Job Expansion: An Additional Benefit of a

Computer Aided Dispatch/Automatic Vehicle Locator (CAD/AVL) System

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## Paper Submitted to ITS 2000 Annual Meeting

3/1/00

Mary D. Stearns, Ph.D.

Project Manager

Operator Performance and Safety Analysis Division, DTS-79,

Volpe National Transportation Systems Center

Research and Special Programs Administration, U. S. Department of
Transportation

######## 55 Broadway

Cambridge, MA 02142

T 617-494-2617, F 617-494-3622

stearnsm@volpe.dot.gov

######## **ABSTRACT**

Job Expansion: An Additional Benefit of a

Computer Aided Dispatch/Automatic Vehicle Locator (CAD/AVL) System

The Denver Regional Transportation District (RTD) acquired a CAD/AVL
system that became fully operational in 1996. The CAD/AVL system added
radio channels and covert alarms in buses, located vehicles in real
time, and monitored schedule adherence. The Operator Performance and
Safety Analysis Division, DTS-79, U. S. Department of Transportation's
Volpe National Transportation Systems Center, with the support of the
Federal Transit Administration\'s (FTA) Advanced Public Transportation
Systems (APTS) Program, examined the human factors consequences of RTD
employees' use of the CAD/AVL system.

Dispatchers spend more time communicating about a greater variety of
topics. The RTD dispatchers receive and transmit more calls as well as
trace transit operations occurring both in real time and
retrospectively. Having information, accurate in place and time, meant
that the dispatchers could provide accurate information about on-street
operations.

RTD initially expected that accurate representation of transit
operations would reduce the number of street supervisors. Because the
street supervisors access to real-time information from mobile data
terminals (MDT) in their vehicles, they have assumed more duties.
Because they have more autonomy, they perform their jobs more
effectively in the field.

Installing information technology in a transit operation leads to many
benefits, not all of which can be anticipated. This paper highlights the
additional benefit that was realized as a result of installing
information technology in a transit operation. The provision of accurate
real time information enhanced the resources that employees had to do
their jobs. It made it possible for them to act more effectively to
support the delivery of transit service. This outcome corresponds to
what has happened when information technology was introduced in other
sectors of the economy.

**INTRODUCTION**

The Denver Regional Transportation District (RTD) installed a Computer
Aided Dispatch/Automatic Vehicle Location (CAD/AVL) system to upgrade
communication, increase the number of radio channels, improve safety on
buses, and provide real time monitoring of buses' schedule adherence.
RTD installed CAD/AVL on its entire vehicle fleet. This paper describes
how the CAD/AVL's information technology helped the RTD employees using
it to work more effectively. Using data collected before and after
CAD/AVL installation, this paper documents how its information
technology assets increased both the number and variety of the duties
performed by the dispatchers and the street supervisors.

RTD anticipated that CAD/AVL use would increase the number of
dispatchers and decrease the number of street supervisors. The
dispatchers and street supervisors continued to perform the same jobs
but they were able to do them differently and more efficiently. There
were also unexpected changes; the CAD/AVL system's capabilities changed,
as well as expanded certain duties. Dispatchers and street supervisors
became more productive both because they expanded the variety of their
duties as well as performing them more efficiently.

###### **BACKGROUND** {#background .unnumbered}

RTD provides public transportation for a metropolitan area that has a
population of 2.3 million, encompasses forty-four municipalities, and
covers 2,400 square miles. RTD operates the 12th largest transit bus
fleet in the United States, as well as a light-rail line.

Between 1992 and 1997, RTD ridership increased while, at the same time,
service was both expanded and improved. RTD ridership increased 23%
while operating hours increased 17%, exclusive of the introduction of
light rail service, and its total hub miles 26%, including contractor
service. ([1]{.underline}) During the same time period, RTD improved its
on-time performance, increased the number of routes, and added service
to distant locations, including the Denver International Airport

In the early 1990's, RTD recognized the need to upgrade its radio system
due to increasing radio congestion. At times of high demand, calls from
bus drivers would drop out of the system due to the limited number of
radio channels. In 1992, RTD acquired a satellite-based CAD/AVL system,
using Global Positioning Satellite (GPS) technology, with differential
error correction, to track vehicle location within 100 feet. RTD
completed acceptance testing of the CAD/AVL system in 1996.

Castle Rock Consultants evaluated Denver RTD's CAD/AVL system for the
Federal Transit Administration, ([1]{.underline}) and Stearns, et al,
([2]{.underline}) documented the human factors consequences, i.e.,
changes in work procedures, usability, workload, and training.

####### CAD/AVL Equipment

As part of the CAD/AVL, the dispatchers acquired new equipment with
enhanced capabilities. CAD/AVL added radio channels to alleviate the
congested communication, displayed real-time vehicle location and
schedule performance, and increased safety through accurate location of
emergencies. Dispatchers also gained the capability to communicate
directly with buses from other divisions, to receive and respond to
covert emergency calls from buses, to "playback" past route performance
of a particular bus, and to show the locations of buses out of service,
for example, during snowstorms.

RTD's dispatchers use dual computer screens (the CAD and AVL screens)
that are located side-by-side. The CAD screen is the control center
because it lists the radio calls by priority. The dispatchers see
vehicles' location on a scalable map on the AVL screen. Dispatchers
access response options using "pull-down" menus and can select the
desired level of detail to display on the AVL screen.

The street supervisors use laptop computers, Mobile Display Terminals
(MDT), while they patrol their sector in a supervisor vehicle. They
check out a MDT at the start of their shift and use it to access real
time operating information. The MDTs are multitasking and have a windows
operating system. The MDT has function keys for frequently used
commands. The MDT design does not require street supervisors to recall
data-entry commands because they can scroll through them. Display
clutter on the MDT is not a problem and they can adjust the screen's
brightness

RTD installed transit control heads (TCH) in every bus, mounted on a
stalk to the right of the steering wheel, which can be rotated to
improve viewing angle. Bus drivers use the TCH as their primary
communication interface with the CAD/AVL system and the dispatchers. The
TCH has a keypad with precoded buttons, a Liquid Crystal Display (LCD),
an internal speaker, and covert microphone. Bus drivers initiate
communication with the Dispatch Center by selecting one of the precoded
buttons to push.

**EMPLOYEE DUTIES**

####### Dispatchers {#dispatchers .unnumbered}

The CAD/AVL system made the dispatchers' communications more efficient.
The AVL screen shows the real-time location of RTD vehicles and updates
the information every two minutes. The dispatchers often need to locate
RTD's maintenance trucks to assign them to assist a disabled bus.
Dispatchers use the AVL display to identify which maintenance vehicle is
closest to the disabled bus. Denver dispatchers can contact Boulder
buses and Boulder dispatchers can contact Denver buses. They can hold
connections between Boulder and Denver buses. Previously, only Boulder
dispatchers could talk to Boulder buses and they had to use
intermediaries to contact vehicles outside their metropolitan area.

The CAD screen shows bus numbers, route assignments, and operator
information. Previously, the dispatchers had to request this
information, by radio, from the bus drivers. Dispatchers do not need
paper records of bus numbers because the CAD screen displays this
information.

Weather and sporting events boost demand for RTD service. The
dispatchers work more efficiently in challenging conditions. When RTD
operates "load and go" service from their "Park & Ride" lots to the
sport stadiums, the dispatchers advise the supervisors of the actual
location of the shuttle service to these lots. There is high demand for
dispatch service during snow emergencies and their call volume may
double. The CAD/AVL system does not "lose calls" during snow emergencies
when there is heavy call volume because bus calls can not drop out of
the radio system. The CAD retains all the messages it receives and
dispatchers respond to them by priority.

The size of the dispatch staff at RTD's Dispatch Center has increased
22%, to eleven, since the implementation of CAD/AVL. In 1996, five
dispatchers were on duty during peak hours compared to three in 1992.
The number of dispatch hours per weekday has increased 46%. The
increased hours cover peak hour operations. Using CAD/AVL software
commands, the lead dispatcher can reassign dispatcher positions quickly,
without changing workstations, to respond to variations in the
operational demands during the course of a day.

##### 

##### **Street Supervisors**

The street supervisors have more radio channels and receive more
information from both their radio and the MDT. Street supervisors can
call buses directly without being patched through by a dispatcher.
Supervisors send and receive messages using the MDT. When the MDT
receives a text message, it places the message in the Received Messages
window and emits an auditory alert, a beep. The MDT beeps at 30-second
intervals until the message is viewed or deleted.

Street supervisors use the MDT to perform many of their tasks. . They
are able to retrieve information about a bus from the MDT in their
vehicle. They can review headway information; request information about
a route or vehicle or a voice channel to talk to a particular bus; and
select, edit, and fill out forms electronically. A supervisor can locate
a bus and determine whether it is ahead, or behind, schedule by entering
the bus number or the route and block on the MDT. The MDT reports the
bus location using a text message. Street supervisors can retrieve bus
drivers\' schedules and extra board assignments from the MDT.

The MDT's do not have an AVL screen. Street supervisors would like to
have the same AVL screen that the dispatchers have. Their laptop
computer could store a map but sending location information would
require the laptop computer to have copious memory and enhanced speed.

Denver RTD employed 25 street supervisors and two supervisors in 1996,
an increase of two supervisors since 1992. The two additional
supervisors do not represent an increase in the supervisors in the field
because they were hired to cover vacations and extra duty shifts to end
the use of part-time substitutes. By 1996 and 1999, the number of street
supervisors increased to 29, including the two supervisors.

#####  {#section-5 .unnumbered}

##### **JOB EXPANSION** {#job-expansion .unnumbered}

##### **Dispatchers** {#dispatchers-1 .unnumbered}

Operation of CAD/AVL created a need for an additional dispatch position
and as well as new duties for the dispatchers. RTD added a second
supervisory lead dispatch position to handle administrative functions,
i.e., adjusting the software parameters for the CAD/AVL system and
operating the "playback" feature. "Playbacks" show whether a bus
actually provided service on a route and how well it adhered to its
schedule. RTD departments request use of the "playback" capability to
resolve questions.

The second lead dispatcher plays back past operations upon request from
other RTD departments and may do several "playbacks" per day. RTD's
Schedule Planning and Customer Service staff request CAD/AVL data to
evaluate route performance and respond to customer complaints about
service. For example, RTD received a complaint from the parents of a
high-school student that the student was constantly late for school due
to a late bus. The "playback" showed that the bus was on time. There
also have been expressions of interest in accessing this database by
emergency services and planning agencies in the Denver area. RTD plans
to place CAD/AVL consoles in other RTD departments so that departmental
personnel can access the system's information.

RTD records the radio calls to the Dispatch Center in an internal daily
report called the "Dispatchers' Daily Activity Log." Dispatchers enter
and code calls, using RTD's problem codes, into the CAD while the
incident is open. The calls recorded in this log are a low estimate of
the total number of calls they receive each day. The log records only
incidents that have been assigned one of RTD's problem codes by the
dispatcher. CAD/AVL transfers information automatically to RTD's main
frame when a problem code has been assigned

Figure 1 shows how the volume of calls during a typical day in 1996 has
increased as compared to 1992. The temporal distribution of calls is
similar between 1992 and 1996. More than one quarter of bus calls to the
Dispatch Center occurred during the afternoon peak hours which
represents one eighth of the day.

![](media/image1.wmf)

Figure 1. Calls to Dispatch by Time of Time, 1992 and 1996

The use of CAD/AVL has shifted the distribution of the types of radio
calls to the Dispatch Center from the bus drivers. Figure 2 shows the
twenty most frequent reasons that bus drivers called the Dispatch Center
classified using RTD\'s problem codes. These twenty most frequent
reasons for contacting a dispatcher represent more than two-thirds of
all the calls received by the dispatchers in 1996.

The number of calls from bus drivers asking for "policy
information/direction" has doubled since 1992 and now is more than
one-fifth of the calls to the dispatchers. "Policy
Information/Direction" calls refer to situations where a bus driver
needs to ask about RTD's operating policy, for example, on transfers.
The bus drivers also make more calls to ask the dispatchers to hold
another bus for connecting passengers. The proportion of these calls
increased from 1% in 1992 to 9% in 1996.

Dispatchers' communications with bus drivers has increased because their
reasons for making a call have changed. Bus drivers can not transmit a
request for information about RTD's policies or request connections
using the coded buttons on the TCH. These requests require verbal
communication with the dispatchers and may require extended explanations
or interpretations. The increased proportion of these calls shows why
the dispatchers are doing more communicating with bus drivers.

![](media/image2.wmf)

Figure 2. Most Frequent Types of Radio Calls Received at the Dispatch
Center, 1992 and 1996

Figure 3 gives additional evidence that CAD/AVL has increased the
communication that dispatchers have with bus drivers. By extrapolating
from the type of calls bus drivers made to the dispatchers in 1992, it
is possible to see if introducing CAD/AVL changed the reasons for
calling the dispatchers. By examining the reasons that bus drivers
called the Dispatch Center in 1992 and allocating them using the
precoded buttons on the TCH, 25% of the calls in 1996 should be
"requests to talk. \" This extrapolation assumes that the bus driver
uses the TCH buttons coded for specific problems such as fare disputes,
bus too full and had to pass up passengers, lift not working, etc., for
these problems. The actual use of the TCH buttons did not correspond to
the extrapolated. Instead, more than 90% of the calls from the bus
drivers in 1996 were "requests to talk." (Figure 3)

**Figure 3. Estimated Vs. Actual Use of TCH Precoded Buttons**

![](media/image3.wmf)

Figure 4 quantifies how much time dispatchers spend performing their
duties and quantifies the increased length of each dispatcher
communication. In 1996, using CAD/AVL, dispatchers spent more time on
each communication, i.e., talking on the radio and phone. By contrast,
they spent less time handling paper and computer data entry.

![](media/image4.wmf)

Figure 4. Dispatcher Activities by Time, 1992 and 1996

In summary, use of the CAD/AVL affected the dispatchers' work practices.
The dispatchers process an increased volume of communication. They spend
more of their time communicating with field personnel. They provide more
interpretations of RTD policies and make more arrangements to provide a
higher level of service for the transit users. They make the information
resident in the CAD/AVL available to other segments of RTD as well as
the community. As a result, RTD has increased the number of dispatchers.

####### Street Supervisors

Street supervisors locate buses using a MDT. They can speak to the bus
driver directly without using a dispatcher as an intermediary. They like
the ability of the MDT to give them information without requesting it
from others, as well as the information they can access quickly such as
bus driver numbers, location, badge number, roster of drivers, route and
block for a bus driver. The street supervisors cover more area and have
more frequent contact with bus drivers even though the work force was
stable in size through 1996 while RTD service expanded.

Because CAD/AVL reduced the street supervisors' duty to perform traffic
checks, they have acquired additional, and more varied, duties. Street
supervisors report that they perform their jobs better using CAD/AVL
because they can access to more real time information. As a result, they
now perform a larger variety of tasks. Because the street supervisors
have more information, they are better-informed members of the RTD field
management team.

The street supervisors realize that the CAD/AVL performs tasks they used
to have to do. The street supervisors said that CAD/AVL has been helpful
and that, \"it doesn\'t seem hard." They commented that CAD/AVL is a
\""great system, ""makes the job so much easier." They view it as a way
to look at the bus schedule electronically. \"With a \'locator system,\'
(there is)\...no need to sit there to tell if a bus will be late.\"

From 1992 to 1996, the daily mileage covered by all the street
supervisor vehicles increased 9%. The increased mileage reflects the
expansion of their duties, to monitor the new bus service to the Denver
International Airport, as well as the expansion of RTD's service area.

Street supervisors contacted the dispatchers slightly less than forty
times per day in 1996 and more than forty times per day in 1992. On
average, each street supervisor contacted dispatch an average of 2.5
times per day in 1992 and 2.3 times in 1996. The trend is down because
the street supervisors can act more autonomously with more information.

Figure 5 enumerates the street supervisors' daily activities, as
extracted from their daily logs. Their activities include contacting bus
drivers; meeting and helping with disabled buses; checking the schedule
adherence on routes; surveillance checks of RTD's park and ride lots,
garages, and downtown stations; checking or creating detours; responding
to accident scenes; tracking lost and found incidents; removing sick
passengers from buses; giving transfer slips to buses in service;
shuttling bus drivers from garage to garage; delivering supplies.

The mean number of route checks per street supervisor decreased from
eight in 1992 to slightly more than two in 1996. Time checks dropped
from five in 1992 to an average per shift of two in 1996. However,
street supervisors have more contact with bus drivers. Personal contact
with bus drivers doubled, from slightly more than five in 1992 to almost
ten in 1996. There is also an increase in activities classified as
"other." This shows that RTD is increasingly using the street
supervisors as a resource to support their field operations.

![](media/image5.wmf)

**Figure 5. Mean Daily Activities Per Street Supervisor, 1992 and 1996**

In summary, the number of street supervisors has remained constant
despite an increase in service and ridership. CAD/AVL and the MDT's have
transformed the street supervisor into an informed member of the RTD in
the field able to handle problems with more independence and more
information. They contact bus drivers more and dispatchers less often.
They have less need to monitor schedule performance due to CAD/AVL's
real time information.

Street supervisor procedures have changed as a result of using CAD/AVL.
They now have real-time schedule information from MDT to check schedule
/route adherence (replacing loose-leaf binders). They use their MDT to
enter reports electronically, i.e., Park and Ride counts, traffic
counts, incident reports, and accident reports. They communicate with
buses directly (instead of using the dispatcher as a go-between). They
send and receive text messages (instead of speaking on the radio) and
find this useful for detour information and personnel matters considered
sensitive. They no longer need to report their location to the Dispatch
Center. The success of providing more information to field personnel is
echoed in their enthusiastic adoption of this capability.

####### CONCLUSION

The implementation of CAD/AVL at the Denver RTD had many benefits. It
permits more communication, provides real time location information, and
monitors schedule performance in real time. At the same time, the
information technology in the CAD/AVL system provided an additional
benefit. RTD can provide its riders a better level of service because
the dispatchers and street supervisors perform more, as well as more
varied, duties.

The dispatchers respond to all the calls from the bus drivers. Calls,
which might have been lost by the previous limited number of radio
channels, reach the Dispatch Center. The dispatchers now spend
proportionally more of their time communicating with bus drivers and
other field support personnel. An increased proportion of these calls
requires detailed explanations.

People, both inside and outside RTD, have recognized the utility of the
information that the Dispatch Center generates for better monitoring the
provision of transit service on the street. The dispatchers provide more
support to RTD's administrative functions. As a result, RTD has created
a second lead dispatch position to process these requests for
information.

RTD expected to reduce the number of street supervisors, given that
CAD/AVL assumed one of their major tasks, monitoring and recording
schedule adherence at the time checkpoints in the field. Instead, they
are better able to work effectively and independently in the field. Real
time information and direct communication with RTD vehicles has made it
possible for street supervisors to talk to bus drivers directly and have
personal contact with bus drivers more often. They communicate directly
with a particular bus, rather than being patched through via the
Dispatch Center, and give immediate feedback to bus drivers about
schedule and driving performance. The street supervisors themselves
recognize that their role in RTD's operations has become even more
critical. They voice the most unequivocal expressions of support for the
CAD/AVL system.

These findings parallel what industry has found following the
introduction of information technology. "The use of IT can change an
individual worker's degree of autonomy in doing his or her job."
([3)]{.underline} The street supervisors' ability to act more
autonomously exemplifies how the access to the MDT has changed how they
do their job. They communicate directly with buses, access schedule and
headway information directly, and take more independent actions to
support and maintain service in the field.

It also has been noted that, contrary to expectations, " IT, may, in
some cases, increase rather than decrease employment. (because )...IT
makes coordination more effective and less expensive, the demand for
coordination and for ...the clerks who provide it may increase..
([3)]{.underline} Bus drivers make more requests for detailed
information because they have learned that they are more likely to get
through to a dispatcher. It is likely that this type of non-urgent
request that can be deferred was set aside prior to CAD/AVL if bus
drivers had difficulty reaching a dispatcher. Because dispatchers can
respond means that the RTD has improved the level of service it
provides.

###### **ACKNOWLEDGEMENTS** {#acknowledgements .unnumbered}

The Volpe National Transportation Systems Center (VNTSC) conducted this
research with the support of the Federal Transit Administration\'s
Advanced Public Transportation Systems (APTS) Program. The author would
like to thank her FTA sponsor, Ronald Boenau, Chief, Advanced Public
Transportation Division, W. Raymond Keng, ITS Engineer, the Volpe Center
APTS Program Manager, Robert S. Ow, and Mike Gil, Manager, Dispatch and
Street Supervision at Denver RTD, for their guidance and support of this
research. E. Donald Sussman, Chief, Operator Performance and Safety
Analysis Division, at the Volpe Center contributed to the conceptual
development of this research. Jonathan Belcher, Central Transportation
Planning Staff, Executive Office of Transportation and Construction,
Commonwealth of Massachusetts, participated in the data collection and
analyses.

###### **ENDNOTES**

1\. Federal Transit Administration, "Denver Regional Transit District
(RTD) Automatic Vehicle Location System." Evaluation Final Report.
Prepared by Castle Rock Consultants, Review Draft, January, 2000.

2\. Mary D. Stearns, E. Donald Sussman, and Jonathan Belcher, (1999)
"Denver RTD's CAD/AVL System-The Human Factors Consequences," Final
Report DOT-VNTSC-FTA-98-8.

3\. Kevin Crowston and Thomas W. Malone, "Information Technology and
Work Organization" in Thomas J. Allen and Michael S. Scott Morton,
eds.*, Information Technology and the Corporation of the 1990s,* (New
York: Oxford University Press, 1994) pp. 256, 265.

**LIST OF FIGURES**

Figure 2. Calls to Dispatch by Time of Time, 1992 and 1996

Figure 2. Most Frequent Types of Radio Calls Received at the Dispatch
Center, 1992 and 1996

**Figure 3. Estimated Vs. Actual Use of TCH Precoded Buttons**

Figure 4. Dispatcher Activities by Time, 1992 and 1996

**Figure 5. Mean Daily Activities Per Street Supervisor, 1992 and 1996**