, some of the errors occurred because of the radio transmissions that were difficult 

to hear. They also minimized errors, associated memory lapses, and numeric transpositions that 

are common with auditory-based communications. New errors types emerged that were linked to 

the visual modality and usability issues such as tapping on the wrong part of the screen or 

28
 

navigation difficulties with the software. Usability errors should decrease with time as designers 

adapt the application to meet the needs of the users and the user adapts to the new user interface. 

The dispatcher, participating in the study, stated that the new system considerably reduced the 

noise in the workplace (since the files were filled out digitally without any voice transmission). 

The radio was used for other types of conversations and emergency calls. Conversations that 

required less time than a Form D were still held over the radio. This practice decreases the radio 

use, hence the noise level in the dispatcher’s work environment. In previous laboratory tests, the 

users also liked the new system for the same reason. 

Another important feature of the smartphone was the ability to browse the internet. The 

dispatchers are required to check the weather information periodically during the day and 

immediately notify the roadway workers and the conductors of the changes. This information 

can be directly accessed using the smartphone, without contacting the dispatcher, decreasing the 

dispatcher’s workload. The smartphone’s browser can be programmed to access only certain 

Web pages to eliminate the possibility of surfing the internet during working hours. Combined 

with the efficiency gains from exchanging movement authorizations using the visual modality, 

this form of communication may enable dispatchers to operate more productively (e.g., handle 

more communications). 

Although it has not been tested in this study as there was only one user in the field, the SMS 

feature of the smartphone gave the roadway workers the possibility to communicate directly with 

the dispatcher without sharing this information directly with others working on or near the 

tracks. This aspect of the system provides a more private medium for communications between 

roadway workers and dispatches and eliminates the party line effect of radio communications. 

The loss of the party line to keep track of movement authorities might normally be associated 

with a loss of safety. As Roth et al. (2001) discovered, the party line serves as an efficient 

method to inform railroad employees about the other track occupancies. However, the 

smartphone provides the same information with its territory status information feature. The users 

have constant access to the track information where they can see the updated information about 

each track. 

29
 

4. Conclusion 

The current study supported the results of Malsch et al. (2001), Oriol et al. (2004), and 

Masquelier et al. (2004) showing data link communications reduce voice radio-related errors and 

improve efficiency when communicating long and complex messages. The new system was 

faster and more effective than radio communication when used to convey long messages such as 

filling out Form Ds. Radio communication was faster than the data link for confirmation 

communications that only require yes/no answers. One reason for this difference appears to be 

the users’ lack of familiarity with the device. The time to convey short messages should improve 

as the users become more proficient with the new system. 

The users expressed many concerns about smartphones. Most of these concerns were related to 

its design. Users thought that the commercial smartphone used in this study was too small and 

delicate to be used in railroad operations. They expressed preference for a rugged device that 

would withstand being dropped and operating in a dusty environment. Another major issue was 

the screen resolution: the screen should be modified so that it is visible in direct sunlight. Other 

concerns were related to the unfamiliarity of the users with the PDA technology. Some users 

were unable to navigate within the menu and unable to go to the main menu once they were on a 

page that was not familiar to them. 

The data link system would reduce the dispatcher’s communication load by eliminating some 

incoming calls related to information requests like schedule updates and weather inquiries. The 

smartphone would receive updated data from the dispatch center, so the train schedule would be 

updated as soon as any change is entered at the control center. As the smartphone has access to 

the internet, the weather information could be checked by the roadway workers without 

contacting the dispatcher. The data link would also reduce the dispatcher’s workload by 

transferring long conversations to the digital medium. During long conversations, the dispatcher 

both receives and sends many messages. With the data link system, the dispatcher could send the 

same amount of information currently contained in multiple voice messages with only one digital 

message. 

4.1 Use of Positioning Technologies 

In railroad operations, one of the main causes of fatality is the unknown location of the workers. 

Even though with the new and improved dispatcher centers, the dispatchers know that the work 

crew is between certain mileposts, but their exact location remains uncertain. Adding the GPS to 

the smartphone should solve this problem. GPS can be used to signal whenever the roadway 

workers leave the protected area. If they mistakenly start working on an unprotected track, the 

dispatcher can warn them and prevent fatalities. While adding safety precautions, this feature 

would also provide close supervision, which is a feature not welcomed by the railroad operators 

who contributed to this study. 

4.2 Use of Handheld Device Printers 

The use of handheld device printers was highly recommended by the superintendent at Cobble 

Hill. He was very excited about the idea that the work crew on the tracks could have a hard copy 

of the form that they fill out using the data link technology. He recommended this feature 

because he was concerned that the roadway worker might forget which permissions he/she has if 

30
 

anything happens to the smartphone. Having hardcopies would let the roadway workers keep 

track of their work and prevent any accidents in case of a smartphone malfunction. Nowadays 

there are printers small enough to carry in the MOW vehicle and especially designed for PDAs, 

with printouts similar to cashier receipts. These printers usually work with batteries but they can 

easily be hooked up to the car’s cigarette lighter with a power plug adaptor. 

4.3 Custom Modifications

The smartphone used in this study mostly proved to be an efficient device for railroad 

operations. The messages conveyed using the data link technology was easier to understand 

since they were free of congestion. However an important issue was the size of the screen. The 

crews on the tracks would need a larger screen that they can easily see. When the screen is small, 

the font is too small and it gets harder to tap on necessary lines with the smartphone’s plastic 

pen. The brightness of the screen was a second issue. As the device would be used mainly 

outside, the screen must be visible under sunshine, so either a brighter screen, or more likely a 

shading device, would be necessary. It also would need to have a screen light that can be used 

during night shifts. 

Keeping up with rapidly changing technology is a challenge. Therefore, projects, using the latest 

technologies, are dealing with a moving target. By the time that this report was prepared, the 

smartphone used on the experiments was outdated and a larger selection of smartphones with 

more capabilities was on the market. 

31
 

Appendix A. NORAC Movement Permit Form D 

NORAC Movement Permit Form D 

FORM D 

NO.(S)________________________ 

DELIVERED TO_________________ 

FORM D No. _______ DATE______/______/______ 

TO _________________________________________________________________________ 

__________________________________________________________________________

1. TEMPORARY SPEED RESTRICTIONS 

LINE TRK(S BETWEEN/AT

SPEED 

PSGR FRT

SPEED SIGNS 

DISPLAYED 

YES NO

2. OPERATE IN _______ DIRECTION(S) ON __________ TRK BETWEEN ________ AND ________ 

ON ________ TRK BETWEEN _____________ AND _____________ DSPR ______ TIME ______ 

ON ________ TRK BETWEEN _____________ AND _____________ DSPR ______ TIME ______ 

ON ________ TRK BETWEEN _____________ AND _____________ DSPR ______ TIME ______ 

3. TRAINS OR TRACK CARS AHEAD __________________________________________________ 

TC PROCEED PAST STOP SIGNAL(S) AT _____________________________________________ 

4. _____ TRK OUT OF SERVICE BETWEEN/AT _________________________________________ 

IN CHARGE OF ________________________________________________________________ 

_____ TRK OUT OF SERVICE BETWEEN/AT _________________________________________ 

IN CHARGE OF ________________________________________________________________ 

5. ____ LINE ____ TRK OBSTRUCTED FOR MAINTENANCE BETWEEN _____________________ 

AND _________________________________________________________________________ 

6. NON-SIGNALLED DCS RULES IN EFFECT ON ______ TRK(S) BETWEEN _______ AND _______ 

7. INT AND CP SIGNALS OUT OF SERVICE ON ______ TRK(S) AT ___________________________ 

8. REMAIN AT ______________________ ON ________ TRK UNTIL ENGINE ARRIVES TO ASSIST 

9. OPERATE AT RESTRICTED SPEED ON _____ TRK TO __________ WHERE TRAIN IS DISABLED 

10. TBS IN SERVICE AT ____________________________________________________________ 

11. CSS RULES OUT OF SERVICE ON ________ TRK(S) BETWEEN ___________ AND ___________ 

12. PROTECT CROSSINGS(S) _________________________________________________________ 

13. OTHER INSTRUCTIONS/INFORMATION ___________________________________________ 

_____________________________________________________________________________ 

_____________________________________________________________________________ 

DISPATCHER_________________ TIME EFFECTIVE _______________

_ 

FORM D CANCELLED, TIME ______, DATE __/__/__, DISPATCHER ______________________ 

32
 

33
 

Appendix B. Smartphone Screenshot 

1. Main Menu

Train and territory information

Train status

Form D / Foul Time 

Request Line 4

Request Lines 2,3 Request Foul Time

Cancel/Fulfill Clear 

My Form Ds My Foul Time

2. Request Line 4

Form D Line 4 Request 

Work site between/at 00.0 Boston

00.0 Boston

Track #: 1

Start Time: 

Duration: 10 min (estimated) 

Send request

 Main Menu

3. Request Foul Time

34
 

Foul Time Request 

Track #: 1

Between/at: 

00.0 Boston

00.0 Boston

Mile Post: 

Start Time: 

End Time: 

Send request

 Main Menu 

4. Train Status

5. Request Lines 2,3

35
 

Form D Lines 2,3 Request 

Operate track-car between: 00.0 Boston

 00.0 Boston

Track #: 1

Direction: East

Send request

 Main Menu

36
 

37
 

Appendix C. Dispatcher Screenshots 

Form D Request

38
 

Time Effective Request 

39
 

Active Form D 

40
 

Cancelled Form D 

41
 

Appendix D. NASA-TLX Scale Form 

Workload Ratings using the NASA-TLX Scale 

Job Title ____________________ Male/Female (please circle) 

Age: Years of Experience: ________ 

Please indicate your ratings for the contributions of each of the following dimensions to your 

task. 

MENTAL DEMAND (thinking, deciding, remembering etc.)

 

 

Low High 

PHYSICAL DEMAND (physical exertion/activity)

Low High 

TEMPORAL DEMAND (time pressure

Low High 

EFFORT (how hard you worked)

Low High 

PERFORMANCE (success in accomplishing the task)

 Good Poor 

FRUSTRATION (irritation, discouraged)

Low High 

OVERALL (your impression of overall workload the task entailed)

Low High 

42
 

Rating Scale Definitions

TITLE ENDPOINTS DESCRIPTIONS 

Low/High 

How much mental and perceptual activity 

was required (e.g., thinking, deciding, 

calculating, remembering, looking, 

searching, etc.)? Was the task easy or 

demanding, simple or complex, exacting 

or forgiving? 

MENTAL DEMAND 

Low/High 

How much physical activity was required 

(e.g., pushing, pulling, turning, 

controlling, activating, etc.)? Was the 

task easy or demanding, slow or brisk, 

slack or strenuous, restful or laborious? 

PHYSICAL DEMAND 

Low/High

How much time pressure did you feel due 

to the rate or pace at which the tasks or 

task elements occurred? Was the pace 

slow and leisurely or rapid and frantic? 

TEMPORAL DEMAND 

EFFORT Low/High 

How hard did you have to work 

(mentally and physically) to accomplish 

your level of performance? 

PERFORMANCE Good/Poor 

How successful do you think you were in 

accomplishing the goals of the task set by 

the experimenter (or yourself)? How 

satisfied were you with your performance 

in accomplishing these goals? 

How insecure, discouraged, irritated, 

stressed and annoyed versus secure, 

gratified, content, relaxed and 

complacent did you feel during the task? 

FRUSTRATION LEVEL Low/High 

43
 

Appendix E. Questionnaires 

DEMOGRAPHIC QUESTIONNAIRE 

1. Job Title: 

2. Years of Experience: 

3. Please provide examples of your interaction with the dispatchers / work crews and 

an average number of these interactions per week. [such as Form D, foul time, train 

schedule update, message relay, other...] 

Type of Interaction Number of times per week 

4. Please rate your familiarity with the following devices or services: 

Very 

unfamiliar 

Unfamiliar Somewhat 

familiar 

Familiar Very 

familiar 

Radio 

Computer 

Beeper / Pager 

Cell Phone 

Internet 

Palm Pilot 

44
 

Usability Questionnaire 

5. Please rate how the information is presented to you according to the following 

attributes: 

Very ideal Ideal Needs some 

improvement 

Change 

completely 

Font size 

Font style (bold, 

underline...) 

Readability 

Organization 

6. Please provide feedback on the organization of the menu: was it easy to navigate 

through the main menu, were the menu names meaningful, what improvements can be 

made on the menu? 

7. Please provide feedback on the PDA that you were using: general comments on 

its use, user friendliness, shape, brightness etc. 

8. Can you compare the radio and the PDA: which one would you prefer for filling 

out Form Ds? Which one was faster and more efficient? Which one do you think is prone 

to errors? 

9. Please indicate any safety concerns that you might have. 

Thank you very much for your cooperation. 

45
 

Glossary 

Block: A length of track with defined limits on which train movements are governed by block 

signals, cab signals, or Form D.

Block Signal: A fixed signal displayed to trains at the entrance to a block to govern use of that 

block. 

Blocking device: A lever, plug, ring or other method of control that restrict the operation of a 

switch or a signal. 

Cab signal: A signal that is located in the engine control compartment and which indicates track 

occupancy or condition. The cab signal is used in conjunction with interlocking signals and 

in lieu of block signals. 

Conductor: The person officially in charge of the train’s overall operation. 

Dark territory: A section of track that is not signaled. In dark territory, the train dispatcher does 

not get automatic indication of the location of the trains, nor does the train get automatic 

signals allowing movement through the territory. 

Data link: Technology that enables information that is now transmitted over radio links to be 

transmitted over data lines. 

Engineer: The person primarily responsible for operating the locomotive. 

Fixed signal: A signal at a fixed location that affects the movement of a train. 

Flagman: When used in relation to roadway worker safety, means an employee designated by 

the railroad to direct or restrict the movement of trains past a point on track to provide ontrack safety for roadway workers, while engaged solely in performing that function.

Foul time: Method of establishing working limits on controlled track in which a roadway worker 

is notified by the train dispatcher or control operator that no trains will operate within a 

specific segment of controlled track until the roadway worker reports clear of the track. 

Fouling a track: Placement of an individual or an item in such a proximity to a track that the 

individual or equipment could be struck by a moving train or on-track equipment, or in any 

case is within 4 ft of the field side of the near running rail. 

Foreman: Roadway worker whose only duty is to protect other members of the crew by dealing 

with the dispatcher. 

FRA: Federal Railroad Administration. 

GPS: (Global Positioning System) Satellite based positioning system. 

HTTP: (Hyper Text Transfer Protocol) underlying protocol used by the World Wide Web. 

HTTP defines how messages are formatted and transmitted, and what actions Web servers 

and browsers should take in response to various commands. 

Interlocking: An interconnection of signals and switch appliances such that their movements 

must succeed each other in a predetermined sequence, assuring that signals cannot be 

displayed simultaneously on conflicting routes. 

46
 

LCD: (Liquid Crystal Screen) Type of display used in digital watches and many portable 

computers. LCD displays utilize two sheets of polarizing material with a liquid crystal 

solution between them. An electric current passed through the liquid causes the crystals to 

align so that light cannot pass through them. Each crystal, therefore, is like a shutter, either 

allowing light to pass through or blocking the light. 

Movement Permit Form D: A form containing written authorization(s), restriction(s), or 

instruction(s), issued by the dispatcher to specified individuals.6

NORAC: Northeast Operating Rules Advisory Committee. 

Personal Digital Assistant (PDA): It is a handheld device with a large touch-screen, organizer 

and basic computing functions. Many have a stylus and support handwriting recognition. A 

typical PDA also has faster processor and more memory than a typical phone, and can run 

more complex software. Most PDA’s run a standardized operating system (OS), such as 

Palm OS or Windows Mobile for Pocket PC. In the spectrum of mobile devices, PDA’s fall 

in-between a laptop computer and a cell phone. 

Roadway worker: Any employee of a railroad, or of a contractor to a railroad, whose duties 

include and who is engaged in the inspection, construction, maintenance or repair of railroad 

tracks, bridges, roadway, signal and communication systems, electric traction systems, 

roadway facilities or roadway maintenance machinery on or near the track or with the 

potential of fouling a track, and employees responsible for their protection. 

Shunt: Activate block or interlocking signals when present on track.7

SMS: (Short Message Service) Globally accepted wireless service that enables the transmission 

of instant alphanumeric messages between mobile subscribers and external systems such as 

web servers, electronic mail, paging, and voice-mail systems. 

Smartphone: A category of mobile device that provides advanced capabilities beyond a typical 

mobile phone. Smartphones run complete operating system software that provides a 

standardized interface and platform for application developers. 

Smartphones are distinct from PDA-based devices running operating systems such as Palm 

OS or Windows Mobile for Pocket PCs. While PDA-based devices usually have a touchscreen for pen input, smartphones usually have a standard phone keypad for input. 

Track car: Equipment, other than trains, operated on a track for inspection or maintenance. 

Track cars might not shunt track circuits. 

Train dispatcher: Railroad employee assigned to control and issue orders governing the 

movement of trains on a specific segment of railroad track in accordance to the operating 

rules of the railroad that apply to that segment of track. 

Train OS Sheet (Train OS): Dispatcher’s term that refers to train schedule usually with time 

updates. 

 

6

 NORAC operating rules 

7

 Roth, E.M. and Malsch, N. 1999 

47
 

48
 

References 

Basu, S. (1999). Real Time Simulation of Rail Dispatcher Operations. Unpublished master’s 

thesis, Massachusetts Institute of Technology, Cambridge, MA. 

CNET News.com. Fried, I. (2000) Kyocera Gets Smart with Cell Phone-PDA Combo 

http://news.com.com/2100-1040-249038.html. 

Federal Railroad Safety Authorization Act of 1994. 

Kyocera. http://www.kyocera-wireless.com. 

Malsch, N., Sheridan, T. and Multer, J. (2001) Measuring the Impact of Data Link Technology 

on Railroad Dispatching Operations. Report No. DOT-VNTSC-FRA-01-04. Washington, 

DC: FRA. 

Malsch, N., Sheridan, T. and Multer, J. (2004) Impact of Data Link Technology on Railroad 

Dispatching Operations. John A. Volpe National Transportation Systems Report DOTVNTSC-FRA-04-04. 

Masquelier, T., Sheridan, T. and Multer, J. (2004) Supporting Railroad Worker Communications 

with a Wireless Handheld Computer: Volume 2: Impact on Dispatcher Performance. Report 

No. DOT-VNTSC-FRA-04-03. Washington, DC: FRA. 

NORAC Operating Rules (2003) Eighth Edition. 

Oriol, N., Sheridan, T. and Multer, J. (2004) Supporting Railroad Worker Communications with 

a Wireless Handheld Computer: Volume 1: Usability for the Roadway Worker. Report No. 

DOT-VNTSC-FRA-04-02. Washington, DC: FRA. 

PDQ Reference Library. http://www.pdqwebdesign.ca/lib/. 

Roth, E.M., Malsch, N. and Multer, J. (2001) Understanding How Train Dispatchers Manage 

and Control Trains, Result of a Cognitive Task Analysis. John A. Volpe National 

Transportation Systems Report DOT-VNTSC-FRA-98-3. 

Vanderhorst, J. (1990) A Comparison of Voice and Data Link Communication in a Railroad 

Environment. Burlington Northern Railroad Company Research & Development Report. 

49