+-----------+----------------------------------------------------------+
| ![](m     | **Effects of Supervisory Train Control Technology on     |
| edia/imag | Operator Attention**                                     |
| e1.wmf){w |                                                          |
| 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-04/10      | > Final Report     | This document is       |
|                        | >                  | available to the       |
|                        | > July 2005        |                        |
|                        |                    | 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 aspects   |   |              |   |       |   |   |              |
| of this          |   |              |   |       |   |   |              |
| collection of    |   |              |   |       |   |   |              |
| information ,    |   |              |   |       |   |   |              |
| including        |   |              |   |       |   |   |              |
| suggestions for  |   |              |   |       |   |   |              |
| reducing this    |   |              |   |       |   |   |              |
| burden to        |   |              |   |       |   |   |              |
| Washington       |   |              |   |       |   |   |              |
| Headquarters     |   |              |   |       |   |   |              |
| Service,         |   |              |   |       |   |   |              |
| Directorate for  |   |              |   |       |   |   |              |
| information      |   |              |   |       |   |   |              |
| Operations and   |   |              |   |       |   |   |              |
| Reports. 1215    |   |              |   |       |   |   |              |
| Jefferson Davis  |   |              |   |       |   |   |              |
| Highway, Suite   |   |              |   |       |   |   |              |
| 1204, Arlington, |   |              |   |       |   |   |              |
| VA. 222202-4302, |   |              |   |       |   |   |              |
| and to the       |   |              |   |       |   |   |              |
| Office of        |   |              |   |       |   |   |              |
| Management and   |   |              |   |       |   |   |              |
| Budget,          |   |              |   |       |   |   |              |
| Paperwork        |   |              |   |       |   |   |              |
| Reduction        |   |              |   |       |   |   |              |
| Project          |   |              |   |       |   |   |              |
| (0704-0188),     |   |              |   |       |   |   |              |
| Washington, DC   |   |              |   |       |   |   |              |
| 20503.           |   |              |   |       |   |   |              |
+------------------+---+--------------+---+-------+---+---+--------------+
| 1\. Agency Use   |   | 2.  Report   |   | 3.  R |   |   |              |
| Only (*Leave     |   |     Date     |   | EPORT |   |   |              |
| blank*)          |   |              |   |       |   |   |              |
|                  |   | July 2005    |   |  TYPE |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |   AND |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   | DATES |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |    CO |   |   |              |
|                  |   |              |   | VERED |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   | Final |   |   |              |
|                  |   |              |   | R     |   |   |              |
|                  |   |              |   | eport |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   | Sept  |   |   |              |
|                  |   |              |   | ember |   |   |              |
|                  |   |              |   | 1     |   |   |              |
|                  |   |              |   | 995 - |   |   |              |
|                  |   |              |   | Jun   |   |   |              |
|                  |   |              |   | e1997 |   |   |              |
+------------------+---+--------------+---+-------+---+---+--------------+
| 4.  Title and    |   |              |   |       | 5 |   |              |
|     subtitle     |   |              |   |       | . |   |              |
|                  |   |              |   |       |   |   |              |
| Effects of       |   |              |   |       |   |   |              |
| Supervisory      |   |              |   |       | F |   |              |
| Train Control    |   |              |   |       | U |   |              |
| Technology on    |   |              |   |       | N |   |              |
| Operator         |   |              |   |       | D |   |              |
| Attention        |   |              |   |       | I |   |              |
|                  |   |              |   |       | N |   |              |
|                  |   |              |   |       | G |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       | N |   |              |
|                  |   |              |   |       | U |   |              |
|                  |   |              |   |       | M |   |              |
|                  |   |              |   |       | B |   |              |
|                  |   |              |   |       | E |   |              |
|                  |   |              |   |       | R |   |              |
|                  |   |              |   |       | S |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       | R |   |              |
|                  |   |              |   |       | 2 |   |              |
|                  |   |              |   |       | 1 |   |              |
|                  |   |              |   |       | 0 |   |              |
|                  |   |              |   |       | 3 |   |              |
|                  |   |              |   |       | / |   |              |
|                  |   |              |   |       | R |   |              |
|                  |   |              |   |       | R |   |              |
|                  |   |              |   |       | 2 |   |              |
|                  |   |              |   |       | 0 |   |              |
|                  |   |              |   |       | 4 |   |              |
+------------------+---+--------------+---+-------+---+---+--------------+
| 6.  AUTHOR(S)    |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
| Helias           |   |              |   |       |   |   |              |
| Marinakos,       |   |              |   |       |   |   |              |
| Thomas Sheridan, |   |              |   |       |   |   |              |
| and Jordan       |   |              |   |       |   |   |              |
| Multer           |   |              |   |       |   |   |              |
+------------------+---+--------------+---+-------+---+---+--------------+
| 7.  PERFORMING   |   |              |   |       | 8 |   |              |
|     ORGANIZATION |   |              |   |       | . |   |              |
|     NAME(S) AND  |   |              |   |       |   |   |              |
|     ADDRESS(ES)  |   |              |   |       |   |   |              |
|                  |   |              |   |       | P |   |              |
| U.S. Department  |   |              |   |       | E |   |              |
| of               |   |              |   |       | R |   |              |
| Transportation   |   |              |   |       | F |   |              |
|                  |   |              |   |       | O |   |              |
| Research and     |   |              |   |       | R |   |              |
| Special Programs |   |              |   |       | M |   |              |
| Administration   |   |              |   |       | I |   |              |
|                  |   |              |   |       | N |   |              |
| John A. Volpe    |   |              |   |       | G |   |              |
| National         |   |              |   |       |   |   |              |
| Transportation   |   |              |   |       |   |   |              |
| Systems Center   |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
| Cambridge, MA    |   |              |   |       | O |   |              |
| 02142-1093       |   |              |   |       | R |   |              |
|                  |   |              |   |       | G |   |              |
|                  |   |              |   |       | A |   |              |
|                  |   |              |   |       | N |   |              |
|                  |   |              |   |       | I |   |              |
|                  |   |              |   |       | Z |   |              |
|                  |   |              |   |       | A |   |              |
|                  |   |              |   |       | T |   |              |
|                  |   |              |   |       | I |   |              |
|                  |   |              |   |       | O |   |              |
|                  |   |              |   |       | N |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       | D |   |              |
|                  |   |              |   |       | O |   |              |
|                  |   |              |   |       | T |   |              |
|                  |   |              |   |       | - |   |              |
|                  |   |              |   |       | V |   |              |
|                  |   |              |   |       | N |   |              |
|                  |   |              |   |       | T |   |              |
|                  |   |              |   |       | S |   |              |
|                  |   |              |   |       | C |   |              |
|                  |   |              |   |       | - |   |              |
|                  |   |              |   |       | F |   |              |
|                  |   |              |   |       | R |   |              |
|                  |   |              |   |       | A |   |              |
|                  |   |              |   |       | - |   |              |
|                  |   |              |   |       | 0 |   |              |
|                  |   |              |   |       | 4 |   |              |
|                  |   |              |   |       | - |   |              |
|                  |   |              |   |       | 0 |   |              |
|                  |   |              |   |       | 7 |   |              |
+------------------+---+--------------+---+-------+---+---+--------------+
| 9.  SPONS        |   |              |   |       | 1 |   |              |
| ORING/MONITORING |   |              |   |       | 0 |   |              |
|     AGENCY       |   |              |   |       | . |   |              |
|     NAME(S) AND  |   |              |   |       |   |   |              |
|     ADDRESS(ES)  |   |              |   |       | S |   |              |
|                  |   |              |   |       | P |   |              |
| U.S. Department  |   |              |   |       | O |   |              |
| of               |   |              |   |       | N |   |              |
| Transportation   |   |              |   |       | S |   |              |
|                  |   |              |   |       | O |   |              |
| Federal Railroad |   |              |   |       | R |   |              |
| Administration   |   |              |   |       | I |   |              |
|                  |   |              |   |       | N |   |              |
| Office of        |   |              |   |       | G |   |              |
| Research and     |   |              |   |       | / |   |              |
| Development Mail |   |              |   |       | M |   |              |
| Stop 20          |   |              |   |       | O |   |              |
|                  |   |              |   |       | N |   |              |
| 1120 Vermont     |   |              |   |       | I |   |              |
| Avenue, NW       |   |              |   |       | T |   |              |
|                  |   |              |   |       | O |   |              |
| Washington, DC   |   |              |   |       | R |   |              |
| 20590            |   |              |   |       | I |   |              |
|                  |   |              |   |       | N |   |              |
|                  |   |              |   |       | 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 |   |              |
|                  |   |              |   |       | 0 |   |              |
+------------------+---+--------------+---+-------+---+---+--------------+
| 1                |   |              |   |       |   |   |              |
| 1. SUPPLEMENTARY |   |              |   |       |   |   |              |
|     NOTES        |   |              |   |       |   |   |              |
+------------------+---+--------------+---+-------+---+---+--------------+
| 12a.             |   |              |   |       | 1 |   |              |
| DISTRIBUT        |   |              |   |       | 2 |   |              |
| ION/AVAILABILITY |   |              |   |       | b |   |              |
| STATEMENT        |   |              |   |       | . |   |              |
|                  |   |              |   |       | D |   |              |
| This document is |   |              |   |       | I |   |              |
| available to the |   |              |   |       | S |   |              |
| public through   |   |              |   |       | T |   |              |
| the National     |   |              |   |       | R |   |              |
| Technical        |   |              |   |       | I |   |              |
| Information      |   |              |   |       | B |   |              |
| Service,         |   |              |   |       | U |   |              |
| Springfield, VA  |   |              |   |       | T |   |              |
| 22161. This      |   |              |   |       | I |   |              |
| document is also |   |              |   |       | O |   |              |
| available on the |   |              |   |       | N |   |              |
| FRA web site at  |   |              |   |       | C |   |              |
| www.fra.dot.gov. |   |              |   |       | O |   |              |
|                  |   |              |   |       | D |   |              |
|                  |   |              |   |       | E |   |              |
+------------------+---+--------------+---+-------+---+---+--------------+
| 13. ABSTRACT     |   |              |   |       |   |   |              |
|     (Maximum 200 |   |              |   |       |   |   |              |
|     words)       |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
| This report      |   |              |   |       |   |   |              |
| describes an     |   |              |   |       |   |   |              |
| experiment       |   |              |   |       |   |   |              |
| evaluating the   |   |              |   |       |   |   |              |
| effects of       |   |              |   |       |   |   |              |
| supervisory      |   |              |   |       |   |   |              |
| control          |   |              |   |       |   |   |              |
| automation on    |   |              |   |       |   |   |              |
| attention        |   |              |   |       |   |   |              |
| allocation while |   |              |   |       |   |   |              |
| operating a      |   |              |   |       |   |   |              |
| train. The study |   |              |   |       |   |   |              |
| compared two     |   |              |   |       |   |   |              |
| levels of        |   |              |   |       |   |   |              |
| supervisory      |   |              |   |       |   |   |              |
| control (partial |   |              |   |       |   |   |              |
| and full) to     |   |              |   |       |   |   |              |
| manual control,  |   |              |   |       |   |   |              |
| in terms of how  |   |              |   |       |   |   |              |
| it affects       |   |              |   |       |   |   |              |
| vigilance        |   |              |   |       |   |   |              |
| detection and    |   |              |   |       |   |   |              |
| situation        |   |              |   |       |   |   |              |
| awareness. Human |   |              |   |       |   |   |              |
| performance was  |   |              |   |       |   |   |              |
| measured using a |   |              |   |       |   |   |              |
| h                |   |              |   |       |   |   |              |
| uman-in-the-loop |   |              |   |       |   |   |              |
| train simulator. |   |              |   |       |   |   |              |
| To evaluate      |   |              |   |       |   |   |              |
| vigilance,       |   |              |   |       |   |   |              |
| participants     |   |              |   |       |   |   |              |
| were asked to    |   |              |   |       |   |   |              |
| detect two types |   |              |   |       |   |   |              |
| of automation    |   |              |   |       |   |   |              |
| failures and     |   |              |   |       |   |   |              |
| react to         |   |              |   |       |   |   |              |
| obstructions on  |   |              |   |       |   |   |              |
| the track.       |   |              |   |       |   |   |              |
| Situation        |   |              |   |       |   |   |              |
| awareness was    |   |              |   |       |   |   |              |
| measured using   |   |              |   |       |   |   |              |
| the Situation    |   |              |   |       |   |   |              |
| Awareness Global |   |              |   |       |   |   |              |
| Assessment       |   |              |   |       |   |   |              |
| Technique        |   |              |   |       |   |   |              |
| (SAGAT) in which |   |              |   |       |   |   |              |
| the simulation   |   |              |   |       |   |   |              |
| was suspended at |   |              |   |       |   |   |              |
| periodic         |   |              |   |       |   |   |              |
| intervals and    |   |              |   |       |   |   |              |
| the subjects     |   |              |   |       |   |   |              |
| answered         |   |              |   |       |   |   |              |
| questions about  |   |              |   |       |   |   |              |
| the system.      |   |              |   |       |   |   |              |
| These answers    |   |              |   |       |   |   |              |
| were compared to |   |              |   |       |   |   |              |
| objective        |   |              |   |       |   |   |              |
| measures of      |   |              |   |       |   |   |              |
| system           |   |              |   |       |   |   |              |
| performance.     |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
| Attention        |   |              |   |       |   |   |              |
| allocation       |   |              |   |       |   |   |              |
| varied with the  |   |              |   |       |   |   |              |
| method by which  |   |              |   |       |   |   |              |
| supervisory      |   |              |   |       |   |   |              |
| control was      |   |              |   |       |   |   |              |
| implemented. In  |   |              |   |       |   |   |              |
| particular,      |   |              |   |       |   |   |              |
| attention        |   |              |   |       |   |   |              |
| allocation for   |   |              |   |       |   |   |              |
| speed control, a |   |              |   |       |   |   |              |
| critical piece   |   |              |   |       |   |   |              |
| of information,  |   |              |   |       |   |   |              |
| varied with the  |   |              |   |       |   |   |              |
| two methods.     |   |              |   |       |   |   |              |
| Partial          |   |              |   |       |   |   |              |
| supervisory      |   |              |   |       |   |   |              |
| control, as      |   |              |   |       |   |   |              |
| implemented in   |   |              |   |       |   |   |              |
| this experiment, |   |              |   |       |   |   |              |
| resulted in a    |   |              |   |       |   |   |              |
| narrowing of     |   |              |   |       |   |   |              |
| attention. The   |   |              |   |       |   |   |              |
| primary focus    |   |              |   |       |   |   |              |
| was on speed     |   |              |   |       |   |   |              |
| information. By  |   |              |   |       |   |   |              |
| contrast, use of |   |              |   |       |   |   |              |
| full supervisory |   |              |   |       |   |   |              |
| control resulted |   |              |   |       |   |   |              |
| in participants  |   |              |   |       |   |   |              |
| spreading their  |   |              |   |       |   |   |              |
| attention more   |   |              |   |       |   |   |              |
| broadly, but at  |   |              |   |       |   |   |              |
| the expense of   |   |              |   |       |   |   |              |
| speed            |   |              |   |       |   |   |              |
| information.     |   |              |   |       |   |   |              |
+------------------+---+--------------+---+-------+---+---+--------------+
| 14. SUBJECT      |   |              |   |       |   | 1 |              |
|     TERMS        |   |              |   |       |   | 5 |              |
|                  |   |              |   |       |   | . |              |
|     attention    |   |              |   |       |   |   |              |
|     allocation,  |   |              |   |       |   | N |              |
|     automation,  |   |              |   |       |   | U |              |
|     high-speed   |   |              |   |       |   | M |              |
|     trains,      |   |              |   |       |   | B |              |
|     situation    |   |              |   |       |   | E |              |
|     awareness,   |   |              |   |       |   | R |              |
|     train        |   |              |   |       |   |   |              |
|     control      |   |              |   |       |   |   |              |
|     technology,  |   |              |   |       |   |   |              |
|     supervisory  |   |              |   |       |   |   |              |
|     control,     |   |              |   |       |   | O |              |
|     vigilance    |   |              |   |       |   | F |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   | P |              |
|                  |   |              |   |       |   | A |              |
|                  |   |              |   |       |   | G |              |
|                  |   |              |   |       |   | E |              |
|                  |   |              |   |       |   | S |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   | 5 |              |
|                  |   |              |   |       |   | 2 |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   | 1 |              |
|                  |   |              |   |       |   | 6 |              |
|                  |   |              |   |       |   | . |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   | P |              |
|                  |   |              |   |       |   | R |              |
|                  |   |              |   |       |   | I |              |
|                  |   |              |   |       |   | C |              |
|                  |   |              |   |       |   | E |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   | C |              |
|                  |   |              |   |       |   | O |              |
|                  |   |              |   |       |   | D |              |
|                  |   |              |   |       |   | E |              |
+------------------+---+--------------+---+-------+---+---+--------------+
| 17. SECURITY     | 1 |              | 1 |       |   |   | LIMITATION   |
|                  | 8 |              | 9 |       |   |   | OF ABSTRACT  |
|   CLASSIFICATION | . |              | . |       |   |   |              |
|     OF REPORT    |   |              |   |       |   |   | Unclassified |
|                  | S |              | S |       |   |   |              |
|     Unclassified | E |              | E |       |   |   |              |
|                  | C |              | C |       |   |   |              |
|                  | U |              | U |       |   |   |              |
|                  | R |              | R |       |   |   |              |
|                  | I |              | I |       |   |   |              |
|                  | T |              | T |       |   |   |              |
|                  | Y |              | Y |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  | C |              | C |       |   |   |              |
|                  | L |              | L |       |   |   |              |
|                  | A |              | A |       |   |   |              |
|                  | S |              | S |       |   |   |              |
|                  | S |              | S |       |   |   |              |
|                  | I |              | I |       |   |   |              |
|                  | F |              | F |       |   |   |              |
|                  | I |              | I |       |   |   |              |
|                  | C |              | C |       |   |   |              |
|                  | A |              | A |       |   |   |              |
|                  | T |              | T |       |   |   |              |
|                  | I |              | I |       |   |   |              |
|                  | O |              | O |       |   |   |              |
|                  | N |              | N |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  | O |              | O |       |   |   |              |
|                  | F |              | F |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  | T |              | A |       |   |   |              |
|                  | H |              | B |       |   |   |              |
|                  | I |              | S |       |   |   |              |
|                  | S |              | T |       |   |   |              |
|                  |   |              | R |       |   |   |              |
|                  |   |              | A |       |   |   |              |
|                  |   |              | C |       |   |   |              |
|                  |   |              | T |       |   |   |              |
|                  | P |              |   |       |   |   |              |
|                  | A |              |   |       |   |   |              |
|                  | G |              |   |       |   |   |              |
|                  | E |              |   |       |   |   |              |
|                  |   |              |   |       |   |   |              |
|                  |   |              | U |       |   |   |              |
|                  |   |              | n |       |   |   |              |
|                  |   |              | c |       |   |   |              |
|                  |   |              | l |       |   |   |              |
|                  | U |              | a |       |   |   |              |
|                  | n |              | s |       |   |   |              |
|                  | c |              | s |       |   |   |              |
|                  | l |              | i |       |   |   |              |
|                  | a |              | f |       |   |   |              |
|                  | s |              | i |       |   |   |              |
|                  | s |              | e |       |   |   |              |
|                  | i |              | d |       |   |   |              |
|                  | f |              |   |       |   |   |              |
|                  | i |              |   |       |   |   |              |
|                  | e |              |   |       |   |   |              |
|                  | d |              |   |       |   |   |              |
+------------------+---+--------------+---+-------+---+---+--------------+

NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89)

> Prescribed by ANSI Std. 239-18
>
> 298-102

METRIC/ENGLISH CONVERSION FACTORS

+---------------+---+---+----------------+---------------+---+---+-----------------+
| **ENGLISH TO  |   |   |                | **METRIC TO   |   |   |                 |
| METRIC**      |   |   |                | ENGLISH**     |   |   |                 |
+===============+===+===+================+===============+===+===+=================+
| **LENGTH      |   |   |                | **LENGTH      |   |   |                 |
| (A            |   |   |                | (A            |   |   |                 |
| PPROXIMATE)** |   |   |                | PPROXIMATE)** |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 inch      | * | * |                | **1           | * |   | **0.04 inch     |
| (in)**        | * | * |                | millimeter    | * |   | (in)**          |
|               | = | 2 |                | (mm)**        | = |   |                 |
|               | * | . |                |               | * |   |                 |
|               | * | 5 |                |               | * |   |                 |
|               |   | c |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | n |                |               |   |   |                 |
|               |   | t |                |               |   |   |                 |
|               |   | i |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | t |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | r |                |               |   |   |                 |
|               |   | s |                |               |   |   |                 |
|               |   | ( |                |               |   |   |                 |
|               |   | c |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | ) |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 foot      | * | * |                | **1           | * |   | **0.4 inch      |
| (ft)**        | * | * |                | centimeter    | * |   | (in)**          |
|               | = | 3 |                | (cm)**        | = |   |                 |
|               | * | 0 |                |               | * |   |                 |
|               | * | c |                |               | * |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | n |                |               |   |   |                 |
|               |   | t |                |               |   |   |                 |
|               |   | i |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | t |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | r |                |               |   |   |                 |
|               |   | s |                |               |   |   |                 |
|               |   | ( |                |               |   |   |                 |
|               |   | c |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | ) |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 yard      | * | * |                | **1 meter     | * |   | **3.3 feet      |
| (yd)**        | * | * |                | (m)**         | * |   | (ft)**          |
|               | = | 0 |                |               | = |   |                 |
|               | * | . |                |               | * |   |                 |
|               | * | 9 |                |               | * |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | t |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | r |                |               |   |   |                 |
|               |   | ( |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | ) |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 mile      | * | * |                | **1 meter     | * |   | **1.1 yards     |
| (mi)**        | * | * |                | (m)**         | * |   | (yd)**          |
|               | = | 1 |                |               | = |   |                 |
|               | * | . |                |               | * |   |                 |
|               | * | 6 |                |               | * |   |                 |
|               |   | k |                |               |   |   |                 |
|               |   | i |                |               |   |   |                 |
|               |   | l |                |               |   |   |                 |
|               |   | o |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | t |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | r |                |               |   |   |                 |
|               |   | s |                |               |   |   |                 |
|               |   | ( |                |               |   |   |                 |
|               |   | k |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | ) |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
|               |   |   |                | **1 kilometer | * |   | **0.6 mile      |
|               |   |   |                | (km)**        | * |   | (mi)**          |
|               |   |   |                |               | = |   |                 |
|               |   |   |                |               | * |   |                 |
|               |   |   |                |               | * |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **AREA        |   |   |                | **AREA        |   |   |                 |
| (A            |   |   |                | (A            |   |   |                 |
| PPROXIMATE)** |   |   |                | PPROXIMATE)** |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 square    | * | * |                | **1 square    | * |   | **0.16 square   |
| inch (sq in,  | * | * |                | centimeter    | * |   | inch (sq in,    |
| in^2^)**      | = | 6 |                | (cm^2^)**     | = |   | in^2^)**        |
|               | * | . |                |               | * |   |                 |
|               | * | 5 |                |               | * |   |                 |
|               |   | s |                |               |   |   |                 |
|               |   | q |                |               |   |   |                 |
|               |   | u |                |               |   |   |                 |
|               |   | a |                |               |   |   |                 |
|               |   | r |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | c |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | n |                |               |   |   |                 |
|               |   | t |                |               |   |   |                 |
|               |   | i |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | t |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | r |                |               |   |   |                 |
|               |   | s |                |               |   |   |                 |
|               |   | ( |                |               |   |   |                 |
|               |   | c |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | ^ |                |               |   |   |                 |
|               |   | 2 |                |               |   |   |                 |
|               |   | ^ |                |               |   |   |                 |
|               |   | ) |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 square    | * | * |                | **1 square    | * |   | **1.2 square    |
| foot (sq ft,  | * | * |                | meter         | * |   | yards (sq yd,   |
| ft^2^)**      | = | 0 |                | (m^2^)**      | = |   | yd^2^)**        |
|               | * | . |                |               | * |   |                 |
|               | * | 0 |                |               | * |   |                 |
|               |   | 9 |                |               |   |   |                 |
|               |   | s |                |               |   |   |                 |
|               |   | q |                |               |   |   |                 |
|               |   | u |                |               |   |   |                 |
|               |   | a |                |               |   |   |                 |
|               |   | r |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | t |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | r |                |               |   |   |                 |
|               |   | ( |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | ^ |                |               |   |   |                 |
|               |   | 2 |                |               |   |   |                 |
|               |   | ^ |                |               |   |   |                 |
|               |   | ) |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 square    | * | * |                | **1 square    | * |   | **0.4 square    |
| yard (sq yd,  | * | * |                | kilometer     | * |   | mile (sq mi,    |
| yd^2^)**      | = | 0 |                | (km^2^)**     | = |   | mi^2^)**        |
|               | * | . |                |               | * |   |                 |
|               | * | 8 |                |               | * |   |                 |
|               |   | s |                |               |   |   |                 |
|               |   | q |                |               |   |   |                 |
|               |   | u |                |               |   |   |                 |
|               |   | a |                |               |   |   |                 |
|               |   | r |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | t |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | r |                |               |   |   |                 |
|               |   | ( |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | ^ |                |               |   |   |                 |
|               |   | 2 |                |               |   |   |                 |
|               |   | ^ |                |               |   |   |                 |
|               |   | ) |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 square    | * | * |                | **10,000      | * |   | **1 hectare     |
| mile (sq mi,  | * | * |                | square meters | * |   | (ha) = 2.5      |
| mi^2^)**      | = | 2 |                | (m^2^)**      | = |   | acres**         |
|               | * | . |                |               | * |   |                 |
|               | * | 6 |                |               | * |   |                 |
|               |   | s |                |               |   |   |                 |
|               |   | q |                |               |   |   |                 |
|               |   | u |                |               |   |   |                 |
|               |   | a |                |               |   |   |                 |
|               |   | r |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | k |                |               |   |   |                 |
|               |   | i |                |               |   |   |                 |
|               |   | l |                |               |   |   |                 |
|               |   | o |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | t |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | r |                |               |   |   |                 |
|               |   | s |                |               |   |   |                 |
|               |   | ( |                |               |   |   |                 |
|               |   | k |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | ^ |                |               |   |   |                 |
|               |   | 2 |                |               |   |   |                 |
|               |   | ^ |                |               |   |   |                 |
|               |   | ) |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 acre =    | * | * |                |               |   |   |                 |
| 0.4 hectare   | * | * |                |               |   |   |                 |
| (he)**        | = | 4 |                |               |   |   |                 |
|               | * | , |                |               |   |   |                 |
|               | * | 0 |                |               |   |   |                 |
|               |   | 0 |                |               |   |   |                 |
|               |   | 0 |                |               |   |   |                 |
|               |   | s |                |               |   |   |                 |
|               |   | q |                |               |   |   |                 |
|               |   | u |                |               |   |   |                 |
|               |   | a |                |               |   |   |                 |
|               |   | r |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | t |                |               |   |   |                 |
|               |   | e |                |               |   |   |                 |
|               |   | r |                |               |   |   |                 |
|               |   | s |                |               |   |   |                 |
|               |   | ( |                |               |   |   |                 |
|               |   | m |                |               |   |   |                 |
|               |   | ^ |                |               |   |   |                 |
|               |   | 2 |                |               |   |   |                 |
|               |   | ^ |                |               |   |   |                 |
|               |   | ) |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **MASS -      |   |   |                | **MASS -      |   |   |                 |
| WEIGHT        |   |   |                | WEIGHT        |   |   |                 |
| (A            |   |   |                | (A            |   |   |                 |
| PPROXIMATE)** |   |   |                | PPROXIMATE)** |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 ounce     | * | * |                | **1 gram      | * | * |                 |
| (oz)**        | * | * |                | (gm)**        | * | * |                 |
|               | = | 2 |                |               | = | 0 |                 |
|               | * | 8 |                |               | * | . |                 |
|               | * | g |                |               | * | 0 |                 |
|               |   | r |                |               |   | 3 |                 |
|               |   | a |                |               |   | 6 |                 |
|               |   | m |                |               |   | o |                 |
|               |   | s |                |               |   | u |                 |
|               |   | ( |                |               |   | n |                 |
|               |   | g |                |               |   | c |                 |
|               |   | m |                |               |   | e |                 |
|               |   | ) |                |               |   | ( |                 |
|               |   | * |                |               |   | o |                 |
|               |   | * |                |               |   | z |                 |
|               |   |   |                |               |   | ) |                 |
|               |   |   |                |               |   | * |                 |
|               |   |   |                |               |   | * |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 pound     | * | * |                | **1 kilogram  | * | * |                 |
| (lb)**        | * | * |                | (kg)**        | * | * |                 |
|               | = | 0 |                |               | = | 2 |                 |
|               | * | . |                |               | * | . |                 |
|               | * | 4 |                |               | * | 2 |                 |
|               |   | 5 |                |               |   | p |                 |
|               |   | k |                |               |   | o |                 |
|               |   | i |                |               |   | u |                 |
|               |   | l |                |               |   | n |                 |
|               |   | o |                |               |   | d |                 |
|               |   | g |                |               |   | s |                 |
|               |   | r |                |               |   | ( |                 |
|               |   | a |                |               |   | l |                 |
|               |   | m |                |               |   | b |                 |
|               |   | ( |                |               |   | ) |                 |
|               |   | k |                |               |   | * |                 |
|               |   | g |                |               |   | * |                 |
|               |   | ) |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
|               |   | * |                |               |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 short ton | * | * |                | **1 tonne     | * | * |                 |
| = 2,000       | * | * |                | (t)**         | * | * |                 |
| pounds (lb)** | = | 0 |                |               | = | 1 |                 |
|               | * | . |                |               | * | , |                 |
|               | * | 9 |                |               | * | 0 |                 |
|               |   | t |                |               |   | 0 |                 |
|               |   | o |                |               | * | 0 |                 |
|               |   | n |                |               | * | k |                 |
|               |   | n |                |               | = | i |                 |
|               |   | e |                |               | * | l |                 |
|               |   | ( |                |               | * | o |                 |
|               |   | t |                |               |   | g |                 |
|               |   | ) |                |               |   | r |                 |
|               |   | * |                |               |   | a |                 |
|               |   | * |                |               |   | m |                 |
|               |   |   |                |               |   | s |                 |
|               |   |   |                |               |   | ( |                 |
|               |   |   |                |               |   | k |                 |
|               |   |   |                |               |   | g |                 |
|               |   |   |                |               |   | ) |                 |
|               |   |   |                |               |   | * |                 |
|               |   |   |                |               |   | * |                 |
|               |   |   |                |               |   |   |                 |
|               |   |   |                |               |   | * |                 |
|               |   |   |                |               |   | * |                 |
|               |   |   |                |               |   | 1 |                 |
|               |   |   |                |               |   | . |                 |
|               |   |   |                |               |   | 1 |                 |
|               |   |   |                |               |   | s |                 |
|               |   |   |                |               |   | h |                 |
|               |   |   |                |               |   | o |                 |
|               |   |   |                |               |   | r |                 |
|               |   |   |                |               |   | t |                 |
|               |   |   |                |               |   | t |                 |
|               |   |   |                |               |   | o |                 |
|               |   |   |                |               |   | n |                 |
|               |   |   |                |               |   | s |                 |
|               |   |   |                |               |   | * |                 |
|               |   |   |                |               |   | * |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **VOLUME      |   |   |                | **VOLUME      |   |   |                 |
| (A            |   |   |                | (A            |   |   |                 |
| PPROXIMATE)** |   |   |                | PPROXIMATE)** |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 teaspoon  | * |   | **5            | **1           | * |   | **0.03 fluid    |
| (tsp)**       | * |   | milliliters    | milliliter    | * |   | ounce (fl oz)** |
|               | = |   | (ml)**         | (ml)**        | = |   |                 |
|               | * |   |                |               | * |   |                 |
|               | * |   |                |               | * |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1           | * |   | **15           | **1 liter     | * |   | **2.1 pints     |
| tablespoon    | * |   | milliliters    | (l)**         | * |   | (pt)**          |
| (tbsp)**      | = |   | (ml)**         |               | = |   |                 |
|               | * |   |                |               | * |   |                 |
|               | * |   |                |               | * |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 fluid     | * |   | **30           | **1 liter     | * |   | **1.06 quarts   |
| ounce (fl     | * |   | milliliters    | (l)**         | * |   | (qt)**          |
| oz)**         | = |   | (ml)**         |               | = |   |                 |
|               | * |   |                |               | * |   |                 |
|               | * |   |                |               | * |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 cup (c)** | * |   | **0.24 liter   | **1 liter     | * |   | **0.26 gallon   |
|               | * |   | (l)**          | (l)**         | * |   | (gal)**         |
|               | = |   |                |               | = |   |                 |
|               | * |   |                |               | * |   |                 |
|               | * |   |                |               | * |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 pint      | * |   | **0.47 liter   |               |   |   |                 |
| (pt)**        | * |   | (l)**          |               |   |   |                 |
|               | = |   |                |               |   |   |                 |
|               | * |   |                |               |   |   |                 |
|               | * |   |                |               |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 quart     | * |   | **0.96 liter   |               |   |   |                 |
| (qt)**        | * |   | (l)**          |               |   |   |                 |
|               | = |   |                |               |   |   |                 |
|               | * |   |                |               |   |   |                 |
|               | * |   |                |               |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 gallon    | * |   | **3.8 liters   |               |   |   |                 |
| (gal)**       | * |   | (l)**          |               |   |   |                 |
|               | = |   |                |               |   |   |                 |
|               | * |   |                |               |   |   |                 |
|               | * |   |                |               |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 cubic     | * |   | **0.03 cubic   | **1 cubic     | * |   | **36 cubic feet |
| foot (cu ft,  | * |   | meter (m^3^)** | meter         | * |   | (cu ft,         |
| ft^3^)**      | = |   |                | (m^3^)**      | = |   | ft^3^)**        |
|               | * |   |                |               | * |   |                 |
|               | * |   |                |               | * |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **1 cubic     | * |   | **0.76 cubic   | **1 cubic     | * |   | **1.3 cubic     |
| yard (cu yd,  | * |   | meter (m^3^)** | meter         | * |   | yards (cu yd,   |
| yd^3^)**      | = |   |                | (m^3^)**      | = |   | yd^3^)**        |
|               | * |   |                |               | * |   |                 |
|               | * |   |                |               | * |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **TEMPERATURE |   |   |                | **TEMPERATURE |   |   |                 |
| (EXACT)**     |   |   |                | (EXACT)**     |   |   |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+
| **\[          | * |   | **y °C**       | **\[(9/5) y + | * | * |                 |
| (x-32)(5/9)\] | * |   |                | 32\] °C**     | * | * |                 |
| °F**          | = |   |                |               | = | x |                 |
|               | * |   |                |               | * | ° |                 |
|               | * |   |                |               | * | F |                 |
|               |   |   |                |               |   | * |                 |
|               |   |   |                |               |   | * |                 |
+---------------+---+---+----------------+---------------+---+---+-----------------+

![](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 .FrontMatter-1-NC}

Increasing train speed makes it more difficult for the train crew to see
the wayside signals and respond in an appropriate and timely manner. As
train speed increases, less time is available for the locomotive
engineer to react, due to the increased distance required for the
vehicle to decelerate. Train control technology (i.e., positive train
control) has been proposed as a way to compensate for the physical and
perceptual limitations of the operator. One type of train control that
has been proposed is supervisory control. In supervisory control, the
train control system operates the train and the locomotive engineer
monitors the train control system. However, studies of supervisory
control show that it has negative as well as positive effects on human
performance.

This study examined the impact of supervisory train control on two
aspects of attention, vigilance, and situation awareness. High-speed
train operations were simulated in a human-in-the-loop train simulator.
Two kinds of supervisory train control: full and partial were compared
to manual control. To evaluate attention allocation in train handling,
participants operated a train during which equipment failures occurred
at very low frequencies and vehicles obstructed the track. The ability
of participants to respond to these events was measured. Situation
awareness was measured by suspending the simulation periodically to
obtain information from the participant regarding his or her knowledge
related to train handling. The participant's answers were compared to
objective information about the locomotive's state.

The study documented in this report was part of a program to examine
human factors issues related to the introduction of new train control
technology in high-speed rail operations. The Federal Railroad
Administration sponsored this work as part of its activities to develop
Intelligent Railroad Systems (Federal Railroad Administration, 2002).

The authors would like to acknowledge the contribution of many people
who were part of this research:

It was a pleasure working with Steven Villareal who developed the sound
enhancement for the High-Speed Train Simulator and Jacob Einhorn who
worked on in-cab displays for high-speed locomotives. Special thanks go
to Dr. Edward Lanzilotta for providing his knowledge regarding software
engineering issues and experimental procedures. Additionally, support
was provided in various forms from the other MIT colleagues as well:
Shinsuk Park, Mark Ottensmeyer, Nicholas Patrick, Suyeong Kim, Dave
Schloerb, Shih-Ken Chen, Jie Ren, Steven Landry, Joe Conti, Shumei Yin
Askey, Bernardo Aumond, and Michalis Kilaras.

This work was completed at the John A. Volpe National Transportation
Systems Center. The opportunity to work in this facility led to many
productive relationships. Thanks are due to John K. Pollard for his
involvement in the project and for providing his hardware expertise and
to Dr. Donald Sussman for his support and interest in this research.
Finally, the authors would like to thank Garold Thomas and Dr. Thomas
Raslear from the Office of Research and Development at Federal Railroad
Administration for sponsoring this research.

# TABLE OF CONTENTS {#table-of-contents .FrontMatter-1-NC}

[**EXECUTIVE SUMMARY vii**](#executive-summary)

[1. INTRODUCTION 1](#introduction)

[Vigilance 2](#vigilance)

[Situation Awareness 3](#situation-awareness)

[2. METHOD 5](#method)

[Overview 5](#overview)

[Experimental Design 5](#experimental-design)

[Participants 8](#participants)

[Facilities: High-Speed Locomotive Simulator
8](#facilities-high-speed-locomotive-simulator)

[Procedures 10](#procedures)

[3. RESULTS AND DISCUSSION 13](#results-and-discussion)

[Vigilance 13](#vigilance-1)

[Situation Awareness 18](#situation-awareness-2)

[Summary 22](#summary)

[APPENDIX A. BONUS AND PENALTY POINT SYSTEM
25](#bonus-and-penalty-point-system)

[APPENDIX B. NEW FEATURES OF HIGH-SPEED TRAIN SIMULATOR
29](#new-features-of-high-speed-train-simulator)

[APPENDIX C. LOCATION OF FAILURE EVENTS 31](#location-of-failure-events)

[APPENDIX D. VIGILANCE DETECTION TASK DATA
33](#vigilance-detection-task-data)

[APPENDIX E. DATA FOR PAGE TEST 37](#data-for-page-test)

[REFERENCES 39](#references)

#  LIST OF FIGURES {#list-of-figures .FrontMatter-1-NC .unnumbered}

**[Figure]{.underline} [Page]{.underline}**

Figure 1. Train Simulator Layout [8](#__RefHeading___Toc108333853)

Figure 2. Instrument Panel [9](#__RefHeading___Toc108333854)

Figure 3. Track Layout [10](#__RefHeading___Toc108333855)

Figure 4. Four Outcomes of Signal Detection Theory
[13](#__RefHeading___Toc108333856)

Figure 5. Graphical Depiction of Signal Detection Theory
[14](#__RefHeading___Toc108333857)

Figure 6. Effects of Train Control Mode on Detection Rate
[15](#__RefHeading___Toc108333858)

Figure 7. Probability of Hits vs. False Alarms by Train Control Mode and
Time (The labels: 1, 2, and 3 represent the time block order)
[16](#__RefHeading___Toc108333859)

Figure 8. Sensitivity and Response Criterion by Time Block and Control
Mode [17](#__RefHeading___Toc108333860)

Figure 9. Distance Stopped from an Obstruction
[18](#__RefHeading___Toc108333861)

Figure 10. Effects of Train Control Mode on Speed Awareness
[19](#__RefHeading___Toc108333862)

Figure 11. Effects of Train Control Mode on Bearing Temperature
Awareness [21](#__RefHeading___Toc108333863)

Figure 12. Effects of Train Control Mode on Position and Motor Condition
[21](#__RefHeading___Toc108333864)

Figure A‑1. Schedule Accuracy Bonus/Penalty Points
[25](#__RefHeading___Toc108333865)

Figure A‑2. Emergency Response Time Bonus Points
[26](#__RefHeading___Toc108333866)

# LIST OF TABLES {#list-of-tables .FrontMatter-1-NC}

[Table]{.underline} [Page]{.underline}

1\. Train Control Condition [5](#__RefHeading___Toc10427057)

2\. Presentation Order of Train Control Modes
[6](#__RefHeading___Toc10427058)

3\. Detection of In-Cab Equipment Failures by Control Mode
[15](#__RefHeading___Toc10427059)

4\. Participant Preferences for Train Control Mode from Exit Interview
[22](#__RefHeading___Toc10427060)

A‑1. Penalties Resulting from Application of the Emergency Brakes
[26](#__RefHeading___Toc10427061)

A‑2. Obstruction Hazards Bonus/Penalty Scheme
[26](#__RefHeading___Toc10427062)

# EXECUTIVE SUMMARY {#executive-summary .FrontMatter-1}

As high-speed passenger operations are adopted in the United States,
train control technology is required to enable the train crew to operate
the train safely. As train speeds increase, the locomotive engineer has
less time to acquire information needed to operate the locomotive and
respond. In high-speed rail operations, train control technology using
decision support aids, supervisory control, or some combination has been
proposed as a means to compensate for the sensory, perceptual, and
cognitive limitations of the locomotive engineer.

This study focused on the impact of supervisory train control technology
on human performance. The successful application of supervisory control
in train operations requires an understanding of how it affects the
train crews that interact with this technology. For example, locomotive
engineers often work long hours with inadequate amounts of rest between
shifts (Thomas, Raslear, and Kuehn, 1997). As a result, engineers can
become less attentive over the course of their shift. Supervisory train
control technology has been proposed to assist the locomotive engineer
in operating the locomotive safely during high speeds over long periods.

However, supervisory train control may change how the locomotive
engineer allocates his or her attention. The question is how do these
changes affect the operator\'s performance and what are the safety
implications of these changes? To control the train, the engineer
collects information both inside and outside the cab. Inside the cab,
the engineer monitors locomotive health by monitoring visual displays,
listening to the sounds made by the locomotive and on-board equipment,
and attends to kinesthetic cues (i.e., vibrations). Outside the cab, the
engineer looks for hazards, monitors wayside signals, landmarks, and
other visual cues needed to anticipate future train movements. The
skills and knowledge needed to operate a train are built up over time as
the engineer learns how to control the train and learns the physical
attributes of the territory over which he will operate. Likewise, the
engineer learns how to effectively allocate his attention between events
inside and outside the cab so that the train operates safely and
efficiently.

How do the locomotive engineer\'s attention allocation strategies change
when supervisory train control technology is introduced? What are the
safety implications of these changes? For example, a key issue in
supervisory control is whether the operator can detect train control
failure and take over safe operation of the train. In relying on
supervisory control, the engineer's ability to intervene promptly in
case of an unexpected event can deteriorate (Huey and Wickens, 1993).
How does supervisory control affect the engineer's ability to detect
unexpected events? What happens when equipment unrelated to the train
control system fails? Detecting a train control failure itself may also
be a challenge for the operator. This study will address these questions
using two paradigms: vigilance and situation awareness. Both concepts
can be used to examine how shifts in attention affect human performance.

Vigilance refers to the capacity of the human operator to sustain
attention and remain alert to stimuli over a prolonged time. The most
significant aspect of the vigilance decrement is that it arises from
searching for a relatively infrequent signal over a prolonged period
(Dember and Warm, 1979).

Very few vigilance studies have been performed with a very low target
rate on the order of one target per 30 minutes (Molloy and Parasuraman,
1996; Loeb and Binford, 1970). Lanzilotta (1995) examined the effects of
supervisory train control on vigilance in a locomotive simulator and
found that operators show more variability in detecting train control
failures with partial supervisory control than full supervisory control.
He concluded that with partial supervisory control, observers exhibited
a greater tendency to attend to events outside the locomotive cab than
with full supervisory control. However, in this study the number of
failures on each trip (6) may have affected the detection performance of
the participant. What would happen in a system in which the number of
failures was smaller? The current study examined this question measuring
participant's ability to detect a small number of failure events.
Instead of six events per trip found in Lanzilotta\'s study,
participants were exposed to only two events per trip.

Situation awareness (SA) is a broader concept than vigilance. Endsley
(1993) defines SA as

> "*the perception of the elements of the environment within a volume of
> time and space, the comprehension of their meaning and the projection
> of their status in the near future.*"

In locomotives with supervisory train control, the engineer can become a
passive processor of information. The engineer needs to know what the
train control is doing as well as what the other components are doing.
However, feedback in train control systems can be inadequate. This loss
of information can make it difficult to detect train control failures
and intervene when failures occur.

In Lanzilotta\'s study examining the effect of supervisory train control
on situation awareness, there was an inverse relationship between
situation awareness and the level of supervisory control. As the level
of supervisory control increased, situation awareness degraded.
Perceived situation awareness was highest in the condition where the
operator controlled the train manually and was lowest in the full
supervisory control condition. However, in this study, situation
awareness was measured by asking participants to rank the train control
modes by their perceived level of situation awareness. This subjective
measure may not give an accurate measure of situation awareness as the
response may be affected by the outcome of the experimental trials. An
objective method that compares an operator\'s knowledge of the system
while it is being operated with information about the actual state of
the system may give a more representative picture of the level of
situation awareness. The current study used such a method developed by
Endsley (1995b) to evaluate the level of situation awareness for
different kinds of train control.

Three control modes for the operation of the train were evaluated:
manual, partial supervisory, and full supervisory control. The three
control modes represent the range of control modes found in current
railroad operations. Under manual control, the human was solely
responsible for controlling the speed of train, while in partial
supervisory control the human operator set the desired speed (i.e.,
cruise control) and the train control system was responsible for
achieving and maintaining it. Operation of the vehicle under full
supervisory control normally required no human intervention, as the
train control system was programmed to respond to the appropriate
signals.

A laboratory experiment, using a human-in-the-loop locomotive simulator,
was conducted to examine the effects of three control modes on operator
attention. A series of events both inside and outside the locomotive
were presented to participants during the course of operating the train
and the ability to detect these events was measured. The participant\'s
task was to control the vehicle speed according to the signal and civil
speed limits indicated in each block, look out for potential hazards,
and respond to them in an appropriate manner. During the course of the
experiment, the simulation was interrupted and the participants were
questioned about their knowledge of the locomotive\'s health and its
track position.

To measure vigilance, two types of equipment failure and an obstruction
were introduced. The failures remained active for a set period, unless
detected and reset by the participant. If not reset by the participant
within the specified time interval, the failure was automatically reset.
The amount of time to complete a round trip (45 minutes) was broken down
into three equal time blocks and the detection rate was measured in each
block. The percentage of failures detected by the participants in each
time block was used as a measure of vigilance (Molloy and Parasuraman,
1996) inside the cab. Outside the cab, vigilance was measured by the
distance from the obstruction where the train stopped. To measure
situation awareness, Endsley\'s Situation Awareness Global Assessment
Technique (SAGAT) was used (1995b). In this method, the simulation was
paused and the displays were blanked at periodic intervals. The
participant was asked several questions about the status of the
locomotive\'s operating condition and its position on the track.

Overall, supervisory train control systems improved situation awareness
and vigilance performance compared to manual operation. However,
differences in the way the supervisory control systems operated
contributed to differences in attention allocation. These differences
were greatest for unexpected events such as equipment failures and
obstructions at highway-railroad grade crossings. A signal detection
analysis indicated that the supervisory control system influenced the
observer's response strategies, but not perceptual sensitivity in
detecting equipment failures. There were no differences in sensitivity
between the three control modes. By contrast, participants in the
partial supervisory control condition exhibited a tendency similar to
the manual control condition, to say in-cab failures did not occur,
while the participants in the full supervisory control condition
exhibited a slight preference to say an in-cab failure did occur.

While participants relied upon the system for routine speed control
decisions, participant had to intervene when an event outside the scope
of the train control system (i.e., an obstruction on the track)
occurred. They responded by deactivating the supervisory control system
and taking over active control of the train. Although the participant
may have detected the obstruction as far away as in the manual mode,
making a decision about the proper amount of braking was delayed while
speed information was gathered. Compared to the manual control
condition, more time was required to understand the situation. This
finding is consistent with Wickens and Kessel's (1979) research showing
that observers were better at detecting a sudden change in system state
when manually controlling the system than when monitoring the system.

The challenge for developers of train control systems is learning how to
design the interface so the operator remains actively engaged in safety
critical tasks. Attention to activities directly related to train
movement is critical to safe operation. However, using technology in a
way that degrades the direct involvement of the operator with the system
can make it more difficult to detect and recover from errors (Huey and
Wickens, 1993). This degradation in safety critical aspects of their
performance was also reflected in the participant's response to
questions about workload and stress. Participants rated the full
supervisory condition as having the lowest workload, but the highest
stress. These comments indicated their discomfort with not being
actively engaged in a safety critical aspect of the train operation.

The partial supervisory control mode method for assisting with speed
control showed some similarity with the full supervisory control system
in its impact on attention allocation. Like the supervisory control
mode, this control mode resulted in participants monitoring events such
as bearing temperature, traction motor status, and block location better
than in the manual mode. It also showed an important difference from the
full supervisory control mode. Unlike the full supervisory control mode,
speed awareness performance was better in the partial supervisory
control mode than in the manual mode. The need to allocate more
attention resources to speed was attributed by the participants to their
difficulty in setting the desired speed.

The results of this experiment indicate that supervisory control systems
can impact operator performance in non-intuitive ways. The two types of
supervisory control in this study both controlled speed, but they
affected human performance differently. The complex relationship between
supervisory control systems and human performance, suggests the need for
human-in-the-loop testing to evaluate new train control systems for
their impact on human performance before they are implemented in revenue
service. Human-in-the-loop testing of supervisory control systems can
identify the likely human errors. Through an iterative design process
and training, some of these errors may be eliminated. For errors that
cannot be eliminated, designers can facilitate recovery by making
actions reversible and creating warnings to alert the operator when they
occur.

# 1. INTRODUCTION

The era of high-speed passenger rail service in the United States began
with the service on the Northeast Corridor. High-speed rail service
plays a central role in mass transportation systems in Europe and Japan.
Examples include the German Inter-City Express (ICE), the French Train à
Grand Vitesse (TGV), and the Japanese Shinkansen.

However, there are safety implications that arise from speed increases
that affect locomotive engineer performance. First, as train speeds
increase, the locomotive engineer has less time to acquire information
needed to operate the locomotive and respond. A study conducted in
France found that the maximum speed for accurate perception of wayside
signals was 137 mph (220 km/h) (Askey, 1995). Second, as speed
increases, the locomotive engineer has less time to slow or stop the
train and must decide to slow or stop the train earlier, due to the
increased stopping distance. As train speed increases beyond the
perceptual and cognitive limits of the locomotive engineer, the
locomotive cannot be safely operated without assistance.

Train control technology can provide this assistance to the engineer. In
high-speed rail operations, train control technology using decision
support aids, supervisory control, or some combination has been proposed
as a means to compensate for the sensory, perceptual, and cognitive
limitations of the locomotive engineer. The use of train control
technology can be divided into two approaches:

[Decision aids]{.underline}. Decision support aids provide information
to assist the engineer in train control. In such an approach, the
locomotive engineer makes decisions regarding vehicle operation and
actively controls the vehicle. Askey (1995) looked at the use of
different levels of decision aids to help the engineer in train control
operations. She found that decision aids improved safety by reducing
time needed to respond to emergency events and by reducing the need for
emergency braking.

[Supervisory control]{.underline}. In this approach, all necessary
information for vehicle operation is passed to the control system that
is responsible for operating the train according to prescribed rules.
The locomotive engineer's role shifts to that of a supervisor who
monitors the proper functioning of the control system.

The type of train control used in the current operational high-speed
rail systems (ICE, TGV, Shinkansen) varies by country. According to
Sheridan, Lanzilotta, and Askey (1994): *"*The German philosophy (ICE)
of rail development emphasizes supervisory control with use of the human
as a system monitor, while the French (TGV) and Japanese (Shinkansen)
depend more on the human for control decisions."

This study focused on the impact of supervisory control on locomotive
engineer performance. The successful application of supervisory control
in train operations requires understanding how it will affect the
engineers who interact with this technology. For example, locomotive
engineers may work long hours with inadequate amounts of rest between
shifts (Thomas, Raslear, and Kuehn, 1997). Trains cover large distances
and locomotive engineers must attend to tasks over prolonged periods. As
a result, operators can become less attentive over the course of their
shift. A supervisory control system could protect against the sleeping
driver, but could create new problems related to attention allocation.

Supervisory control may also change how the locomotive engineer
allocates his or her attention. The question is how do these changes
affect the operator\'s performance and what are the safety implications
of these changes? To operate the train, the engineer acquires
information inside and outside the cab. Inside the cab, the engineer
monitors locomotive health by monitoring visual displays, listening to
the sounds made by the locomotive and on-board equipment, and attends to
kinesthetic cues (i.e., vibrations). Outside the cab, the engineer looks
for hazards, monitors wayside signals, landmarks, and other visual cues
needed for anticipating future train movements. The skills and knowledge
needed to operate a train build up over time as engineers learn how to
control the train and the physical attributes of the territory over
which they operate. Likewise, engineers learn how to effectively
allocate attention between events inside and outside the cab so that the
train operates safely and efficiently.

How do the locomotive engineer\'s attention allocation strategies change
when supervising train control systems? What are the safety implications
of these changes? For example, a key issue in supervisory control is
whether the engineer can detect equipment failure and take over safe
control of the train. In relying on supervisory control, the engineer's
ability to intervene promptly in case of an unexpected event can
deteriorate (Huey and Wickens, 1993). How does supervisory control
affect the engineer's ability to detect unexpected events? This study
will address these questions using two paradigms: vigilance and
situation awareness. Both concepts can be used to examine how shifts in
attention affect human performance.

## Vigilance

Vigilance refers to the capacity of the human operator to sustain
attention and remain alert to stimuli over prolonged periods. Vigilance
studies originated during World War II when the Royal Air Force (RAF)
commissioned Norman H. Mackworth (1961) to study the radar observers'
decrement in detection rate of enemy submarines. He discovered that a
vigilance decrement occurred after only 30 minutes. The most significant
aspect of the vigilance decrement was that it arose from searching for a
relatively infrequent signal over a prolonged period of time (Dember and
Warm, 1979).

While vigilance has been studied extensively in the context of
laboratory tasks, relatively few studies have been performed in
environments that closely simulate actual work settings, the main reason
being the difficulty of applying signal detection theory. An important
question is the extent to which data from laboratory tasks can be
extrapolated to operational tasks because of the event rate used. For
the majority of vigilance studies, a target rate of 1 target per minute
is considered low. However, in an operational setting, "events" that
need to be distinguished and acted upon, such as failures, occur much
less frequently. Few studies have been performed with a very low target
rate on the order of 1 target per 30 minutes (Molloy and Parasuraman,
1996; Loeb and Binford, 1970). Lanzilotta (1995) examined the effects of
supervisory control on vigilance in a human-in-the-loop locomotive
simulator and found that operators showed more variability in detecting
equipment failures with partial supervisory control than full
supervisory control. He concluded that with the partial supervisory
control, observers exhibited a greater tendency to attend to events
outside the locomotive cab than with full supervisory control. However,
in this study the number of failures on each 45-minute trip (6) may have
affected the participant's detection performance (1 failure per
7.3-minute period). What would happen in a system in which the number of
failures was smaller? The current study examined this question using a
small number of failure events. Instead of 6 events per 45-minute trip
found in Lanzilotta\'s study, participants were exposed to only 2 events
per 45-minute trip (1 failure per 22.5-minute period).

## Situation Awareness

Situation awareness (SA) is a broader concept than vigilance. Endsley
(1993) defines SA as

> "*the perception of the elements of the environment within a volume of
> time and space, the comprehension of their meaning and the projection
> of their status in the near future*."

For the locomotive engineer, situation awareness represents the
operator\'s mental model of the state of the system. Endsley proposed
that this mental model could exist at several levels. First, the
engineer must perceive the system status. Second, the perceived
information must be integrated and compared to the operational goals of
the system to provide comprehension. Third, the operator uses
understanding of the system to predict future events and enabling
proactive behavior. In locomotives with supervisory control systems, the
engineer can become a passive processor of information. The engineer
needs to understand what the train control system is doing. However,
feedback in supervisory control systems is frequently inadequate. This
loss of information can make it difficult to detect control failures and
take over control when failures occur.

In Lanzilotta\'s study examining the effect of supervisory train control
on situation awareness, there was an inverse relationship between
situation awareness and the amount of supervisory control. As the level
of supervisory control increased, situation awareness degraded.
Perceived situation awareness was highest in the condition where the
operator controlled the train manually and was lowest in the full
supervisory control condition. However, in that study, situation
awareness was measured by asking participants to rank the supervisory
control modes by their perceived level of situation awareness. This
subjective measure may not give an accurate measure of situation
awareness as the response may be affected by the outcome of the
experimental trials.

An objective method, that compares an operator\'s knowledge of the
system while it is being operated with information about the actual
state of the system, may give a more representative picture of situation
awareness. The current study used such a method developed by Endsley
(1995b) to evaluate the level of situation awareness for different
levels of supervisory train control.

Endsley\'s (1995b) method is called Situation Awareness Global
Assessment Technique (SAGAT). In this method, participants answer
questions about their current perceptions of the situation at randomly
selected times during the simulation. The simulation is suspended and
the displays are blanked while the participant answers questions. After
the simulation has ended, answers to the experimenter\'s questions are
compared to the real situation as measured by the computer simulation to
provide an objective measure of situation awareness.

To summarize, the purpose of the current research was to determine the
implications of supervisory train control in high-speed train operations
with regard to vigilance monitoring and situation awareness. Using a
human-in-the-loop locomotive simulator, train control failures were
introduced to learn how quickly operators could detect the failures when
the number of events requiring action by the operators was very low for
different levels of supervisory control. Situation awareness
measurements were collected during the simulation, using the SAGAT
developed by Endsley.

Three train control modes were evaluated: manual, partial, and full
supervisory control. Under manual control, the operator actively
controlled the train. Under partial supervisory control, the human
operator set the desired speed (i.e., cruise control) and the train
control system was responsible for achieving and maintaining it. Under
full supervisory control, no human intervention was required as the
train control system was programmed to adjust train speed in response to
the appropriate signals and civil speed limits.

# 2. METHOD

## Overview

A laboratory experiment, using a human-in-the-loop locomotive simulator,
was conducted to examine the effects of three train control modes on
operator attention. Specifically, the experiment examined the effects of
train control in the situation where action by the engineer was not
required for a long period (low event rate). As part of this study, two
levels of supervisory train control (full supervisory control, partial
supervisory control), and manual control operation were evaluated for
their effects on vigilance and situation awareness. A series of events
inside and outside the locomotive were presented to participants while
operating the train and the ability to detect these events was measured.

To measure vigilance, two types of train control failure and an
obstruction were introduced. The failures remained active for a set
period, unless detected and reset by the participant. If not reset by
the participant within the specified time interval, the failure was
automatically reset. The time to complete a round trip (45 minutes) was
broken down into three 15-minute blocks and the detection rate was
measured in each block. The percentage of failures detected by the
participants in each time block was used as a measure of vigilance
(Molloy and Parasuraman, 1996) inside the cab. Outside the cab,
vigilance was measured by the distance from the obstruction where the
train stopped.

To measure situation awareness, Endsley\'s Situation Awareness Global
Assessment Technique was used (1995b). In this method, the simulation
was paused and the displays were blanked at periodic intervals. The
participant was asked several questions about the status of the
locomotive\'s operating condition and its position on the track.

## Experimental Design

The independent variable was train control mode. There were two types of
supervisory control and one type of manual control as shown in Table 1.
All participants were exposed to all train control conditions.

  -----------------------------------------------------------------------
  []{#__RefHeading___Toc10427057 .anchor}Table 1. Train Control Condition

  Type of Train Control

  Full Supervisory

  Partial Supervisory

  Manual
  -----------------------------------------------------------------------

To counterbalance possible learning effects across participants, each
participant was introduced to the control modes in the order shown in
Table 2. To encourage the participant to perform according to the
objectives of the experiment, an incentive system was implemented.
Points were awarded or taken away according to the bonus and penalty
schedule described in Appendix A. Points were converted to monetary
rewards at a rate of one dollar per 1000 points.

  -------------------------------- ------------------- ------------------- -------------------
  []{#__RefHeading___Toc10427058                                           
  .anchor}Table 2. Presentation                                            
  Order of Train Control Modes                                             

  Participant                      Presentation order                      

                                   1                   2                   3

  1                                Full Supervisory    Manual              Partial Supervisory

  2                                Full Supervisory    Partial Supervisory Manual

  3                                Manual              Partial Supervisory Full Supervisory

  4                                Manual              Full Supervisory    Partial Supervisory

  5                                Partial Supervisory Full Supervisory    Manual

  6                                Partial Supervisory Manual              Partial Supervisory
  -------------------------------- ------------------- ------------------- -------------------

### Failure Detection

To assess vigilance performance inside the cab, two types of equipment
failures were introduced. Appendix C shows the track position where the
failures occurred.

[Motor failure]{.underline}. Under normal operating conditions, electric
current flowed through each of four motors when thrust was applied. The
ammeters gauge displayed the amount of current flowing through each
motor. A motor failure occurred when current failed to flow through one
of the motors, indicated on the ammeter gauge. If the participant
detected a motor failure, the participant was instructed to remove power
from all the motors by pulling the control lever back to the braking
position, press the appropriate key for resetting the failure, and
resume operation. A motor failure lasted 12 seconds unless reset by the
participant. If the participant failed to reset the motor failure within
that time, the system was automatically reset.

[Bearing failure]{.underline}. In principle, bearing temperature
normally follows the speed of the train with some time lag, but never
rises above a threshold (131^o^ F) for safety reasons. In practice, the
bearing temperature fluctuated around a mean value, depending on the
average speed of the vehicle. When a bearing failed, the temperature
increased at a rate almost double the maximum rate regardless of the
train's speed. Detecting a bearing failure required the participant to
observe this abnormal temperature change. The participant was instructed
to press a reset key to correct the bearing failure. The bearing failure
lasted 20 seconds unless reset by the participant. If the participant
failed to reset the bearing failure within that time, it was reset
automatically.

Within each combination of control mode and time block nine equipment
failures occurred. With nine combinations of control mode and time
block, 81 equipment failures occurred. Appendix D shows the responses
made to the equipment failures and obstructions for each participant.
The average number of failures (motor or bearing) for a round trip was
two, one for each type of failure.

Bonus points were awarded for detecting and resetting the failures.
Penalty points were given for pressing the reset key when no failure
existed. The incentive system is described in Appendix A.

### Obstruction Detection

There were five grade crossings in this experiment. At each grade
crossing, highway motor vehicles could cross in front of the train from
either direction. These motor vehicles were visible at over 0.3 miles
(0.5 km) from the train. Each block containing grade crossings had a
civil speed limit of 62-mph (100 km/hr). Traffic at the grade crossings
arrived according to a probabilistic process. A car would proceed across
the crossing only if there was sufficient distance to clear the crossing
before the train arrived. However, it was possible for a car to become
disabled as it was crossing the tracks, which would obstruct the track.
The participant was instructed to bring the train to a complete stop
before the intersection if a disabled motor vehicle was detected. If the
participant could not avoid a collision, a crack appeared on the
locomotive cab window. The crack remained on the window for the
remainder of the trip.

It was important for the participant to quickly determine whether the
train should stop or proceed. The participant had to balance the
consequences of a collision with the costs of schedule delays due to
braking the train. It was up to the participant to evaluate the
situation and determine the best course of action. This type of
emergency was used to assess the effects of train control in attending
to events outside the locomotive.

If the participant collided with an obstruction, the participant was
instructed to stop the train and notify the dispatcher. The participant
then continued on the trip. The cracked window remained displayed for
the remainder of the trip. The participant was awarded points for
detecting and avoiding the hazard according the schedule shown in
Appendix A.

### Situation Awareness

Situation awareness was measured using a technique developed by Endsley
(1995b), whereby the simulation was temporarily paused while the
experimenter asked the participant questions about the state of the
train and its position. While the simulation was paused, the
out-the-window view and instrument panel appeared blank. The train
remained in the same position until the question and answer session was
completed. The participant then resumed operating the train at the same
speed and position at which the simulation was paused. The experimenter
asked the participant to give answers about the train\'s position with
respect to block number, milepost, train speed, and bearing temperature.

$\text{MAE} = \sum_{i = 1}^{n}\frac{|x - \hat{x}|}{n}$Two measures were
used to assess situation awareness: percent of correctly answered
questions or Mean Absolute Error (*MAE*). *MAE* is a measure of
deviation between the participant's response and the actual state of the
variable. It was defined as:

where *x* was the participant\'s response, $\hat{x}$ was the actual
value and *n* was the number of participants. Speed and bearing
temperature were calculated using MAE. For motor current, block number
and milepost answers were classified either as correct or wrong and
reported as a percent of the correct answers.

## Participants

Fifteen people participated in the experiment. Twelve participants were
undergraduate or graduate students at the Massachusetts Institute of
Technology (MIT). The remaining three participants were people who
responded to notices placed on the MIT campus requesting participation
in the experiment. Two students participated in a pilot study for
fine-tuning the experiment, while the remaining 13 participated in the
actual experimental trials. Data from one participant was thrown out
after inspection showed that he repeatedly failed to comply with speed
limits. Each participant was paid \$10 per hour.

## Facilities: High-Speed Locomotive Simulator

The High-Speed Locomotive Simulator was a real-time human-in-the-loop
locomotive simulator developed to conduct human factors research in
high-speed rail operations. The computer hardware consisted of two
Silicon Graphics (SGI) personal Iris Workstations, one SGI Indigo-2
workstation, an IBM compatible 486 computer, a Barco projector, and
projection screen. The participant sat in the cab where the controls and
instrument displays were located. Figure 1 shows the layout. The
out-the-window view was displayed on a wall-mounted projection screen in
front of the cab.

The operator controlled the locomotive's speed with a lever that
combined both throttle and brake functions. When the control lever was
in the center (vertical) position, the train control was in neutral.
Pushing the control lever forward away from the operator accelerated the
train; pulling the lever toward the operator decelerated the train. The
operator had push buttons to the left and right of the instrument
display for controlling the emergency brake, alerter, bell, horn, and
traction motors. The SGI Indigo-II workstation generated the
out-the-window view as well as computing the vehicle dynamics that
enable the operator to control the train. One personal Iris displayed
the instrument panel shown in Figure 2, while the other personal Iris
served as the dispatcher workstation. All three machines communicated
with each other over a Local Area Network (LAN). Appendix B describes
the features added to the locomotive simulator for this experiment.

![](media/image8.png){width="5.048611111111111in"
height="4.039583333333334in"}

The simulator exhibited three control modes: manual control, partial
supervisory control, and full supervisory control. In manual control,
the operator was solely responsible for controlling the speed and the
position of the vehicle using the combined control lever. The partial
supervisory control system was designed to maintain a constant speed set
by the operator. When operating the train in partial supervisory control
mode, the operator set the desired speed. In this mode, the train
control applied the proper amount of thrust to achieve and maintain the
set speed. Partial supervisory control did not affect braking, so the
operator had to apply the brakes manually when needed. In full
supervisory control, speed control of the vehicle was exclusively
assumed by the train control system, which was responsible for setting
the speed in accordance to the speed limits of each block. Speed control
included application of both the throttle and brakes. In both the full
and partial supervisory control modes, manual application of the brakes
by the operator disengaged the supervisory control system. The full
supervisory control system controlled the speed of the vehicle without
human intervention.

The territory in the experiment was comprised of two fictional stations,
named East Station and West Station and a single track between the two
stations, as shown in Figure 3. Thirty-one miles (50 km) of single track
separated the two stations. Loops at the end of each station were used
to reverse the vehicle's direction on the main track. One-way travel
time from station to station was approximately 20 minutes. Travel time
around the loops was almost 5 minutes. Hence, the round trip lasted
roughly 45 minutes.

The current simulation used block signaling to communicate permission to
occupy the track and speed limits. With block signaling, the track was
divided into sections. In the current simulation, all blocks between
stations were 1.24 miles (2 km), and all blocks in the loop sections
were 0.62 miles (1 km) in length. A color-coded signal was located at
each block boundary. This signal indicated the maximum speed permitted
through the block ahead. It was the responsibility of the operator to
identify the signal and modify the train speed accordingly. Normally,
only one train can occupy a block at any given time. A red signal
indicated that another train currently occupied the block. An
approaching train was not permitted to enter that block. As trains
approached a block occupied by another train, the signals for each block
became increasingly restrictive. This system was designed to prevent
collisions between trains by slowing the approaching train in time to
stop before entering the occupied block.

In addition to the speed limits imposed by the block signal system,
there were also civil speed limits. These speed limits were dictated by
specific right-of-way characteristics or track geometry. In the current
simulation, the civil speed limits varied depending upon whether the
block contained a grade crossing. Blocks with grade crossings had lower
civil speed limits than blocks without them. In all cases, the
prevailing speed limit was the lesser of the block signal limit and the
civil speed limit.

## Procedures

### Training 

Due to the complexity of the task and to familiarize the participants
with train operations, each participant was given a written tutorial to
read prior to their participation in the experiment. The tutorial
covered general operating rules that govern railroad operations, how to
operate the locomotive simulator, and described the experimental task.

Upon arriving for the experiment, the participant filled out a consent
form and completed a multiple-choice test. The test served as a tool to
assess their understanding of the material in the tutorial and as a
participant selection tool. The test took approximately 10 minutes.
Participants scoring correctly on 50 percent or better proceeded to the
training phase of the study. All participants achieved this criterion.
The experimenter used the test results to identify potential problems
with the material that needed to be clarified during the training
sessions that followed.

The training session lasted three hours and gave hands-on exposure to
the system. During the first hour, the experimenter demonstrated the
proper train operation. Next, the experimenter familiarized the
participant with the emergency scenarios and the appropriate responses.
The remaining two hours were devoted to practice operating the
locomotive simulator with and without the failure scenarios to become
acquainted with the train control system and its operating modes. During
this period, the participant completed a run from station to station
using one control mode. During the practice runs, the experimenter was
physically present in the cab and monitored how the participants
controlled the locomotive. The experimenter recommended proper actions
under each control mode. The experimenter also gave the participant
suggestions regarding speed compliance. These practice runs lasted about
one hour and a half. During the final half-hour of training, the
participant completed a run from station to station with the opportunity
to experiment with the simulator in any control mode. During this run,
the experimenter split his time between the cab and the dispatcher
workstation. Additionally, the experimenter suspended the simulation
three to four times to familiarize the participants with the
interruptions of the simulation that would take place during the
experiment to assess situation awareness.

After the training session ended, the experimenter gave the participant
a short break and asked whether he or she felt ready to begin the
experiment or wanted additional practice operating the train. The
participant either requested additional practice trips or proceeded to
the experimental trials.

### Experimental Task

The participant\'s task was to control the vehicle speed according to
the signal and civil speed limits indicated in each block, look out for
potential hazards and respond to them in an appropriate manner.

The participant operated the simulated locomotive from West Station to
East Station as shown in Figure 3 and back (one trip), using one
particular control mode. At the end of a round trip, the participant was
given a brief rest and then began another round trip under a different
control mode. Each participant completed three round trips, one for each
control mode. Each trip lasted about 45 minutes. Between trips, the
participant rested for 10 minutes or longer before proceeding to the
next trial. Following completion of the three trips, the participant
answered questions regarding their preferences and the workload and
stress imposed by the three control modes.

# 3. RESULTS AND DISCUSSION

## Vigilance

Signal detection theory was used to measure the participant's ability to
detect equipment failures. In signal detection theory, detection is a
function of two processes: the observer's perceptual sensitivity and
response bias. This theory enables separation of the effects of
perceptual sensitivity, in this case, the observer's ability to detect
equipment failures, from response bias. Response bias represents the
observer's tendency to favor one response over another (MacMillan and
Creelman, 1991) (i.e., willingness to say "yes" or "no").

In signal detection theory, events can be categorized in a 2 x 2 matrix
showing the relationship between the state of the world and the
observer's response to that state. Figure 4 shows the four possible
categories. A hit occurs when a signal is present and the observer
reports that the signal is present. A false alarm occurs when a signal
is absent and the observer reports that the signal is present. A miss
occurs when a signal is present and the observer reports that the signal
is absent. A correct rejection occurs when a signal is absent and the
observer reports that the signal is absent.

  --------------------------------- --------- ---------------------- ----------------------
                                              State of the World     

                                              Signal                 Noise

  Observer's Response               Yes       Hit                    False\
                                                                     alarm

                                    No        Miss                   Correct rejection

  []{#__RefHeading___Toc108333856                                    
  .anchor}Figure 4. Four Outcomes                                    
  of Signal Detection Theory                                         
  --------------------------------- --------- ---------------------- ----------------------

Figure 5 shows how signal detection theory characterizes the
relationship between the observer's responses for two hypothetical
distributions. The distribution on the right represents the probability
that a signal (i.e., an equipment failure) was present. The distribution
on the left represents a probability that noise (i.e., equipment
functioned properly) was present. The observer's ability to detect
equipment failure (sensitivity) is reflected by the amount of overlap in
the two distributions. Sensitivity increases as the amount of overlap in
the two distribution decreases. Response bias is represented by the
vertical line showing the response criterion. When the value of the
event is to the right of the criterion, the observer will say "yes."
When the value of the event is to the left of the criterion, the
observer will say "no." The response criterion is neutral (zero) when
the false alarm rate and miss rate are equal. Moving the criterion to
the left increases the likelihood that the observer will say "yes,"
while moving the criterion to the right increases the likelihood that
the observer will say "no." Numerically, a positive bias represents the
tendency to say no, while a negative bias represents the tendency to say
yes.

Sensitivity is typically measured numerically by an index called d prime
and response bias is typically measured numerically by an index called
beta (β). D prime (d\') corresponds to the separation of the mean of two
distributions expressed in units of their standard deviations as shown
in Figure 5. The response bias, was measured by the ratio of the
probability of saying "yes" when the signal is present to the
probability of saying "yes" when only noise is present. For the reader
interested in learning more about signal detection theory, refer to
books by Green and Swets (1988), Egan (1975), or MacMillan and Creelman
(1991).

In this experiment, an alternative measure of sensitivity and response
bias was used. D prime and beta cannot be calculated if either hits or
false alarms equal zero or 100 percent, as was the case for several
conditions. Therefore, nonparametric measures were used to measure
sensitivity and response bias. A prime (A\') was used (Grier, 1971) to
measure sensitivity and B double prime (B\'\') was used to measure
response bias. A\' measures the area under curve for the measured data
point and numerically corresponds to the ratio of hits to false alarms
for a given event state. For A prime, values ranged between zero and
one. For B double prime, values ranged between minus one and plus one.

To evaluate participants' ability to detect equipment failures, the
number of hits and false alarms were recorded. The results for the train
equipment failures are summarized in tabular form in Table 3 and
graphically in Figure 6. Figure 6 shows the percentage of correctly
detected signals (for both motor and bearing failures) in each time
block for by control mode. In detecting the train equipment failures,
evidence of a statistically significant vigilance decrement is present
for all three control modes.[^1] For all three conditions, detection of
equipment failure declined over time. Detection of the equipment
failures under the full supervisory mode was consistently higher than
for the other two control modes across all time blocks. Detection
performance was the worst in the partial supervisory mode, with the
manual control mode falling between the two supervisory control modes.
The difference in detection performance between the modes was not
statistically significant. However, Lanzilotta (1995) found the same
pattern in his study. The lack of statistical significance may be due to
the small size of the effect and the small number of data points on
which the statistical test was based.

![](media/image11.wmf){width="4.366666666666666in"
height="2.8652777777777776in"}

  -------------------------------- ------------ ----------------- ------------ ------------
  []{#__RefHeading___Toc10427059                                               
  .anchor}Table 3. Detection of                                                
  In-Cab Equipment Failures by                                                 
  Control Mode                                                                 

                                   Time block 1 Time block 2      Time block 3 Control Mode
                                                                               Total

                                   Hits                                        

  Full Supervisory                 8            7                 7            22

  Partial Supervisory              6            6                 6            18

  Manual                           8            7                 6            21

  Time Block Total                 22           20                19           61

                                   False Alarms                                

  Full Supervisory                 3            3                 0            6

  Partial Supervisory              2            1                 0            3

  Manual                           0            2                 0            2

  Time Block Total                 5            6                 0            11
  -------------------------------- ------------ ----------------- ------------ ------------

False alarms decreased over time for the two supervisory control
conditions. By contrast, in the manual control condition, false alarms
exhibited an inverted u-shaped function, where the number of false
alarms went from zero to two and back to zero.

As shown in Figure 7, the two distributions can also be characterized by
the relationship between the probability of hits and false alarms. The
vertical axis shows the probability of hits and the horizontal axis
shows the probability of false alarms. Sensitivity increases as points
on the curve move from the lower right-hand corner to the upper
left-hand corner of the chart. Response bias changes from positive to
negative as the data points move from the lower left-hand corner to the
upper right-hand corner.

When the detection rate and false alarms were examined together, the
results show declines in the number of hits and in the number of false
alarms over time. This observation suggests that participants changed
their response bias over time. For both control mode and time block,
sensitivity appeared to change little. Changes in sensitivity are
reflected in this chart by differences in the position of the data
points along the minor diagonal line.

The impact of control mode and time on detecting equipment failures can
be more easily seen by separating the effects of sensitivity and
response bias. Figure 8 shows the impact of sensitivity and response
bias separately by control mode and time sequence. The top graphs in
Figure 8 show the impact of time block and control mode on sensitivity.
There is little change in sensitivity across time block or control mode.
Sensitivity is relatively high across time and control mode. The
differences in sensitivity were not statistically significant.

By contrast, differences were observed for effect of time block and
control mode on response bias. The bottom two graphs in Figure 8 show
the impact of time block and control mode on response bias. For time
block, the response is similar for the first two time blocks. Here the
response criterion is neutral with a B\'\' value close to zero. However,
for the third time block, the response criterion is highly positive,
with a B\'\' at 1.0. These differences were statistically significant
(B\'\'=1.0 comparing time block 1 to time block 3, confidence level
~0.95~ =0.47; B\'\'=0.96 comparing time block 2 to time block 3,
confidence level ~0.95~ = 0.45). Thus, participants shifted their
response criterion over time so they were highly likely to say, "no, an
equipment failure was not present." This is consistent with past
research in the vigilance decrement literature (Getty, Swets, Pickett,
and Gonthier, 1995). The observers moved their response criterion (i.e.,
response bias) as time elapsed so that there were fewer false alarms and
fewer hits to reflect the actual probability with which those events
were likely to occur.

[]{#__RefHeading___Toc108333860
.anchor}![](media/image16.wmf){width="3.3181102362204724in"
height="2.849212598425197in"}![](media/image17.wmf){width="3.338976377952756in"
height="2.8598425196850394in"}![](media/image18.wmf){width="3.3283464566929135in"
height="2.87007874015748in"}![](media/image19.wmf){width="3.30748031496063in"
height="2.849212598425197in"}Figure 8. Sensitivity and Response
Criterion by Time Block and Control Mode

Response criterion differences were also observed between the three
control modes. In the full supervisory mode, participants exhibited
slightly negative response criterion, meaning that participants were
slightly more likely to say, "yes, an equipment failure occurred" than
"no." By contrast, for both the partial supervisory mode and manual
control mode, response criterion was positive. Participants were more
likely to say, "No, an equipment failure did not occur" or miss
reporting an equipment failure when it did occur. The response bias
differences between the full supervisory control mode and the two other
modes were not statistically significant at the 95 percent confidence
level. The response criterion difference between the full supervisory
mode and the manual mode was statistically significant at the 90 percent
confidence level. The lack of statistical significance at the 95 percent
confidence level may have been due to the small sample size (27 data
points per condition). The response criterion differences between the
partial control mode and the manual mode were not statistically
significant. This behavior suggests that observers would be less likely
to miss equipment failures when operating full supervisory train control
systems than partial or manual train control systems.

Vigilance monitoring out-the-window between the three control modes
differed from the vigilance monitoring associated with the in-cab
displays. Figure 9 shows the distance from the obstruction that the
vehicle stopped for the three train control modes. Upon detecting an
obstruction, all participants made a full service brake application.
Next, the participants decided if and when to apply the emergency
brakes. In every case but one, participants applied the emergency brakes
to avoid a collision.

Participants stopped farthest from the obstruction in the manual control
condition followed by the partial supervisory control condition and the
full supervisory condition. The differences between the manual mode and
both supervisory modes were statistically significant. Using the t-test,
the t value for the comparison between manual mode and full supervisory
control was t ~(18)~ = 2.037, p \< 0.05.[^2] For the comparison between
manual mode and partial supervisory control, the t value was t ~(18)~ =
1.901, p \< 0.05. The difference in stopping distance between the two
supervisory control modes was not statistically significant.

## Situation Awareness

During the experimental trials, the simulation was suspended and each
participant was asked to report the following items: speed, block
number, milepost, brake pressure, bearing temperature and current
through the motors. Because the brake pressure was stable over time,
there was little deviation in the brake pressure gauges. As a result,
there were no reported significant deviations from the actual brake
pressure.

The results for the remaining situation awareness measures are presented
in Figure 10, Figure 11, and Figure 12. Figure 10 shows the relationship
between train control mode and speed situation awareness. Figure 11
shows the relationship between train control mode and bearing
temperature situation awareness. Figure 12 shows the relationship
between train control mode and situation awareness with respect to train
position and motor status.

For speed awareness, the MAE was lowest in the partial supervisory
control mode, followed by the manual control mode and the full
supervisory control mode, respectively. A smaller error indicated better
situation awareness. These differences were statistically
significant.[^3]

Speed awareness was the only measure for which participants performed
best in the partial supervisory control mode. However, as Table 4 shows,
none of the participants preferred this hybrid control mode. Comments
from the participants suggest that the operational implementation of the
partial supervisory control mode affected the participants\' attention
allocation strategies. Many participants complained of difficulty
setting the train controls. In the supervisory control mode,
participants set the speed using the keyboard function keys while using
the control lever to brake or accelerate manually. As a result, they
paid more attention to the speedometer, compared to the other control
modes to make sure that the train control was achieving the set speed.
The difficulty setting the speed control may have contributed to the
lower detection rate for in-cab equipment failures compared to the other
modes and the higher situation awareness scores for train speed.

In the full supervisory control mode, participants reported less time
monitoring speed than in the other modes, while spending more time
attending to other visual displays in the locomotive. To quote one
participant:

> "*The full supervisory mode imposed the least workload since I could
> keep an eye on what was happening, yet I didn't have to worry as much
> about watching the speed. I had to check to make sure that train
> control system was following the speed limits, but I didn't actually
> have to adjust the speed myself. So I could spend my time
> systematically checking all the information.*"

Participants spent less time monitoring train speed, since the
supervisory control system controlled both acceleration and braking and
focused more attention elsewhere.

For all other measures of situation awareness (temperature, position,
and traction motor awareness), a different pattern emerged from that
found with speed awareness. The best performance was observed in the
full supervisory control mode, followed by the partial supervisory
control mode and manual control mode showing the poorest situation
awareness. For temperature, the MAE was lowest for the full supervisory
control followed by the partial supervisory control mode and the manual
control mode, respectively. This difference was statistically
significant.[^4] This supports many of the participants\' comments that
they spent more time monitoring other displays inside the cab compared
to the speedometer in the full supervisory control mode.

For train position (as indicated by block number and milepost) and motor
status, participants gave the highest percentage of correct answers in
the full supervisory control mode.

By contrast, in the manual control mode, block position and motor status
awareness were lower than the two supervisory control modes. For
milepost, situation awareness was equal between the manual control mode
and the partial supervisory control mode.

At the conclusion of the experiment, participants were asked to indicate
which control mode created the lowest workload and highest stress level.
Participants were also asked to indicate their preferred control mode.
The results are shown in Table 4. For workload, participants felt the
full supervisory control mode imposed the lowest workload. For the two
remaining modes, participants felt the partial supervisory control mode
imposed greater workload than the manual control mode. For stress level,
participants felt that both supervisory control modes imposed more
stress than the manual control mode. Of the two supervisory control
modes, full supervisory control was more stressful than the partial
supervisory control. A comment by one of the participants described how
the control mode affected their stress levels.

> "*I believe that the partial supervisory control and full supervisory
> control imposed the greatest amount of stress when an obstruction was
> detected because after setting the speed, I would remove my hands from
> the control and begin to focus on other potential problems and
> information that I had to know. When an obstruction occurred, I had to
> jump from passively driving to actively driving and grab the controls
> in order to slow down.*"

This comment reflects the challenge required in transitioning between
train control modes. Responding to an obstruction on the track in a
supervisory mode required the participant to transition from a passive
monitor of train speed to an active controller of train speed. Once the
obstruction was detected, the participant had a relatively short period
to determine what the train was doing and decide how to respond.

While the majority of participants felt full supervisory control imposed
the lowest workload, they preferred operating the train manually to full
supervisory control. Participants cited a feeling of control over the
vehicle along with active engagement in the task, as explanations. No
participant chose the partial supervisory control condition as the
preferred mode of operation. Participants who preferred the full
supervisory control mode cited the lower workload associated with this
condition.

  -------------------------------- -------------- -------------- --------------
  []{#__RefHeading___Toc10427060                                 
  .anchor}**Table 4. Participant                                 
  Preferences for Train Control                                  
  Mode from Exit Interview**                                     

                                   Train Control                 
                                   Mode                          

                                   Full           Partial        Manual

  Lowest Workload (%)              83             0              17

  Most Stressful (%)               75             25             0

  Preference (%)                   33             0              67
  -------------------------------- -------------- -------------- --------------

## Summary

Overall, supervisory train control systems improved situation awareness
and vigilance performance compared to manual operation. However,
differences in the way the supervisory control systems operated
contributed to differences in attention allocation. These differences
were greatest for unexpected events such as equipment failures and
obstructions at highway-railroad grade crossings. A signal detection
analysis indicated that the supervisory control system influenced the
observer's response strategies, but not perceptual sensitivity in
detecting equipment failures. There were no differences in sensitivity
between the three control modes. By contrast, participants in the
partial supervisory control condition exhibited a tendency similar to
the manual control condition, to say in-cab failures did not occur,
while the participants in the full supervisory control condition
exhibited a slight preference to say an in-cab failure did occur.

In the full supervisory control system, the system adjusted speed based
upon information from the in-cab signal system. If the speed limit
changed, the train control system made the adjustment without assistance
from the operator. This assistance enabled the participant to attend to
other tasks. Compared to manual operation, participants showed greater
situation awareness for non-speed-related events such as bearing
temperature, traction motor status, milepost, and block location.

However, participants showed greater difficulty with speed-related tasks
compared to the manual control mode. Participants exhibited the poorest
situation awareness for speed in the full supervisory control condition.
The implications of this behavior can be seen in obstruction detection.
Participants took longest to stop when an obstruction was present in
full supervisory control. Obstruction detection performance in the
partial supervisory control mode was similar to the full supervisory
control mode. While the participant relied upon the system for routine
speed control decisions, the participant had to intervene when an event
outside the scope of the train control system (i.e., an obstruction on
the track) occurred. The participant responded by deactivating the
supervisory control system and taking over active control of the train.
Although the participant may have detected the obstruction as early or
earlier than in the manual mode, making a decision about the proper
amount of braking was delayed while speed information was gathered.
Compared to the manual control condition, more time was required to
understand the situation. Where supervisory control systems are provided
to enable train control operations that could not take place safely
without them (i.e., high-speed operation), the likelihood for the
locomotive engineer to successfully intervene when the train control
system encounters an event it is not prepared to handle, will decrease.
This finding is consistent with Wickens and Kessel's (1979) research
showing that observers were better at detecting a sudden change in
system state when manually controlling the system than when monitoring
the system.

The challenge for developers of train control systems is learning how to
design the interface so the operator remains actively engaged in safety
critical tasks. Attention to activities directly related to train
movement is critical to safe operation. However, using technology in a
way that degrades the direct involvement of the operator with the system
can make it more difficult to detect and recover from errors (Huey and
Wickens, 1993). This degradation in safety critical aspects of their
performance was also reflected in the participant's response to
questions about workload and stress. Participants rated the full
supervisory condition as having the lowest workload, but the highest
stress. These comments indicated their discomfort with not being
actively engaged in a safety critical aspect of the train operation.

The partial supervisory control mode method for assisting with speed
control showed some similarity with the full supervisory control system
in its impact on attention allocation. Like the supervisory control
mode, this control mode resulted in participants monitoring events such
as bearing temperature, traction motor status, and block location better
than in manual mode. It also showed an important difference from the
full supervisory control mode. Unlike the full supervisory control mode,
performance in the speed awareness was better in the partial supervisory
control mode than in the manual mode.

The participants attributed need to allocate more attention resources to
speed to their difficulty in setting the desired speed. The partial
supervisory control system in this study increased perceived workload
compared to the manual control mode and focused the participant's
attention more narrowly than the full supervisory control mode.
Participants attended more closely to the speed display compared to the
full supervisory control mode. This design may have prevented
participants from allocating their attention as broadly as in the full
supervisory mode and contributed to the vigilance decrement for
unexpected events like equipment failures. Additionally, greater speed
awareness failed to translate into better performance when it came time
to take over active control of the train when the train control system
was not equipped to handle the situation. Again, participants took
longer to stop in response to a track obstruction compared to manual
control.

The current study examined equipment failures that were unrelated to the
supervisory control system, itself. However, the problem of reliance may
be compounded if the supervisory control system, itself fails without
adequate warning to the operator. Stanton and Young (1998) discuss three
studies examining the use of adaptive cruise control in motor vehicles.
These studies evaluated the ability of motorists to detect and respond
to adaptive cruise control failures. When the adaptive cruise control
failed, drivers collided with moving or stationary vehicles more
frequently compared to manual operation. Expectations by the driver that
the cruise control technology would deal with this situation may have
contributed to this detection failure. In other words, the driver
trusted the system based upon experience showing reliable behavior. The
more reliable the control system appears to be, the more the operator
may depend on the control system. For highly reliable control systems,
failures may be very difficult to detect without an adequate warning.

The results of this experiment indicate that supervisory control systems
can impact operator performance in non-intuitive ways. The two types of
supervisory control in this study both controlled speed, but they
affected human performance differently. The complex relationship between
supervisory control systems and human performance, suggests the need for
human-in-the-loop testing to evaluate new train control systems for
their impact on human performance before they are implemented in revenue
service. Human-in-the-loop testing of supervisory control systems can
identify the likely human errors. Through an iterative design process
and training, some of these errors may be eliminated. For errors that
cannot be eliminated, designers can facilitate recovery by making
actions reversible and creating warnings to alert the operator when they
occur.

# BONUS AND PENALTY POINT SYSTEM {#bonus-and-penalty-point-system .Closing}

An incentive system was created to encourage participants to attend to
the schedule and failure events. For each participant, the points were
converted to money at the rate of one dollar for every 1000 points. A
participant with a negative score would receive no money beyond what all
participants were paid for participating in the study. Participants were
paid after completing the experiment. Bonus or penalty points were
awarded for the following behaviors:

-   Schedule accuracy,

-   Response to motor failure,

-   Response to bearing failure,

-   Response to brake failures,

-   Application of emergency brake,

-   Response to a grade crossing obstruction, and

-   Answers to situation awareness questions.

Figure A-1 shows the number of points awarded to the participant for
schedule accuracy. Completing the trip in less then 45 minutes results
the participant receiving (bonus) points. Completing the trip in more
than 45 minutes results in the participant losing points (penalty).
Figure A-2 summarizes the incentive system applied to motor and bearing
failures.

When a brake failure occurred, participants were given 800 points for
observing and resetting the brakes. Penalties were given for application
of the emergency brakes. Table A-1 shows the penalty schedule for brake
applications under different circumstances. In fact, penalties regarding
inappropriate application of the emergency brakes will result as shown
in Table A-1.

  --------------------------------------------- -------------------------
  []{#__RefHeading___Toc10427061                
  .anchor}**Table A‑1. Penalties Resulting from 
  Application of the Emergency Brakes**         

  Emergency Stop braking                        Penalties

  Triggered by ATP:                             -2000

  Triggered by the Alerter:                     -2000

  Triggered by the operator - collision         -100
  avoidance:                                    

  Triggered by the operator - no reason:        -300
  --------------------------------------------- -------------------------

For obstructions at grade crossings, bonus and penalty points were
assessed according to the schedule shown in Table A-2.

  ------------------------------------------------- ---------------------
  []{#__RefHeading___Toc10427062 .anchor}**Table    
  A‑2. Obstruction Hazards Bonus/Penalty Scheme**   

  Obstruction Outcome                               Bonus/Penalty

  Collision avoidance:                              +1000

  Collision Speed: \>=55.9 mph                      -1000

  Collision 43.5 mph \<= Speed \<= 90 mph           -800

  Collision 24.8 mph \<= Speed \<= 43.5 mph         -600

  Collision 6.2 mph \<= Speed \<= 24.8 mph          -450

  Collision Speed\<= 6.2 mph                        -250
  ------------------------------------------------- ---------------------

Participants were awarded 1000 bonus points for each correct answer to
the situation awareness questions. Participants received no points if
the answer was incorrect.

# NEW FEATURES OF HIGH-SPEED TRAIN SIMULATOR  {#new-features-of-high-speed-train-simulator .Closing}

For the purposes of the present research, several new features were
added to the train simulator. These features are described below:

-   [Suspend/resume capabilities in the train simulator]{.underline}.
    This feature is designed for gathering situation awareness data.
    This feature enables the experimenter to suspend the simulation and
    ask questions relevant to the state of the vehicle. Two versions
    were designed and implemented: in the version used in the
    experiment, the out-the-window view and dashboard displays were
    blanked. Only the communications window remains active so that the
    participant can communicate with the experimenter. In the other
    version, both screens are just frozen but not blanked. One can
    invoke the later version by using the -noblank flag in the command
    line argument when running the train simulation. In any case,
    provision has been made for the simulator to record everything
    pertaining to the state of the train as well as the participant's
    response. Additional provision was made to reset the simulation
    clock.

```{=html}
<!-- -->
```
-   [Enable the experimenter to activate/deactivate Automatic Train
    Protection from the CTC screen]{.underline}. This option can be
    invoked using the -atp flag when running the CTC simulation.

```{=html}
<!-- -->
```
-   [A new version of the autopilot]{.underline}. In the previous
    version of the simulator, the full supervisory control mode
    (autopilot), once invoked, would control the speed of the train
    adhering only to civil speed limits. When a signal was present the
    autopilot would fail to recognize it and the vehicle operator needed
    to assume manual control to adjust the vehicle speed. In the current
    version, the full supervisory control mode would recognize civil and
    signal speed limits simultaneously and adhere to the lesser of the
    two, thus replicating existing train supervisory control mode such
    as the one used in the German ICE high speed train. Under normal
    conditions, the operator need not interfere with speed control of
    the train but only monitor that the full supervisory control mode
    adheres to the speed limits of each block. This version of the full
    supervisory control mode can be realized using the -full_auto flag
    in the command line argument when running the train simulation.

```{=html}
<!-- -->
```
-   [A bearing failure]{.underline}. In this scenario, the temperature
    of a faulty bearing rises due to increased friction in its rollers.
    The rate at which the temperature goes up under failure conditions
    is higher than under normal conditions.

```{=html}
<!-- -->
```
-   [A failure reset mode to gather vigilance data]{.underline}. In
    older versions of the simulator, once the failures were set they
    remained active until the participant noticed them. In the current
    version, the software can reset the failures according to the time
    that elapsed or the distance that the train traveled since the onset
    of the failure, in the event that the participant has not been able
    to spot and reset them in time. This mode was selected using the
    -fail_reset option in the command line argument of the main
    simulation. The programmer must enter the keywords time followed by
    the time in milliseconds the failure will remain active, or distance
    followed by the distance that the vehicle will travel before the
    failure is reset in the failure input file.

# LOCATION OF FAILURE EVENTS {#location-of-failure-events .Closing}

The positions on the track at which failure events were set to occur are
shown below.

  --------------------------------------- --------------- ------- ---------------
  Distance from station (miles)           Direction       Time    
                                                          block   

  Motor Failure                                                   

  8.2                                     Eastbound       1^st^   

  25.2                                    Eastbound       2^nd^   

  19.0                                    Westbound       3^rd^   

  Bearing failure                                                 

  20.7                                    Eastbound       1^st^   

  1.9                                     Westbound       2^nd^   

  16.2                                    Westbound       3^rd^   

  Grading crossing                                                

  0.9                                     Eastbound               \-

  13.3                                    Eastbound               \-

  14.1                                    Eastbound               \-

  14.0                                    Westbound               \-

  16.5                                    Westbound               \-

  29.9                                    Westbound               \-
  --------------------------------------- --------------- ------- ---------------

# VIGILANCE DETECTION TASK DATA {#vigilance-detection-task-data .Closing}

+----------------+--------------+--------------+----------------------+
| Subject 1      |              |              |                      |
+----------------+--------------+--------------+----------------------+
| Control mode   | Task         | Response     | Reaction             |
+----------------+--------------+--------------+----------------------+
| Full           | m1           | hit          | 8.205 s              |
| Supervisory    |              |              |                      |
|                | b3           | miss         | \-                   |
|                |              |              |                      |
|                | o6           | No collision | Stop 299.27 ft       |
+----------------+--------------+--------------+----------------------+
| Partial        | m2           | hit          | 2.28 s               |
| Supervisory    |              |              |                      |
|                | b3           | hit          | 5.595 s              |
|                |              |              |                      |
|                | o5           | No collision | Stop 262.92 ft       |
+----------------+--------------+--------------+----------------------+
| Manual         | b1           | hit          | 8.22 s               |
|                |              |              |                      |
|                | b2           | hit          | 15 s                 |
|                |              |              |                      |
|                | m3           | hit          | 1.981 s              |
|                |              |              |                      |
|                | o4           | No collision | Stop 607.18 ft       |
+----------------+--------------+--------------+----------------------+

+---------------+--------------+--------------+-----------------------+
| Subject 2     |              |              |                       |
+---------------+--------------+--------------+-----------------------+
| Control mode  | Task         | Response     | Reaction              |
+---------------+--------------+--------------+-----------------------+
| Full          | b1           | hit          | 7.206 s               |
| Supervisory   |              |              |                       |
|               | b2           | hit          | 13.194 s              |
|               |              |              |                       |
|               | m3           | hit          | 3                     |
|               |              |              |                       |
|               | o1           | No collision | Stop 217.74 ft        |
+---------------+--------------+--------------+-----------------------+
| Partial       | b2           | miss         | \-                    |
| Supervisory   |              |              |                       |
|               | m3           | hit          | 3.1                   |
|               |              |              |                       |
|               | o3           | No collision | Stop 292.68 ft        |
+---------------+--------------+--------------+-----------------------+
| Manual        | m1           | hit          | 9.48                  |
|               |              |              |                       |
|               | b3           | miss         | \-                    |
|               |              |              |                       |
|               | o6           | No collision | Stop 261.15           |
+---------------+--------------+--------------+-----------------------+

+-----------------+--------------+--------------+-----------------------+
| Subject 3       |              |              |                       |
+-----------------+--------------+--------------+-----------------------+
| Control mode    | Task         | Response     | Reaction              |
+-----------------+--------------+--------------+-----------------------+
| Full            | b2           | hit          | 9.86 s                |
| Supervisory     |              |              |                       |
|                 | m3           | hit          | 8.7 s                 |
|                 |              |              |                       |
|                 | o3           | No collision | Stop 459.31 ft        |
+-----------------+--------------+--------------+-----------------------+
| Partial         | m1           | hit          | 5.45 s                |
| Supervisory     |              |              |                       |
|                 | b3           | hit          | 13.1 s                |
|                 |              |              |                       |
|                 | o6           | No collision | Stop 86.77 ft         |
+-----------------+--------------+--------------+-----------------------+
| Manual          | b1           | hit          | 12.85 s               |
|                 |              |              |                       |
|                 | m2           | miss         | \-                    |
|                 |              |              |                       |
|                 | b3           | hit          | 15.7 s                |
|                 |              |              |                       |
|                 | o1           | No collision | 645.56 ft             |
+-----------------+--------------+--------------+-----------------------+

> Legend
>
> b = bearing failure s = seconds
>
> m = motor failure ft = feet
>
> o = obstruction

+----------------+--------------+--------------+----------------------+
| Subject 4      |              |              |                      |
+----------------+--------------+--------------+----------------------+
| Control mode   | Task         | Response     | Reaction             |
+----------------+--------------+--------------+----------------------+
| Full           | b2           | miss         | \-                   |
| Supervisory    |              |              |                      |
|                | m3           | hit          | 7.38 s               |
|                |              |              |                      |
|                | o3           | No collision | Stop 365.81 ft       |
+----------------+--------------+--------------+----------------------+
| Partial        | m1           | hit          | 2.945 s              |
| Supervisory    |              |              |                      |
|                | m3           | miss         | \-                   |
|                |              |              |                      |
|                | o6           | No collision | Stop 249.90 ft       |
+----------------+--------------+--------------+----------------------+
| Manual         | b1           | hit          | 6.364 s              |
|                |              |              |                      |
|                | m2           | miss         | \-                   |
|                |              |              |                      |
|                | b3           | miss         | \-                   |
+----------------+--------------+--------------+----------------------+

+----------------+--------------+--------------+----------------------+
| Subject 5      |              |              |                      |
+----------------+--------------+--------------+----------------------+
| Control mode   | Task         | Response     | Reaction             |
+----------------+--------------+--------------+----------------------+
| Full           | b1           | hit          | 12.98 s              |
| Supervisory    |              |              |                      |
|                | m2           | hit          | 3.54 s               |
|                |              |              |                      |
|                | o5           | No collision | Stop 14.43 ft        |
+----------------+--------------+--------------+----------------------+
| Partial        | m1           | miss         | \-                   |
| Supervisory    |              |              |                      |
|                | m3           | hit          | 3.06 s               |
|                |              |              |                      |
|                | o6           | No collision | Stop 12.17 ft        |
+----------------+--------------+--------------+----------------------+
| Manual         | b1           | hit          | 3.46 s               |
|                |              |              |                      |
|                | m2           | hit          | 3.66 s               |
|                |              |              |                      |
|                | b3           | hit          | 17.6 s               |
|                |              |              |                      |
|                | 04           | No collision | Stop 310.95 ft       |
+----------------+--------------+--------------+----------------------+

+----------------+--------------+--------------+----------------------+
| Subject 6      |              |              |                      |
+----------------+--------------+--------------+----------------------+
| Control mode   | Task         | Response     | Reaction             |
+----------------+--------------+--------------+----------------------+
| Full           | b1           | hit          | 15.59 s              |
| Supervisory    |              |              |                      |
|                | m2           | miss         | \-                   |
|                |              |              |                      |
|                | b3           | hit          | 15.74                |
|                |              |              |                      |
|                | o5           | No collision | Stop 123.58 ft       |
+----------------+--------------+--------------+----------------------+
| Partial        | m2           | hit          | 7.8 s                |
| Supervisory    |              |              |                      |
|                | b1           | miss         | \-                   |
|                |              |              |                      |
|                | o6           | No collision | Stop 55.77 ft        |
+----------------+--------------+--------------+----------------------+
| Manual         | b1           | hit          | 8.154 s              |
|                |              |              |                      |
|                | m2           | hit          | 6.24 s               |
|                |              |              |                      |
|                | o1           | No collision | Stop 229.95 ft       |
+----------------+--------------+--------------+----------------------+

> [Legend]{.underline}
>
> b = bearing failure s = seconds
>
> m = motor failure ft = feet
>
> o = obstruction

+----------------+--------------+--------------+----------------------+
| Subject 7      |              |              |                      |
+----------------+--------------+--------------+----------------------+
| Control mode   | Task         | Response     | Reaction             |
+----------------+--------------+--------------+----------------------+
| Full           | b1           | hit          | 16.06 s              |
| Supervisory    |              |              |                      |
|                | m2           | hit          | 3.13 s               |
|                |              |              |                      |
|                | o5           | No collision | Stop 89.17 ft        |
+----------------+--------------+--------------+----------------------+
| Partial        | m1           | hit          | 2.465 s              |
| Supervisory    |              |              |                      |
|                | b2           | hit          | 17.132 s             |
|                |              |              |                      |
|                | o6           | No collision | 292.61 ft            |
+----------------+--------------+--------------+----------------------+
| Manual         | b2           | hit          | 16.87 s              |
|                |              |              |                      |
|                | b3           | hit          | 19.68 s              |
|                |              |              |                      |
|                | o1           | No collision | Stop 283.46 ft       |
+----------------+--------------+--------------+----------------------+

+----------------+--------------+--------------+----------------------+
| Subject 8      |              |              |                      |
+----------------+--------------+--------------+----------------------+
| Control mode   | Task         | Response     | Reaction             |
+----------------+--------------+--------------+----------------------+
| Full           | m1           | miss         | \-                   |
| Supervisory    |              |              |                      |
|                | b2           | hit          | 15.6 s               |
|                |              |              |                      |
|                | o5           | No collision | Stop 185.30 ft       |
+----------------+--------------+--------------+----------------------+
| Partial        | m1           | miss         | \-                   |
| Supervisory    |              |              |                      |
|                | b2           | miss         | \-                   |
|                |              |              |                      |
|                | m3           | hit          | 3.48 s               |
|                |              |              |                      |
|                | o6           | No collision | 171.1 m              |
+----------------+--------------+--------------+----------------------+
| Manual         | m1           | hit          | 10.8 s               |
|                |              |              |                      |
|                | m3           | hit          | 7.2 s                |
|                |              |              |                      |
|                | o1           | No collision | Stop 225.81 ft       |
+----------------+--------------+--------------+----------------------+

+----------------+--------------+--------------+----------------------+
| Subject 9      |              |              |                      |
+----------------+--------------+--------------+----------------------+
| Control mode   | Task         | Response     | Reaction             |
+----------------+--------------+--------------+----------------------+
| Full           | m1           | hit          | 3.545 s              |
| Supervisory    |              |              |                      |
|                | b3           | hit          | 17.405 s             |
|                |              |              |                      |
|                | o6           | collision    | \-                   |
+----------------+--------------+--------------+----------------------+
| Partial        | m2           | hit          | 6.481 s              |
| Supervisory    |              |              |                      |
|                | b3           | miss         | \-                   |
|                |              |              |                      |
|                | o5           | No collision | Stop 518.37 ft       |
+----------------+--------------+--------------+----------------------+
| Manual         | m1           | miss         | \-                   |
|                |              |              |                      |
|                | b2           | miss         | \-                   |
|                |              |              |                      |
|                | m3           | hit          | s                    |
|                |              |              |                      |
|                | o1           | No collision | Stop 435.23 ft       |
+----------------+--------------+--------------+----------------------+

> [Legend]{.underline}
>
> b = bearing failure s = seconds
>
> m = motor failure ft = feet
>
> o = obstruction

+----------------+--------------+--------------+----------------------+
| Subject 10     |              |              |                      |
+----------------+--------------+--------------+----------------------+
| Control mode   | Task         | Response     | Reaction             |
+----------------+--------------+--------------+----------------------+
| Full           | b2           | hit          | 16.2 s               |
| Supervisory    |              |              |                      |
|                | m3           | hit          | 3 s                  |
+----------------+--------------+--------------+----------------------+
| Partial        | b1           | hit          | 7.32 s               |
| Supervisory    |              |              |                      |
|                | m2           | miss         | \-                   |
|                |              |              |                      |
|                | b3           | miss         | \-                   |
|                |              |              |                      |
|                | o5           | collision    | \-                   |
+----------------+--------------+--------------+----------------------+
| Manual         | m1           | hit          | 3.125 s              |
|                |              |              |                      |
|                | b2           | hit          | 13.8 s               |
|                |              |              |                      |
|                | o6           | No collision | Stop 163.66 m        |
+----------------+--------------+--------------+----------------------+

+----------------+--------------+--------------+----------------------+
| Subject 11     |              |              |                      |
+----------------+--------------+--------------+----------------------+
| Control mode   | Task         | Response     | Reaction             |
+----------------+--------------+--------------+----------------------+
| Full           | m1           | hit          | 3.125 s              |
| Supervisory    |              |              |                      |
|                | m3           | miss         | \-                   |
|                |              |              |                      |
|                | o5           | No collision | Stop 95.75 m         |
+----------------+--------------+--------------+----------------------+
| Partial        | b1           | hit          | 8.288 s              |
| Supervisory    |              |              |                      |
|                | m2           | hit          | 4.51 s               |
|                |              |              |                      |
|                | b3           | hit          | 11.04 s              |
|                |              |              |                      |
|                | o2           | collision    | Stop 62.79 m         |
+----------------+--------------+--------------+----------------------+
| Manual         | m2           | hit          | 3.361 s              |
|                |              |              |                      |
|                | m3           | miss         | \-                   |
|                |              |              |                      |
|                | o4           | No collision | Stop 125.44 m        |
+----------------+--------------+--------------+----------------------+

+----------------+--------------+--------------+----------------------+
| Subject 12     |              |              |                      |
+----------------+--------------+--------------+----------------------+
| Control mode   | Task         | Response     | Reaction             |
+----------------+--------------+--------------+----------------------+
| Full           | b1           | hit          | 12.91 s              |
| Supervisory    |              |              |                      |
|                | m2           | hit          | 4.4 s                |
|                |              |              |                      |
|                | b3           | hit          | 15.34 s              |
|                |              |              |                      |
|                | o4           | No collision | Stop 134.88 m        |
+----------------+--------------+--------------+----------------------+
| Partial        | m1           | hit          | 2.9 s                |
| Supervisory    |              |              |                      |
|                | b2           | hit          | 7.261 s              |
|                |              |              |                      |
|                | m3           | miss         | \-                   |
|                |              |              |                      |
|                | o5           | No collision | Stop at 142.92 m     |
+----------------+--------------+--------------+----------------------+
| Manual         | b2           | hit          | 8.4 s                |
|                |              |              |                      |
|                | o3           | No collision | Stop 199.39 m        |
+----------------+--------------+--------------+----------------------+

> [Legend]{.underline}
>
> b = bearing failure s = seconds
>
> m = motor failure ft = feet
>
> o = obstruction

# DATA FOR PAGE TEST {#data-for-page-test .Closing}

Differences between the participants\' speed estimates and the actual
speed were used to compute the Mean Absolute Error (*MAE*) in the speed
category. The numbers in parentheses indicate the ranks as required by
the test. Details on how the ranks are used by the test can be found in
Hollander and Wolfe (1973), page 147.

  -------------- --------------------- --------------------- -------------
  Participant    Speed Deviation (mph)                       
                 by Control Modes                            

                 Full\                 Partial\              Manual
                 Supervisory           Supervisory           

  1              1.9 (3)               1.1 (1)               1.4 (2)

  2              17.4 (3)              2.9 (1)               16.8 (2)

  3              13.0 (3)              3.1 (2)               2.8 (1)

  4              14.9 (3)              4.1 (1)               5.6 (2)

  5              1.2 (1)               10.6 (3)              6.2 (2)

  6              5.3 (3)               1.4 (2)               0.2 (1)

  7              3.1 (2)               1.2 (1)               4.7 (3)

  8              10.6 (3)              1 (1)                 1.3 (2)

  9              6.2 (1)               9.3 (3)               8.7 (2)

  10             9.3 (3)               5.5 (1)               9.3 (2)

  11             6.0 (3)               0.4 (1)               2.3 (2)

  12             3.2 (1)               6.8 (2)               8.7 (3)
  -------------- --------------------- --------------------- -------------

Differences between the participants\' temperature estimates and the
actual temperature were used to compute the *MAE* in the temperature
category. The numbers in parentheses indicate the ranks as required by
the test. Details on how the ranks are used by the test can be found in
Hollander and Wolfe (1973), page 147.

  ------------- --------------------- ------------------------- ----------
  Participant   Temperature Deviation                           
                (^o^F) by Control                               
                Mode                                            

                Full Supervisory      Partial Supervisory       Manual

  1             39 (1)                44 (2)                    52 (3)

  2             39 (1)                40 (2)                    55 (3)

  3             37 (1)                38 (2)                    50 (3)

  4             40 (3)                34 (1)                    38 (2)

  5             33 (1)                35 (2)                    40 (3)

  6             37 (1)                37 (2)                    37 (3)

  7             33 (2)                35 (3)                    32 (1)

  8             50 (3)                37 (1)                    44 (2)

  9             33 (1)                37 (3)                    35 (2)

  10            34 (2)                33 (1)                    34 (3)

  11            35 (1)                41 (2)                    42 (3)

  12            35 (1)                45 (3)                    38 (2)
  ------------- --------------------- ------------------------- ----------

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[^1]: The statistical analysis was based upon the Page test. The Page
    test is a distribution-free test for ordered alternatives based on
    Friedman rank sums. A discussion of this test is found on page 147
    in Hollander and Wolfe, (1973). The test statistic L=41.5 is greater
    than the critical value for *l* (0.05,3,3)=41 at the 5 percent level
    of significance.

[^2]: The t-value represents a ratio of systematic errors or
    unsystematic errors. It measures the difference between two sample
    means divided by the standard deviation for the sample. The phrase
    \"p \< .05\" means there are 5 chances in 100 that the observed
    result was due to chance.

[^3]: The test statistic L=154 was greater than the critical value for
    *l* (0.05,3,12)=153, p\<0.05. The data for this test is presented in
    Appendix G.

[^4]: The test statistic L=156 was larger than the critical value
    *l*(0.05,3,12)=153, p\<0.05. The data for this test is presented in
    Appendix G.