+-----------+----------------------------------------------------------+
| ![](m     | **Supporting Railroad Roadway Worker Communications with |
| edia/imag | a Wireless Handheld Computer: Volume 2:\                 |
| e1.wmf){w | Impact on Dispatcher Performance**                       |
| idth="2.9 |                                                          |
| 895833333 |                                                          |
| 333335in" |                                                          |
| height="  |                                                          |
| 1.4486111 |                                                          |
| 11111111i |                                                          |
| n"}![](me |                                                          |
| dia/image |                                                          |
| 2.wmf){wi |                                                          |
| dth="0.46 |                                                          |
| 111111111 |                                                          |
| 111114in" |                                                          |
| hei       |                                                          |
| ght="0.50 |                                                          |
| 347222222 |                                                          |
| 22222in"} |                                                          |
|           |                                                          |
| U.S.      |                                                          |
| D         |                                                          |
| epartment |                                                          |
|           |                                                          |
| of        |                                                          |
| Trans     |                                                          |
| portation |                                                          |
|           |                                                          |
| **Federal |                                                          |
| R         |                                                          |
| ailroad** |                                                          |
|           |                                                          |
| **Adminis |                                                          |
| tration** |                                                          |
+-----------+----------------------------------------------------------+

+----------------------+-----------------------------------------------+
| Office of Research   | U.S. Department of Transportation             |
|                      |                                               |
| and Development      | Research and Special Programs Administration  |
|                      |                                               |
| Washington, DC 20590 | John A. Volpe National Transportation Systems |
|                      | Center                                        |
|                      |                                               |
|                      | Cambridge, MA 02142                           |
+----------------------+-----------------------------------------------+

![](media/image3.png){width="5.5in" height="3.251388888888889in"}

+------------------------+--------------------+------------------------+
| DOT/FRA/ORD-04/13.II   | > Final Report     | This document is       |
|                        | >                  | available to the       |
|                        | > April 2002       |                        |
|                        |                    | public through the     |
|                        |                    | National Technical     |
|                        |                    |                        |
|                        |                    | Information Service,   |
|                        |                    | Springfield, VA 22161  |
|                        |                    |                        |
|                        |                    | This document is also  |
|                        |                    | available on           |
|                        |                    |                        |
|                        |                    | the FRA website at     |
|                        |                    | www.fra.dot.gov        |
+------------------------+--------------------+------------------------+

+-----------------------------------------------------------------------+
| > Notice                                                              |
|                                                                       |
| This document is disseminated under the sponsorship of the Department |
| of Transportation in the interest of information exchange. The United |
| States Government assumes no liability for its contents or use        |
| thereof.                                                              |
+-----------------------------------------------------------------------+
|                                                                       |
+-----------------------------------------------------------------------+
| > Notice                                                              |
|                                                                       |
| The United States Government does not endorse products or             |
| manufacturers. Trade or manufacturers' names appear herein solely     |
| because they are considered essential to the objective of this        |
| report.                                                               |
+-----------------------------------------------------------------------+

+----------------+-----+----------+-----------+---+---+-----------------+
| REPORT         |     |          |           | * |   |                 |
| DOCUMENTATION  |     |          |           | F |   |                 |
| PAGE           |     |          |           | o |   |                 |
|                |     |          |           | r |   |                 |
|                |     |          |           | m |   |                 |
|                |     |          |           | A |   |                 |
|                |     |          |           | p |   |                 |
|                |     |          |           | p |   |                 |
|                |     |          |           | r |   |                 |
|                |     |          |           | o |   |                 |
|                |     |          |           | v |   |                 |
|                |     |          |           | e |   |                 |
|                |     |          |           | d |   |                 |
|                |     |          |           | * |   |                 |
|                |     |          |           |   |   |                 |
|                |     |          |           | * |   |                 |
|                |     |          |           | O |   |                 |
|                |     |          |           | M |   |                 |
|                |     |          |           | B |   |                 |
|                |     |          |           | N |   |                 |
|                |     |          |           | o |   |                 |
|                |     |          |           | . |   |                 |
|                |     |          |           | 0 |   |                 |
|                |     |          |           | 7 |   |                 |
|                |     |          |           | 0 |   |                 |
|                |     |          |           | 4 |   |                 |
|                |     |          |           | - |   |                 |
|                |     |          |           | 0 |   |                 |
|                |     |          |           | 1 |   |                 |
|                |     |          |           | 8 |   |                 |
|                |     |          |           | 8 |   |                 |
|                |     |          |           | * |   |                 |
+----------------+-----+----------+-----------+---+---+-----------------+
| Public         |     |          |           |   |   |                 |
| reporting      |     |          |           |   |   |                 |
| burden for     |     |          |           |   |   |                 |
| this           |     |          |           |   |   |                 |
| collection of  |     |          |           |   |   |                 |
| information is |     |          |           |   |   |                 |
| estimated to   |     |          |           |   |   |                 |
| average 1 hour |     |          |           |   |   |                 |
| per response,  |     |          |           |   |   |                 |
| including the  |     |          |           |   |   |                 |
| time for       |     |          |           |   |   |                 |
| reviewing      |     |          |           |   |   |                 |
| instructions,  |     |          |           |   |   |                 |
| searching      |     |          |           |   |   |                 |
| existing data  |     |          |           |   |   |                 |
| sources,       |     |          |           |   |   |                 |
| gathering and  |     |          |           |   |   |                 |
| maintaining    |     |          |           |   |   |                 |
| the data       |     |          |           |   |   |                 |
| needed, and    |     |          |           |   |   |                 |
| completing and |     |          |           |   |   |                 |
| reviewing the  |     |          |           |   |   |                 |
| collection of  |     |          |           |   |   |                 |
| information.   |     |          |           |   |   |                 |
| Send comments  |     |          |           |   |   |                 |
| regarding this |     |          |           |   |   |                 |
| burden         |     |          |           |   |   |                 |
| estimate or    |     |          |           |   |   |                 |
| any other      |     |          |           |   |   |                 |
| aspect of this |     |          |           |   |   |                 |
| collection of  |     |          |           |   |   |                 |
| information,   |     |          |           |   |   |                 |
| including      |     |          |           |   |   |                 |
| suggestions    |     |          |           |   |   |                 |
| for reducing   |     |          |           |   |   |                 |
| this burden,   |     |          |           |   |   |                 |
| to Washington  |     |          |           |   |   |                 |
| Headquarters   |     |          |           |   |   |                 |
| Services,      |     |          |           |   |   |                 |
| Directorate    |     |          |           |   |   |                 |
| for            |     |          |           |   |   |                 |
| Information    |     |          |           |   |   |                 |
| Operations and |     |          |           |   |   |                 |
| Reports, 1215  |     |          |           |   |   |                 |
| Jefferson      |     |          |           |   |   |                 |
| Davis Highway, |     |          |           |   |   |                 |
| Suite 1204,    |     |          |           |   |   |                 |
| Arlington, VA  |     |          |           |   |   |                 |
| 22202-4302,    |     |          |           |   |   |                 |
| and to the     |     |          |           |   |   |                 |
| Office of      |     |          |           |   |   |                 |
| Management and |     |          |           |   |   |                 |
| Budget,        |     |          |           |   |   |                 |
| Paperwork      |     |          |           |   |   |                 |
| Reduction      |     |          |           |   |   |                 |
| Project        |     |          |           |   |   |                 |
| (0704-0188),   |     |          |           |   |   |                 |
| Washington, DC |     |          |           |   |   |                 |
| 20503.         |     |          |           |   |   |                 |
+----------------+-----+----------+-----------+---+---+-----------------+
| 1\. AGENCY USE |     | 2\.      |           | 3 |   |                 |
| ONLY (Leave    |     | REPORT   |           | \ |   |                 |
| blank)         |     | DATE     |           | . |   |                 |
|                |     |          |           | R |   |                 |
|                |     | October  |           | E |   |                 |
|                |     | 2004     |           | P |   |                 |
|                |     |          |           | O |   |                 |
|                |     |          |           | R |   |                 |
|                |     |          |           | T |   |                 |
|                |     |          |           | T |   |                 |
|                |     |          |           | Y |   |                 |
|                |     |          |           | P |   |                 |
|                |     |          |           | E |   |                 |
|                |     |          |           | A |   |                 |
|                |     |          |           | N |   |                 |
|                |     |          |           | D |   |                 |
|                |     |          |           | D |   |                 |
|                |     |          |           | A |   |                 |
|                |     |          |           | T |   |                 |
|                |     |          |           | E |   |                 |
|                |     |          |           | S |   |                 |
|                |     |          |           | C |   |                 |
|                |     |          |           | O |   |                 |
|                |     |          |           | V |   |                 |
|                |     |          |           | E |   |                 |
|                |     |          |           | R |   |                 |
|                |     |          |           | E |   |                 |
|                |     |          |           | D |   |                 |
|                |     |          |           |   |   |                 |
|                |     |          |           | F |   |                 |
|                |     |          |           | i |   |                 |
|                |     |          |           | n |   |                 |
|                |     |          |           | a |   |                 |
|                |     |          |           | l |   |                 |
|                |     |          |           | R |   |                 |
|                |     |          |           | e |   |                 |
|                |     |          |           | p |   |                 |
|                |     |          |           | o |   |                 |
|                |     |          |           | r |   |                 |
|                |     |          |           | t |   |                 |
|                |     |          |           |   |   |                 |
|                |     |          |           | J |   |                 |
|                |     |          |           | u |   |                 |
|                |     |          |           | n |   |                 |
|                |     |          |           | e |   |                 |
|                |     |          |           | 2 |   |                 |
|                |     |          |           | 0 |   |                 |
|                |     |          |           | 0 |   |                 |
|                |     |          |           | 0 |   |                 |
|                |     |          |           | - |   |                 |
|                |     |          |           | O |   |                 |
|                |     |          |           | c |   |                 |
|                |     |          |           | t |   |                 |
|                |     |          |           | o |   |                 |
|                |     |          |           | b |   |                 |
|                |     |          |           | e |   |                 |
|                |     |          |           | r |   |                 |
|                |     |          |           | 2 |   |                 |
|                |     |          |           | 0 |   |                 |
|                |     |          |           | 0 |   |                 |
|                |     |          |           | 1 |   |                 |
+----------------+-----+----------+-----------+---+---+-----------------+
| 4\. TITLE AND  |     |          |           |   | 5 |                 |
| SUBTITLE       |     |          |           |   | \ |                 |
|                |     |          |           |   | . |                 |
| Supporting     |     |          |           |   | F |                 |
| Railroad       |     |          |           |   | U |                 |
| Roadway Worker |     |          |           |   | N |                 |
| Communications |     |          |           |   | D |                 |
| with a         |     |          |           |   | I |                 |
| Wireless       |     |          |           |   | N |                 |
| Handheld       |     |          |           |   | G |                 |
| Computer:      |     |          |           |   | N |                 |
| Volume 2:      |     |          |           |   | U |                 |
| Impact on      |     |          |           |   | M |                 |
| Dispatcher     |     |          |           |   | B |                 |
| Performance    |     |          |           |   | E |                 |
|                |     |          |           |   | R |                 |
|                |     |          |           |   | S |                 |
|                |     |          |           |   |   |                 |
|                |     |          |           |   | R |                 |
|                |     |          |           |   | 2 |                 |
|                |     |          |           |   | 1 |                 |
|                |     |          |           |   | 0 |                 |
|                |     |          |           |   | 3 |                 |
|                |     |          |           |   | / |                 |
|                |     |          |           |   | R |                 |
|                |     |          |           |   | R |                 |
|                |     |          |           |   | 2 |                 |
|                |     |          |           |   | 0 |                 |
|                |     |          |           |   | 4 |                 |
+----------------+-----+----------+-----------+---+---+-----------------+
| 6\. AUTHOR(S)  |     |          |           |   |   |                 |
|                |     |          |           |   |   |                 |
| Timothée       |     |          |           |   |   |                 |
| Masquelier,    |     |          |           |   |   |                 |
| Thomas         |     |          |           |   |   |                 |
| Sheridan, and  |     |          |           |   |   |                 |
| Jordan Multer  |     |          |           |   |   |                 |
+----------------+-----+----------+-----------+---+---+-----------------+
| 7\. PERFORMING |     |          |           |   | 8 |                 |
| ORGANIZATION   |     |          |           |   | \ |                 |
| NAME(S) AND    |     |          |           |   | . |                 |
| ADDRESS(ES)    |     |          |           |   | P |                 |
|                |     |          |           |   | E |                 |
| U.S.           |     |          |           |   | R |                 |
| Department of  |     |          |           |   | F |                 |
| Transportation |     |          |           |   | O |                 |
|                |     |          |           |   | R |                 |
| Research and   |     |          |           |   | M |                 |
| Special        |     |          |           |   | I |                 |
| Programs       |     |          |           |   | N |                 |
| Administration |     |          |           |   | G |                 |
|                |     |          |           |   | O |                 |
| John A. Volpe  |     |          |           |   | R |                 |
| National       |     |          |           |   | G |                 |
| Transportation |     |          |           |   | A |                 |
| Systems Center |     |          |           |   | N |                 |
|                |     |          |           |   | I |                 |
| Cambridge, MA  |     |          |           |   | Z |                 |
| 02142-1093     |     |          |           |   | A |                 |
|                |     |          |           |   | T |                 |
|                |     |          |           |   | I |                 |
|                |     |          |           |   | O |                 |
|                |     |          |           |   | N |                 |
|                |     |          |           |   | R |                 |
|                |     |          |           |   | E |                 |
|                |     |          |           |   | P |                 |
|                |     |          |           |   | O |                 |
|                |     |          |           |   | R |                 |
|                |     |          |           |   | T |                 |
|                |     |          |           |   | N |                 |
|                |     |          |           |   | U |                 |
|                |     |          |           |   | M |                 |
|                |     |          |           |   | B |                 |
|                |     |          |           |   | E |                 |
|                |     |          |           |   | R |                 |
|                |     |          |           |   |   |                 |
|                |     |          |           |   | # |                 |
|                |     |          |           |   | # |                 |
|                |     |          |           |   | # |                 |
|                |     |          |           |   |   |                 |
|                |     |          |           |   |   |                 |
|                |     |          |           |   | { |                 |
|                |     |          |           |   | # |                 |
|                |     |          |           |   | s |                 |
|                |     |          |           |   | e |                 |
|                |     |          |           |   | c |                 |
|                |     |          |           |   | t |                 |
|                |     |          |           |   | i |                 |
|                |     |          |           |   | o |                 |
|                |     |          |           |   | n |                 |
|                |     |          |           |   |   |                 |
|                |     |          |           |   | . |                 |
|                |     |          |           |   | u |                 |
|                |     |          |           |   | n |                 |
|                |     |          |           |   | n |                 |
|                |     |          |           |   | u |                 |
|                |     |          |           |   | m |                 |
|                |     |          |           |   | b |                 |
|                |     |          |           |   | e |                 |
|                |     |          |           |   | r |                 |
|                |     |          |           |   | e |                 |
|                |     |          |           |   | d |                 |
|                |     |          |           |   | } |                 |
|                |     |          |           |   |   |                 |
|                |     |          |           |   | D |                 |
|                |     |          |           |   | O |                 |
|                |     |          |           |   | T |                 |
|                |     |          |           |   | - |                 |
|                |     |          |           |   | V |                 |
|                |     |          |           |   | N |                 |
|                |     |          |           |   | T |                 |
|                |     |          |           |   | S |                 |
|                |     |          |           |   | C |                 |
|                |     |          |           |   | - |                 |
|                |     |          |           |   | F |                 |
|                |     |          |           |   | R |                 |
|                |     |          |           |   | A |                 |
|                |     |          |           |   | - |                 |
|                |     |          |           |   | 0 |                 |
|                |     |          |           |   | 4 |                 |
|                |     |          |           |   | - |                 |
|                |     |          |           |   | 0 |                 |
|                |     |          |           |   | 3 |                 |
+----------------+-----+----------+-----------+---+---+-----------------+
| 9\.            |     |          |           |   | 1 |                 |
| SPONSOR        |     |          |           |   | 0 |                 |
| ING/MONITORING |     |          |           |   | \ |                 |
| AGENCY NAME(S) |     |          |           |   | . |                 |
| AND            |     |          |           |   | S |                 |
| ADDRESS(ES)    |     |          |           |   | P |                 |
|                |     |          |           |   | O |                 |
| U.S.           |     |          |           |   | N |                 |
| Department of  |     |          |           |   | S |                 |
| Transportation |     |          |           |   | O |                 |
|                |     |          |           |   | R |                 |
| Federal        |     |          |           |   | I |                 |
| Railroad       |     |          |           |   | N |                 |
| Administration |     |          |           |   | G |                 |
|                |     |          |           |   | / |                 |
| Office of      |     |          |           |   | M |                 |
| Research and   |     |          |           |   | O |                 |
| Development    |     |          |           |   | N |                 |
|                |     |          |           |   | I |                 |
| 1120 Vermont   |     |          |           |   | T |                 |
| Avenue, NW     |     |          |           |   | O |                 |
| Mail Stop 20   |     |          |           |   | R |                 |
|                |     |          |           |   | I |                 |
| Washington,    |     |          |           |   | N |                 |
| DC. 20590      |     |          |           |   | G |                 |
|                |     |          |           |   | \ |                 |
|                |     |          |           |   | A |                 |
|                |     |          |           |   | G |                 |
|                |     |          |           |   | E |                 |
|                |     |          |           |   | N |                 |
|                |     |          |           |   | C |                 |
|                |     |          |           |   | Y |                 |
|                |     |          |           |   | R |                 |
|                |     |          |           |   | E |                 |
|                |     |          |           |   | P |                 |
|                |     |          |           |   | O |                 |
|                |     |          |           |   | R |                 |
|                |     |          |           |   | T |                 |
|                |     |          |           |   | N |                 |
|                |     |          |           |   | U |                 |
|                |     |          |           |   | M |                 |
|                |     |          |           |   | B |                 |
|                |     |          |           |   | E |                 |
|                |     |          |           |   | R |                 |
|                |     |          |           |   |   |                 |
|                |     |          |           |   | D |                 |
|                |     |          |           |   | O |                 |
|                |     |          |           |   | T |                 |
|                |     |          |           |   | / |                 |
|                |     |          |           |   | F |                 |
|                |     |          |           |   | R |                 |
|                |     |          |           |   | A |                 |
|                |     |          |           |   | / |                 |
|                |     |          |           |   | O |                 |
|                |     |          |           |   | R |                 |
|                |     |          |           |   | D |                 |
|                |     |          |           |   | - |                 |
|                |     |          |           |   | 0 |                 |
|                |     |          |           |   | 4 |                 |
|                |     |          |           |   | / |                 |
|                |     |          |           |   | 1 |                 |
|                |     |          |           |   | 3 |                 |
|                |     |          |           |   | . |                 |
|                |     |          |           |   | I |                 |
|                |     |          |           |   | I |                 |
+----------------+-----+----------+-----------+---+---+-----------------+
| 11\.           |     |          |           |   |   |                 |
| SUPPLEMENTARY  |     |          |           |   |   |                 |
| NOTES          |     |          |           |   |   |                 |
+----------------+-----+----------+-----------+---+---+-----------------+
| 12a.           |     |          |           |   | 1 |                 |
| DISTRIBUTIO    |     |          |           |   | 2 |                 |
| N/AVAILABILITY |     |          |           |   | b |                 |
| STATEMENT      |     |          |           |   | . |                 |
|                |     |          |           |   | D |                 |
| This document  |     |          |           |   | I |                 |
| is available   |     |          |           |   | S |                 |
| to the public  |     |          |           |   | T |                 |
| through the    |     |          |           |   | R |                 |
| National       |     |          |           |   | I |                 |
| Technical      |     |          |           |   | B |                 |
| Information    |     |          |           |   | U |                 |
| Service,       |     |          |           |   | T |                 |
| Springfield,   |     |          |           |   | I |                 |
| Virginia       |     |          |           |   | O |                 |
| 22161. This    |     |          |           |   | N |                 |
| document is    |     |          |           |   | C |                 |
| also available |     |          |           |   | O |                 |
| on the FRA     |     |          |           |   | D |                 |
| website at     |     |          |           |   | E |                 |
| ww             |     |          |           |   |   |                 |
| w.fra.dot.gov. |     |          |           |   |   |                 |
+----------------+-----+----------+-----------+---+---+-----------------+
| 13\. ABSTRACT  |     |          |           |   |   |                 |
| (Maximum 200   |     |          |           |   |   |                 |
| words)         |     |          |           |   |   |                 |
|                |     |          |           |   |   |                 |
| This report is |     |          |           |   |   |                 |
| the second in  |     |          |           |   |   |                 |
| a series       |     |          |           |   |   |                 |
| documenting    |     |          |           |   |   |                 |
| the            |     |          |           |   |   |                 |
| development    |     |          |           |   |   |                 |
| and evaluation |     |          |           |   |   |                 |
| of a software  |     |          |           |   |   |                 |
| application to |     |          |           |   |   |                 |
| facilitate     |     |          |           |   |   |                 |
| communications |     |          |           |   |   |                 |
| for railroad   |     |          |           |   |   |                 |
| roadway        |     |          |           |   |   |                 |
| workers. 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.     |     |          |           |   |   |                 |
| Using a global |     |          |           |   |   |                 |
| positioning    |     |          |           |   |   |                 |
| system (GPS)   |     |          |           |   |   |                 |
| receiver, the  |     |          |           |   |   |                 |
| application    |     |          |           |   |   |                 |
| can also show  |     |          |           |   |   |                 |
| the location   |     |          |           |   |   |                 |
| of the device. |     |          |           |   |   |                 |
| The study's    |     |          |           |   |   |                 |
| goal was to    |     |          |           |   |   |                 |
| understand the |     |          |           |   |   |                 |
| safety         |     |          |           |   |   |                 |
| implications   |     |          |           |   |   |                 |
| of digital     |     |          |           |   |   |                 |
| wireless       |     |          |           |   |   |                 |
| communications |     |          |           |   |   |                 |
| and            |     |          |           |   |   |                 |
| positioning    |     |          |           |   |   |                 |
| technologies   |     |          |           |   |   |                 |
| on roadway     |     |          |           |   |   |                 |
| worker safety  |     |          |           |   |   |                 |
| and            |     |          |           |   |   |                 |
| performance.   |     |          |           |   |   |                 |
|                |     |          |           |   |   |                 |
| The current    |     |          |           |   |   |                 |
| prototype      |     |          |           |   |   |                 |
| operated on a  |     |          |           |   |   |                 |
| cell phone     |     |          |           |   |   |                 |
| integrated     |     |          |           |   |   |                 |
| with a         |     |          |           |   |   |                 |
| personal       |     |          |           |   |   |                 |
| digital        |     |          |           |   |   |                 |
| assistant      |     |          |           |   |   |                 |
| (PDA). It was  |     |          |           |   |   |                 |
| connected to a |     |          |           |   |   |                 |
| GPS receiver   |     |          |           |   |   |                 |
| and exchanged  |     |          |           |   |   |                 |
| messages with  |     |          |           |   |   |                 |
| the dispatcher |     |          |           |   |   |                 |
| using wireless |     |          |           |   |   |                 |
| Internet       |     |          |           |   |   |                 |
| access.        |     |          |           |   |   |                 |
|                |     |          |           |   |   |                 |
| Roadway        |     |          |           |   |   |                 |
| workers and    |     |          |           |   |   |                 |
| dispatchers    |     |          |           |   |   |                 |
| participated   |     |          |           |   |   |                 |
| in focus       |     |          |           |   |   |                 |
| groups to      |     |          |           |   |   |                 |
| acquire        |     |          |           |   |   |                 |
| information    |     |          |           |   |   |                 |
| about the      |     |          |           |   |   |                 |
| tasks they     |     |          |           |   |   |                 |
| perform and to |     |          |           |   |   |                 |
| identify       |     |          |           |   |   |                 |
| usability      |     |          |           |   |   |                 |
| concerns.      |     |          |           |   |   |                 |
|                |     |          |           |   |   |                 |
| An experiment  |     |          |           |   |   |                 |
| was conducted  |     |          |           |   |   |                 |
| to evaluate    |     |          |           |   |   |                 |
| the current    |     |          |           |   |   |                 |
| prototype's    |     |          |           |   |   |                 |
| impact on the  |     |          |           |   |   |                 |
| dispatcher.    |     |          |           |   |   |                 |
| Overall,       |     |          |           |   |   |                 |
| interactions   |     |          |           |   |   |                 |
| between        |     |          |           |   |   |                 |
| dispatchers    |     |          |           |   |   |                 |
| and roadway    |     |          |           |   |   |                 |
| workers using  |     |          |           |   |   |                 |
| digital        |     |          |           |   |   |                 |
| communications |     |          |           |   |   |                 |
| were slower    |     |          |           |   |   |                 |
| but more       |     |          |           |   |   |                 |
| accurate than  |     |          |           |   |   |                 |
| the same       |     |          |           |   |   |                 |
| interactions   |     |          |           |   |   |                 |
| over the       |     |          |           |   |   |                 |
| radio.         |     |          |           |   |   |                 |
| Dispatcher     |     |          |           |   |   |                 |
| valued the     |     |          |           |   |   |                 |
| tracking       |     |          |           |   |   |                 |
| display based  |     |          |           |   |   |                 |
| on GPS         |     |          |           |   |   |                 |
| information,   |     |          |           |   |   |                 |
| although it    |     |          |           |   |   |                 |
| increased      |     |          |           |   |   |                 |
| workload.      |     |          |           |   |   |                 |
+----------------+-----+----------+-----------+---+---+-----------------+
| 14\. SUBJECT   |     |          |           |   |   | 15\. NUMBER OF  |
| TERMS          |     |          |           |   |   | PAGES           |
|                |     |          |           |   |   |                 |
| cognitive task |     |          |           |   |   | 88              |
| analysis, data |     |          |           |   |   |                 |
| link           |     |          |           |   |   |                 |
| c              |     |          |           |   |   |                 |
| ommunications, |     |          |           |   |   |                 |
| de             |     |          |           |   |   |                 |
| cision-making, |     |          |           |   |   |                 |
| intelligent    |     |          |           |   |   |                 |
| railroad       |     |          |           |   |   |                 |
| systems,       |     |          |           |   |   |                 |
| railroad       |     |          |           |   |   |                 |
| dispatcher,    |     |          |           |   |   |                 |
| roadway        |     |          |           |   |   |                 |
| worker, track  |     |          |           |   |   |                 |
| allocation,    |     |          |           |   |   |                 |
| train routing, |     |          |           |   |   |                 |
| usability      |     |          |           |   |   |                 |
+----------------+-----+----------+-----------+---+---+-----------------+
|                |     |          |           |   |   | 16\. PRICE CODE |
+----------------+-----+----------+-----------+---+---+-----------------+
| 17\. SECURITY  | 1   |          | 19\.      |   |   | 20\. LIMITATION |
| C              | 8\. |          | SECURITY  |   |   | OF ABSTRACT     |
| LASSIFICATION\ | SE  |          | CLASSI    |   |   |                 |
| OF REPORT      | CUR |          | FICATION\ |   |   | ####  {#section |
|                | ITY |          | OF        |   |   | -1 .unnumbered} |
| Unclassified   | CLA |          | ABSTRACT  |   |   |                 |
|                | SSI |          |           |   |   |                 |
|                | FIC |          | Unc       |   |   |                 |
|                | ATI |          | lassified |   |   |                 |
|                | ON\ |          |           |   |   |                 |
|                | OF  |          |           |   |   |                 |
|                | T   |          |           |   |   |                 |
|                | HIS |          |           |   |   |                 |
|                | P   |          |           |   |   |                 |
|                | AGE |          |           |   |   |                 |
|                |     |          |           |   |   |                 |
|                | Unc |          |           |   |   |                 |
|                | las |          |           |   |   |                 |
|                | sif |          |           |   |   |                 |
|                | ied |          |           |   |   |                 |
+----------------+-----+----------+-----------+---+---+-----------------+

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

METRIC/ENGLISH CONVERSION FACTORS

<table style="width:100%;">
<colgroup>
<col style="width: 23%" />
<col style="width: 1%" />
<col style="width: 0%" />
<col style="width: 23%" />
<col style="width: 0%" />
<col style="width: 23%" />
<col style="width: 0%" />
<col style="width: 1%" />
<col style="width: 0%" />
<col style="width: 0%" />
<col style="width: 24%" />
</colgroup>
<thead>
<tr class="header">
<th colspan="5"><strong>ENGLISH TO METRIC</strong></th>
<th colspan="6"><strong>METRIC TO ENGLISH</strong></th>
</tr>
<tr class="odd">
<th colspan="5"><strong>LENGTH (APPROXIMATE)</strong></th>
<th colspan="6"><strong>LENGTH (APPROXIMATE)</strong></th>
</tr>
</thead>
<tbody>
<tr class="odd">
<td><strong>1 inch (in)</strong></td>
<td><strong>=</strong></td>
<td colspan="2"><strong>2.5 centimeters (cm)</strong></td>
<td colspan="2"><strong>1 millimeter (mm)</strong></td>
<td colspan="3"><strong>=</strong></td>
<td colspan="2"><strong>0.04 inch (in)</strong></td>
</tr>
<tr class="even">
<td><strong>1 foot (ft)</strong></td>
<td><strong>=</strong></td>
<td colspan="2"><strong>30 centimeters (cm)</strong></td>
<td colspan="2"><strong>1 centimeter (cm)</strong></td>
<td colspan="3"><strong>=</strong></td>
<td colspan="2"><strong>0.4 inch (in)</strong></td>
</tr>
<tr class="odd">
<td><strong>1 yard (yd)</strong></td>
<td><strong>=</strong></td>
<td colspan="2"><strong>0.9 meter (m)</strong></td>
<td colspan="2"><strong>1 meter (m)</strong></td>
<td colspan="3"><strong>=</strong></td>
<td colspan="2"><strong>3.3 feet (ft)</strong></td>
</tr>
<tr class="even">
<td><strong>1 mile (mi)</strong></td>
<td><strong>=</strong></td>
<td colspan="2"><strong>1.6 kilometers (km)</strong></td>
<td colspan="2"><strong>1 meter (m)</strong></td>
<td colspan="3"><strong>=</strong></td>
<td colspan="2"><strong>1.1 yards (yd)</strong></td>
</tr>
<tr class="odd">
<td></td>
<td></td>
<td colspan="2"></td>
<td colspan="2"><strong>1 kilometer (km)</strong></td>
<td colspan="3"><strong>=</strong></td>
<td colspan="2"><strong>0.6 mile (mi)</strong></td>
</tr>
<tr class="even">
<td colspan="5"><strong>AREA (APPROXIMATE)</strong></td>
<td colspan="6"><strong>AREA (APPROXIMATE)</strong></td>
</tr>
<tr class="odd">
<td><strong>1 square inch (sq in, in<sup>2</sup>)</strong></td>
<td><strong>=</strong></td>
<td colspan="2"><strong>6.5 square centimeters
(cm<sup>2</sup>)</strong></td>
<td colspan="2"><strong>1 square centimeter
(cm<sup>2</sup>)</strong></td>
<td colspan="3"><strong>=</strong></td>
<td colspan="2"><strong>0.16 square inch (sq in,
in<sup>2</sup>)</strong></td>
</tr>
<tr class="even">
<td><strong>1 square foot (sq ft, ft<sup>2</sup>)</strong></td>
<td><strong>=</strong></td>
<td colspan="2"><strong>0.09 square meter (m<sup>2</sup>)</strong></td>
<td colspan="2"><strong>1 square meter (m<sup>2</sup>)</strong></td>
<td colspan="3"><strong>=</strong></td>
<td colspan="2"><strong>1.2 square yards (sq yd,
yd<sup>2</sup>)</strong></td>
</tr>
<tr class="odd">
<td><strong>1 square yard (sq yd, yd<sup>2</sup>)</strong></td>
<td><strong>=</strong></td>
<td colspan="2"><strong>0.8 square meter (m<sup>2</sup>)</strong></td>
<td colspan="2"><strong>1 square kilometer
(km<sup>2</sup>)</strong></td>
<td colspan="3"><strong>=</strong></td>
<td colspan="2"><strong>0.4 square mile (sq mi,
mi<sup>2</sup>)</strong></td>
</tr>
<tr class="even">
<td><strong>1 square mile (sq mi, mi<sup>2</sup>)</strong></td>
<td><strong>=</strong></td>
<td colspan="2"><strong>2.6 square kilometers
(km<sup>2</sup>)</strong></td>
<td colspan="2"><strong>10,000 square meters
(m<sup>2</sup>)</strong></td>
<td colspan="3"><strong>=</strong></td>
<td colspan="2"><strong>1 hectare (ha) = 2.5 acres</strong></td>
</tr>
<tr class="odd">
<td><strong>1 acre = 0.4 hectare (he)</strong></td>
<td><strong>=</strong></td>
<td colspan="2"><strong>4,000 square meters
(m<sup>2</sup>)</strong></td>
<td colspan="2"></td>
<td colspan="3"></td>
<td colspan="2"></td>
</tr>
<tr class="even">
<td colspan="5"><strong>MASS - WEIGHT (APPROXIMATE)</strong></td>
<td colspan="6"><strong>MASS - WEIGHT (APPROXIMATE)</strong></td>
</tr>
<tr class="odd">
<td><strong>1 ounce (oz)</strong></td>
<td><strong>=</strong></td>
<td colspan="2"><strong>28 grams (gm)</strong></td>
<td colspan="2"><strong>1 gram (gm)</strong></td>
<td colspan="2"><strong>=</strong></td>
<td colspan="3"><strong>0.036 ounce (oz)</strong></td>
</tr>
<tr class="even">
<td><strong>1 pound (lb)</strong></td>
<td><strong>=</strong></td>
<td colspan="2"><strong>0.45 kilogram (kg)</strong></td>
<td colspan="2"><strong>1 kilogram (kg)</strong></td>
<td colspan="2"><strong>=</strong></td>
<td colspan="3"><strong>2.2 pounds (lb)</strong></td>
</tr>
<tr class="odd">
<td><strong>1 short ton = 2,000 pounds (lb)</strong></td>
<td><strong>=</strong></td>
<td colspan="2"><strong>0.9 tonne (t)</strong></td>
<td colspan="2"><strong>1 tonne (t)</strong></td>
<td colspan="2"><p><strong>=</strong></p>
<p><strong>=</strong></p></td>
<td colspan="3"><p><strong>1,000 kilograms (kg)</strong></p>
<p><strong>1.1 short tons</strong></p></td>
</tr>
<tr class="even">
<td colspan="5"><strong>VOLUME (APPROXIMATE)</strong></td>
<td colspan="6"><strong>VOLUME (APPROXIMATE)</strong></td>
</tr>
<tr class="odd">
<td><strong>1 teaspoon (tsp)</strong></td>
<td colspan="2"><strong>=</strong></td>
<td colspan="2"><strong>5 milliliters (ml)</strong></td>
<td colspan="2"><strong>1 milliliter (ml)</strong></td>
<td colspan="3"><strong>=</strong></td>
<td><strong>0.03 fluid ounce (fl oz)</strong></td>
</tr>
<tr class="even">
<td><strong>1 tablespoon (tbsp)</strong></td>
<td colspan="2"><strong>=</strong></td>
<td colspan="2"><strong>15 milliliters (ml)</strong></td>
<td colspan="2"><strong>1 liter (l)</strong></td>
<td colspan="3"><strong>=</strong></td>
<td><strong>2.1 pints (pt)</strong></td>
</tr>
<tr class="odd">
<td><strong>1 fluid ounce (fl oz)</strong></td>
<td colspan="2"><strong>=</strong></td>
<td colspan="2"><strong>30 milliliters (ml)</strong></td>
<td colspan="2"><strong>1 liter (l)</strong></td>
<td colspan="3"><strong>=</strong></td>
<td><strong>1.06 quarts (qt)</strong></td>
</tr>
<tr class="even">
<td><strong>1 cup (c)</strong></td>
<td colspan="2"><strong>=</strong></td>
<td colspan="2"><strong>0.24 liter (l)</strong></td>
<td colspan="2"><strong>1 liter (l)</strong></td>
<td colspan="3"><strong>=</strong></td>
<td><strong>0.26 gallon (gal)</strong></td>
</tr>
<tr class="odd">
<td><strong>1 pint (pt)</strong></td>
<td colspan="2"><strong>=</strong></td>
<td colspan="2"><strong>0.47 liter (l)</strong></td>
<td colspan="2"></td>
<td colspan="3"></td>
<td></td>
</tr>
<tr class="even">
<td><strong>1 quart (qt)</strong></td>
<td colspan="2"><strong>=</strong></td>
<td colspan="2"><strong>0.96 liter (l)</strong></td>
<td colspan="2"></td>
<td colspan="3"></td>
<td></td>
</tr>
<tr class="odd">
<td><strong>1 gallon (gal)</strong></td>
<td colspan="2"><strong>=</strong></td>
<td colspan="2"><strong>3.8 liters (l)</strong></td>
<td colspan="2"></td>
<td colspan="3"></td>
<td></td>
</tr>
<tr class="even">
<td><strong>1 cubic foot (cu ft, ft<sup>3</sup>)</strong></td>
<td colspan="2"><strong>=</strong></td>
<td colspan="2"><strong>0.03 cubic meter (m<sup>3</sup>)</strong></td>
<td colspan="2"><strong>1 cubic meter (m<sup>3</sup>)</strong></td>
<td colspan="3"><strong>=</strong></td>
<td><strong>36 cubic feet (cu ft, ft<sup>3</sup>)</strong></td>
</tr>
<tr class="odd">
<td><strong>1 cubic yard (cu yd, yd<sup>3</sup>)</strong></td>
<td colspan="2"><strong>=</strong></td>
<td colspan="2"><strong>0.76 cubic meter (m<sup>3</sup>)</strong></td>
<td colspan="2"><strong>1 cubic meter (m<sup>3</sup>)</strong></td>
<td colspan="3"><strong>=</strong></td>
<td><strong>1.3 cubic yards (cu yd, yd<sup>3</sup>)</strong></td>
</tr>
<tr class="even">
<td colspan="5"><strong>TEMPERATURE (EXACT)</strong></td>
<td colspan="6"><strong>TEMPERATURE (EXACT)</strong></td>
</tr>
<tr class="odd">
<td><strong>[(x-32)(5/9)] °F</strong></td>
<td colspan="2"><strong>=</strong></td>
<td colspan="2"><strong>y °C</strong></td>
<td colspan="2"><strong>[(9/5) y + 32] °C</strong></td>
<td colspan="2"><strong>=</strong></td>
<td colspan="2"><strong>x °F</strong></td>
</tr>
</tbody>
</table>

![](media/image4.wmf)

![](media/image5.wmf)

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**

# Acknowledgments {#acknowledgments .WW-Contents-1}

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 Office of Research and
Development sponsored the research, as part of its activities to develop
Intelligent Railroad Systems (Federal Railroad Administration, 2002).

The authors would like to acknowledge several people who helped in the
development of this work. First, Nicolas Oriol, from MIT developed the
first prototype for railroad roadway workers that served as the launch
pad for the current project. Nicolas Malsch and Santanu Basu, also from
MIT, designed the train dispatcher simulator used to evaluate our
system. John K. Pollard, Andrew Kendra, Monica Gil, and, Ed Lanzilotta
from the Volpe National Transportation Systems Center, and Emilie Roth,
from Cognitive Engineering provided help in their own field of
expertise.

George Fitter from Amtrak, helped to organize observation sessions on
track cars. Glenn Underwood, from Amtrak, provided the invaluable help
of arranging visits to the Central Traffic Control Center at Boston
South Station, and focus groups with dispatchers, as well as gathering
volunteers for our evaluation experiment. All the participants, who were
willing to test the system, provided excellent ideas to improve it and
showed great enthusiasm.

# Table of Contents {#table-of-contents .WW-Contents-1}

[Section]{.underline} Page

[Executive Summary ix](#executive-summary)

[1. Introduction 1](#introduction)

[1.1 Improving Railroad Safety through Better Communication
1](#improving-railroad-safety-through-better-communication)

[1.2 Research Objective 3](#research-objective)

[2. Identifying User Requirements 5](#identifying-user-requirements)

[2.1 Methodology 5](#methodology)

[2.1.1 Observation Sessions 5](#observation-sessions)

[2.1.2 Focus Groups 5](#focus-groups)

[2.2 Communication between Roadway Workers and Dispatchers
5](#communication-between-roadway-workers-and-dispatchers)

[2.2.1 Structured Messages 5](#structured-messages)

[2.2.2 Unstructured Messages 7](#unstructured-messages)

[2.2.3 Radio Communication Problems 7](#radio-communication-problems)

[2.3 Track Foreman's Tasks 8](#track-foremans-tasks)

[2.3.1 Unsafe Actions Associated with Lack of Situation Awareness
9](#unsafe-actions-associated-with-lack-of-situation-awareness)

[2.4 Track Inspectors' Tasks 9](#track-inspectors-tasks)

[2.4.1 Description 9](#description)

[2.5 Dispatchers' Tasks 10](#dispatchers-tasks)

[2.5.1 Overview 10](#overview)

[2.5.2 Observed Interactions with Roadway Workers
11](#observed-interactions-with-roadway-workers)

[2.5.3 Interaction with Track Cars 12](#interaction-with-track-cars)

[2.5.4 General Considerations 12](#general-considerations)

[2.6 Prototype Design Goals 13](#prototype-design-goals)

[2.6.1 Improve Communication 13](#improve-communication)

[2.6.2 Improve Situation Awareness 13](#improve-situation-awareness)

[2.6.3 Better Problem Reporting 13](#better-problem-reporting)

[3. Description of the Current Prototype
15](#description-of-the-current-prototype)

[3.1 Overview 15](#overview-1)

[3.2 Operating the Device 16](#operating-the-device)

[3.2.1 Request Information 17](#request-information)

[3.2.2 Request Work Authorization 18](#request-work-authorization)

[3.3 New Features 21](#new-features)

[3.3.1 Timely Asynchronous Communication
21](#timely-asynchronous-communication)

[3.3.2 Locate Track Position 21](#locate-track-position)

[4. Prototype Evaluation 25](#prototype-evaluation)

[4.1 Overview 25](#overview-2)

[4.2 Demonstration and Feedback 25](#demonstration-and-feedback)

[4.2.1 Roadway Workers 25](#roadway-workers)

[4.2.2 Track Inspectors 25](#track-inspectors)

[4.2.3 Dispatchers 27](#dispatchers)

[4.3 Dispatcher Experiment 27](#dispatcher-experiment)

[4.3.1 Experimental Design 29](#experimental-design)

[4.3.2 Participants 31](#participants)

[4.3.3 Procedure 31](#procedure)

[4.3.4 Results 32](#results)

[5. Summary and Recommendations 37](#summary-and-recommendations)

[5.1 Summary 37](#summary)

[5.2 Recommendations 38](#recommendations)

[5.2.1 Develop Hazard Alerts for Roadway Workers
39](#develop-hazard-alerts-for-roadway-workers)

[5.2.2 Evaluate Effectiveness of Graphic Display
39](#evaluate-effectiveness-of-graphic-display)

[5.2.3 Decision Support and Reporting Tool for Track Inspectors
39](#decision-support-and-reporting-tool-for-track-inspectors)

[5.2.4 Track Work Authorization Status for Dispatchers
40](#track-work-authorization-status-for-dispatchers)

[5.2.5 Improve Processing of Work Authorizations
40](#improve-processing-of-work-authorizations)

[Appendix A. System Architecture 41](#system-architecture)

[Appendix B. Questionnaires 47](#questionnaires)

[Appendix C. Adapted NASA TLX Rating Scale
51](#adapted-nasa-tlx-rating-scale)

[Appendix D. Form D AND FOUL TIME 53](#form-d-and-foul-time)

[Appendix E. Focus Group questions 57](#focus-group-questions)

[Appendix F. Wireless Technology Protocols and Positioning Technologies
61](#wireless-technology-protocols-and-positioning-technologies)

[Glossary 67](#glossary)

[References 71](#references)

# List of Figures {#list-of-figures .WW-Contents-1}

[Figure]{.underline} Page

1\. Track Chart Display [11](#__RefHeading___Toc46910748)

2\. Qualcomm® pdQ™ Smartphone [15](#__RefHeading___Toc46910749)

3\. Axiom Smart Antenna GPS Receiver [15](#__RefHeading___Toc46910750)

4\. System Architecture [16](#__RefHeading___Toc46910751)

5\. Main Menu [17](#__RefHeading___Toc46910752)

6\. Train OS Request [18](#__RefHeading___Toc46910753)

7\. Train OS Response [18](#__RefHeading___Toc46910754)

8\. Foul Time Request (Roadway Worker Screen 1)
[19](#__RefHeading___Toc46910755)

9\. Foul Time Request (Roadway Worker Screen 2)
[19](#__RefHeading___Toc46910756)

10\. Foul Time Request (Dispatcher Screen 1)
[19](#__RefHeading___Toc46910757)

11\. Foul Time Request (Roadway Worker Screen 3)
[20](#__RefHeading___Toc46910758)

12\. Foul Time Request (Roadway Worker Screen 4)
[20](#__RefHeading___Toc46910759)

13\. Foul Time Request (Dispatcher Screen 2)
[20](#__RefHeading___Toc46910760)

14\. Street Map Display [22](#__RefHeading___Toc46910761)

15\. GPS Track Display [23](#__RefHeading___Toc46910762)

16\. Track Car Ride Seen from the Street Map Display
[26](#__RefHeading___Toc46910763)

17\. Layout of Dispatcher Simulator [28](#__RefHeading___Toc46910764)

18\. Work Authorization Status Display [29](#__RefHeading___Toc46910765)

19\. Work Authorization Processing Times
[32](#__RefHeading___Toc46910766)

F‑1. WAP Architecture [62](#__RefHeading___Toc46910767)

F‑2. Palm VII™ Architecture [63](#__RefHeading___Toc46910768)

# List of Tables {#list-of-tables .WW-Contents-1}

[Table]{.underline} Page

1\. Problems on the Tracks [10](#__RefHeading___Toc3258223)

2\. Representation of Color Code for Monitoring Track Status
[11](#__RefHeading___Toc3258224)

3\. Train Delay by Communication Mode [33](#__RefHeading___Toc3258225)

4\. Dispatchers' Errors [34](#__RefHeading___Toc3258226)

5\. Workload Ratings [35](#__RefHeading___Toc3258227)

A‑1. Smartphone Operating Characteristics
[42](#__RefHeading___Toc3258228)

A‑2. New Types of Requests [44](#__RefHeading___Toc3258229)

A‑3. Tracking Files Format [44](#__RefHeading___Toc3258230)

A‑4. Map Data base Format [45](#__RefHeading___Toc3258231)

A‑5. Map Data base File Format [46](#__RefHeading___Toc3258232)

# Executive summary {#executive-summary .Contents-1a}

This report describes the continuing development and evaluation of an
application to enable roadway workers to communicate using digital
communications. The original application was developed on a handheld
computer with a wireless modem. The application was moved to another
hardware platform (a cell phone with an integrated handheld computer)
that provided improved communication functionality and the ability to
provide location information using global positioning system (GPS). The
report also documents the additional user requirements identified by
observing and talking with railroad employees who might use it or
interact with it.

New technology in the form of digital communications and location
finding systems offer the potential to improve the safety and
productivity of railroad operations. The use of digital communications
has been proposed as a medium to supplement voice radio. Digital
communications uses bandwidth more efficiently than analog
communications. Information transmitted digitally can be presented
aurally or visually. These characteristics offer solutions to 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.

The first task was to continue the process of identifying user
requirements of roadway workers, begun by Oriol, Sheridan, and Multer
(2004). The communication link between roadway workers and train
dispatchers was of particular interest. To accomplish this objective, a
cognitive task analysis was conducted. Data was collected through focus
groups and observation sessions with dispatchers and roadway workers.
Communications between the two groups were observed at the Traffic
Control Center and in the field. Dispatchers were interviewed about
their conversations with roadway workers, and roadway workers were
interviewed about their conversations with dispatchers. In the initial
work, user requirements were identified for track foreman. In this
study, the requirements of track inspectors were also identified.

The current analysis of user requirements supported Oriol et al. (2004)
findings. Messages exchanged between dispatchers and railroad workers
fell into two categories: structured and unstructured. Structured
messages followed a protocol governed by the railroad's operating rules
that prescribe their content and format. Examples include movement
permits, authorization to foul the track, authority to pass a stop
signal, and submission of speed restrictions. Unstructured messages
varied in format and content. Examples include verbal permission for
signal maintenance, detailed description of job being performed on the
track, and updates about expected time to complete a given job.

Communications took place over the radio and the cell phone, with the
radio serving as the primary communication device. There was a consensus
among all interviewed persons that the voice radio channel was
overloaded. Since few channels are available, interruptions on the same
channel are frequent.

The current study identified lack of situation awareness related to
their location on the track as contributing to unsafe events. Track
crews working at fixed locations as well as track inspectors
occasionally lost their bearing when working on or near the track.
Location finding technology like GPS could support the roadway worker in
monitoring their track location. In addition, this information could
enable the dispatcher to determine the position of track cars and crews
without requiring voice communication.

The first prototype enabled roadway workers to request real-time train
and territory status information and request work authorization. A
second prototype was created that added two features: two-way
asynchronous communications and location determination.

The first prototype was limited to one-way asynchronous communication.
The operator of the application could not receive timely notification
when the dispatcher responded to a work request. The operator had to
check the application to see if the dispatcher had replied to a request.

Wireless devices with two-way asynchronous communications make it
possible for the roadway worker to receive timely notification of
messages initiated by others. The Short Message Service (SMS) provides a
mechanism to reach the handheld device from the web. The prototype
evaluated in this study, a cell phone with an integrated Personal
Digital Assistant (PDA), included this feature.

An external GPS receiver was attached to the hardware via a serial
cable. Because of the small size and low resolution of the display, an
application displaying the device's location on the display itself, was
not developed. Instead, an application was created for the dispatcher
that could display a map of the railroad worker's surroundings based on
the GPS information. Two types of map displays were created, one showing
location on a street map, the other showing the location on a track
display. The application shows movement over time. When the location
report feature was activated, the handset periodically retrieved the
location from the GPS receiver and sent it to a web server where the
dispatcher could retrieve the information.

To evaluate the prototype, it was first demonstrated to railroad
workers, and dispatchers. Global feedback was positive, and everyone
welcomed a system that could solve the radio congestion problem. The GPS
functionality seemed to have the most benefit to localize track cars.
Nevertheless, some railroad workers did not like the idea of being
tracked and others seemed reluctant to use new information technologies.

An experiment was conducted to evaluate the prototype from the
dispatcher's perspective. The main questions were how dispatching
efficiency and global railroad safety could be enhanced if the railroad
workers used the handheld device instead of the radio. The experimental
participant was in charge of routing trains on a railroad dispatcher
simulator and dealing with railroad workers using either the radio or
the new device.

Digital communications between dispatchers and railroad workers,
although slower, produced fewer errors compared to the same interactions
over the radio. Some aspects of performance (blocking errors, routing
errors) were improved with the device. The tracking display was expected
to have more impact. The task seemed to be too demanding for the
subjects to fully benefit from the tracking display.

All the participants showed great enthusiasm and gave constructive
feedback regarding use of the handheld application. They thought it
would improve communications by reducing radio congestion and
communication errors and assist in locating track vehicles and roadway
workers on the right-of-way.

Adapting to the new technology for both dispatchers and roadway workers
poses a variety of challenges. For example, monitoring the location of
all roadway workers on the track would substantially increase a
dispatcher's workload. Many of the dispatchers also felt that the
willingness to adopt the new technology would vary with age. Younger
people were expected to learn and take advantage of the new technologies
more quickly and with greater enthusiasm. They also worried about the
intangible (i.e., non-verbal) aspects of communication that may be lost
moving from a predominantly oral communication medium to a visual
medium. The dispatchers were also concerned about rule compliance with
respect to the use of GPS and other location finding technologies. The
application of this technology would only assist them, if they "turned
the feature on" when the roadway workers were on the track right-of-way.

Roadway workers were also concerned about how the new information
technologies would affect them. While many roadway workers showed
enthusiasm for the application, some were reticent about relying upon it
as a safety-critical device. Roadway workers also expressed concern
about how their privacy would be affected when their location could be
tracked by the application. They were particularly concerned that their
location might be monitored when they were not working on the track,
despite the fact that the GPS receiver that reports this information,
was under the control of the roadway worker.

The current set of features was evaluated from the dispatcher's
perspective in a laboratory experiment. In this experiment, work
authorization transactions took longer in the data link condition than
with voice radio. This behavior contrasted with Malsch et al., (1999)
results where data link reduced transmission of work authorization times
by a factor of two. This difference between the two experiments suggests
that the design of the dispatcher interface plays an important role in
its usability and effectiveness in facilitating dispatcher performance.
The information on the dispatcher displays was organized differently. In
addition, information showing requested track segments was displayed on
the monitor showing the track network in Malsch's study, but not in
Oriol's. Seeing the requested track in the context of other activities
taking place may have contributed to faster decision-making by the
dispatcher.

In both studies, there were fewer communications errors in the data link
condition than in the radio condition. Malsch et al., (1999) also
observed this behavior in their study. Auditory communications were more
prone to errors because their transient nature placed higher memory
demands on the dispatcher.

The number of protection and routing errors were also smaller in the
data link condition. It was less taxing for dispatchers to process the
work authorization requests in visual form than to have to listen to the
radio and write down parameters, while planning train movements and
authorizing maintenance work. This would explain why mental workload was
rated higher in the radio condition.

While the tracking display appeared to be useful in assisting the
dispatcher to locate track cars, monitoring roadway workers on the track
posed a greater challenge. The dispatchers identified only 40 percent of
roadway workers working without authorization and no location reporting
errors were caught. The task seemed to be too demanding for the subjects
to fully benefit from the tracking display. The tracking display was
expected to have more impact. The dispatcher's mental workload may be
too high for him/her to fully benefit from a tracking display.

# Introduction

## Improving Railroad Safety through Better Communication

Safe and efficient railroad operations require continuous coordination
among key groups of railroad operating personnel. Mainline railroad
operations involve three main groups of employees:

-   **Railroad dispatchers** allocate track for the movement of trains
    or for maintenance. Their most important responsibilities are to
    ensure safe movement of trains and personnel on the tracks, ensure
    that passenger trains meet schedules, and in case of emergency,
    coordinate rescue missions. The dispatcher is responsible for the
    proper separation of trains, track equipment, and personnel.

-   **Locomotive engineers and conductors** operate the trains, and are
    responsible for following the directions dictated by wayside signals
    and dispatchers.

-   **Roadway workers** engage 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 tracks.

To maintain safety, trains, track equipment, and roadway workers must be
separated in both space and time. Railroad communication systems enable
the key groups to coordinate their activities and maintain safe
separation. Current technology supporting railroad communications relies
primarily on voice radio.

The characteristics of voice radio and the way railroad operations are
conducted contribute to several problems. First, the available voice
radio bandwidth is inadequate to support current communication needs
(Federal Railroad Administration, 1994; Roth, Malsch, and Multer, 2001).
The Federal Communications Commission (FCC) has allocated 96 channels
for railroad operations. However, within any geographic region a much
smaller number of channels are available (e.g., 3 or 4). Voice
communications for main line operations are typically restricted to a
single channel. In addition, only one person can communicate on a
channel at a time. Other workers who want to use the same channel must
wait until it is clear. As a result, voice radio channels are congested.

Second, the temporal nature of information communicated by voice radio
imposes a significant burden on the operator's memory. Railroad workers
must often record important information on paper. However, the time it
takes to record this information places a burden on the dispatcher's
memory and increases workload.

Depending upon the type of territory, railroad employees may also
receive information through the track infrastructure. In signal
territory, the track equipment provides dispatchers with information
about signal states, switch states, and train location. In signal
territory with track circuits, trains shunt (activate) the track circuit
at the block entrance and exit. The track infrastructure relays this
information to the dispatcher and indicates the train's location.
However, a train's location is known only within a given block, which
can vary in length from several hundred feet to many miles. Some track
equipment like hi-railers (see glossary) do not reliably shunt track
circuits. As a result, track inspectors riding in a hi-railer report
their position frequently to the dispatcher. In dark territory, this
information is unavailable. The dispatcher must rely solely on voice
communications with the train crew to learn their track location.

New technology in the form of digital data link communications and
location finding systems such as GPS offer the potential to improve the
safety and productivity of railroad operations. The use of digital
telecommunications 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. 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.

A significant percentage of the communications between railroad
employees revolves around locating railroad assets in the form of
trains, track equipment, and roadway workers. Maintaining adequate
separation between these vehicles requires following railroad operating
rules that promote safe separation. The operating rules require a set of
structured exchanges between the dispatcher and the train crew or
roadway crew to obtain the authority to occupy a section of track. A key
element in each of the messages is the track location being requested.
The reference to a location is normally by milepost, a sign posted on
the track that specifies the track location numerically. However, the
reference may be approximate. For example, a roadway crew may request
track authority between milepost 110.3 and 120.5. However, relationship
of the milepost signs to an actual location on the ground is
approximate. The reference to tenths of mile is a judgment on the part
of the roadway worker and there may be some error in this reference.
Similarly, knowing the location of a train in signal territory is
approximate. The dispatcher knows a train is in a particular block, but
does not know where in the block, with any confidence.

Some accidents may be attributed to roadway worker or train crew
disorientation. In some cases, roadway workers or train crews lose track
of the limits of their authority and move outside those limits. For
example, in multiple track territory, a roadway worker may receive
permission to work on one track, but mistakenly work on another track
for which there is no protection. Conversely, a train crew may plan to
stop before entering a work zone, but fail to stop in time because they
miss the visual cues that signal the beginning of the work zone. Either
situation can result in the injury of a roadway worker.

Crews can avoid these accidents if they receive more accurate
information of train location, their own location, the location of
others, and equipment on the track. New technologies for locating people
and equipment make it possible to address this problem. Currently, two
train location technologies are under development and are being tested
for use in North America:

-   Transponder/Interrogator system: transponders are placed along the
    track at suitable intervals and key locations. Each equipped train
    carries an interrogator (consisting of a reader and an antenna) that
    activates the transponder by emitting a signal to it when the
    locomotive approaches. In response, the transponder transmits back
    some identification information (including location).

-   Global positioning system (GPS): trains use onboard GPS receivers
    (or differential GPS receivers) to compute their positions.

A location determination system may also consist of a combination of two
or more systems such as:

-   GPS for calculating position

-   Tachometer for dead reckoning

-   Fiber-optic gyro for detecting curves

-   Digital track map in an on on-board computer

## Research Objective

The current study was part of a research program to measure how digital
communications impacts human performance in railroad operations. A goal
of this study was to understand the safety implications and usability
requirements for roadway workers to take advantage of such technology.

The first study examined the potential of digital communications from
the dispatcher's point of view (Malsch, Sheridan, and Multer; 2004). The
use of digital communications by dispatchers was compared to voice
radio, using a human-in-the-loop railroad dispatcher simulator. The
results indicated messages intended to convey detailed information were
more accurately understood using electronic communications than when
voice radio was used. Dispatchers liked receiving more information to
help decide the order in which they answered requests from trains or
work crews in compared to voice radio. Voice radio calls were more
likely to be answered on a first-come first-served basis. With this
architecture, they could assign priorities to incoming messages and deal
with the most important ones first. The dispatchers valued avoiding the
need to repeat a message many times due to low quality radio
transmissions.

Oriol, Sheridan, and Multer (2004) examined the use of digital
communications from the roadway worker's perspective. The first
prototype of a communication application was designed to operate on a
handheld computer with a wireless modem (Palm VII™). The application was
evaluated for its usability and the ability of roadway workers to
perform their communication tasks compared to voice radio. Interactions
between dispatchers and roadway workers were slower but more accurate
with the handheld application compared to the same interactions using
the voice radio.

This report describes the continuing development and evaluation of the
application to enable roadway workers to communicate using digital
communications. The application was moved to a different hardware
platform that provided additional communication functionality and the
ability to provide location information using GPS. The report also
documents the additional user requirements identified by observing and
talking with the railroad employees who might use it or would interact
with it.

The purpose of the experiment described in this report was to evaluate
its impact on dispatcher performance when roadway workers use this
device in addition to voice communications.

# Identifying User Requirements

This section describes the communication-related tasks performed by
dispatchers and several types of Amtrak roadway workers, and the
information requirements needed to support those tasks. The information
described here adds to roadway worker requirements reported by Oriol,
Sheridan, and Multer (2004).

## Methodology

### Observation Sessions

Observations were made during two track car rides with Amtrak track
inspectors. Both trips took place on the Northeast Corridor between
Boston and New Haven. The first trip went from Cove, Massachusetts to
Plains, Massachusetts, and the second trip went from Kingston, Rhode
Island, to Transfer, Massachusetts. During both trips, the track
inspectors were questioned about the tasks they perform and their
interactions with dispatchers. Observations of dispatchers were also
made at Amtrak's Central Traffic Control Center in Boston,
Massachusetts.

### Focus Groups

Two focus groups were conducted with dispatchers at Amtrak's Central
Traffic Control Center, in Boston, Massachusetts. The goal was to
document the dispatcher's interactions with roadway workers and to
obtain feedback on the revised prototype. Each session lasted 2 hours.
The first hour was devoted to documenting the interactions between
dispatchers and roadway workers in general, and the second hour was
devoted to demonstrating the prototype and soliciting feedback to
improve its usability. (See Prototype Evaluation for the results of the
second part). Appendix F lists the questions asked during each session.
Both sessions were tape-recorded.

There were two participants in the first focus group and three in the
second group. All participants were professional Amtrak dispatchers from
the Boston division. Three dispatchers had less than 3 years of
experience, one dispatcher had 13 years experience, and one dispatcher
had 26 years of experience.

## Communication between Roadway Workers and Dispatchers

Information is currently exchanged mostly over the radio and
occasionally over the telephone. Messages exchanged between dispatchers
and roadway workers can be divided into two types: structured and
unstructured. Structured messages followed a protocol governed by
operating rules that everybody must follow. These messages included
various forms of movement authorities and authorization to work on the
track. Unstructured messages comprised all other messages and did not
follow a formal protocol. Examples of each message type are discussed in
the following sections.

### Structured Messages

Different kinds of structured messages are exchanged over the radio. For
safety reasons, the receiver must always repeat a structured message to
make sure the information was accurately heard and understood. However,
as one dispatcher said, "We are not automatons. You'd be hard pressed to
find someone who literally communicates the way the book says."

Here are several examples of structured messages that dispatchers use on
the Northeast Corridor between Boston and New Haven:

1.  Form D movement authority and additions to Form D.

The dispatcher issues Form Ds to authorize or restrict movements (NORAC
operating rules, 1999). Form Ds are also issued to convey instructions
not covered in the operating rules. Although Form Ds are intended mainly
for train movements, according to one of the interviewed dispatchers, 90
percent are issued to work crews and only 10 percent to trains. A
roadway worker may receive a Form D line 4 "if the work involves
on-track equipment or will disturb the track or catenary structure so
that it would be unsafe for normal speed." Appendix E shows a Form D.

The Form D provides several kinds of authority. One type of authority is
used to take a track out of service (Form D, Line 4).[^1] A second
authorization gives track cars and other mobile equipment (Form D Line 2
and 3) track movement authority. Line 2 indicates the parameters for the
limits of authority and the direction in which the equipment can move.
Line 3 indicates the trains or track cars ahead, as well as stop signals
that the vehicle is allowed to pass.

Once a dispatcher issues a Form D, very limited information may be added
to it. This information includes: cancellation facts, permission to
continue to operate a track car in a given direction under new limits
(line 2), and "track is clear" information (line 13), train or track car
ahead has cleared the limits of the following track car's (line 2).
Appendix E provides a more detailed description of a Form D.

2.  Foul Time (track and time).

A qualified roadway worker whose duties will not disturb the track or
catenary structure may receive verbal authorization to foul the track
from the dispatcher. Granting Foul Time to roadway workers (also
referred to as track and time) has become a major part of a dispatcher's
job in the Northeast Corridor. Depending on the territory under
consideration, a dispatcher controlling territory between Boston and New
Haven may easily have three to seven active Foul Time authorizations in
effect at the same time.

3.  Rule 241: Authority to pass a stop signal.

Rule 241 enables trains or track cars to pass a stop signal. Railroad
operating rules normally prohibit trains and track cars from going past
a stop signal. A dispatcher will most often issue authority to pass a
stop signal to track cars since they need this authorization to enter
each interlocking. Almost every time permission to operate a track car
is issued (Form D Line 2), it is followed by permission for the track
car to proceed past a stop signal (Form D Line 3 or rule 241). The
choice of authority to pass a stop signal depends on the dispatcher's
preferences.

4.  Speed restrictions.

Repair crews dictate new speed restrictions to dispatchers. These speed
restrictions are sent daily to trains and dispatchers and may be
included in a Form D.

### Unstructured Messages

Before requesting work authorization, a roadway worker may call the
dispatcher for schedule updates and for unscheduled train information.
This kind of unstructured communication occurs frequently.

Dispatchers also spend a lot of time relaying information, between a
roadway worker crew and the foreman, or between different crews.
Dispatchers may relay messages between different crews or among members
of a work crew when they are too far apart to communicate by radio
directly. The work crews carry radios that are less powerful than those
available to the dispatcher.

Another type of interaction between dispatchers and roadway workers
occurs while the latter are already working under protection.
Dispatchers frequently ask work crews for details related to the time
component of their work authorization. For example, how long will it
take to remove equipment from the track? Dispatchers also ask for
details about the work being performed on the track. This information
gives them information about track availability in case it is needed
unexpectedly for other purposes.

Dispatchers occasionally call track cars to determine their current
position. Indeed, a track car's position is usually known only as being
within a given section where it has movement authorization (Form D Line
2 and 3), and these sections are sometimes very large.

A number of different situations can arise in railroad operations when a
dispatcher must issue verbal permission to a roadway worker. For
example, a signal worker may need verbal permission to put an
interlocking into local mode or to temporally shut it down. These verbal
permissions do not always follow the same pattern.

### Radio Communication Problems

There was a clear consensus from all of the interviewed dispatchers and
roadway workers that voice radio channels are congested. Few channels
are available; therefore, interruptions by other calls are very
frequent. Radio seems adapted to short messages, but long dialogues
intended to convey detailed information should be conducted in a more
private way. One dispatcher remarked, "There have been times when I've
had to repeat myself five to six times to get some information across,
or ask someone to repeat himself four, five, or six times before I can
get everything I need from them. When the radios are blocking each other
out, we don't know it. We can't tell that this is happening."

It was indicated that very often, when dispatchers are attending to one
request, other calls come on the radio on other channels. The dispatcher
can attend to only one call at a time and so these other calls
temporarily go unanswered. In the field, some people call repeatedly,
because they believe that the dispatcher is ignoring them, when in fact
the dispatcher is aware of them, but communicating with someone else on
another channel. This situation is mutually frustrating for both the
dispatcher and the individuals trying to reach the dispatcher.

Dispatchers reported that roadway workers often used the radio for non
work-related communications, and unnecessarily overloaded the channels.
"A lot of times, they are joking around," said one dispatcher.

From the roadway worker's point of view, obtaining work authorization
can be time-consuming. When a channel is in use by someone else, the
roadway worker has to wait for the channel to become free before calling
the dispatcher. When a roadway worker's request for work authorization
is taking place, it may be interrupted by communications between others
on the same channel. If a structured message is interrupted, the process
must be repeated resulting in a longer transaction.

The dispatchers also described equipment-related problems. Some
dispatchers reported receiving radio communications from outside their
territories such as the New York and Maryland areas. In some instances,
the train numbers or milepost locations from these communications
outside their territory were the same and created confusion for the
dispatcher. The phone and radio communication systems occasionally bleed
through each other, deteriorating communication quality. Finally, the
presence of dead spots (where radio communication is blocked) along the
tracks impeded communications with train crews and roadway workers.

## Track Foreman's Tasks

Roadway workers' tasks include inspection, construction, maintenance, or
repair of railroad track, bridges, roadway, signal, and communication
systems, electric traction systems, roadway facilities, and roadway
maintenance machinery on or near the track. According to the
instructions given in the Amtrak Roadway Worker Protection Class, and in
written materials (Amtrak Roadway Worker Protection Manual, 1997)
whenever a roadway worker wants to perform a job on the track, the
following steps must be followed:

1.  Collect information.

-   Identify milepost number.

-   Identify track numbers.

-   Identify the type of territory.

-   Identify the dispatcher who controls the territory.

-   Find out train schedule around working site.

2.  Conduct a job briefing with entire crew.

3.  Call for Foul Time or Form D when necessary.

4.  Give the track back to the dispatcher on time.

5.  At the end of the tour of duty, make sure work area is safe and
    secure.

In step 1, the track foreman must read the schedule and territory
information from their Operating Rulebook. On Amtrak's Northeast
Corridor, this book only contains scheduled passenger trains.
Unscheduled trains (freight, work-extra trains, etc.) and commuter
trains with higher frequency are not shown in the rulebook. The track
foreman must obtain current information about the location of all the
trains that could interfere with their work. The roadway worker calls
the dispatcher for schedule changes and for nonscheduled train
information.

In step 3, the roadway workers exchange structured messages with the
dispatcher as in the previous section.

### Unsafe Actions Associated with Lack of Situation Awareness

Besides the radio communication problems described above, roadway
workers are confronted with a variety of other challenges related to
situation awareness.

One problem is orientation. Roadway workers may lose their bearing and
work on the wrong track in multiple track territory or work outside the
limits of their authority. This disorientation can lead to critical
mistakes, such as asking for work authorization on the wrong track, or
watching for approaching trains in the wrong direction.

Another problem is the presence of unscheduled and delayed trains, as
roadway workers must always ask the dispatcher about unscheduled or
delayed trains before asking for work authorization. However, in
territories where scheduled operations predominate, they sometimes rely
on their memory (or time tables) to judge if a track is available. They
may forget about possible unscheduled trains, and foul the track without
permission.

Finally, roadway workers sometimes leave their work sites and forget to
cancel their track authority. Failure to cancel a track authority can
delay train movements and other maintenance activities.

## Track Inspectors' Tasks

### Description

The track inspector is in charge of inspecting the tracks for defects.
They request movement authority to operate on a specific track section.
Since track vehicles normally do not shunt the track, they call the
dispatcher each time they clear an interlocking to let the dispatcher
know their position. When a train approaches a track vehicle on an
adjacent track, the track vehicle will stop (by law), and turn off its
headlights (by courtesy).

Track inspectors monitor the condition of the following items:

-   Ties, rails, clips, track surface, ballast

-   Track alignment and settlement

-   Drainage problems

-   Broken rails

-   Missing clips or rail fasteners or loose bolts.

On the track between Boston and New Haven, each track is normally
inspected twice a week and a report is written after each inspection. A
typical track car ride takes 4 to 6 hours. The track may be inspected
more often if conditions warrant (i.e., a heat inspection is conducted
if the air temperature rises above 85^o^ F).

Table 1 describes the actions taken for problems of different
importance. For minimal problems, the track inspector will fix it on the
spot. For moderate problems, inspectors typically will record the data
on track conditions on a blank piece of paper and then type out the
information on a form once they get back to the office. For serious and
critical problems, Amtrak inspectors use the MW1000 rulebook (a book of
inspection rules and tolerance levels) to assist them in deciding what
actions to take. For example, if a rail is bent an inspector will
measure the curvature, and then look in the rulebook to determine the
appropriate speed restriction. The rulebook also specifies how many
miles from the problem warning signs should be placed. For serious
problems, an inspector may impose a speed restriction and then notify
the dispatcher. The dispatcher will then relay the speed restriction to
the trains. For critical problems, an inspector calls the dispatcher to
remove the track from service.

  ------------------------------- --------------------------- -------------------
  []{#__RefHeading___Toc3258223                               
  .anchor}Table 1. Problems on                                
  the Tracks                                                  

  Problem Importance              Track Inspector Action      Example

  Minimal                         Fix it yourself             Stone on the track

  Moderate                        Write in daily report       Missing clip

  Serious                         Restrict speed              Bent rail

  Critical                        Remove track from service   Broken rail
  ------------------------------- --------------------------- -------------------

### Unsafe events related to lack of situation awareness {#unsafe-events-related-to-lack-of-situation-awareness .Appendix-3}

Track inspectors described several unsafe situations related to the loss
of situation awareness. Track inspectors were occasionally confused
about their location. One interviewee described a case where a track
inspector thought he was at one interlocking when he was actually at
another. The two interlockings shared similar characteristics. One track
inspector commented, "One can get distracted... can get comfortable and
lose track of things."

Another kind of unsafe situation occurs when the track inspector
misunderstands the limits of the work authority. The track inspectors
interviewed for this study indicated that being on the wrong track (at a
given mile post) was a more common error than being at the wrong
location entirely (i.e., at the wrong milepost or interlocking).

Unscheduled trains also posed a concern for track car operators. For
safety reasons, a track car must stop whenever a train passes by on the
adjacent track. The track inspector appreciated a warning when a train
approached, and helpful dispatchers would alert the track inspector when
an unscheduled train approached on the adjacent track.

## Dispatchers' Tasks

### Overview

Dispatchers route trains and allocate track to roadway workers. Their
most important responsibilities are to ensure safe movement of trains
and personnel on the tracks, ensure that passenger trains meet schedules
and, in case of emergency, coordinate rescue missions.

The current study focused on signal territories, where dispatchers
receive automatic indication of train location. The existing train
location system uses track circuits that trains shunt (activate) at the
entrances and exits of blocks. Consequently, a train's location is known
only within a given block, which can be more than 10 miles long. An
experienced dispatcher will estimate a train's position from the train's
speed and the time it entered a block. In the Northeast Corridor, a few
trains are GPS-equipped, but the GPS information is not currently
integrated in the main computer system. If desired, dispatchers could
retrieve the GPS information, but it is not generally done.

Each dispatcher is in charge of a specific territory where he/she has
authority to route the trains, take tracks out of service, and grant
work authorizations. Each dispatcher has a workstation to control the
switches and signals. This workstation also displays a representation of
the track (see Figure 1). Track displays use scale compression
extensively to show more details around crucial points such as stations
and interlockings. Table 2 shows the meaning of the colors shown for the
status of each block.

  ------------------------------- -----------------------------------------------------------------
  []{#__RefHeading___Toc3258224   
  .anchor}Table 2. Representation 
  of Color Code for Monitoring    
  Track Status                    

  Color                           Meaning

  White                           Indicates that the track segment is available for routing trains
                                  or other uses.

  Red                             Means train or track vehicle occupancy. A train currently
                                  occupies that block.

  Green                           Indicates that the track segment has been cleared (authorized for
                                  use) for train movement. The train has not yet entered this
                                  block.

  Blue                            Indicates that a track section is authorized for track
                                  maintenance. This means that a portion of track has been
                                  protected for use by maintenance of way crews or track equipment.
                                  When the dispatcher gives track authority to a work crew, the
                                  dispatcher temporarily loses control over that section of track.
                                  Trains cannot enter this track segment unless authorized by the
                                  roadway worker responsible for that block.
  ------------------------------- -----------------------------------------------------------------

![](media/image6.wmf){width="5.997222222222222in"
height="1.382638888888889in"}

[]{#__RefHeading___Toc46910748 .anchor}Figure 1. Track Chart Display

### Observed Interactions with Roadway Workers

On the territory between Boston and New Haven, interactions between
dispatchers and roadway workers comprise a larger percentage of their
communication workload, than interactions with train crews. The
interviewed dispatchers estimated that, about 90 percent of radio and
telephone communications took place with roadway workers and track
inspectors. The remaining 10 percent of communications took place with
train crews and other dispatchers.

When a dispatcher received a request for roadway worker protection, the
following steps were followed. After receiving the request, the
dispatcher decided whether to grant, modify, or deny the request.
Normally, the dispatcher granted the request only if it did not delay
any train. If the request was denied, the roadway worker might submit
another request or negotiate with the dispatcher to obtain track
authorization.

If the dispatcher intended to grant work authorization, the dispatcher
proceeded to protect the requested track. At the Traffic Control Center,
the dispatcher could use the track display to protect the track segment
in question using software that controlled various switched and signals
in the field. Where the dispatcher could not protect the track remotely,
the work crew can apply a blocking device (see glossary) to the switches
and signals that control access to the track. Operation of these
switches is restricted and the protected track will display stop signals
at both ends.

Once a track is blocked, the dispatcher temporarily loses authority over
that track. The dispatcher will not be able to reverse or normalize a
switch that is part of the blocked track. If a change in switch is
called for, the roadway worker can change the switch local mode or ask
the dispatcher to make the change. This is a common request. In this
situation, dispatchers unblock the track, reverse or normalize the
switch, and block the track again.

While the roadway worker crew works, the track foreman communicates
intermittently with the dispatcher. These interactions include modifying
the existing work authorization, requesting additional work
authorizations, submitting speed restrictions, and requesting
information such as updates on train location. Once the job is complete,
the roadway worker returns control of the track to the dispatcher, who
releases the track for other uses.

### Interaction with Track Cars

Track cars place a significant demand on the dispatcher's attention
because they normally do not shunt (activate) the track circuits used to
detect the presence of trains. Therefore, dispatchers don't know where
they are within their limits of authority.

Track sections can be very long (10 miles or more), and track cars
usually travel very slowly. The vehicle used for track inspection
between New Haven and Boston moves at a maximum speed of 30 miles per
hour. Moreover, track car operators frequently stop to inspect the
tracks. Therefore, it is very hard for dispatchers to accurately
determine a track car's position.

Dispatchers need timely information about their location to manage track
use in the safest and most productive way. For these reasons,
dispatchers and track inspectors communicate frequently. Between Boston
and New Haven, track car operators call the dispatcher when they have
cleared an interlocking. Dispatchers call track cars very often to know
their positions.

### General Considerations

Many factors make the dispatcher's job challenging. High communication
workload strains the dispatcher's attention and memory. Demands on track
use are high and the margin for flexibility can be low. In passenger
operations, trains need to stay on schedule and there are limited
routing options available. Dispatching requires keeping track of the
progress of multiple trains, some of which are outside the area
controlled by the dispatcher center.

Lastly, efficiently managing the track requires knowledge that is not
readily available from workstation displays (i.e., speed limits,
characteristics of trains, location of nearby streets, track elevation,
bridge height). Dispatchers acquire this information with experience.
With the centralization of dispatching facilities, dispatchers have
little opportunity to "walk the tracks" to learn a territory's
characteristics. Dispatchers often have trouble visualizing the physical
layout of the tracks and surrounding geography.

The track display is an abstract representation, as it does not display
information related to physical characteristics of the track (curves,
grade crossings, roads in the neighborhood of the tracks etc.). This
knowledge becomes critical during unplanned events like grade crossing
accidents, derailments, and track washouts when the dispatcher must find
solutions to these track outages. More information about dispatchers'
cognitive demands can be found in Roth, Malsch, and Multer (2001).

## Prototype Design Goals

### Improve Communication

The analysis of user requirements suggests a number of areas where new
technology can support railroad employees' information-related tasks and
communications. Field observations and interviews conducted for this
study reinforce the findings of Roth, Malsch, and Multer (2001) and
Oriol (2000), suggesting that digital communications can enable roadway
workers to obtain information while reducing workload for the
dispatcher. The verbal exchanges between dispatchers and roadway workers
and train crews are subject to errors resulting from the limitations of
voice radio. Using digital communications for electronic exchange of
movement authorizations and work authorization can reduce these
communication-related errors. Shifting some communications to data link
may alleviate the congestion and address other problems associated with
voice radio. A wireless handheld device carried by roadway workers could
serve this purpose. Given the encouraging results that Oriol received
with the first prototype (Oriol, 2000), a second prototype was
developed.

### Improve Situation Awareness

The analysis of user requirements also indicated that roadway workers
can become disoriented when working on the track. A positioning device
would be useful to solve orientation problems and location errors. The
ability to locate roadway workers, trains, and track equipment could
benefit roadway workers, train crews, and dispatchers alike. It might
also contribute to lowering the amount of communications related to
locating personnel and equipment on the track.

Many applications for roadway workers could be developed based on this
location information. For example, an alarm system could automatically
send a warning to a roadway worker when a train is approaching.
Alternatively, location information would be useful to automatically
alert a track car operator when approaching the limits of their
authority.

### Better Problem Reporting

The analysis of user requirements also identified a need for better
reporting of track problems. A handheld device could support the track
inspector in recording problems, tracking the history of problems over
time (e.g., how does it compare to the recorded value the last time the
inspection was conducted), and actions to be taken. Location information
(provided by a positioning device) could be automatically associated
with a reported problem, to make sure the problem site is accurately
located.

# Description of the current prototype

## Overview

This section briefly describes the application's functions and how it
operates. Appendix A describes the system architecture in more detail.

The application enables the roadway worker to request information about
the territory such as train status, rules in effect, and track out of
service. The application can also be used to request and cancel work
authorizations. The current application had functions that were lacking
in the first prototype: a positioning capability, and an asynchronous
two-way communication capability (text messaging).

The first prototype, which was developed on a Palm VII, was transferred
to a Qualcomm® pdQ™ Smartphone 800. The Smartphone shown in Figure 2 is
a cell phone containing an integrated PDA. The PDA used the same Palm
operating system as the first prototype, enabling the application to
perform the same tasks as the first prototype. The current prototype
also exhibited the ability to send and receive short text messages
(SMS). This enabled the dispatcher or roadway worker to alert each other
when a request for track authorization was initiated or answered. It
addressed a shortcoming in the first prototype in sending and receiving
messages in a timely fashion.

The Qualcomm® pdQ™ Smartphone was also connected via its serial port to
an Axiom Smart Antenna GPS receiver, shown in Figure 3. The phone is
also connected by a wireless modem to a web server and a dispatcher
workstation, as illustrated in Figure 4. The dispatcher workstation
communicated with the server through a standard web browser. The mobile
elements (cell phone and GPS receiver) were light and small enough to be
carried easily by roadway workers.

![](media/image7.png){width="2.1354166666666665in"
height="3.0006944444444446in"}

[]{#__RefHeading___Toc46910749 .anchor}Figure 2. Qualcomm® pdQ™
Smartphone

![](media/image8.jpeg){width="3.6243055555555554in"
height="1.761111111111111in"}

[]{#__RefHeading___Toc46910750 .anchor}Figure 3. Axiom Smart Antenna GPS
Receiver

![](media/image9.wmf){width="6.001388888888889in"
height="6.219444444444444in"}

[]{#__RefHeading___Toc46910751 .anchor}Figure 4. System Architecture

## Operating the Device

The handheld device enables a roadway worker to perform two kinds of
actions: request information about trains and territory, and request
work authorization. To perform these tasks, the operator selects options
and enters information using a pointing device or stylus on a
touch-sensitive screen. The operator begins by selecting the type of
information to be obtained or the type of work authority to be requested
from the main menu shown in Figure 5. Selecting an option results in
another screen showing the appropriate parameters for requesting
information or work authorization. Where appropriate, a drop-down menu
shows the potential options for each field. The operator selects an
option using the stylus. In the other fields, the operator uses the
stylus to enter text or numerical information using the built-in
displays. After completing all the relevant fields on the request form,
information is communicated through a wireless link to a web server. If
an information request is sent, the server sends the requested
information back to the roadway worker directly. If a work authorization
is sent, the server relays the request to the dispatcher for action and
sends the message "Please Wait" to the roadway worker.

![](media/image10.wmf){width="2.2090277777777776in"
height="2.345833333333333in"}

[]{#__RefHeading___Toc46910752 .anchor}Figure 5. Main Menu

### Request Information 

The application is intended to enable a roadway worker to get real time
information about trains by querying the same information used by the
dispatchers to determine track status. The precision of train and track
equipment location is dependent upon the type of train control system. A
system with Central Traffic Control could show train location at the
block level. Like the dispatcher, the roadway worker could determine
what block a train was in, but not where in the block the train was
located. In dark territory or for equipment that does not shunt track
circuits, the precision with which train location is known is lower.
Location can be determined only to the extent the limits of the
authority are known. As a result, the benefits of this application would
be considerably greater in signal territory. The benefits of using this
application will improve in dark territory as technologies such as
Global Positioning System (GPS) are introduced that provide information
about train location to the dispatcher.

Nevertheless, this database can be updated to provide the timeliest
snapshot of train status and track usage. Since the prototype could not
access Amtrak's information system, the train timetable between Boston
and New Haven was used on the web server. The application can query this
database to get the following kinds of information:

-   Train Status (the last known location of a train) given a train
    number.

```{=html}
<!-- -->
```
-   Train On Sheets (timetables) given a track section and a time
    window, or train numbers.

-   Territory Information (speed limit, rules that apply) given a track
    section.

Figure 6 and Figure 7 show an example request for "Train On Sheet"
(timetable) and the results of this request.

![](media/image11.png){width="2.8958333333333335in"
height="2.6458333333333335in"}

[]{#__RefHeading___Toc46910753 .anchor}Figure 6. Train OS Request

![](media/image12.png){width="2.8854166666666665in"
height="2.6354166666666665in"}

[]{#__RefHeading___Toc46910754 .anchor}Figure 7. Train OS Response

### Request Work Authorization 

The application software also handles the several types of work
authorization requests and cancellations (Foul Time and Form Ds). In all
cases, the roadway workers communicate with the dispatcher through an
Internet browser interface. The work authorization procedures include:

-   Request work authorization (requires dispatcher consent);

-   Cancel work authorization (automatic);

-   Show work authorizations the roadway worker owns and their status
    (automatic); and

-   Show active work authorizations on a specific track section
    (automatic).

In actual railroad operations, the dispatcher would communicate with the
roadway worker through the computer aided dispatch (CAD) system. For
this study, a fictitious CAD system was developed to play this role. In
this fictitious system, the dispatcher's workstation communicated with
the server through a standard web browser. It displayed all the work
authorization requests in a list, and enabled the dispatcher to accept
or reject them. The system also displayed active, rejected, or canceled
work authorizations.

Figure 8-Figure 13 show the screens that the roadway worker and
dispatcher would see in a transaction in order to successfully request
Foul Time. In Figure 8, the roadway worker completes a Foul Time request
form and sends the request. In Figure 9, the roadway worker receives a
message to wait for the dispatcher to answer. When the Foul Time request
is sent, the dispatcher sees the request appear in the middle frame
labeled "Requested Foul Time" shown in Figure 10. Selecting this item
shows the details of the request in the right hand frame of Figure 10.
The dispatcher can grant, modify, or deny the request. If the dispatcher
grants the request, the dispatcher reenters all the parameters (for
safety purposes) and sends the response.

![](media/image13.wmf){width="2.6145833333333335in"
height="2.0208333333333335in"}

[]{#__RefHeading___Toc46910755
.anchor}![](media/image14.png){width="2.6354166666666665in"
height="2.0416666666666665in"}Figure 8. Foul Time Request (Roadway
Worker Screen 1)

[]{#__RefHeading___Toc46910756 .anchor}Figure 9. Foul Time Request
(Roadway Worker Screen 2)

![](media/image15.wmf){width="5.997916666666667in"
height="4.499305555555556in"}

[]{#__RefHeading___Toc46910757 .anchor}Figure 10. Foul Time Request
(Dispatcher Screen 1)

After granting the initial request, the roadway worker receives a
message that summarizes the Foul Time granted by the dispatcher as shown
in Figure 11. The roadway worker must acknowledge receiving the Foul
Time request granted by the dispatcher by selecting "Accept" or reject
the Foul Time granted by the dispatcher. If the roadway worker accepts
work authorization granted by the dispatcher, a confirmation message is
displayed on the device as shown in Figure 12, and sent to the
dispatcher. The dispatcher will see "Foul Time Request" disappear from
the "Requested Foul Time" frame, and appear in the frame marked "Active
Foul Time" as shown in Figure 13. The Foul Time work authorization will
remain on this screen until it is cancelled.

![](media/image16.png){width="2.8958333333333335in"
height="2.0104166666666665in"}

[]{#__RefHeading___Toc46910758
.anchor}![](media/image17.wmf){width="2.9166666666666665in"
height="2.0208333333333335in"}Figure 11. Foul Time Request (Roadway
Worker Screen 3)

[]{#__RefHeading___Toc46910759 .anchor}Figure 12. Foul Time Request
(Roadway Worker Screen 4)

![](media/image18.png){width="5.95625in" height="4.475in"}

[]{#__RefHeading___Toc46910760 .anchor}Figure 13. Foul Time Request
(Dispatcher Screen 2)

## New Features

### Timely Asynchronous Communication

One of the first prototype's main limitations was its ability to receive
messages. The operator of the Palm VII™ always had to initiate a
communication. The dispatcher had no way to directly contact a roadway
worker in a timely manner through the prototype unless the roadway
monitored the device continuously. For example, after sending a work
authorization request, the roadway worker had to check periodically if
the dispatcher had responded. Continuous monitoring of the device for
new messages would increase the roadway worker's time devoted to
communication related tasks.

Short Message Service (SMS) provides a form of asynchronous
communication to reach the handheld device from the web. Like paging
services, SMS enables someone to send brief text messages to a recipient
over the Internet. The current hardware platform can use SMS to send and
receive messages. SMS is also discussed in Appendix F.

SMS enabled the following new functions to be implemented:

-   Notification when a Foul Time request has been granted or refused.

-   Notification when a Form D has been processed.

-   Notification when a Form D has received a Time Effective.

-   Sending a message by clicking on a roadway worker on the tracking
    display

-   Sending an unstructured message to anybody at anytime.

### Locate Track Position

The cognitive task analysis (CTA) suggested that providing more precise
location information would help in addressing roadway worker orientation
problems and communication workload. Knowledge of roadway workers
location could benefit both the roadway workers and dispatchers. A
GPS-based system could be used to warn roadway workers when they
approach the limits of their authority. This information would also be
useful to alert the dispatcher when the roadway worker works outside
their limits of authority, as well as tracking more precisely the
location trains, track equipment, and work crews.

After reviewing location-finding technologies, standard GPS technology
was incorporated into the current prototype. Appendix F summarizes the
technologies considered. When the location report feature is activated,
the handset periodically retrieves the location from the GPS receiver
via the serial port and sends it to the web server (the period can be
changed, a test was performed with 1 minute and 5 minute periods). The
dispatcher workstation can display this information in several ways.

For a dispatcher's workstation, a street map display and a GPS track
display were developed to show the location and movement of equipment
and employees on the track. One type of display (Figure 14) shows
location as a function of street location. This type of display is
useful when the dispatcher needs information for tasks such as routing
taxis to pick up and drop off train crews, determining where Hi-railers
are getting on and off the track, and finding the nearest street to a
malfunctioning grade crossing. The current prototype can show the
roadway worker's location on a map of the roadway worker's surroundings
based on the GPS information. The second type of display, shown in
Figure 15, shows the location of the GPS receiver on the track. These
displays are consistent with the visual representation with which the
dispatcher normally works.

![](media/image19.wmf){width="5.999305555555556in"
height="6.189583333333333in"}

[]{#__RefHeading___Toc46910761 .anchor}Figure 14. Street Map Display

![](media/image20.wmf){width="5.99375in" height="3.170138888888889in"}

[]{#__RefHeading___Toc46910762 .anchor}Figure 15. GPS Track Display

The street map and GPS track displays share the following features:

-   Show location over time;

-   Provide detailed information at a location (i.e., roadway worker's
    name, location report time, validity, latitude, longitude, mile
    post);

-   Able to send an SMS to the roadway worker;

-   Access history of roadway worker's movements;

-   Panning and zooming capabilities.

The GPS tracking information was not integrated into the current track
display that dispatchers use (Figure 1) to monitor the track, for two
reasons:

-   In territories with multiple tracks, the track display shows the
    adjacent tracks. However, GPS positioning technology is not accurate
    enough to discriminate between track numbers. Therefore, the
    information display could show the roadway worker's location on the
    wrong track or on multiple tracks.

-   Track displays are not drawn to scale. They show more detail around
    interlockings and stations and fewer details around other areas.
    Accurate to within only 60 feet, GPS may not provide enough
    precision to indicate location at some points on the track
    display[^2].

# Prototype Evaluation

## Overview

To evaluate the current prototype, the application was demonstrated to
roadway workers, track car operators, and dispatchers to obtain user
feedback. Next, a laboratory experiment was conducted to evaluate the
application using objective measures.[^3] Oriol (2000) previously
evaluated the application in a laboratory experiment from the roadway
worker's perspective. The current experiment measures the impact of the
GPS and 2-way asynchronous communication devices from the dispatcher's
perspective. It compared dispatching efficiency and safety for two modes
of communication with roadway workers: data link, using the current
application, and voice radio.

## Demonstration and Feedback

### Roadway Workers

The application was informally demonstrated to several roadway workers
at Amtrak's Boston Maintenance of Way facility. The procedures for
obtaining Train On Sheet information and Foul Time were demonstrated.
Roadway worker impressions varied with their age. Some of the older
roadway workers regarded the new device as a toy and remarked that the
concept was interesting, but they would never use it in place of the
radio. Younger roadway workers seemed more willing to accept the
handheld device. Roadway workers' willingness to try new technologies
could be a potential obstacle for the adoption of this application.

### Track Inspectors

The prototype was also demonstrated to an Amtrak track inspector during
a track car ride from Kingston, Rhode Island to Transfer, Massachusetts
on the Boston/New Haven line. During the trip, the location of the
vehicle was monitored and recorded on the device and Train OS request
was demonstrated. Figure 16 shows the tracking information on the street
map display.

Among the interviewed persons, the tracking function evoked a concern
that they could be monitored constantly. Roadway workers were concerned
that someone could track their location whether they were "on or off the
job." Roadway workers often wait for an available time window before
working on the tracks and do not want to be tracked when they are off
the track. This concern is not unique to railroad employees.
Transportation workers in other industry report these concerns when GPS
was introduced (Stearns, Sussman, and Belcher; 1999). The
location-reporting feature is under the control of the roadway worker
and can be switched off at anytime.

![](media/image21.png){width="5.09375in" height="7.3125in"}

[]{#__RefHeading___Toc46910763 .anchor}Figure 16. Track Car Ride Seen
from the Street Map Display

### Dispatchers

Two focus groups were conducted with dispatchers (see Section 2.1 for a
description of the methodology). Instructions on how to perform two
tasks were given: a Train On Sheet request, a Foul Time request, as well
as the use of the tracking displays. The discussions focused on the
interactions between dispatchers and roadway workers (in particular
track inspectors) and the use of the handheld application.

Global feedback was positive, and dispatchers expressed enthusiasm for
the application. The dispatchers welcomed a device that would reduce
radio congestion and workload. Most dispatchers liked the tracking
function and thought it would enhance track safety. The dispatchers
thought both display types were useful. They saw the most benefit for
monitoring track cars, which do not shunt the tracks. The dispatchers
particularly liked the feature for contacting a roadway worker via SMS,
by right clicking on a point on the tracking display with a mouse.

However, some of the dispatchers thought that keeping track of
[all]{.underline} workers on the tracks was just too much
responsibility. A related concern was who should carry the device on the
tracks. Everyone agreed that not all roadway workers in the same crew
would need the device, but they agreed the crew foreman would need one.
However, when the foreman is physically far from the crew, at least one
other person in the crew should carry the device.

Another concern of the voice radio condition was being able to overhear
the conversations of others. Some dispatchers regarded overhearing
conversations on the radio as dangerous, since it enables roadway
workers to work on the track without protection. Those dispatchers
thought that the prototype's function that enables a roadway worker to
see other people's Form Ds was equally dangerous. In a related concern,
some dispatchers were afraid that the opportunity for roadway workers to
obtain the same information available to the dispatcher might empower
roadway workers to the point that they would not need to speak to the
dispatcher anymore.

Other dispatchers believed that the ability to monitor conversations or
see the Form Ds in effect by others was beneficial. For example, if a
crew took a track out of service and a second crew was aware of that
activity and desired to work on the same track, the second crew could
contact the first one directly. This could minimize dispatcher workload
by eliminating the need to relay information through the dispatcher. The
dispatchers who liked this feature asked if a function could be added
that permitted a dispatcher to carbon-copy other people after giving
track authorization to the foreman making the request.

Listening to the conversations of others was identified as beneficial by
some dispatchers. They often monitored the radio to hear the train crews
or Maintenance of Way crews talking to each other. They felt that this
activity facilitated their situation awareness and sometimes enabled
them to detect errors made by the other parties. Dispatchers were
concerned about losing this information if radio was negated.

## Dispatcher Experiment

The participant routed trains on a railroad dispatcher simulator and
interacted with roadway workers and track inspectors using either the
radio (radio condition), or the message console and the tracking display
(data link condition). The experimenter and one assistant played the
role of roadway workers and track inspectors who communicated with the
participant (dispatcher). Figure 17 shows an overview of the
experimenter and dispatcher workstations.

![](media/image22.png){width="0.6506944444444445in"
height="0.49583333333333335in"}

[]{#__RefHeading___Toc46910764 .anchor}Figure 17. Layout of Dispatcher
Simulator

#### Dispatcher's Workstation {#dispatchers-workstation .unnumbered}

The MIT/Volpe Railroad Dispatcher Simulator was designed for managing
track in CTC territory. A complete description of the simulator can be
found in Basu, (2001). The dispatcher can view the track on two monitors
and can allocate track to trains, and track equipment or roadway workers
using a variety of keyboard and mouse commands. Trains were moved on the
tracks according to a schedule.

For the data link condition, the dispatcher also used:

1.  The message display (Figure 10).

2.  The GPS tracking display (Figure 15). The tracking display also
    contained a work authorization status window below the window
    containing the tracking information (for easier comparisons). As
    shown in Figure 18 the work authorization status display consisted
    of four windows showing the following types of messages:

-   Active Form D

-   Active Foul Time

-   Cancelled Form D

-   Cancelled Foul Time

[]{#__RefHeading___Toc46910765
.anchor}![](media/image23.wmf){width="5.995138888888889in"
height="2.7444444444444445in"}Figure 18. Work Authorization Status
Display

For the radio condition, the dispatcher used the following materials:

1.  A radio.

2.  Paper work authorization forms (Foul Time and Form D sheets shown in
    Appendix E).

3.  Two boxes to place cancelled and rejected work authorization sheets.

#### Experimenter's Workstation {#experimenters-workstation .unnumbered}

There were two monitors at the experimenter's workstation. One monitor
gave an overview of the tracks (both track chart display and tracking
display), and the other monitor emulated roadway worker's activities.

Simulation software was used to emulate the behavior of roadway workers.
This software sent requests to a web server exactly the way the handheld
prototype did. Work authorization requests and cancellations, as well as
GPS location reports were simulated. The software performed a list of
scheduled tasks associated with track work. The experimenter can skip
tasks to adapt to the dispatcher's answers. The application also timed
the delay between a work authorization request and the dispatcher's
response. Details of this software can be found in Appendix B.

### Experimental Design

#### Independent variable {#independent-variable .unnumbered}

The independent variable was a type of communication system. It had two
levels, voice radio and data link. Each dispatcher experienced both
levels. The experiment was counterbalanced so that half the participants
started with voice radio and the other half started with the data link
condition.

#### Dependent variables {#dependent-variables .unnumbered}

Data was collected on the following dependent variables:

-   **Work authorization transaction times:** the duration (in seconds)
    between the time a work authorization (Foul Time and Form D) was
    requested and the time it was granted or refused.

-   **Train delays:** time delay with respect to the schedule for each
    train.

-   **Track car call frequency:** (radio condition only) frequency of
    the number of times a dispatcher called the track car to obtain its
    position.

In addition, data was collected for the data link condition on the
following two variables:

-   **Detect failure to request work authorization:** in the simulation,
    roadway workers sometimes go on the tracks without asking for work
    authorization, or stay even if work authorization was refused, or
    stayed after it is cancelled. The dispatcher was asked to note each
    time this happened. The number generated by participant was compared
    with the actual number. It assumes the GPS location report function
    is activated all day long, and that a roadway worker shows up on the
    display only if he/she is entered into the traffic envelope.

-   **Detect roadway workers' errors in location reporting:** in the
    simulation, roadway workers mistake their location (i.e., show up
    somewhere on the tracking display, and ask for work authorization
    somewhere else). The percentage of the mistakes the dispatcher
    caught were measured.

-   **Dispatcher's errors:** The frequency of the following errors were
    recorded:

    -   Communication errors:

        -   Omission errors in work authorization parameters (i.e.,
            participant forgot the track number).

        -   Commission errors in work authorization parameters (i.e.
            parameters a roadway worker said or typed did not match the
            parameters the dispatcher said or typed).

    -   Block protection errors:

        -   Blocking a track section after granting the work
            authorization (the dispatcher was asked to block the track
            before granting the work authorization).

        -   Blocking the wrong track section.

        -   Forgetting to block a track section.

        -   Releasing the track section before the work authorization is
            cancelled.

        -   Forgetting to release a track section. An error was recorded
            if the track was not released within 30 seconds after
            cancellation of the work authorization.

    -   Routing errors:

        -   Trains colliding with each other.

        -   Trains colliding with Maintenance of Way crews.

        -   Trains colliding with track cars.

```{=html}
<!-- -->
```
-   **Workload ratings:** A subjective rating scale adapted from the
    NASA TLX was used (see Appendix D). The participant completed this
    scale after each condition.

#### Questionnaire {#questionnaire .unnumbered}

Each participant completed a questionnaire that documented their
familiarity with computers and GPS and provided an opportunity to give
feedback on the new device (see Appendix C).

#### Scenario description {#scenario-description .unnumbered}

Two equally demanding variations of the scenarios were created (see
Appendix B for technical details). Scenario 2 consisted of a variation
of Scenario 1, but used different permutations of locations and track
numbers. The common characteristics are listed below:

-   Duration: about 70 minutes

-   One mobile track car and three stationary Maintenance of Way crews
    involved

-   Track car inspector asks for Form Ds five times

-   Maintenance of Way crews asks for Foul Time 21 times

-   Maintenance of Way crew makes a mistake in reporting location twice
    in the data link condition

-   Maintenance of Way crew goes on the track without work authorization
    six times

To simplify the simulation, the participant was asked:

-   To grant all the Form Ds, but not necessarily when they were
    requested.

-   To grant each Foul Time with the exact requested parameters or deny
    request. Negotiations were not allowed.

### Participants

Six professional dispatchers from Amtrak's Boston Division of the
Northeast Corridor were recruited for this experiment. Each participant
was paid at the same hourly rate they received to perform their normal
duties. The dispatchers were all men and ranged in age from 32 to 52
with a mean age of 42. The dispatchers ranged in experience from 2 to 26
years with a mean of 10 years.

### Procedure

The experiment lasted approximately 5½ hours. After arriving, the
participant completed a brief questionnaire. The experimenter explained
the operating rules and the scenarios. There were two trials, one with
each communication device. Prior to each trial, the experimenter trained
the participant to operate the dispatcher simulator using the
appropriate communication device (radio or data link). The participant
practiced operating the simulator for approximately 15 minutes. During
each 90-minute trial, the participant routed trains and interacted with
roadway workers. After completing each trial, the participant completed
a modified NASA TLX workload rating scale. After completing the second
trial and modified NASA TLX workload scale, the participant completed
another questionnaire.

### Results

#### Work authorization transaction time {#work-authorization-transaction-time .unnumbered}

Transaction times were recorded for both Foul Time and Form Ds. Since
granting track authorizations requires more steps than denying track
authorization, the two activities were separated. For Foul Time
authorizations, processing times were separated according to whether the
dispatcher granted or denied the request. As a result, there were six
categories: granted Foul Times, refused Foul Times, and granted Form Ds,
for both the radio and the device experiments.[^4]

Figure 19 compares the processing times for three transaction types by
communication mode: granting Foul Time, denying Foul Time, and granting
a Form D. Each data point shows the average transaction times and the 95
percent confidence interval. The processing times were on average about
1.5 times longer with the PDA compared to radio. For two comparisons,
granting Foul Time and denying Foul Time, the differences between the
radio conditions and the data link conditions was statistically
significant (t~n=100~ =3.84, p \< 0.0002 for granted Foul Times; t~n=95~
=3.95, p \< 0.0001 for denied Foul Times). The difference between the
radio condition and the data link condition for Form D transactions was
not statistically significant, although the difference was consistent
with the behavior observed with the Foul Time transactions.

![](media/image24.wmf){width="6.0in" height="3.501388888888889in"}

[]{#__RefHeading___Toc46910766 .anchor}Figure 19. Work Authorization
Processing Times

In some cases, the dispatchers did not respond to requests in the data
link condition. It appeared that the dispatcher forgot about the
outstanding requests. Failure to answer a work authorization request did
not happen in the radio condition.

The differences between the radio and use of the handheld application
can be explained partly by the dispatcher's greater experience using
voice radio. The dispatchers use the radio everyday. One dispatcher said
during the radio practice scenario, "You know, I don't need to practice.
This is what I do every day. We can start the experiment right now."

On the other hand, the dispatchers had only 1½ hours to learn how to use
the data link device. The dispatchers also varied in their familiarity
with using computers (see questionnaire results).

A similar experiment comparing the use of data link communications with
radio suggests another explanation. Malsch et al., (2004) compared
dispatcher performance in the use of radio to a form of data link
modeled after an email system. This data link system displayed work
authorizations in visual form, like the current system. The data link
interface also displayed track requests on the track display used by the
dispatcher to monitor and control train movements as well as protect the
track. In the Malsch et al., study, dispatchers performed better in the
data link condition sending complex messages (i.e., granting Foul Time)
than in the radio condition, and they performed worse for simple
messages (i.e., denying Foul Time). Similarly, dispatchers were less
likely to forget to answer messages in the data link system compared to
the voice radio condition. Variations in the interface design and the
features present may have contributed to the differences.

These differences contributed to higher physical workload. While the
number of messages to answer was lower in the current study, the
transaction times were higher. The mean transaction time was 196 seconds
in the data link condition compared to 154 seconds in Malsch's study. In
the current study, the dispatchers rated the data link condition as
requiring greater physical workload than the voice radio condition.

#### Train delays {#train-delays .unnumbered}

The percentage of scheduled trains delayed and the length of the delay
were measured for each condition. More than twice as many trains were
delayed with the data link application as with the radio. Approximately
29 percent of trains were delayed in the data link condition compared to
12 percent in the radio condition. Although, the average delay in the
data link condition was twice as long in the data link condition, the
difference of 24 seconds between the two conditions is probably not
meaningful. The largest train delay between the two conditions differed
by 4 minutes.

+------------------------------------------+----------+----------------+
| []{#__RefHeading___Toc3258225            |          |                |
| .anchor}Table 3. Train Delay by          |          |                |
| Communication Mode                       |          |                |
+------------------------------------------+----------+----------------+
|                                          | C        |                |
|                                          | ondition |                |
+------------------------------------------+----------+----------------+
|                                          | Radio    | Data Link      |
+------------------------------------------+----------+----------------+
| ::: definition                           | 12%      | 29%            |
| Percentage of delayed trains             |          |                |
| :::                                      |          |                |
+------------------------------------------+----------+----------------+
| Mean train delay (s)                     | 24       | 48             |
+------------------------------------------+----------+----------------+
| Maximum delay (m)                        | 6.5      | 10             |
+------------------------------------------+----------+----------------+

#### Requests for track car position (Radio only) {#requests-for-track-car-position-radio-only .unnumbered}

The percentage of calls the dispatcher made to request track car
position as a function of all radio communications was calculated in the
radio condition. The track car calls represented about 10 percent of the
total communication transactions. These communications could be avoided
if track cars were equipped with GPS and reported their position to the
dispatcher as they did in this study.

#### Detection of roadway workers' location errors (Data link only) {#detection-of-roadway-workers-location-errors-data-link-only .unnumbered}

In the data link condition, the dispatcher was asked to check the
roadway worker's location on the tracking display before granting work
authorization. Dispatchers detected none of the 12 location errors made
by roadway workers (i.e., they appeared on the track display in a
different location from the authorized track). Dispatchers detected 41
percent of the errors committed by roadway workers working without
authorization.

In both cases, a higher detection rate was expected. The attention
associated with filling out forms in the data link condition may have
contributed to dispatchers spending less time monitoring the track
display. Another possibility is that the track display on which the
roadway worker's position was shown contributed to difficulties in
accurately locating their position.

#### Dispatchers' communication errors {#dispatchers-communication-errors .unnumbered}

Table 4 shows the dispatcher's errors by communication mode. The error
data was normalized to account for differences in exposure in each
trial. Communication and protection errors were normalized by dividing
the number of communications by the total number of work authorization
requests. Routing errors were normalized by dividing the number of
errors by the total number of trains.

  --------------------------------------------------- --------- ----------
  []{#__RefHeading___Toc3258226 .anchor}Table 4.                
  Dispatchers' Errors                                           

  Error Category                                      Radio (%) Device (%)

  Communication errors as percent of work                       
  authorization requests                                        

  Omit work authorization parameter                   18        0

  Incorrect work authorization parameter              17        6

  **Protection errors as percent of work                        
  authorization requests**                                      

  Block track section after granting work             1         0
  authorization                                                 

  Block incorrect track section                       5         1

  Remove protection before the work authorization     2         0
  cancelled                                                     

  Forget to protect track section                     2         2

  Forget to release track section                     9         5

  **Routing errors as percent of number of trains**             

  Train collides with another train                   0         0

  Train collides with MOW crew                        10        0

  Train collides with track car                       0         0
  --------------------------------------------------- --------- ----------

The data link condition resulted in fewer errors than the same
interactions over the radio. Dispatchers forgot to enter required
parameters for a work authorization request 18 percent of the time
compared to zero errors in the data link condition. The error checking
routines in the data link condition ensured that the dispatcher entered
information in all the required fields. The error checking routines did
not eliminate entering incorrect parameters in preparing a work
authorization. However, the number of incorrect errors was considerably
less in the data link condition. The dispatcher made almost three times
as many errors using incorrect parameters in the radio condition as in
the data link condition. In this error category, the dispatcher gave a
work authorization parameter that didn't match the parameters given by
the roadway worker.

The dispatcher also made more protection errors in the radio condition.
For all categories, except one (forgetting to protect a track section),
the dispatcher made more protection errors in the radio condition. Using
paper copies of work authorizations was not as safe as using electronic
work authorizations.

Finally, the percentage of routing errors resulting in a hazardous event
was smaller in the data link condition. Overall, routing errors were
non-existent for two of the three categories. There were no collisions
between trains or between trains and track cars. The dispatcher made
routing errors that could lead the train to collide with the maintenance
of way (MOW) crew 10 percent of the time. No errors were made in the
data link condition. This improved performance in the data link
condition may be attributed to the roadway crews carrying GPS receivers,
which gave the dispatcher more precise knowledge of the crew's track
location.

#### Workload ratings {#workload-ratings .unnumbered}

Table 5 shows the participant's workload ratings, for both radio and
data link. Each dimension was rated on a scale from zero to ten, where
zero represented the lowest workload and ten the highest workload.

  ------------------------------- ---------------------------------- --------- ---------
  []{#__RefHeading___Toc3258227                                                
  .anchor}Table 5. Workload                                                    
  Ratings                                                                      

  Scale                           Description                        Radio     Device

  Mental Demand                   How much mental and perceptual     7.2       6.2
                                  activity was required? (e.g.,                
                                  thinking, deciding, estimating,              
                                  anticipating, remembering,                   
                                  looking, etc)? Was the task easy             
                                  or demanding, simple or complex,             
                                  exacting or forgiving?                       

  Physical Demand                 How much physical activity was     5.3       6.2
                                  required (e.g., pointing,                    
                                  clicking, typing)? Was the task              
                                  easy or demanding, slow or brisk,            
                                  slack or strenuous, restful or               
                                  laborious?                                   

  Temporal Demand                 How much time pressure did you     6.3       7.2
                                  feel due to the train routing                
                                  activity and the work                        
                                  authorization requests frequency?            
                                  Was the pace slow and leisurely or           
                                  rapid and frantic?                           

  Performance                     How successful do you think you    6.2       5.0
                                  were in playing the role of                  
                                  dispatcher (i.e., how many routing           
                                  errors, trains delayed, uncaught             
                                  RW errors, granted or refused work           
                                  authorizations by mistake, etc.)?            
                                  How satisfied were you with your             
                                  performance?                                 

  Effort                          How hard did you have to work      6.0       6.7
                                  (mentally and physically) to                 
                                  accomplish your level of                     
                                  performance?                                 

  Frustration Level               How insecure, discouraged,         4.2       5.5
                                  irritated, stressed, and annoyed             
                                  versus secure, gratified, content,           
                                  relaxed, and complacent did you              
                                  feel during the task?                        
  ------------------------------- ---------------------------------- --------- ---------

Dispatchers rated their workload level lower in the data link condition
for only one measure, mental demand. The dispatchers rated the mental
demand higher in voice radio than the data link scenario. This attribute
may be associated with the memorial requirement of voice radio. Voice
radio placed a higher burden on the dispatchers memory compared to data
link, where the dispatcher could view most of the essential information
on the computer monitor.

For the remaining workload ratings, physical demand, temporal demand,
performance, and effort the dispatchers rated their workload level to be
lower in the voice radio condition. Physical demand was rated higher in
the data link condition. This may have been due to data entry
requirements in completing the electronic forms. Temporal demand was
also rated higher with data link. This belief is consistent with the
fact that work authorization transactions took about 1.5 times longer on
average in the data link condition.

Dispatchers felt their performance was better with voice radio. This
rating is consistent with their performance processing work
authorization requests and scheduling train movements. In all cases,
work authorization requests were processed faster in the radio
condition. There were also fewer train delays in the radio condition. It
may also reflect the dispatchers familiarity with the radio which they
use everyday in their job. Similarly, dispatcher effort was rated lower
in the voice radio condition. Again, this is not surprising since the
dispatchers use the radio everyday, but they had only 90 minutes to
learn how to operate the handheld application.

# Summary and Recommendations

## Summary

An analysis of track foreman user requirements supported the previous
work of Oriol (2000). Improving communications between track foremen and
dispatchers requires an application that supports two tasks: requesting
information about trains and track condition, and the ability to request
work authorizations. The current study also identified a safety concern
that could be addressed using digital communications and GPS. Roadway
workers sometimes become disoriented on the track. Incorporating a GPS
receiver into the handheld device could improve the roadway worker's
situation awareness and minimize the likelihood of disorientation.
Providing the location of roadway workers on the tracks and in track
vehicles could also reduce the communication load for dispatchers and
enhance their situation awareness. This capability was added to the
current application.

An evaluation of the current set of features was analyzed from the
dispatcher's perspective in a laboratory experiment. In this experiment,
work authorization transactions took longer in the data link condition
than with voice radio. This behavior contrasted with Malsch et al.,
(1999) results where data link reduced transmission of work
authorization times by a factor of two. This difference between the two
experiments suggests that the design of the dispatcher interface plays
an important role in its usability and effectiveness in facilitating
dispatcher performance. There were fewer communications errors in the
data link condition than in the radio condition. Malsch et al., (1999)
also observed this behavior in their study. Auditory communications were
more prone to errors because their transient nature placed higher
memorial demands on the dispatcher.

The number of protection and routing errors were also smaller in the
data link condition. It was less taxing for dispatchers to process the
work authorization requests in visual form than to have to listen to the
radio and write down parameters, while planning train movements and
authorizing maintenance work. This would explain why mental workload was
rated higher in the radio condition.

While the tracking display appeared to be useful in assisting the
dispatcher to locate track cars, monitoring roadway workers on the track
posed a greater challenge. The dispatchers identified only 40 percent of
roadway workers working without authorization and no location reporting
errors were caught. The task seemed to be too demanding for the subjects
to fully benefit from the tracking display. The tracking display was
also expected to have more impact on the dispatcher's workload. The
dispatcher's mental workload may be too high for him/her to fully
benefit from a tracking display.

Trains tend to be delayed more with the data link condition, but again
it is believed that delays should decrease with use. Malsch (1999) found
similar delays for data link.

All the participants showed great enthusiasm and gave constructive
feedback regarding use of the handheld application. They thought it
would improve communications by reducing radio congestion and
communication errors and assist in locating track vehicles and roadway
workers on the right-of-way.

Adapting to the new technology for both dispatchers and roadway workers
poses a variety of questions and challenges. For example, would the
dispatcher take on the responsibility for monitoring every roadway
worker's position or just the track foreman responsible for
communicating with the dispatcher? Monitoring the location of all
roadway workers on the track would substantially increase dispatcher's
workload. Given current workload levels, some dispatchers felt that the
additional work required to keep track of all roadway workers was just
too much responsibility for the dispatcher. One dispatcher suggested
that if such a system were implemented, the size of the dispatcher's
territory should be reduced to compensate for the increase in workload.

Many of the dispatchers also felt that the willingness to adopt the new
technology would vary with age. Younger people were expected to learn
and take advantage of the new technologies more quickly and with greater
enthusiasm. They also worried about the intangible (i.e., nonverbal)
aspects of communication that may be lost moving from a predominantly
oral communication medium to a visual medium. The dispatchers were also
concerned about rule compliance with respect to the use of GPS and other
location finding technologies. The application of this technology would
only assist the dispatchers, if the roadway workers "turned the feature
on" when they were on the track right-of-way. Finally, integrating this
kind of a visual display into existing visual displays will present a
challenge to system designers. Current information displays distort the
geographic representation of track to present large quantities of
information to the dispatcher in a form that is useful. The resolution
of such displays with respect to the actual location of trains,
equipment, and roadway workers is relatively low. The ability to more
precisely locate these assets will require designers to think about how
dispatchers will use this information.

Roadway workers were also concerned about how the new information
technologies would affect them. While many roadway workers showed
enthusiasm for the application, some were reluctant about relying upon
it as a safety critical device. Roadway workers also expressed concern
about how their privacy would be affected when their location could be
tracked by the application. They were particularly concerned that
location might be monitored when they were not working on the track. The
GPS receiver that reports this information is under the control of the
roadway worker, and this feature could be switched off at any time.

## Recommendations

This section makes suggestions for improving the roadway worker
communication application. Dispatchers and roadway workers made many of
the suggestions during the focus group, observation sessions, and the
experiment.

The current prototype represents an interim solution to providing a
hardware and software interface for roadway workers to communicate more
effectively with dispatchers. Computer, communications, and location
finding technologies continue to improve. The current prototype has a
form factor the size of a brick, which makes it possible to view more
information on most cell phones today. However, the prototype is heavy
compared to most cell phones.

The prototype's display can be difficult to see in bright sunshine. New
generations of PDAs display information at higher resolutions and can
display color. The current generation of wireless communications devices
sends information at the relatively slow speed of 14.4 kilobytes/second.
The next generation of wireless devices should be able to send
information at considerably higher rates allowing the communication of
graphics as well as text. The current prototype uses a GPS receiver,
external to the communication device. Newer handheld devices will
incorporate location-finding technologies into the communication
hardware.

Because track foremen are highly mobile and must carry their
communication devices on their bodies, the hardware must be relatively
small and easily portable. Their current communication related tasks
mean that a simple, easy-to-use application tailored to the needs of
these specific tasks (requesting information and work authorization)
would suffice.

Other roadway workers have different communication-related requirements
and work in a different environment. This means that the tasks that need
to be supported and the interface that supports them may be different
from the interface designed for track foremen. For example, track
inspectors work in vehicles that can support a larger display. A display
the size of a 13-inch CRT could support the display of a graphic
interface similar to the dispatcher's. Roadway workers could also have
greater data entry requirements and could benefit from a keyboard to
enter text-based information. The Burlington Northern Santa Fe Railroad
is currently testing a device with these characteristics for requesting
work authorizations.

### Develop Hazard Alerts for Roadway Workers

A warning notification could be sent to the roadway worker when trains
are approaching a work zone or passing by on an adjacent track. A
reliable alarm could also assist crew watchmen in their jobs. This
information would provide an additional source of information to the
crew watchman, charged with watching for approaching trains.

Similarly, operators of track vehicles could receive a warning when
approaching the limits of an authority. BNSF is currently developing
such an application for use in Hi-railers. Such a system would be useful
to prevent cases of a roadway worker going outside the limits of their
authority.

### Evaluate Effectiveness of Graphic Display 

The current prototype displays territory information in textual form.
This was necessary in the current prototype because the graphically
displayed information requires greater bandwidth than the same
information presented in text form and the slow transmission rate of
current technology would result in an unacceptably slow response rate.
With greater bandwidth and faster transmission rates, it will become
possible to provide information graphically. The challenge will be to
determine if and how graphic information can be displayed in a usable
form. Some of the questions that need to be answered include:

-   What kind of graphic display should be used (i.e., a track chart
    display)?

```{=html}
<!-- -->
```
-   What information should be shown (tracks, interlockings, stations,
    trains, track car, maintenance of way crews, etc.)?

-   Are multiple formats necessary (e.g., track layout vs. street map),
    and what navigation controls will be needed to enable the roadway
    worker to quickly find the information being sought?

### Decision Support and Reporting Tool for Track Inspectors

The CTA indicated that track inspectors use their paper-based rulebook
for evaluating the nature of track problems they identify. They also
must report these problems currently using paper-based forms. These
activities could be facilitated with computer-assisted support. The
following examples show the kind of computer-assisted support that could
improve the track inspector's productivity:

-   Store the electronic form that reports problems observed during
    track inspection.

-   Automatically determine location associated with reported problems.

-   Store the MW 1000 rulebook.

-   Store the data recorded to allow for comparison over time to help
    the inspector make judgments about what recommendations to make to
    the track department supervisor (e.g., is this a problem that is
    degrading rapidly and should it be addressed soon, or is it a slowly
    changing problem?).

The Federal Railroad Administration (FRA) is developing an application
for FRA track inspectors that contain some of these features.

### Track Work Authorization Status for Dispatchers

Several dispatchers suggested providing audio alarms whenever new work
authorization requests arrive, and are cancelled. The alarms may help
dispatchers retain new work and cancellation requests when workload
levels are high.

### Improve Processing of Work Authorizations 

The dispatchers who participated in the experiment offered three
suggestions for managing work authorizations:

-   The dispatcher should confirm the cancellation of work
    authorizations.

-   Add a comments field to electronic work authorization forms for
    additional unstructured messages.

-   Provide the capability to notify others besides the primary
    recipient when a work authorization is given.

# System Architecture {#system-architecture .Appendix-1}

## Overview {#overview-3 .Appendix-2}

The system involves a Qualcomm® pdQ™ Smartphone 800 connected via its
serial port to an Axiom Smart Antenna GPS receiver, a dispatcher
terminal, and a web server (see Figure 4). The phone connects to the
Internet via an integrated wireless modem to communicate with the web
server. The dispatcher terminal communicates with the server through a
standard web browser. Below is a complete description of each element.

## Axiom Smart Antenna GPS Receiver {#axiom-smart-antenna-gps-receiver .Appendix-2}

### Specifications {#specifications .Appendix-3}

The Axiom Smart Antenna is an integrated GPS and antenna packaged in a
sturdy plastic enclosure and supplied with a DB-9 interface cable
(normally designed to use with Notebook PCs), see Figure 3. The output
data protocol is per NMEA standard at 4800 bauds. The Smart Antenna is
differential ready (RTCM-104 format of differential correction). Here
are some specifications:

-   Channels 12

-   Voltage 3.0 to 5.5V DC

-   Current 160mA @ 5.5V DC

-   Baud Rate 4800 bauds 8N1

-   Data Protocol NMEA format

-   Size 3.5" x 2.15" x 1.15"

-   Weight 4.0 ounces (including magnets, not including cable)

More information can be found at <http://www.axiomnav.com/smart.asp>

### GPS configuration {#gps-configuration .Appendix-3}

To connect the GPS to the phone, a DB-9 Male/DB-9 Male null modem
adapter (small connector that exchanges pins 2 and 3) was used along
with a pdQ™ data cable. For power, a 7.2V radio controlled car battery
was used. Diodes were used to drop the voltage. The 2200mAh battery
capacity was sufficient to power the GPS receiver for more than 10
hours.

## Qualcomm® pdQ™ Smartphone {#qualcomm-pdq-smartphone .Appendix-2}

### Specifications {#specifications-1 .Appendix-3}

The pdQ™ Smartphone has a large touch screen for a cell phone. However,
the main drawback of the pdQ™ is probably its size. The cell phone's
form factor is the size of a brick, making it bulky compared to other
cell phones. The screen is also more dim and difficult to read in bright
light than the prototype using the Palm VII™. The pdQ™ 800 functions
just like a Palm III with a wireless modem. Table A-1 shows the main
characteristics:

  ------------------------------- ---------------------------------------------------
  []{#__RefHeading___Toc3258228   
  .anchor}Table A‑1. Smartphone   
  Operating Characteristics       

  Characteristic                  Description

  Operating system                Palm OS ® 3.0

  RAM                             2 MB

  Internet access                 PPP connection within 3-5 seconds

  Modem speed                     14.4 kbps

  Touch screen                    36x12 characters, 1.9x2.4 inches, 160 x 240 pixels

  Size                            6.2" x 2.6" x 1.4" (15.7 cm x 6.7 cm x 3.5 cm)

  Weight                          10 ounces (285 g)
  ------------------------------- ---------------------------------------------------

Additional information on the Smartphone can be found at
[http://www.kyocera-wireless.com/classic/pdq/pdq_series.htm](http://www.kyocera-wireless.com/pdq/pdq_doc.htm)

### HTML forms {#html-forms .Appendix-3}

To handle the data base queries and work authorization requests and
cancellations, HTML forms stored on the pdQ™ were used (see Description
of the current prototype for screen shots).

The pdQ™ was sold with a web browser called a pdQ Browser™, which
provides limited web surfing. Images and JavaScript were not supported.
The HTML forms used to query the web server were stored in the pdQ
Browser™ cache memory. When a form is submitted, the handset connects to
the Internet automatically (if not already connected), and the form data
is sent to the web server using a post method.

### Location report application {#location-report-application .Appendix-3}

A small Palm OS ® application was written to report location
periodically. The period is a parameter that can be changed. Tests were
performed with 1 minute and 5 minute periods.

The application was written in a C-like language using Code Warrior® for
the Palm OS® Platform as a development environment. Functions were also
used from the libraries of the pdQ™ Software Development Kit.

Here are the tasks performed by this application:

-   Opens the serial port.

-   Fills a buffer with GPS data (NMEA sentences).

-   Finds latitude, longitude, UTC time and validity (char that takes
    the value 'A' if data are valid, 'V' otherwise).

-   Sends data to the web server using the
    PDQRegProcessURL(registryRefNum, URL) function of the pdQ™ Software
    Development Kit.

-   Sets an alarm that will launch this application at t = now + period.

-   Closes the serial port.

### Mapping application {#mapping-application .Appendix-3}

Although this feature has not been evaluated yet, some software was
installed to display maps of the roadway worker's surroundings based on
the GPS information. Some commercial Palm OS® software by GPSPilot.com
was used: Atlas v3.12 and GPS Pilot Cartographer 3.5

Atlas displays a map of the surroundings based on GPS latitude and
longitude, and it pinpoints the users' location. If you are moving, it
displays an arrow to indicate where you are heading. It can also give
speed, direction in degrees, latitude, longitude, altitude, and UTC
time.

Cartographer is a Windows application that enables the user to create
their own map database and download it into the Palm OS™ device.
Cartographer supports .bmp Windows bitmaps, gif, and JPG maps.

## Web server {#web-server .Appendix-2}

The web server is now running on a computer at the Volpe National
Transportation Systems Center.

### Perl script {#perl-script .Appendix-3}

A CGI script in Perl was written to build an interface between the web
server and the Java query servers. It reads the HTML forms as sent by
the handheld device, stores a file with the request and finally reads
and returns the requested information to the handset.

### Java server {#java-server .Appendix-3}

The Java server consists of 5 query servers written in Java: database,
dispatcher, file, dispatcher terminal refresh, and simulation query
servers. Every second, these query servers look for requests sent by the
handheld device or by a dispatcher. When a request has arrived, the
appropriate query server reads the request, processes it, and writes the
answer for the CGI script to send it back to the original petitioner. A
detailed description of the purpose of each server can be found in
Oriol, 2000.

Two new types of requests, as shown in Table A-2, were defined to handle
the GPS location reports when a roadway worker clears the tracks.

[]{#__RefHeading___Toc3258229 .anchor}Table A‑2. New Types of Requests

+------------+----------------------------+----------------------------+
| **Type of  | Location Report            | **Track clearing**         |
| request**  |                            |                            |
+------------+----------------------------+----------------------------+
| **Pa       | \- tq = di                 | \- tq = di                 |
| rameters** |                            |                            |
|            | \- op = GPS                | \- op = CT                 |
|            |                            |                            |
|            | \- d = %phone_number%      | \- d = %phone_number%      |
|            |                            |                            |
|            | \- p1 = validity ('A' or   |                            |
|            | 'V')                       |                            |
|            |                            |                            |
|            | \- p2 = UTC time           |                            |
|            |                            |                            |
|            | \- p3 = latitude           |                            |
|            |                            |                            |
|            | \- p4 = longitude          |                            |
+------------+----------------------------+----------------------------+
| **Action** | Writes GPS data (validity, | Removes the GPS data text  |
|            | time, latitude, and        | file                       |
|            | longitude) in a text file  | %                          |
|            | (see format below) (that   | roadway_worker's_name%.txt |
|            | will be read by the        | so that the roadway worker |
|            | tracking applet). The text | disappears from the        |
|            | file is named              | tracking display.          |
|            | %                          |                            |
|            | roadway_worker's_name%.txt |                            |
|            | and put in directory:      |                            |
+------------+----------------------------+----------------------------+
| **HTML     | Message for the roadway    | Message for the roadway    |
| Response** | worker to let him/her know | worker to let him/her know |
|            | that his/her position has  | that his/her tracking file |
|            | been successfully          | has been cleared.          |
|            | reported.                  |                            |
+------------+----------------------------+----------------------------+

GPS data were written in tracking files (text files) on the server,
which were read by the tracking applet (see next paragraph). Those text
files were named %roadway_worker's_name%.txt and put in a directory.
Comma-separated values were used for the variables shown in Table A-3.

[]{#__RefHeading___Toc3258230 .anchor}Table A‑3. Tracking Files Format

  --------------- ---------------------------------- ---------------------------
  Variable        Description                        Format

  Date            Date when location reported on the mm/dd/yyyy ddd
                  server                             

  **Time**        Time when location reported on the hh.mm.ss
                  server                             

  **UTC**         UTC time                           hh:mm:ss

  **Validity**    Validity of the GPS data:          'A'=normal, 'V'=warning

  **Latitude**    Latitude: -90\<Latitude\<90,       2 digits for degrees and 4
                                                     for minutes (e.g., 4807.038
                                                     means 48 deg 07.038' N)

  **Longitude**   Longitude: -180\<Longitude\<180    3 digits for degrees and 4
                                                     for minutes. (e.g.,
                                                     -01131.324 means 11 deg
                                                     31.324' W)

  **Mile Post**   Milepost at which roadway worker   Computed from the latitude
                  is located                         and longitude and the track
                                                     profiles

  **Branch**      Branch where roadway worker is     Computed from the latitude
                  located                            and longitude and the track
                                                     profiles
  --------------- ---------------------------------- ---------------------------

Since access to Amtrak's track profiles was unavailable, the computation
of the branch and the milepost was simulated.

## Dispatcher terminal {#dispatcher-terminal .Appendix-2}

### Message console {#message-console .Appendix-3}

When the system is running, any web browser can be turned into a
dispatcher message console. To enter the system, the dispatcher must
enter the correct web address and select a territory. Next, the
dispatcher must login using the appropriate password. The system will
show all the incoming messages that affect the selected territory.

The message console consists of a set of HTML frames. It displays
requested Form Ds and Foul Times and enables the dispatcher to grant or
deny them by posting HTML forms to the web server. It can also display
active, cancelled, and rejected work authorizations. The message console
refreshes periodically.

### Tracking applet {#tracking-applet .Appendix-3}

#### Overview {#overview-4 .Appendix-4 .unnumbered}

The tracking application consists of a Java applet that can run on any
Java-enabled web browser. The applet uses Java 2.0 Swing software for
Graphical User Interface (GUI) classes. Most browsers today are not
Swing enabled, but a plug-in to run Swing applet can be downloaded for
free from <http://java.sun.com/products/plugin/1.3/>

The applet periodically checks for new tracking files (or new lines in
an existing tracking file) and updates the roadway worker's locations if
needed. It can show position on the track and street map displays to
pinpoint the worker's positions. Both kinds of displays can show
previous locations. By right clicking on a worker, the dispatcher can:

-   Send an SMS

-   Get more information about a point (i.e., roadway worker's name,
    time, validity, latitude, longitude, mile post).

-   Access the roadway worker's location file showing the history of
    where the person or vehicle associated with the GPS receiver has
    been.

-   View a local street map from Mapblast.com® based on the latitude and
    longitude.

#### Street map display {#street-map-display .Appendix-4 .unnumbered}

The street map display was designed to work with a set of maps (possibly
of different scales). The maps should be in GIF or JPEG format and use
the format shown in Table A-4. Explanations about the format can be
found in Table A-5.

  ------------------------------- --------- -------- ------- ----------- ------------ ----------- ------------
  []{#__RefHeading___Toc3258231                                                                   
  .anchor}Table A‑4. Map Data                                                                     
  base Format                                                                                     

  Name                            File      Height   Width   LatTopL     LongTopL     LatBotR     LongBotR

  MIT                             mit.gif   600      600     42.371751   -71.110177   42.346185   -71.077817
  ------------------------------- --------- -------- ------- ----------- ------------ ----------- ------------

  ------------------------------- ----------------------------------------------------------
  []{#__RefHeading___Toc3258232   
  .anchor}Table A‑5. Map Data     
  base File Format                

  **Field**                       **Explanation**

  Name                            Map name used in the applet

  **File**                        Name of the map file

  **Height**                      Map height in pixels

  **Width**                       Map width in pixels

  **LatTopL**                     Latitude at the top left corner (between --90 and 90)

  **LongTopL**                    Longitude at the top left corner (between --180 and 180)

  **LatBotR**                     Latitude at the bottom right corner (between --90 and 90)

  **LongBotR**                    Longitude at the bottom right corner (between --180 and
                                  180)
  ------------------------------- ----------------------------------------------------------

#### Location tracking display {#location-tracking-display .Appendix-4 .unnumbered}

The location tracking display has been designed to work with different
track branches. For each of them, it handles zooming and navigation
along the track.

For simplicity, the same track information files as those of PDA were
used (see Oriol, 2000). Nevertheless, only the location's names and
mileposts were read.

# Questionnaires {#questionnaires .Appendix-1}

![](media/image25.wmf){width="5.248611111111111in" height="8.2875in"}

![](media/image26.wmf)

![](media/image27.wmf)

# Adapted NASA TLX Rating Scale {#adapted-nasa-tlx-rating-scale .Appendix-1}

![](media/image28.wmf){width="6.502083333333333in"
height="4.966666666666667in"}

# Form D AND FOUL TIME {#form-d-and-foul-time .Appendix-1}

## Form D {#form-d .Appendix-2}

![](media/image29.png){width="5.841666666666667in"
height="7.882638888888889in"}

A brief explanation of the use of the different lines of a Form D
follows (see rules 160-173). The brackets indicate the rules that apply
for each line from the NORAC Operating Rulebook.

1 \[175\]: Speed restrictions. Train Speed Restriction Bulletins (TSRB)
are used in place of line 1.

2 \[400,402-405, 502, 803, 805, 806, 808\]: Direction of travel. Written
to give authority to track cars to operate on a specific track between
two interlockings.

3 \[803, 805, 806, 807\]: Written to inform track cars about trains or
track cars ahead. A track car is allowed to move behind trains, never in
front of them. The second part of line 3 is used to give permission to
pass a stop signal. Rule 241 is usually used in place of second part of
line 3. Some dispatchers use line 3 and not rule 241.

4 \[132-134\]: Track goes out of service in charge of some employees
(flagman/conductor/ foreman).

5 \[132, 135\]: Rebuild grade crossing without disturbing the track.
Just nearby road.

6,7 \[406\]: Form D Control System (DCS), Control Point (CP) (see rules
400).

8,9 \[137\]: Used when a rescue train is heading towards the train being
rescued.

10 \[174\]: Temporary Block Station.

11 \[561\]: Cab Signal System (CSS).

12 \[138\]: Used when a grade crossing malfunctions.

13 \[132, 177, 400, 404, 406, 506, 507, 805, 806\]: General purpose.
Used for example to describe where barricades are.

Dispatchers most frequently use lines 2, 3, and 4. Lines 2 and 3 are
issued to track cars and work-extra trains. Line 4 is issued to repair
crew foreman, flagmen, and point conductors.

## Foul Time {#foul-time .Appendix-2}

+-----------------------------------------------------------------------+
| **FOUL TIME**                                                         |
|                                                                       |
| DELIVERED TO \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_                     |
|                                                                       |
| ON \_\_\_\_\_ TRK BETWEEN \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ AND    |
| \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_                                  |
|                                                                       |
| MILE POST \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_                        |
|                                                                       |
| START TIME \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_                       |
|                                                                       |
| END TIME \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_                         |
|                                                                       |
| TRAIN DISPATCHER                                                      |
| \_\                                                                   |
| _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ |
+-----------------------------------------------------------------------+

This Foul Time sheet was adapted from the NORAC operating rules.

# Focus Group questions {#focus-group-questions .Appendix-1}

**Draft Focus Group Questions**

**Introduction**

Welcome.

Thanks for taking the time to join in this group discussion on New Tools
for Dispatcher/Roadway Worker Communication.

I'm Emilie Roth, and I work as a contractor for the Volpe National
Transportation Systems Center.

This is Timothee Masquelier and Monica Gil who are working with me on
this project for the Volpe Center.

The Volpe National Transportation Systems Center and the Human-Machine
Systems Laboratory of MIT are developing new tools to support
communications between dispatchers and roadway workers. For example, we
are developing a handheld device that could be used by roadway workers
to transmit and receive messages digitally (e.g., Form D) instead of
using voice radio.

As part of this work we are conducting focus groups to obtain input from
dispatchers to help in developing the new tools. We will also be
conducting similar group meetings with roadway workers.

The goals of the focus group are to obtain:

-   input on the kinds of communication that occur between dispatchers
    and roadway workers, the things that contribute to effective
    communication, and the things that can get in the way, that should
    be considered in designing new tools;

-   feedback on a prototype handheld communication device that we are
    going to be demonstrating to you; and

-   suggestions for additional features that would enhance the
    usefulness and acceptance of the new tools.

Your opinions and insights are very important to us and will help shape
the kinds of aids that we develop.

We expect that you will have different points of view. Please feel free
to share your point of view even if it differs from what others have
said.

We are tape-recording the session because we don't want to miss any of
your comments. No names will be included in any reports. Your comments
are confidential.

Keep in mind that we are just as interested in negative comments as
positive comments, and at times the negative comments are the most
helpful.

If you want to follow up on something that someone has said, if you want
to agree, or disagree, or give an example, feel free to do that. I am
here to ask questions, listen, and make sure that everyone has a chance
to share. We are interested in hearing from each of you. So if you are
talking a lot, I may ask you to give others a chance. And, if you aren't
saying much, I may call on you. We just want to make sure we hear from
all of you.

Feel free to get up and get more refreshments if you would like. Let's
begin.

**Opening Question:**

Tell us who you are, what territory/territories you control, and a
little about your railroad background \[5 min.\]

**Introductory Questions:**

Our focus today is communication that dispatchers have with roadway
workers over radio and phone.

First, can you say about what proportion of your radio and phone
communication is with roadway workers \[5 min.\]

What type of roadway workers do you communicate with most? \[5 min.\]

*Probes: Get a sense of frequency and duration*

**Transition Questions**

What types of things do roadway workers typically call you about? \[5
min.\]

*Probes: Get a sense of priority level of these communications*

What are the types of things you typically call roadway workers about?
\[5 min.\]

Can you talk about some of the problems that come up in communicating
with roadway workers over radio or phone? \[10 min.\]

*Probes: Make sure to cover both 'Process' (mechanics) of the radio
communication media as well as 'Content' (what people say over the
radio)*

**Key Questions:**

Have you ever experienced situations (or heard of situations) where a
roadway worker was working on a track that was different from the track
that the dispatcher gave permission for (e.g., due to communication
misunderstandings; or disorientation on the part of the roadway worker?)
\[10 min.\]

*Party Line*

One of the things about radio communication is that it has a
'party-line' aspect, you can overhear communication between others and
others can overhear your communications.

Can you talk about some of the benefits of this 'party-line' aspect? Are
there situations where it helps to overhear others or have others
overhear you? \[10 min.\]

Can you talk about some of the drawbacks of this 'party-line' aspect?
Are there situations where this 'party-line' aspect causes problems? \[5
min.\]

*GPS*

Global positioning system technology now makes it possible to get very
accurate location information.

If we could give you more accurate information on the location of
roadway workers on the tracks (say on a display) do you think it would
be helpful to you? \[5 min.\]

How about more accurate information on the location of trains, right now
you know that a train is occupying a block, do you think that would be
helpful to you to have more precise location information? \[5 min.\]

**DEMO**

**Part II - Focus on handheld device:**

**KEY Questions:**

Which features of the ones we have demonstrated or described seem most
useful? \[10 min.\]

Do you think this device will meet the communication needs of roadway
workers and dispatchers? In what way? \[5 min.\]

Do you think this device will improve communication between roadway
workers and dispatchers? In what way? \[5 min.\]

Do you think this device will reduce errors in communication between
roadway workers and dispatchers? In what way? \[5 min.\]

What obstacles do you see in using/success of this system? \[10 min.\]

What other features/enhancements would you recommend for making your
work easier?

\[5 min.\]

What other features/enhancements would you recommend for improving
overall safety? \[5 min.\]

OK, a couple of specific questions:

-   How often should we update the locations for roadway workers and
    track cars (15 min? 5 min? 1 min?) \[5 min.\]

> *Probe: Why is this update rate necessary?*

-   In your opinion, what would be the best way to display the location
    of roadway workers and track cars?

    -   Should we integrate the roadway worker location into your
        existing track layout displays, or should we have separate
        displays that you can bring up?

    -   Is it better to display their location on a track chart or a 2-D
        map? \[5 min.\]

**Ending Questions**

All things considered, do you think that a handheld device like the one
we demonstrated to you is a good idea? \[5 min.\]

Is there anything that we should have asked about but didn't? Anything
that you came wanting to say, but you didn't get a chance to? \[5 min.\]

# Wireless Technology Protocols and Positioning Technologies {#wireless-technology-protocols-and-positioning-technologies .Appendix-1}

Before selecting a wireless technology protocol and a positioning
technology for our prototype, we reviewed several state-of-the-art
technologies. The results are described in this appendix.

## Wireless technology protocols {#wireless-technology-protocols .Appendix-2}

### Wireless Internet {#wireless-internet .Appendix-3}

Several technologies enable wireless connection to the Internet.

#### Regular PPP connection through a wireless modem {#regular-ppp-connection-through-a-wireless-modem .unnumbered}

Point-to-Point Protocol (PPP) is the Internet standard for transmission
of IP packets over serial telephone lines. The handheld device
establishes a PPP connection to an Internet Service Provider (ISP)
through a wireless modem (internal or external), exactly as a PC would
do. This technology is being used by most PDAs (and very few cell
phones) to connect to the Internet. Once connected to the Internet, the
device has access to hosts and services, such as e-mail and web pages.

Wireless modem connection speeds are slower when using personal
computers through a landline. A typical PDA connection speed ranges
between 9,600 to 14,400 bps. Dial-up connections through the phone line
are most frequently 56,000 bps. Next generation wireless applications
will communicate at faster speeds. The second challenge is that web
pages are designed for regular desktop PC's with their larger, color
monitors. Compared to the typical 15" or 17" computer monitor, PDAs have
tiny screens with low resolution, and are predominantly monochromatic.
This is changing as well, and one can expect to see more color in the
future.

#### Wireless Application Protocol (WAP) {#wireless-application-protocol-wap .unnumbered}

WAP (Wireless Application Protocol) is an open specification that allows
wireless devices such as phones, pagers, and PDAs to retrieve
information from the Internet. WAP differs from PPP in that the client
is not the mobile device itself. The WAP gateway serves as an
intermediary between the device and Internet (Figure F-1). This gateway
translates mobile device requests (WAP requests) into HTTP requests, and
redirects the web server's HTTP responses to the mobile device through
WAP.

![](media/image30.png){width="4.979166666666667in" height="2.5in"}

[]{#__RefHeading___Toc46910767 .anchor}Figure F‑1. WAP Architecture

Navigating normal web pages with a cell phone would be difficult. Cell
phones lack a pointing device for selecting and entering information.
Therefore, a part of the WAP standard outlines how to design Internet
pages that are cell phone friendly. These pages are written in WML (WAP
Markup Language) and can be navigated using the numbers on the cell
phone keypad. WAP web pages cannot be viewed in a normal web browser and
a cell phone cannot view the HTML pages on traditional web sites.

[Palm VII™ technology]{.underline}

3Com® has developed it's own proprietary wireless Internet technology
using a packet oriented protocol. Standard web browsing is not
supported, but the handheld device is able to query a proxy server in
3Com® Corporation's Data Center (Figure F-2). This proxy server is
responsible for converting the standard Internet protocols and content
from a web page into a form that is tuned for transmission across a
wireless network and display on a small device.

![](media/image31.wmf){width="5.195138888888889in"
height="3.5097222222222224in"}

[]{#__RefHeading___Toc46910768 .anchor}Figure F‑2. Palm VII™
Architecture

### Short Message Service (SMS) {#short-message-service-sms .Appendix-3}

Short message service (SMS) is a globally accepted wireless service that
enables the transmission of alphanumeric messages between mobile
subscribers and external systems such as web servers, electronic mail,
paging, and voice-mail systems. Messages must be no longer than 160
alphanumeric characters. SMS is a reliable, low-cost communication
mechanism for brief messages.

## Positioning technologies {#positioning-technologies .Appendix-2}

### Global positioning system (GPS) {#global-positioning-system-gps .Appendix-3}

The global positioning system (GPS) is a worldwide radio-navigation
system formed from a constellation of 24
[satellites](http://trimble.com/gps/howgps/moreinfo/aa_m2a.htm) in
geo-synchronous orbit around the earth and their [ground
stations](http://trimble.com/gps/howgps/moreinfo/aa_m2b.htm). Today,
designers have shrunk GPS receivers to fit on a few integrated circuits.
They have also become inexpensive consumer appliances.

The GPS receiver computes its position using triangulations from
satellites, whose positions are known. Measurement of the distance from
one satellite gives a sphere on which the receiver is located. Two
measurements from two satellites give a circle (intersection of two
spheres). Three measurements from three satellites give two points
(intersection of a circle and a sphere). To decide which one is the true
location requires a fourth measurement. However, one of the two points
is usually a ridiculous answer (either too far from earth or moving at
an impossible velocity) and can be rejected without a measurement. In
fact, it will be shown in the next paragraph that a fourth measurement
is needed, but for different reasons.

The distance from a satellite is measured by timing how long it takes
for a signal sent from the satellite to arrive at the receiver. Since
the travel times are tiny (60 ms assuming the satellite is right above
the receiver), one needs to know when the signal was sent very
accurately. An error of a thousandth of a second would lead to
approximately 200 miles of error. This is the reason why the satellites
have atomic clocks. GPS receivers lack atomic clocks because they are
too expensive (between \$50,000 and \$100,000). Instead, a fourth
satellite is used. Because of the GPS receiver clock error, the fourth
sphere will not intersect the three others. The receiver can then
compute a single time correction that, once subtracted from all its
timing measurements, would cause them all to intersect at a single
point. Consequently, any GPS receiver needs to have at least four
channels so that it can make the four measurements simultaneously.

The satellite positions must be known precisely. On the ground, all GPS
receivers have an almanac programmed into their computers that tells
them where in the sky each satellite is, moment by moment. The basic
orbits are quite exact but some ephemeris errors remain, and that is why
the GPS satellites are constantly monitored by the U.S. Department of
Defense. Once the Department of Defense has measured a satellite's exact
position, they relay that information back up to the satellite itself.
The satellite then includes this new corrected position information in
the timing signals that it is broadcasting.

Until February 5th 2000, the U.S. government degraded the accuracy of
the civil GPS signal. The policy was called "Selective Availability" or
"SA," and the idea behind it was to make sure that no hostile force or
terrorist group could use GPS to make weapons with accurate guidance
systems. Fortunately, the Department of Defense has now stopped adding
noise into the GPS signals. The decision to discontinue SA is the latest
measure in an on-going effort to make GPS more responsive to civil and
commercial users worldwide. To ensure that potential adversaries do not
use GPS, the military is now dedicated to the development and deployment
of regional denial capabilities in lieu of global degradation.

Nevertheless, several kinds of errors still decrease system accuracy.
First, the speed of light is only constant in a vacuum. The GPS signal
slows down when crossing the ionosphere and the troposphere. Second,
when it gets to the ground, the signal may bounce off various local
obstructions before arriving at the receiver. Third, tiny inaccuracies
remain in the satellite atomic clock and in its estimated position. Due
to these errors, the GPS signal is accurate to about 60 feet.

### Differential global positioning system (DGPS) {#differential-global-positioning-system-dgps .Appendix-3}

The differential global positioning system (DGPS) is a technology that
eliminates most of the GPS errors using ground stations whose positions
are known. The idea is that the satellites are so far out in space that
the little distances traveled here on earth are insignificant. Therefore
if two receivers are fairly close to each other (say within a few
hundred miles) the signals that reach both of them will have traveled
through virtually the same slice of atmosphere, and so will have
virtually the same errors. The ground stations receive the same GPS
signals as the roving receivers but instead of working like a normal GPS
receiver they attack the equations *backward*: instead of using timing
signals to calculate their positions, they use their known positions to
calculate timing. The ground stations determine what the travel time of
the GPS signals *should* be, and compares it with what they actually
*are*. The difference is an "error correction" factor. The error
corrections for all satellites are then encoded into a standard format
and transmitted to the roving receivers via a radio data link. Thanks to
these corrections, each roving receiver is able to compute its location
much more accurately.

Many new GPS receivers are being designed to accept corrections
("differential ready" GPS), and some are even equipped with built-in
radio receivers. Many federal agencies (i.e., United States Coast Guard,
the Federal Aviation Administration's Wide Area Augmentation System)
broadcast corrections. DGPS accuracy can reach 15 feet in moving
applications and in some cases even less, depending on the distance from
the differential beacon. Nationwide DGPS (NDGPS) expands DGPS developed
by the Coast Guard to support FRA's Positive Train Control initiative
and the Federal Highway Administration's Intelligent Transportation
System provides support for DGPS on a nationwide scale.

### Inverted DGPS {#inverted-dgps .Appendix-3}

Inverted DGPS is a smart permutation of DGPS that can save money in
certain tracking applications. The idea is to use mobile standard GPS
units that transmit their positions to the tracking office via a
wireless data link, and apply differential corrections only there.

Therefore, only one differential correction receiver is needed, and the
GPS units do not have to be differential ready. The drawback is that the
mobile units do not know their precise position.

### Cell phone location technologies {#cell-phone-location-technologies .Appendix-3}

Many mobile network-based technologies used to locate cell phones are
available on the market. Accuracy varies a little from one technology to
another, but is usually around only a few tens of feet. When the user
makes a phone call, the local antennas measure some of the signal
characteristics in order to compute the cell phone location. There are
three main methods (and many hybrid ones):

1.  **The Time Difference of Arrival (TDOA) method:** the wireless
    phone's signal is received at various antenna sites. Since each
    antenna is at a (usually) different distance from the caller, the
    signal arrives at a (very) slightly different time. The technique
    requires signal timing information from at least three different
    antenna sites. The receivers, each synchronized by an atomic clock,
    send the caller's voice call and timing data on to the mobile
    switch, where the times are compared and computed to generate a
    latitude and longitude for the caller.

2.  **The Angle of Arrival (AOA) method:** the wireless phone's signal
    is received at various antenna sites. Each antenna site is also
    equipped with additional gear to detect the compass direction from
    which the caller's signal is arriving. The receivers send the
    caller's voice call and compass data on to the mobile switch, where
    the angles are compared and computed to generate a latitude and
    longitude for the caller.

3.  **The Location Pattern Matching (LMP) method:** the receivers send
    the caller's voice call to the mobile switch, where sophisticated
    equipment analyzes the acoustic radio signal, and then compares it
    to a data base of standard signal characteristics. These
    characteristics include signal reflections (multi-path), echoes and
    other signal "anomalies." When a computerized match is made, the
    location of the caller can be determined. The technique is effective
    in urban environments where tall buildings and other obstructions
    are located.

### SnapTrack® technology {#snaptrack-technology .Appendix-3}

SnapTrack® Inc., has developed a server-aided GPS technology to locate
cell phones. The idea is that the handset's position is first estimated
using cell phone location technologies. Then a server, connected to a
DGPS sends aiding data to the phone: a list of satellites in view from
the handset, and their relative Doppler offsets. SnapTrack® technology
is currently the fastest, most accurate (about 12 feet in an open site),
and most cost-effective wireless device location technology.

# Glossary {#glossary .Appendix-1a}

**Block Signal:** A fixed signal displayed to trains at the entrance to
a block to govern use of that block. ^1^

**Block:** A length of track with defined limits on which train
movements are governed by block signals, cab signals, or Form D. ^1^

**Blocking device:** A lever, plug, ring or other method of control that
restricts the operation of a switch or a signal. ^2^

**Cab signal:** A signal that is located in the engine control
compartment, which indicates track occupancy or condition. The cab
signal is used in conjunction with interlocking signals and in lieu of
block signals. ^1^

**Controlled track:** Track upon which the railroad's operating rules
require that all movements of trains must be authorized by a train
dispatcher or a control operator. ^2^

**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. ^3^

**Data link:** Technology that enables information that is now
transmitted over radio links to be transmitted over data lines. ^3^

**DGPS:** Differential GPS. Positioning technology that uses both
satellites and ground stations.

**Engineer:** The person primarily responsible for operating the
locomotive.

**Fixed signal:** A signal at a fixed location that affects the movement
of a train. ^1^

**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 on-track safety for roadway
workers, while engaged solely in performing that function. ^2^

**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.
^2^

**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 four feet
of the field side of the near running rail. ^2^

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

**Crew Watchman:** A person assigned to signal others of the approach of
a train. ^2^

**GIF:** (Graphics Interchange Format) bit-mapped graphics file format.
GIF supports color and various resolutions. It also includes data
compression, making it especially effective for scanned photos.

**Global positioning system** (**GPS):** A satellite based positioning
system. GPS provides specially coded satellite signals that can be
processed in a GPS receiver, enabling the receiver to compute position,
velocity, and time. Four GPS satellite signals are used to compute
positions in three dimensions and the time offset in the receiver clock.

**Hi-railer:** A motor vehicle equipped to move on either the highway or
railroad tracks.

**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 signals appliances
such that their movements must succeed each other in a predetermined
sequence, assuring that signals cannot be displayed simultaneously on
conflicting routes. ^2^

**JPEG:** (Joint Photographic Experts Group) "glossy" compressed graphic
file format supporting 24-bit, over 16 million colors.

**Movement Permit Form D:** A form containing written authorization(s),
restriction(s), or instruction(s), issued by the dispatcher to specified
individuals. [^5]

**NDGPS:** Nationwide Differential Global Positioning System. An
augmentation of GPS operated by the U.S. Coast Guard provides integrity
monitoring of GPS and positioning accuracy of one to three meters.

**NORAC:** Northeast Operating Rules Advisory Committee.

**NMEA standard:** National Marine Electronics Association's standard
for data communication between marine instruments (e.g., GPS).

**On-track safety:** State of freedom from the danger of being struck by
a moving railroad train or other railroad equipment, provided by
operating and safety rules that govern track occupancy by personnel,
trains, or on-track equipment. [^6]

**PPP:** (Point to Point Protocol) Communication protocol for a modem to
connect to the Internet through an access provider.

**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. ^1^

**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.

**TCP/IP:** (Transport Control Protocol / Internet Protocol) Suite of
communications protocols used to connect hosts on the Internet.

**Track car:** Equipment, other than trains, operated on a track for
inspection or maintenance. Track cars might not shunt track circuits.
^2^

**Traffic Envelope:** Area between clearance points (25 feet from the
centerline of outside track) and rails and overhead power lines.

**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. ^2^

**Train On Sheet (Train OS):** Dispatcher's term that refers to train
schedule usually with time updates.

**Wireless Application Protocol (WAP):** Is an application environment
and set of communication protocols for wireless devices designed to
enable manufacturer, vendor, and technology-independent access to the
Internet and advanced telephony services.

# References {#references .Appendix-1a}

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Transport Canada.

Amtrak Roadway Worker Protection Manual (1997). Northeast Corridor,
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An Introduction to SnapTrack Server-Aided GPS Technology. (July 25,
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Basu, S. (1999). Real Time Simulation of Rail Dispatcher Operations.
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Basu, S. (2001). System Architecture and Operation of the MIT/Volpe
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Code of Federal Regulations. (October 1998). Title 49\--Transportation.
Chapter II\--Federal Railroad Administration, Part 214-Railroad
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2001\].

Ditmeyer, S.R. and Smith, M.E. (1993) Data Links and Planning Tools:
Enhancing the Ability to Plan and Manage Train Operations. Rail
International, pp 69-77.

Federal Railroad Administration. (2002). A Vision for the Future:
Intelligent Railroad Systems *Five-Year Strategic Plan for Railroad
Research, Development, and Demonstrations*. Report No. FRA/RDV-02/02
Washington, DC: U.S. Department of Transportation.

FRA Report. (2000) Railroad Safety Statistics, Annual Report 1999.

Federal Railroad Administration. (1994). *Railroad Communications and
Train Control: Report* *to Congress*. Washington, DC: U.S. Department of
Transportation.

GPS Smart Antenna. (July 25, 2001). Axiom. \[On-line\]. Available:
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\[July 25, 2001\].

Kyocera pdQ Smartphone Series Product Detail Page. (July 25, 2001).
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2001\].

Lestime, H. (1998) ETCS. Development of Train Control Systems for
European High-Speed Lines. Rail International Tokyo Seminar.

Malsch, N. (1999) Design and Testing of a Railroad Dispatching Simulator
Using Data link Technology. M.S. Thesis, Cambridge, MA: MIT.

Malsch, N., Sheridan, T., and Multer, J. (2004). *Impact of Data Link
Technology on Railroad Dispatching Operations.* Report No.
DOT/FRA/ORD-04/11. Washington, DC: U.S. Department of Transportation,
Federal Railroad Administration.

Martland C.,D. (1995).Modeling Railroad Line Performance. Railroad
Application Special Interest Group, Newsletter, 1995

NORAC Operating Rules (1997).

Oriol, N., Sheridan, T. and Multer, J. (2004). *Supporting Railroad
Roadway Worker Communications with a Wireless Handheld Computer: Volume
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U.S. Washington, DC: Department of Transportation, Federal Railroad
Administration

Oriol, N. (2000). Design and Evaluation of a Communication Device to
Enhance Railroad Worker Safety. Master's thesis, Cambridge, MA: MIT.

Palm VIIx Hand-held Description. (copyright 2000). Palm, Inc.
\[Online\]. Available: www.palm.com/products/palmvii \[March 12, 2001\].

Roth, E.M., Malsch, N., and Multer, J. (2001). *Understanding How Train
Dispatchers Manage and Control Trains: Results of a Cognitive Task
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Sheridan, T. (1992) Telerobotics, Automation, and Human Supervisory
Control. MIT Press.

SOFA Working Group. (October 1999) Findings and Recommendations of the
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Stearns, Mary D., Sussman, E. Donald and Jonathan Belcher. (1999).
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2001\].

[^1]: The reference to line 4 indicates where on the Form D the
    authorization is written.

[^2]: The use of Nationwide Differential Global Positioning System
    (NDGPS) could provide significantly better precision than GPS alone.

[^3]: Ideally, the usability and effectiveness of the application should
    be evaluated in a field environment. Until the authors can obtain
    permission to work with a railroad to test the application in the
    field, the laboratory environment provided an interim solution to
    testing the application.

[^4]: The participant was asked to grant all Form D requests in an
    effort to simplify the experiment.

[^5]: NORAC operating rules

[^6]: Roadway Worker Protection Manual (RWP manual)

[^7]: Roth, E.M. and Malsch, N.1999