Manual TABLE OF CONTENTS Module 7.

TABLE OF CONTENTS

MODULE 7. INFORMATION DISSEMINATION

TABLE OF CONTENTS

7.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3

MODULE OBJECTIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4
MODULE SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4

7.2 DESIGN PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4

IDENTIFY NEEDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4
IDENTIFY INFORMATION DISSEMINATION PARTNERS . . . . . . . . . . . . . . . . . 7-6
BUILD CONSENSUS AMONG PARTNERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6
Identify Differences in Operating Philosophies Among Partners . . . . . . . . . . . . . . 7-6
Establish Common Ground Between Partners . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7
ESTABLISH GOALS AND OBJECTIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7
ESTABLISH PERFORMANCE CRITERIA AND MEASURES . . . . . . . . . . . . . . . . 7-8
Information Credibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8
Market Penetration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8
Traveler Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9
FUNCTIONAL REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-10
DEFINE FUNCTIONAL RELATIONSHIPS, DATA REQUIREMENTS, AND
INFORMATION FLOWS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11
IDENTIFY AND SCREEN TECHNOLOGIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11
DEVELOP IMPLEMENTATION PLAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-12
IDENTIFY FUNDING SOURCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-13
IMPLEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-14
EVALUATE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-14

7.3 TECHNIQUES AND TECHNOLOGIES . . . . . . . . . . . . . . . . . . . 7-15

ON-ROADWAY INFORMATION TECHNOLOGIES . . . . . . . . . . . . . . . . . . . . . . 7-15
Types of DMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16
Light-Reflecting DMSs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17
Fold-out. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-18
Scroll (or Tape). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-18
Rotating Drum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-19
Reflective Disk Matrix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-19
Light-Emitting DMSs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-19
Neon or Blank-Out Signs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-19
Lamp (Incandescent Bulb) Matrix Signs. . . . . . . . . . . . . . . . . . . . . . . . . . 7-19
Fixed-Grid or Shuttered Matrix Fiber-optic Signs. . . . . . . . . . . . . . . . . . 7-19
Fixed-Grid or Matrix Light-Emitting Diode (LED) Signs. . . . . . . . . . . . . 7-20
Hybrid DMSs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-20
Reflective Disks with Fiberoptics/LEDs. . . . . . . . . . . . . . . . . . . . . . . . . . 7-20
Static/DMS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-20
Advantages and Disadvantages of the DMS Technologies . . . . . . . . . . . . . . . . . 7-20

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IN-VEHICLE INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-21

Auditory In-Vehicle Information Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . 7-21
Highway Advisory Radio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-21
Automated HAR (AHAR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-24
Cellular Telephone “Hotlines” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-25
Commercial Radio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-26
Citizen-Band Radio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-26
Visual In-vehicle Information Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-26
Video Display Terminals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-26
Head-Up Displays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-27
OFF-ROADWAY INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-27
Television . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-28
Telephones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-28
Pagers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-28
Personal Data Assistants (PDAs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-29
Computers (Internet) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-29
Kiosks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-29

7.4 LESSONS LEARNED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-30

NTCIP STANDARDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-30
INFORMATION MESSAGE DESIGN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-30
ENVIRONMENTAL ISSUES CONCERNING DMSs . . . . . . . . . . . . . . . . . . . . . . 7-31
Sun Position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-31
Weathering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-31
“AT-REST” DISPLAY CONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-31

7.5 EXAMPLE OF AN INFORMATION DISSEMINATION

SYSTEM: TRANSCOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-31
ORGANIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-31
OPERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-32
FUTURE ACTIVITIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-33

7.6 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-35

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MODULE 7. INFORMATION DISSEMINATION

Figure 7-1. Dynamic Message Signing on New Jersey Turnpike.

7.1 INTRODUCTION information system. However, in an

effective freeway management system,
It is well known that the key to successful dynamic methods of conveying information
driving task performance is efficient to motorists or travelers are often needed to
information gathering and processing.(1) better operate and control the system.
Likewise, properly communicating with
motorists is critical to successful freeway Freeway management systems rely on
traffic management and operations. various information dissemination
Motorists rely on a wide variety of components to apprise all types of travelers
information to properly accomplish the (motorists, transit users, commercial vehicle
control, guidance, and navigational aspects operators, etc.) of current and anticipated
of the driving task. The roadway alignment travel conditions so that informed mode,
and general terrain itself provides a great departure time, and route choice decisions
deal of this information through visual can be made.
“cues;” sources such as pavement markings
and regulatory, warning, and guide signs Information dissemination is also managed in
also contribute greatly to the overall order to improve travel conditions in the

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corridor by influencing traveler behavior (by and technologies being utilized for
recommending diversion routes around an information dissemination within the
incident, for example). This information can integrated regional transportation
be disseminated from a variety of sources management system.
(State departments of transportation, transit
agencies, private-sector information service 7.2 DESIGN PROCESS
providers, etc.) using a variety of methods
(dynamic message signs, commercial radio Decisions about when, where, and how to
traffic reports, traffic information kiosks, disseminate travel-related information to the
etc.). public have become much more complex in
recent years, due to improved traffic/
MODULE OBJECTIVES weather/transit surveillance capabilities and
expanded information dissemination options.
The objectives of this module are threefold: As with the other components that can be
included in a freeway management system,
C To describe how to define, establish, and the decisions necessary to develop and
coordinate effective traveler information integrate information dissemination into the
components in a freeway management system can be best accomplished by
system. following the basic decision process
described in Module 2. Specific application
C To identify existing and emerging of this process to the task of incorporating
technologies available to facilitate information dissemination into a freeway
information dissemination to travelers. management system is discussed in the
following sections.
C To illustrate how information
dissemination components can integrate IDENTIFY NEEDS
with each other and with other
components of a freeway management The first step in the decision process is to
system. identify the need to be addressed through
information dissemination, or stated another
MODULE SCOPE way, the information needs that exist in the
freeway corridor. Two basic categories of
This module addresses both traditional and information dissemination exist:
emerging information dissemination
processes and technologies for freeway C Pre-trip planning.
management systems. Whereas a number of
technologies (i.e., dynamic message signs, C En route guidance and information.
highway advisory radio) have been around
for a number of years, there are new Table 7-1 presents examples of some of the
opportunities today. In the past, information specific types of need and/or information
was distributed in response to an incident. needs in these categories. Certain
Today, the focus is to provide a continuous information may be needed both pre-trip and
flow of information to travelers, businesses, en route, whereas other information may be
and commercial carriers in order to make needed for either one or the other. To the
their trip travel time more predictable. The extent possible, these information needs
focus of this module is to emphasize the should be further defined by the following:
need for integration among all components

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Table 7-1. Information Need Categories.

Category Examples of Information Need

pre-trip planning C current/anticipated traffic conditions
- speeds
- incident locations
- other congestion locations
- upcoming road closures
C weather effects
- pavement conditions
- road closures
C route guidance
- around incidents
- to special events
C transit information
- bus schedules and status
- transfer locations
- rideshare matching (preplanning and real-time
matching)
en route guidance and C current traffic conditions
information - speeds
- incident locations
- other congestion locations
C weather effects
- pavement conditions
- road closures
C route guidance
- around incidents
- to special events
C lane/shoulder/ramp use status

C Audience. is also important early on to identify those

factors or issues that will influence the ability
C Location. of agencies and/or the private sector to
provide that information. Tort liability
C Time-of-day. concerns can be one such factor. Some
agencies may avoid providing current
These characteristics affect how well pavement condition information, for
information can be received by the users, and example, for fear of establishing a precedent
what types of responses can be expected that may be used against them if they fail to
from the users who have that information warn of that pavement condition (or a
available. similar one) in the future. Preestablished
agreements between public agencies and
In addition to the needs to be addressed private sector companies regarding access to
through information dissemination efforts, it

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agency data may also influence the direction BUILD CONSENSUS AMONG
of future dissemination efforts. PARTNERS

The problem identification step of the Identify Differences in Operating

decision process also includes an inventory Philosophies Among Partners
of existing information sources, including
media reports and private sector initiatives. Developing a consensus regarding the
The inventory can include such data items as importance of information dissemination and
target audiences, accessibility, frequency of its role as part of an overall freeway
reports, and information accuracy. If management system is the next step in the
possible, assessments of user satisfaction decision process. It is important that project
with the information should also be obtained. partners take ownership of the effort up
front, or it may never work. To make this
IDENTIFY INFORMATION happen, it is important to identify and
DISSEMINATION PARTNERS understand the differences in operational
philosophies of the different partners
The key partners in the development of the involved.
information dissemination component of a
freeway management system include the For example, highway and transit agencies
following: may view the presence of some degree of
recurrent congestion on the freeway in very
C Traditional State and local public sector different ways if an HOV lane is included
agencies (transportation and public within the freeway right-of-way. Whereas
works, transit, toll authorities, law diverting freeway traffic to arterial streets
enforcement). might be a primary goal of the highway
agency, the transit agency may desire to
C Commercial media. promote bus utilization and the HOV lane as
a means of reducing that congestion.
C Private sector traffic reporting services Partners need to communicate these
(distributing through commercial media concerns to each other so that a consensus
venues or through direct subscription to about goals can be reached.
motorists).
The partners must also be aware of the
C Local fleet operators (delivery services, differences in operational philosophies
taxis, etc.). between public agencies and private sector
entities. Whereas equity concerns typically
In some cases, the owners/operators of drive public agency decisions regarding the
major traffic generators (malls, tourist dissemination of travel-related information,
attractions, annual special event promotions, marketing opportunities and profit motives
etc.) could also be important partners to will generally dictate private sector interests,
include in the decision-making process. perceptions, and decisions. A clear under-
standing of the differences among these
philosophies is required.

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Establish Common Ground Between ESTABLISH GOALS AND

Partners OBJECTIVES

Once operational and philosophical differ- Once a consensus has been established
ences among the various partners have been among the partners involved with
identified, the next step is to establish areas information dissemination efforts, it is
of common concern or priorities between the necessary to define the goals and specific
partners with respect to travel-related objectives that are going to be addressed
information dissemination. Common ground through this component of the freeway
must be established both at the upper management system. As discussed in
management and political level, and at the Module 2, goals are broad statements of the
day-to-day operations level. Information intent of the system or one of its
dissemination requires upper management components, whereas objectives are specific
and political support of a common vision of statements about what the system or
information availability in order to ensure component of that system will attempt to
continued funding support. Meanwhile, accomplish. A given goal may have more
consensus among partners at the operations than one objective specified to reach that
level is needed to promote true operations goal. Table 7-2 presents examples of goals
integration among the various information and objectives an agency might have for the
dissemination components utilized within the information dissemination component of its
corridor. freeway management system.

Table 7-2. Examples of Goals and Objectives for Information Dissemination.

Category Examples
Goals C Reduce motorist demands upstream of a freeway
incident
C Reduce motorist errors in locating unfamiliar
destinations
C Reduce transit user uncertainty about bus arrivals
Objectives C Warn motorists of adverse weather conditions
C Notify motorists of downstream incidents
C Advise motorists when to seek alternative routes
C Provide motorists with origin-to-destination route
guidance assistance
C Inform motorists at park-and-ride lots when the next
bus will arrive

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In general terms, each of the objectives C The information must be accurate.

developed for information dissemination
should be specific enough to answer the C The information must be timely.
following questions: (1)
C The information must be relevant to its
C Who is being communicated with? intended audience.

C What responses are desired or While these are generally accepted concepts,
anticipated? it is sometimes difficult to identify and obtain
objective and quantifiable measures with
C Where will the responses take place? which to judge them. This task is further
complicated by the fact that the measures
ESTABLISH PERFORMANCE themselves may depend on the specific
CRITERIA AND MEASURES message or unit of information that a partner
is trying to convey. Examples of perfor-
In order to assess the extent to which mance measures that could be used to
information dissemination efforts within a evaluate the credibility of information being
freeway management system are meeting disseminated to motorists are provided in
goals and objectives, a set of performance Table 7-3. Local concerns and capabilities
criteria and measures-of-effectiveness will dictate which performance measures are
pertaining to these efforts must be identified. most appropriate for evaluating information
Relative to information dissemination, credibility in a given locale.
performance criteria have three different
dimensions that are of interest: Market Penetration

C Information credibility. Market penetration refers to the percentage

of the potential audience reached by the
C Market penetration. information dissemination efforts.
Performance criteria regarding market
C Traveler response. penetration may be appropriate for
evaluating certain system goals and
These three dimensions are interrelated. The technologies, particularly those emerging as
following sections provide additional details part of Advanced Traveler Information
and examples of criteria for each of the Systems (ATIS). It is expected that some
above dimensions. technologies, such as in-vehicle dynamic
route guidance, will require only limited
Information Credibility market penetration in order to achieve
operational benefits. Other technologies,
An information dissemination tool must be such as information kiosks in major traffic
credible to travelers if it is to be utilized and generators, may require agencies to strive
have an impact upon traffic operations. The for as great a market penetration as possible
following criteria define how credibility is in order to distribute the information to a
established: (2) wider audience and possibly attract private
sector advertising and sponsorship.

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Table 7-3. Examples of Performance Measures for Information Dissemination.

Category Examples
Information accuracy C Difference in the number of incidents in the system and
number of incidents reported
C Difference between reported expected arrival times of buses
and the times the buses actually arrive at a transit station
C Number of complaints received from the public about
inaccurate information (by device and type of information)
Information timeliness C Average delay time between when an incident is verified and
when information about the incident is disseminated to
travelers
Information relevance C Number of travelers who access a given information
component or unit

Traveler Response possible to adequately measure the overall

effects of many types of information or
Ultimately, the purpose of providing dissemination modes upon traffic volumes,
information to travelers is to effect some- speeds, or delays. The day-to-day variances
change in traveler behavior that will cause an in travel patterns themselves may mask the
improvement in safety or operations. Thus, effects of any information disseminated
performance measures are also needed to during a specific event such as an incident,
determine the extent to which information particularly if the information is intended for
dissemination accomplishes this purpose. a very specific audience (such as vehicles
Changes in traveler mode, departure time, within a freeway traffic stream destined for
and route (if appropriate) are appropriate for a specific downstream exit).
evaluating the effectiveness of real-time
travel-related information. However, it may Consequently, it may sometimes be
be very difficult and expensive to obtain necessary to include performance measures
actual data for these measures. Traveler that evaluate the effect of information
opinions about the effectiveness of the dissemination at an individual traveler’s
information being provided can be another level. For example, trip diaries that identify
important eval-uation measure. Reductions a specific driver’s travels on any given day
in travel time, turning and route choice may need to be compared to determine
errors, or similar measures may also be whether the presence of information had any
useful to evaluate certain types of influence on driving behavior for that select
information. (3) group with drivers on that particular day.
This approach can be very costly and
It is important to recognize that because of manpower intensive, however.
the complex travel patterns of travelers at
any point in the roadway, it may not be

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FUNCTIONAL REQUIREMENTS The ITS National Architecture should serve

as the basic building block of the functional
The functional requirements of information requirements definition process for
dissemination components in a freeway information dissemination.(4) The functions
management system define specific actions described in the National Architecture must
or activities that are to be performed in order then be detailed to match the needs and
to achieve one or more of the objectives. desires of the local agencies.
Initially, the functions should be defined
without considering the dissemination Details regarding who should receive
technology or system architecture that will information, as well as when and where that
be employed. Functions simply specify what should occur, all become a part of the
information will be disseminated and functional definitions. The intent of this step
possibly when and where it is to be in the design process is not only to specify
presented, not how this will be done. Table functions independent of the technology that
7-4 presents some examples of functional could be used to achieve those functions, but
requirements for various information also to highlight what and why other
dissemination objectives. components of the freeway management
system must link with the information
dissemination components.

Table 7-4. Examples of Functional Requirements for

Information Dissemination Objectives.

Examples of Objectives Examples of Possible Functions

C Warn motorists of adverse C Notify freeway motorists of downstream roadway
weather conditions flooding whenever more than 100 mm of water
collects in an underpass section
C Notify motorists approaching an entrance ramp
whenever the freeway is closed because of adverse
weather conditions such as high winds or ice
C Notify motorists of C Within “X” minutes of its occurrence, notify freeway
downstream incidents motorists of any incident that occurs in the travel
lanes within the next exit or decision point
C Advise motorists when to C If the road is closed due to an accident, recommend
seek alternative routes that freeway motorists traveling to the CBD exit at
an upstream connector to a parallel toll road
whenever travel times to the CBD on the freeway
are more than “X” minutes longer than on the toll
road

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For example, an information dissemination Locations of potential information

function that gives route specific travel times dissemination conflicts can be identified
requires that travel time monitoring be a beforehand (a highway and a transit agency
function in the freeway management system. may want to display information at the same
Likewise, a function of notifying motorists roadway location, for example). Perhaps
about downstream lane-blocking incidents more commonly, locations and situations
within a set time also affects the design of where information sharing between partners
the freeway surveillance component of the can occur may be identified, and result in a
freeway management system (what type of more efficient system design.
vehicle detection technology can be used,
how close together detectors must be IDENTIFY AND SCREEN
placed, etc.). As a final example, notifying TECHNOLOGIES
motorists that lanes are closed downstream
for maintenance work implies that a Once the system requirements for
mechanism for determining when and where information dissemination have been
such closures occur is available via direct developed, it is then appropriate to assess
communication between the maintenance the actual technologies available to meet the
and operations divisions of the functional and system architectural
transportation agency, observation of the requirements that have been developed for
closure via closed-circuit television, or other meeting the goals and objectives of
methods. information dissemination. Technologies
that are available for information
DEFINE FUNCTIONAL dissemination can be grouped into one of
RELATIONSHIPS, DATA three categories:
REQUIREMENTS, AND
INFORMATION FLOWS C Those located on the roadway where the
information transfer to the traveler
The purpose of defining functional occurs at a specific point or within a
relationships, data requirements, and very small segment of roadway (i.e.,
information flows is to establish an using dynamic message signs or highway
understanding of how the various advisory radios.)
information dissemination functions that are
to be accomplished will be integrated with C Those located within the vehicle where
each other and with the other components in the information transfer is not
the freeway management system. In this constrained to a point or a small segment
step, the relationships between information of roadway (e.g., using radio, cellular
dissemination functions are further refined to telephone, or in-vehicle navigation
incorporate local issues, concerns, and devices).
capabilities.
C Those located off of or away from the
The relationships between the desired roadway altogether (e.g., using
information dissemination functions and television, computer linkages, or kiosks
necessary data flows to those functions can in major traffic generators).
be particularly important when designing a
freeway management system, especially if A review of the technologies in each of these
several partners are involved in the three categories is provided later in this
information dissemination process. module. This review can serve as the

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starting point for the technology screening Implementation plan development is

process. However, technology in the governed by federal guidelines, and is
information dissemination realm continues to required for all new or expanded traffic
change rapidly and should be reassessed control system projects that utilize federal
each time this point is reached in the decision funds.(6) Actually, an implementation plan is
process. a good idea for all traffic control system
projects, regardless of whether or not they
Initial screening can be used to determine utilize federal funds.
which of the three basic categories can be
used to effectively accomplish each of the Module 2 described the general guidelines
specified information dissemination regarding overall plan development for a
functions. More than one of the categories freeway management system. In this
may be useable. Then, within each category, section, special issues of plan development
a more detailed screening and evaluation are discussed that relate specifically to the
process can help select among the various information dissemination components of a
alternatives of that technology. Screening freeway management system.
should include such considerations as the
following:(5) Because information dissemination must be
coordinated among the various partners, a
C Legibility (for visual information portion of the plan should be devoted to a
components). discussion of the management structure and
the agreements that will be utilized to
C Reliability. achieve this coordination. Items to be
included in this portion of the plan are as
C Costs to the user and public agency follows:
(these should be life-cycle costs,
discussed in greater detail in Module C Names of contact person(s) for each
11). partner.

C Potential market size. C Protocols and methods to be utilized to

coordinate.
If, for some reason, the screening process
does not identify technologies that can C Definition of each partner’s
adequately perform the functions that were responsibilities regarding information
established, then the analyst must step exchange.
backwards and reassess the objectives and/or
functions of the information dissemination C Estimates of each partner’s financial
component of the freeway management contribution to the effort (cash, in-kind
system. Objectives and associated functions exchange of equipment or services, etc.).
may have to be scaled back or otherwise
modified. C Letters or memoranda of agreement
regarding the desire to coordinate among
DEVELOP IMPLEMENTATION partners.
PLAN
Additional details may need to be included in
The next step in the process is the the letter of agreement if some of the
development of an implementation plan. partners will jointly operate some of the

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information dissemination technologies to be information dissemination rules for the

implemented. For example, a transportation system they have learned to decide what
agency may wish to allow law enforcement messages need to be displayed, on which
personnel to access and utilize their dynamic signs they should be displayed, etc.
message signs or highway advisory radio
equipment for managing major incidents IDENTIFY FUNDING SOURCES
during late-night hours when the
transportation agency does not have Identification of funding source alternatives
someone on duty. actually occurs as part of the plan
development process. As with the other
A detailed implementation plan is also components of freeway management
needed in order to properly coordinate systems, the partners involved in information
information dissemination within the freeway dissemination can share costs through some
management system. Whereas the letters of combination of the following:
agreement and discussion of the
management structure lay out broad C Individual agency hardware purchases
administrative boundaries and consensus to and operation/maintenance which is
coordinate, the implementation plan spells coordinated with another agency’s
out in detail how this will occur. efforts in the region.

An implementation plan may include specific C In-kind contribution of equipment and

preplanned actions that will be taken in services to a pooled service.
response to certain common or expected
situations (i.e., which dynamic message signs C Establishment of user fee schedules
will be activated and what will be displayed (direct or indirect).
on them in response to an incident that
occurs on a specific section of freeway), as Several different cooperative institutional
well as more general rules that will be used arrangements have been successfully utilized
to decide what information to present for to distribute information dissemination costs
unusual, unexpected situations. For in a rational and equitable manner to public
example, the TransGuide Traffic and private partners. For the TRANSCOM
Management System in San Antonio, Texas organization in New York/New Jersey, cash
has over 60,000 preplanned “scenarios” and in-kind contributions from each member
coded into a computerized database. agency fund the operations of the
Depending on the time of day, location of an organization.(9) Each partner has an official
incident, and the number of lanes that are assigned to the TRANSCOM executive
blocked, a specific scenario is selected that committee, which works together to
defines which dynamic message signs and establish the actual fee structure,
lane control signals are to be activated and management policies, and other matters of
the messages that are to be displayed on concern to the agencies as a group.
each (i.e., “LEFT LANE CLOSED
AHEAD”). Most of the time, system In Boston, the SmarTraveler cellular call-in
operators simply activate one of these system is sponsored in large part by FHWA
preplanned actions. Occasionally, a freeway and the Massachusetts Highway Depart-
problem develops for which preplanned ment, but is managed by a private-sector
actions have not been developed. In these limited partnership, SmartRoute. (10) Several
cases, system operators use basic other private-sector companies (cellular

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telephone companies, a paging company, the credibility of the overall system with the
and broadcast media) purchase some of the traveler can be severely degraded by having
information being managed and the devices in place and not using them or by
disseminated, which has helped offset some having the devices display wrong
of the costs to the public agencies. (11) information. One of the problems reported
by officials of the INFORM project in New
In San Antonio, Texas, both public and York was that the DMSs for the project
private-sector partners have entered into a were installed early on in the contract and
Cooperative Industry Product Agreement to then sat there unused for several years as the
facilitate the development and agencies built the rest of the infrastructure.
implementation of the software that will Since it was not immediately apparent to
decode the video and data transmissions motorists why the devices could not be used
from a low-power television station that the to communicate about downstream roadway
Texas Department of Transportation has and traffic conditions, public opinion about
purchased and will operate. (12) This has the project suffered.
allowed the various potential beneficiaries of
the system (i.e., media stations, fleet Another important facet of information
operators, etc.) to contribute to software dissemination implementation is the
development for a relatively small price (and development of training necessary to assist
risk). Furthermore, it provides a mechanism travelers in correctly interpreting and
to allow future partners to enter into the responding to some of the information
agreement in a fair and equitable manner. (12) dissemination technologies. For example,
the Texas Department of Transportation in
IMPLEMENT Fort Worth displays the meaning of lane
control signals mounted over each travel
Implementation of information dissemination lane periodically throughout the freeway
components in the freeway management network. As a result, motorist compre-
system occurs as a natural result of following hension of the available symbols for the
the systems engineering process. Module 2 signals are somewhat higher in Fort Worth
described, in general terms, the than in other locations in Texas. (13) Other
implementation activities that should occur possible training alternatives include public
at this point in the process. In addition to service announcements or mailing inserts in
the issues brought out in that module, other local utility bills.
concerns that pertain directly to information
dissemination include: EVALUATE

C Implementation schedule. The final step in the design process is to

evaluate the effectiveness of the information
C User training. dissemination component of the freeway
management system. However, this eval-
Information dissemination is the main link uation should not be considered a one-time
between the freeway management system activity, but should be part of a periodic
and the motoring public. Experience review of the effectiveness of the
indicates that the implementation of information dissemination components and
information dissemination devices should of the overall system. As discussed
occur only after the surveillance and control previously, it is rather difficult to measure
infrastructure has been installed. Otherwise, the impact of information dissemination

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upon overall traffic measures, because of the Specific technologies available in each of
stochastic nature of travel demands and these categories are discussed below.
behavior in a given freeway corridor, as well
as the events which cause disruptions to ON-ROADWAY INFORMATION
these demands (incidents, special events, TECHNOLOGIES
etc.).
One of the most fundamental technologies
Care should be taken not to overestimate the available for disseminating traffic-related
benefits achieved by the implementation of information from the roadside is that of
information dissemination components in a dynamic message signs (DMS). DMSs are
freeway management system. Specifically, it sometimes referred to as changeable
is important to recognize that travel patterns message signs (CMS) or variable message
in a freeway corridor are quite dynamic, and signs (VMS). DMSs allow operating
that some drivers will divert naturally when agencies to visually disseminate travel
they encounter freeway congestion information to motorists on a near real-time
regardless of whether or not they receive basis. DMSs use words, numbers, or
information beforehand about that symbols to convey information. They are
congestion. Therefore, information extremely flexible and powerful traffic
dissemination should be considered as management tools in freeway operations.
having an incremental effect upon traffic
conditions by modifying where and how DMSs can be either portable or fixed, and
some travelers respond to congestion (where can be operated either on a fixed-time basis
travel routes are changed, how many with on-site control or interconnected with
motorists change departure times, how many a traffic control center to provide remote
changed modes, etc.). control.(14) DMSs can be used to perform the
following functions:
7.3 TECHNIQUES AND
C Inform motorists of varying traffic,
TECHNOLOGIES roadway, and environmental conditions.
Information dissemination components of a C Provide specific information relative to
freeway management system can range from the location and delays associated with
a single device owned and operated by one incidents.
agency, to an integrated collection of devices
and mechanisms under the control of several C Advise motorists on detour routes
agencies and several private sector entities. because of construction or roadway
In this handbook, a basic distinction is made closure.
between kinds of information depending on
which of three main locations it comes from: C Suggest alternate routes to avoid
freeway congestion.
C On-roadway information.
C Reassure drivers on unfamiliar alternate
C In-vehicle information. routes.
C Off-roadway information (typically at C Redirect diverted drivers back to
origin of a trip). freeways.

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Table 7-5 lists the applications for which Light-reflecting signs reflect light from some
DMSs can be used.(14) external source such as the sun, headlights,
or overhead lighting. Figure 7-2 shows
Types of DMS examples of different types of light-reflecting
DMSs. In comparison, light-emitting DMSs
DMSs can be conveniently classified into generate their own light on or behind the
three categories, namely: viewing surface. Examples of different types
of light-emitting DMSs are shown in figure
C Light-reflecting. 7-3.

C Light-emitting. Some manufacturers have combined two

DMS technologies (e.g., reflective disk and
C Hybrid. fiber-optic) to produce hybrid displays that

Table 7-5. Applications of DMSs. (14)

Category Applications
Traffic management and C Freeway traffic advisory and incident
diversion C Freeway-to-freeway diversion
C Special events
C Adverse road and weather conditions
C Speed advisory
Warning of adverse conditions C Adverse weather and environmental conditions
(fog, smog, snow, rain, dust, wind, etc.)
C Adverse road conditions (ice, snow, slippery
pavement, high water, etc.)
C Low bridge clearance
Control at crossings C Bridge control
C Tunnel control
C Mountain pass control
C Weigh station control
C Toll station control
Control during construction and C Advisory of upcoming construction/maintenance
maintenance operations C Speed advisory
C Path control
Special-use lane and roadway C Reversible lanes
control C Exclusive lanes
C Contraflow lanes
C Restricted roadways
C Temporary freeway shoulder use control

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Figure 7-2. Examples of Light-Reflecting DMS Technologies.

exhibit the qualities of both. Some agencies Light-Reflecting DMSs

have also combined DMSs with static
displays to form what can also be considered The basic categories of light-reflecting
to be hybrid displays. DMSs are as follows:

Several references are available that describe C Fold-out.

the operational and performance
characteristics of various DMSs (see C Scroll.
references 1, 14, 15, 16) The following
paragraphs, taken from those references, C Rotating drum.
briefly describe the different types of DMSs
in each category. C Reflective disk matrix.

Basic operations and characteristics of each

are described below.

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Figure 7-3. Examples of Light-Emitting DMS Technologies.

Fold-out. A fold-out sign is a conventional roadway conditions, or to indicate whether

highway sign with a hinged viewing face. truck weigh stations are open or closed.
This type of sign can either display two
messages (one with the hinged face closed, Scroll (or Tape). A scroll sign uses a tape
one with it open) or show a message only or film upon which desired messages are
when the hinged face is open (no message is imprinted. The tape is then rolled one way
displayed when the hinged face is closed). or the other (or up or down) to place a
Typically, signing materials that conform desired message within a display window.
directly to the Manual on Uniform Traffic As with fold-out signs, scroll signs can use
Control Devices (MUTCD) are used to colors and other message characteristics that
make each message. For freeway conform with the MUTCD. Typically, up to
applications, they are most often used to 8 to 12 messages can be stored on the tape.
indicate icy bridge or other hazardous The inclusion of more than 12 messages can

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create long change-times if one or more of C Fixed-grid or shuttered matrix fiber-

the messages is at the opposite end of the optic.
tape.
C Fixed-grid or matrix light-emitting diode
Rotating Drum. Rotating drum signs are (LED).
made up of one to four multifaced drums,
each containing two to six messages. Each Neon or Blank-Out Signs. Neon signs use
face of each drum portrays one line of a neon tubing to form characters and messages
fixed message, and pivots about its axis in that are to be displayed. Two basic sign
order to display the appropriate face for a designs are possible:
given message. Colors and lettering
characteristics that conform to the MUTCD C Separate each message on the sign face.
can also be used on rotating drum signs.
C Stack the neon tubing for each message
Reflective Disk Matrix. These types of one over another.
DMSs were very popular for freeway
management purposes in the 1970s due to The stacked design has reported drawbacks,
their low energy requirements relative to in that emitted light will be diffused as it
light-emitting DMS technologies. The passes through the overlayed neon tubing,
viewing face of a reflective disk matrix DMS reducing its legibility. Conversely, the
is comprised of an array of permanently separate message design will require a fairly
magnetized, pivoted indicators that are flat large sign face in order to display even a
matte black on one side and reflective yellow moderate number of messages.
or a similar color on the other. The
indicators may be square, rectangular, or Lamp (Incandescent Bulb) Matrix Signs.
circular in shape. An electrical current A lamp matrix DMS relies on an array of
activated when a given pixel is to be turned incandescent bulbs affixed to a dark
flips the indicator from a black matte finish background to create the characters needed
to the reflective side. The sign itself can for a given message. The DMS can be a
exist of a series of arrays of these indicators continuous array of bulbs, or a series of
(e.g., 5 pixels by 7 pixels, or similar grid for array modules, each of which can display a
each letter position), or a continuous grid or single character in the overall message. This
matrix over the entire sign face. The latter design provides considerable message
provides more flexibility to operators, but at flexibility, limited only by the size of the sign
a higher purchase price. (typically 4 lines of text, each comprised of
12 to 20 characters).
Light-Emitting DMSs
Fixed-Grid or Shuttered Matrix Fiber-
The following types of light-emitting DMS optic Signs. Fiberoptic DMSs funnel light
technologies are described in this section: energy from a light source through fiber
bundles to the sign face. For a fixed-grid
C Neon or blank-out. fiberoptic sign, the ends of these bundles
(pixels) are positioned on the sign face to
C Lamp (incandescent mulb) matrix. create a given message. Sets of bundles and
a separate light source are then used for each
message portrayed on the sign. Conversely,

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the shuttered matrix fiberoptic DMS manufacturers have combined fiberoptic or

positions the ends of the fiber bundles on the LED technologies into these types of signs
sign face in an array similar to that used for to give them the visual boost they need.
other matrix signs. The light sources for all During the times of the day that the sun
of the fiber bundles remain on constantly, shines upon the sign and provides adequate
and shutters at the ends of the bundles open visibility, the light sources are turned off by
and close to create the characters needed to the sign. In addition to providing the
display each message. As with the lamp additional visual boost during nighttime
matrix DMS, the shuttered fiberoptic signs conditions, this technology also eliminates
can be either a continuous array of pixels or the need for external lighting on the sign.
a series of array modules, each of which This eliminates the potential for glare off of
portrays a single character. Because of its the sign face as well. Some agencies are
flexibility, this tends to be the more common retrofitting reflective disk DMSs with hybrid
type of fiberoptic DMS utilized for freeway reflective disk/fiberoptic technology.(15)
traffic management purposes.
Static/DMS. The other major type of
Fixed-Grid or Matrix Light-Emitting hybrid DMS currently in use employs
Diode (LED) Signs. Light-emitting diodes components of both static signing and one of
(LEDs) are semiconductors that glow when the DMS technologies into a single sign.
voltage is applied. Recent advances in LED This can reduce costs in situations when part
technology have allowed DMS of a message will be constant and another
manufacturers to utilize this technology to part of the message will be changed.(1) Also,
construct both fixed-grid and matrix style the static components can be constructed to
DMSs. Typically, several individual LEDs conform to MUTCD principles. However,
are “clustered” together in order to create this approach does limit the use of the sign
each pixel. Early versions of the LED DMSs to the specific situations addressed by the
experienced difficulties in maintaining static component of the message.
acceptable performance levels over time.
However, LED manufacturers have strived Advantages and Disadvantages of the
to alleviate many of these types of problems DMS Technologies
in the next generation of DMSs that have
been developed. (16) The selection of appropriate DMS
technology is a complex task requiring
Hybrid DMSs analysis of trade-offs between display
capability to fulfill a specific need and
Two of the most common types of hybrid display cost (including operating and
DMSs are the following: maintenance considerations). Further
complicating the selection process is the
C Reflective disk with fiberoptics/LEDs. large number of signing techniques available,
each possessing quite different design and
C Static sign/DMS combination. operating features. Tables 7-6 through 7-8
present a summary of the advantages and
Reflective Disks with Fiberoptics/LEDs. disadvantages that have been reported for
To combat the times of the day and each type of DMS technology (see
environmental conditions when reflective references 1, 14, 15, 16).
disk DMSs are not very visible, some

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Table 7-6. Advantages and Disadvantages of Light-Reflecting DMSs.(Adapted from 1,2,14-16)

Type Advantages Disadvantages

Foldout Simple operation Limited capacity (1 or 2 messages)

Can conform to MUTCD regulatory Higher potential for environmental

and warning signing principles and mechanical failures (i.e., panels
jamming)

Scroll Simple operation Limited capacity (8 to 12 messages)

Can conform to MUTCD regulatory Time to change messages may be

and warning signing principles significant

Rotating Drum Simple operation Limited character size

Can conform to MUTCD regulatory Limited message capabilities (but

and warning signing principles more than fold-out or scroll)

Disk Matrix Total message display flexibility Visibility typically lower than
similar size light-emitting matrix
Wider angle of legibility than DMSs
fiberoptic or LED DMSs (see Table
7-7) Disks sometimes stick or fail
prematurely due to excessive dirt or
Low power consumption relative to moisture
light-emitting DMSs
Illumination is required at night,
sometimes causing glare or blurring
problems

Too often agencies will purchase DMSs information can be disseminated to the
before signing objectives and messages are motorist by audio or visual means. The
determined. Often, this causes following sections describe the basic types of
disappointment in the DMSs when these in-vehicle information technologies.
agencies cannot display the desired
messages, or when the signs provide lower Auditory In-Vehicle Information
than expected target value and legibility for Technologies
the environmental conditions present at the
site.(2) Conversely, agencies may end up Highway Advisory Radio
purchasing a more expensive DMS with
capabilities that exceed their actual needs. Although not as widely used as dynamic
message signs, Highway Advisory Radio
IN-VEHICLE INFORMATION (HAR) is another means of providing
highway users with information in their
Another realm of information system vehicles. Traditionally, information is relayed
technologies available are those located to highway users through the AM radio
within the vehicle itself. In-vehicle receiver in their vehicles. Upstream of the

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Table 7-7. Advantages and Disadvantages of Light-Emitting DMSs.(Adapted from 1,2,14-16)

Type Advantages Disadvantages

Neon (blank out) Simple operation Limited message capacity

Requires a fairly large sign for even

moderate number of messages

Current designs to not allow for

nighttime dimming

Lamp (Incandescent) Simple, proven operation Continuous energy supply required

Matrix to display message
High target value
High operation and maintenance
Message flexibility costs (energy, bulb replacement)

Fixed Grid Fiberoptic Low power usage Narrow cone of vision

Can display symbols and messages Limited message capacity

Shuttered Matrix Simple operation Narrow cone of vision

Fiberoptic
Message flexibility Mechanical component (shutters)
increases potential maintenance
Low failure rates reported costs

Fixed Grid LED Low power usage Narrow cone of vision

Solid state devices (no bulbs) Limited message capability

Reported reliability of LED lamps Intensity adversely affected by high

is very high temperatures

Long-term performance not known

Super-bright LED lamps must be

used for adequate daytime visibility

Matrix LED Low power usage Narrow cone of vision

Solid state devices (no bulbs) Intensity adversely affected by high

temperatures
Reported reliability of LED lamps
is very high Long-term performance not known

Super-bright LED lamps must be

used for adequate daytime visibility

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Table 7-8. Advantages and Disadvantages of Hybrid DMSs.(Adapted from 1,2 14-16)

Type Advantages Disadvantages

Disk Matrix with Some energy conservation (light- Use of LED technology limited to
Fiberoptics or LEDs emitting technology is turned off in date (long-term performance not
daytime conditions) known)

Eliminates need for nighttime More complex operation

illumination of sign (maintenance may be more costly)

Combined Static/DMS Portions of sign can conform to Static portions of sign limits
MUTCD regulatory and warning message flexibility
signing principles
Light-emitting DMS technology
Some cost savings is possible may wash out static portions of sign
relative to full-matrix DMSs if too bright

HAR signal, users are instructed to tune C Notification of highway construction or

their vehicle radios to a specific frequency maintenance.
via roadside or overhead signs. Usually, the
information is relayed to the users by a pre- C Alternate route information.
recorded message, although live messages
can also be broadcast. C Advisories within and regarding
transportation terminals (airports, special
Message transmissions can be controlled events, and other major traffic
either on-site or from a remote location generators, etc.).
through telephone or radio interconnects.
Most HAR systems operate at the 530 or One of the major advantages of using HAR
1610 kHz frequency level; however, any is that information is received through a
available frequency can be used as long as a different sensory channel (audio), which
low enough power level is used. A license reduces information overload received
from the Federal Communication visually while driving.(17) Also, longer and
Commission is required to operate a HAR more complex messages can be provided to
system at high power levels (10 watts or motorists than can be accomplished using
greater). DMSs. However, traditional HAR systems
have their drawbacks. They require motorist
HAR is used in many different applications. action (i.e., tuning radio to appropriate
With respect to freeway management, uses frequency) in order to receive information.
of HAR are similar to those of DMSs, and Also, if a motorist misses one part of an
include the following: HAR message, he or she must listen to the
entire message again in order to obtain the
C Warning of roadway incidents or missed part.
congestion.
There are two types of HAR systems:
C Warning of adverse environmental vertical “whip” antenna systems and
conditions (fog, ice, etc.). induction cable antenna systems. Vertical
“whip” antenna systems use individual

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antennas or a series of antennas C Interference with other radio systems in

electronically connected together to transmit the area is minimized.
information. The signal radiates from the
antenna in all directions providing a circular Disadvantages of induction cable HAR
area of transmission. Vertical antenna systems include the following:
systems have the following advantages:
C Induction cable systems are more
C They are small. expensive to purchase and maintain since
the cable must extend the full length of
C They are easy to install. the desired coverage area.

C They can be placed within several C Once installed, induction cable HAR
hundred feet of the roadway. systems cannot be transported from one
location to another.
C They are less costly to purchase and
install than induction cable systems. Automated HAR (AHAR)

Vertical antenna systems also have the One of the disadvantages of HAR systems is
following disadvantages: that they require advance signing to notify
motorists of the availability of information,
C They are subject to damage by weather, and an action by the motorist to activate and
accidents, and vandalism. receive that information. Automated
highway advisory radio (AHAR) systems
C They often require special equipment to have been proposed that require no actions
ensure that the signal is stable, reliable, by the motorist to obtain radio information.
and easily tuneable. These systems emit a special electronic
notification signal upstream of an HAR
C Motorists can lose the HAR signal when message, which interrupts the specially-
traveling through tunnels, canyons, etc. designed radio/cassette/compact disc player
to broadcast the message to the motorist.
Induction cable antenna systems use a cable
installed either under the pavement or FHWA sponsored the prototype
adjacent to the roadway. This type of development and pilot testing of an AHAR
antenna design produces a strong but highly system in the early 1980s. (18,19) However,
localized signal within a short lateral distance the difficulties associated with producing and
30 to 45 m (100 to 150 ft) from the cable. marketing a receiver within a price range
Induction cable systems have the following acceptable to motorists hindered further
advantages: AHAR implementation. However, recent
emphasis on ITS has sparked renewed
C The signal is strong enough to provide interest in AHAR systems. Michigan is
full coverage of a multilane facility experimenting with alternative AHAR
without causing interference to other designs at this time. (20) Meanwhile, Europe
HAR systems. has been experimenting with a version of
these types of systems (termed the Radio
C Messages can be individualized by Data System [RDS] Traffic Management
direction of travel. Channel [TMC]) for the past few years.
This system relies on a silent data channel

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broadcast via FM from existing radio Many metropolitan areas have established
stations. With an appropriate radio receiver, cellular “hotlines” for motorists to call in and
a motorist is then able to receive information report accident information to the highway
from the closest or strongest FM radio signal agency. Examples include #77 and *SP.
at that location. (15) The public agency must negotiate with the
cellular companies to provide the toll free
Cellular Telephone “Hotlines” calls.

An in-vehicle communication technology Recommendations for establishing cellular

that has seen dramatic growth in the past telephone “hot-line” systems include the
few years is cellular telephones, which gives following:
the motorist the ability to call special
“hotline” systems for traffic information C The call must be toll-free to users.
from within their vehicle. Originally, these
systems allowed motorists and transit users C The telephone number must be easy to
to call for information to assist in pre-trip remember and dial.
decisions from their homes. Information can
now be accessed en route via cellular C The information must be concise.
telephone, and decisions can be made
whether to alter travel routes. The creation C If a menu system is used, a long and
of call-in systems has been a popular traffic tedious menu selection process should be
impact mitigation strategy for many major avoided.
urban freeway reconstruction projects in
recent years. (21) C A sufficient number of telephone lines
should be provided to prevent the
One of the more successful examples of this majority of users from receiving a busy
technology is the two SmarTraveler systems signal.
now in place in Boston and Cincinnati. (10)
Both systems employ special telephone C If a system is going to be used to gather
numbers to keep the service free to cellular information from users, there must be a
telephone users. Touch-tone menus allow method of ensuring the accuracy of the
callers to receive route-specific traffic incoming information.
information (delays, construction activity,
recommended alternative routes), bus and C “Official” use of tipster information
train scheduling, and special event should include procedures for verifying
transportation information. that information.

This type of in-vehicle communication has C If incident information is to be received,

the advantage over HAR of giving the a human operator is recommended so
motorist some control over the type and that secondary questions can be asked to
amount of information he/she wants to clarify confusing or unclear reports.
obtain through the touch-tone menus. In
addition, it is also possible to generate two- As with HAR systems, this technology also
way communication between the motorist requires action by the motorist to access
and the information source. information. There are also significant
operating costs associated with this
technology, as any calls made using cellular

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telephones must be paid for by either the and cooperation between themselves and the
motorist, or a public agency, or else media traffic reporters. For example, some
absorbed by the corporation providing agencies allow private traffic reporting
cellular telephone communication agencies to place personnel in the traffic
capabilities in the region. Finally, there is management center to obtain information on
some concern that cellular telephone usage traffic conditions and expected agency
while driving may degrade motorist attention responses in an accurate and timely manner.
and operating capabilities. Manufacturers
have developed “hands-free” telephones that Citizen-Band Radio
allow motorists to listen and talk without
holding the telephone receiver. Even though it was once considered an
excellent means of providing motorists with
Commercial Radio two-way communications from their vehicle,
Citizen-Band (CB) radio has declined in
The public has learned to depend upon the popularity in recent years. However, there
media to provide them with “almost” real- are still a significant number of vehicles,
time traffic information. Commercial radio particularly commercial vehicles and trucks,
has proven to be a good means of providing equipped with CB radios. In the past, CB
travelers with traffic information both in and radios have been used primarily in motorist-
out of their vehicles. Traffic and roadway aid systems. A disabled or passing traveler
condition reports have become standard broadcasts a request for assistance on
programming items on many commercial channel 9. The channel is monitored 24
radio stations. Commercial radio has the hours a day, 7 days a week by a police or
best potential of reaching the greatest volunteer organization, which dispatches aid
number of commuters, since most of them to the stranded traveler. The primary
have radios in the vehicles they drive to and advantage of a CB radio system is that it
from work. permits two-way communication between
the traveler and the response agency. The
The primary disadvantage of using effective range of many CB radios is
commercial radio relates to the accuracy of approximately 32 kms (20 mi), depending
the information. Traffic reports often are upon geographic conditions.
transmitted only when normal scheduling
permits. This may cause considerable time Visual In-vehicle Information
delays between when an incident occurs and Technologies
when it is reported by the media. Often,
many incidents go unreported or are cleared Video Display Terminals
by the time they are reported on the radio
and television. The accuracy of the One of the newer technologies for
information provided by commercial radio is communicating with motorists in their
a function of the time between the vehicles is through a video display terminal
broadcaster’s last communication with the (VDT) mounted in the dashboard. This is
incident reporting source and the number of primarily a private sector industry, which has
incidents that have occurred and/or have not been used widely for information
been cleared during that time. distribution. These systems can be used to
provide motorists with route guidance and
Some transportation agencies have made navigational information in one of two
substantial efforts to improve coordination different formats. One approach is to

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present the driver navigation and route C VDTs may also add to the visual clutter
guidance information in the form of maps or already inside the vehicle.
equivalent displays. With these systems, a
global picture of the traffic network can be Head-Up Displays
provided. Recommended routes can be
highlighted on the video map display as well. As technology continues to improve, the
In another approach, simple symbolic signals Head-Up Display (HUD) has become
(e.g., arrows, text instructions, or a another alternative to in-vehicle VDTs for
combination of both) guide the driver along presenting visual navigational and route
a recommended route. Some prototype guidance information to motorists.
systems use a variety of displays depending Although originally developed for the
upon whether or not the vehicle is in motion, aviation industry, several automobile
the functions selected, and level of manufacturers are beginning to develop
informational and navigational displays HUDs for presenting vehicle status and
available. navigational information to drivers.

In-vehicle VDTs offer a number of A wide variety of options for displaying

advantages over available technologies in information may be available using HUDs.
providing information to motorists while Through both icons and alpha-numeric text,
driving. These include the following: navigation and route guidance information
may be projected directly into the driver’s
C Travel information is more readily field of view. This is expected to reduce the
accessible to the driver (providing need for visual scanning between two
continuous access to current position, information sources (the inside instrument
routing, and navigational information). panel and the outside environment), and the
associated visual accommodation time.
C Computer-generated navigational maps
and displays are logical extensions of However, as might be expected, numerous
traditional forms of providing drivers concerns exist regarding the safety and
with route guidance and navigation applicability of using HUDs in the driving
information. environment.(23) Currently, most HUDs
under development and implementation
Information can be displayed in text, provide drivers with only relatively simple
graphics, or both and tailored to the needs information, such as speed indications.
and desires of each motorist.
OFF-ROADWAY INFORMATION
There are also limitations to in-vehicle
VDTs. These include the following: The final type of information systems
discussed in this module are those that
C Drivers have to take their eyes off the drivers access off-roadway, at their homes,
roadway in order to receive the offices, shopping malls, etc. A major thrust
information. of ITS development and implementation
focuses on putting more information into the
C In-vehicle VDTs present the driver with hands of motorists and passengers so as to
complex maps and diagrams that may improve departure time, mode choice, and
create a potential to overload the driver route choice decisions. This emphasis has
with too much information. resulted in increased utilization of a number

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of traditional information technologies, and displays accompanied by voice messages can

has yielded a number of new off-roadway be used to provide users with information.
information sources and several new Traffic reports can also be provided by
dissemination technologies. Off-roadway interrupting normal programming. The
information dissemination technologies primary disad-vantage of using public access
include the following: television is that the information is available
only to cable subscribers. Travelers living
C Television. outside the service area or not subscribing to
the particular cable company do not have
C Telephones. access to the information.

C Pagers. One freeway traffic management center in

the U.S. has developed the capabilities to
C Personal Data Assistants (PDAs). provide video and digital data directly to
television signals. (12) They broadcast live
C Computers. video, a computerized map display, and
current control and management actions
C Kiosks. being implemented (which DMSs have been
activated). These signals are scrambled so
Television that only those with the appropriate software
and hardware can properly receive the
Television (together with radio) was one of signal. This is believed to reduce the need
the first off-roadway motorist information for censoring the images that are being
technologies available to motorists. Even presented, since they are not available to the
today, commercial television stations in most public at large.
major cities provide traffic reports to
viewers as part of their morning programs to Telephones
indicate incident locations, traffic signal
malfunctions, and other traffic “hotspots.” As discussed earlier, telephone “hotlines”
These locations are usually shown on some can allow both freeway and transit users to
type of wall-mounted or computer-generated obtain pre-trip information via their
map display. telephones at home or work, or in their car
if they are willing to pay for cellular airtime
Public access television is a means of charges to call the hotline. Information can
overcoming many of the disadvantages be provided using recorded messages,
associated with privately owned media synthesized voice messages, or human
stations. Many city governments are operators. A touch-tone menu system can
responsible for franchising cable television be used to tailor information to a specific
service within the corporate limits of the route or travel corridor. Telephone calls are
city. As part of awarding the franchise to a also a means of developing real-time
company, many city governments offer their rideshare matching systems that are being
own programming on one or more of these explored in several U.S. locations.
dedicated channels. Public access channels
can be used by traffic management agencies Pagers
to broadcast continuous traffic information
during peak hours. Either “crawl” messages A more recent technology now used to help
across the bottom of the screen or map disseminate travel information to users away

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from the vehicle are personal pagers. In disseminate information to travelers. As

Bellevue, Washington (east of Seattle), with PDAs, two-way communications
alphanumeric pagers provide their owners between the computer user and the travel
with hourly information regarding available information center can be established by
carpools looking for riders as well as current telephone modem or an RF communication
traffic conditions on the Puget Sound-area link. This two-way flow of information
freeway system.(24) The Genesis project of allows the user to request information
the ITS Guidestar program in Minneapolis, specifically tailored to his or her needs (route
Minnesota and TRANSCOM in New Jersey planning, traffic information on specific
also utilize alphanumeric pager technology roadway links, transit bus schedule and
to disseminate travel conditions in real-time status, etc.).
to its owners. A key constraint of pager
technology is that broadcast messages are Kiosks
limited to a small number of characters.
Consequently, efforts are underway to The last off-roadway information dissem-
determine which information is most relevant ination device to be discussed is the
to pager owners and how to format that information kiosk. Kiosks are video
information succinctly, but accurately.(25) monitors mounted on a stand-alone cabinet,
in a wall, or on a counter-top. They may
Personal Data Assistants (PDAs) have input devices such as keypads, track-
balls, or touch-screen displays. Kiosks can
Personal Data Assistants (PDAs) are the serve as an important point of access to
next higher level of sophistication in off- travel information networks in a variety of
roadway information dissemination public locations, including the following:
technology. PDAs are computer products
that have enough power to support C Hotels.
applications such as time management and
handwriting recognition. By adding radio C Restaurants.
frequency (RF) communications technology,
PDAs allow users to interact directly with C Airports.
travel information systems. This interaction
allows users to obtain route planning C Gas stations (truck stops).
assistance, traffic information broadcasts,
and other pertinent information. Through C Retail establishments (shopping malls).
keypad entry, the user can log on to the
information system, request pertinent Kiosks are one type of information
information, and then log off. PDAs offer dissemination technology where
the user increased communication and private/public partnerships are particularly
information transmission/receiving power relevant. For instance, some agencies are
over alphanumeric pagers. However, they looking to the private sector (through
are more complex to use and expensive to advertising revenue) to help defray the
purchase. (25) operating and maintenance costs of these
systems.(26, 27) Proper kiosk placement is
Computers (Internet) also a critical issue. Many kiosks are not
well utilized because they are not located
Personal computers, both desktop and where they can draw attention and reach
laptop/notebook, can also be used to their intended market.(27)

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7.4 LESSONS LEARNED dissemination subsystem. Evidence already

exists on some of the newer ATIS
NTCIP STANDARDS technologies that improper message designs
have an adverse impact upon customer (i.e.,
Equipment compatibility, especially with motorist) interpretation of the worth and
respect to communications, has long been a usefulness of these technologies.(29)
problem for many transportation agencies Without proper attention to packaging, the
operating various components of freeway intended audience may not be able to
management systems. Incompatibilities adequately perceive, interpret, and respond
between DMS and HAR hardware from to the information. The following factors
different vendors have required the agency are critical to proper message design:
to have separate systems to communicate
with each type of DMS or HAR. This has C Message load.
made it difficult to operate the equipment
efficiently and in an integrated manner. C Message length.

In response to these and other problems, a C Message format.

National Transportation Communications
Interface Protocol (NTCIP) is under Message load refers to the quantity of
development to reduce the difficulties information that is included in a given
associated with developing an integrated message. Message load is an important
freeway management system. These consideration for DMS operations, because
protocols establish standard communications the driver must attend to many different
linkages between various types of hardware tasks at the same time, while trying to read
and software used for traffic management and comprehend a message. If the message
purposes. This ultimately reduces the need presents too much information, message
for an agency to select and stay with a overload may occur. Some transportation
particular vendor or model of equipment. agencies have reported traffic slowing down
and other adverse operational problems in
In the information dissemination arena, the vicinity of DMSs when messages are too
standards have been proposed, or are under long. (1)
development, for DMS and for HAR.
Standards for other equipment are likely to Message length refers to the number of
emerge as the need arises. Partners are words or characters that are displayed on
strongly encouraged to utilize NTCIP one or more lines of a sign or sequence.
standards where possible. Obviously, message length and load are
related. However, message length and how
INFORMATION MESSAGE DESIGN the message is formatted, or “chunked,”
both affect message load.
Although traditionally a concern associated
with public agency information dissemination Message formatting is a term that refers to
mechanisms such as DMS and HAR, the the arrangement of message elements (words
proper design and packaging of the or lines) on an information dissemination
information being disseminated is critical to device (e.g., a sign) to form a message. Use
successfully meeting the goals and objectives of abbreviations also relates to message
for all components of an information formatting. Placement of message elements
on the wrong line or in the wrong sequence

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will result in confusion and increased large extent by a regular sign maintenance
message reading and comprehension times. (pixel lens cleaning, light bulb replacement)
program.
The completed and detailed set of guidelines
regarding message design from which these “AT-REST” DISPLAY CONDITIONS
paragraphs were drawn are available
elsewhere. (2) Another DMS-specific issue is what to do
with the signs when there is nothing special
ENVIRONMENTAL ISSUES to report to travelers. There are generally
CONCERNING DMSs two schools of thought regarding when
information should be provided in
Because they are located outdoors next to dissemination devices.(2) One perspective is
the freeway, the effectiveness of DMSs as an that some type of information such as
information source is also affected by current time and temperature, an agency
environmental factors. Two factors that can slogan, etc., should be provided at all times.
be significant are sun position and Proponents argue that this indicates to
weathering effects. motorists that the devices are working. The
other perspective is to display information
Sun Position only when there is something new to tell
travelers. Proponents of this school of
Both sunlight falling directly upon the face thought argue that, according to human
of a DMS and sunlight located directly factors principles, trivial or non-traffic
behind the DMS adversely affect a driver’s specific information should be avoided so
ability to see the message. Sign positions that the devices do not lose credibility with
with the rear surfaces oriented west- the travelers.
southwest and east-northeast should
therefore be avoided if possible. The west- 7.5 EXAMPLE OF AN
southwest orientation is more problematic,
however, because the setting sun tends to be INFORMATION
more intense than the rising sun.(1) DISSEMINATION SYSTEM:
TRANSCOM
Weathering
ORGANIZATION
Because of their proximity to freeway travel
lanes, road grime can be a problem for
TRANSCOM (Transportation Operations
certain DMSs, and significantly reduce the
Coordinating Committee) is a consortium of
distances at which they are legible.
14 transportation and public safety agencies
Consequently, DMS manufacturers often
in the New York, New Jersey, and
place clear Lexan covers over the DMS face
Connecticut area whose goal is to provide a
to protect the sign from road grime and
cooperative, coordinated approach to
other environmental effects. One study
regional traffic management. TRANSCOM
suggests that legibility distances of a fixed-
is funded, staffed, and governed by its
grid fiberoptic DMS (a freeway lane control
member agencies. It has an Operations
signal without a Lexan cover) may be
Information Center (OIC) that is staffed 24
reduced by as much as 25 percent after 18
hours per day, 7 days per week.
months in the field. (29) It appears that these
TRANSCOM shares incident information via
losses in legibility can be minimized to a

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alphanumeric pager, phone, and fax to more dissemination and incident response in the
than 200 highway and transit facilities, police region. These include the following:
agencies, and radio traffic services. It also
serves as a forum for incident and special C Regionwide initiatives for coordinated
event management planning, construction deployment and operation of VMSs,
coordination, and for shared testing and HAR, and enhanced traffic monitoring
implementation of regional traffic and via CCTV.
transportation management technologies.
C An enhanced traffic advisory/diversion
The planning process for TRANSCOM system at the intersection of the New
began at the end of 1984. TRANSCOM Jersey Turnpike and Garden State
began operations in 1986. Originally, the Parkway, which will focus on alternative
Port Authority of New York envisioned routing for New Jersey transit buses.
TRANSCOM as a coordinating mechanism
to facilitate traffic flow and operations at the C Expansion of traffic monitoring along
Hudson River crossings. However, the I-287 Tappan Zee Bridge corridor.
TRANSCOM’s focus quickly expanded to C Initiation of the TRANSMIT
all traffic facilities in the region. (TRANSCOM’s System for Monitoring
Incidents and Traffic) Operational Test.
TRANSCOM is managed by a steering This project uses vehicles with
committee made up of senior and mid-level transponders on a highway system
managers from each agency. This committee equipped with readers/antennas.
directs the technical and operational focus of
TRANSCOM. Meanwhile, an executive TRANSCOM receives information regarding
committee consisting of the chief executive incidents and transit facility conditions from
officer from each agency decides major all over the area. The OIC is normally
policies pertaining to TRANSCOM. staffed with two operators who receive,
collate, and disseminate transportation-
Although TRANSCOM is a public sector related information. The information is
information dissemination example, it is relayed to the agencies affected by the
considering moving towards a public/private incident via alphanumeric pagers, facsimile
partnership. Public/private partnerships are machines, and voice communications. This
a much more appropriate example of what is information is then disseminated by the
likely to occur in the future. various agencies according to their
capabilities. In some instances,
OPERATIONS TRANSCOM has been granted authority to
operate the information dissemination
The TRANSCOM OIC receives information technologies for certain agencies. (9)
regarding incidents and transit facilities from
all over the metropolitan area. The TRANSCOM operations are fully funded by
operations personnel in the OIC are its member agencies. This funding consists
employees of one of the member agencies of both monetary contributions and in-kind
and generally have some background in services such as providing operators to staff
dispatch, operations, or media reporting. the OIC.
The TRANSCOM partnership has allowed
several projects to be developed and
implemented to facilitate information

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FUTURE ACTIVITIES effectively manage travel in the congested

northeast corridor. The TRANSMIT system
The executive and steering committees are is an example of this commitment to future
looking at a number of issues relating to operations. (30) TRANSCOM is participating
future TRANSCOM operations. with other agencies in the development of a
TRANSCOM will continue to pursue computerized Information Exchange
research and testing of advanced Network (IEN) to automate the information
technologies to help the region more retrieval and dissemination process.

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7.6 REFERENCES
1. Dudek, C.L. Guidelines on the Use of Changeable Message Signs. Report No. FHWA-
TS-90-043. FHWA, U.S. Department of Transportation, Washington, DC, May 1991.

2. Dudek, C.L. and Huchingson, R.D. Manual on Real-Time Motorist Information

Displays. Report No. FHWA-IP-86-016. FHWA, U.S. Department of Transportation,
Washington, DC, August 1986.

3. Inman, V., Sanchez, R., Porter, C., and Bernstein, L. TravTek Evaluation Yoked Driver
Study. Report No. FHWA-RD-94-139. FHWA, U.S. Department of Transportation,
Washington, DC, October 1995.

4. Building the ITI: Putting the National Architecture into Action. Report No. FHWA-JPO-
96-011. FHWA, U.S. Department of Transportation, Washington, DC, April 1996.

5. Vorce, K.E. and Plass, M. A Practical Approach to Changeable Message Sign System
Design and Deployment: The I-595 Experience in South Florida. Proceedings, Third ITS
World Conference, Orlando, FL, October 1996.

6. Implementation Plan Guidance (23 CFR 655 409). Federal-Aid Policy Guide. FHWA,
U.S. Department of Transportation, Washington, DC, December 1994.

7. McGowan, P.F., Olson, M.D., and Irwin, P.L. Texas Department of Transportation
Advanced Traffic Management System, San Antonio, Texas. Compendium of Technical
Papers, 64th Annual Meeting of the Institute of Transportation Engineers, Dallas, TX,
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8. Roper, D.H., Murphy, R.J., and Zimowski, R.F. Alternative Route Planning: Successful
Incident Traffic Management. Special Report No. 153, TRB, National Research Council,
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9. Wilson, F.J. The TRANSCOM Coalition: Multi-Jurisdictional Issues in ITS. ITS

Quarterly, Vol. IV, No. 2, Spring 1996, pp 83-95.

10. Bregman, S., Koses, D.G., and Wilson, A.P. Targeting the Car Phone Market: Findings
from a Survey of Callers Using Cellular Telephones to Access the SmarTraveler
Advanced Traveler Information System. Proceedings, Third ITS World Conference,
Orlando, FL, October 1996.

11. Dial and Drive -- or Don’t. Inside IVHS, Vol. 5, No. 3, January 30, 1995.

12. Dellenback, S.W., and McGowan, P.F. Advanced Traveler Information Systems Using
Low Power Television Stations. Proceedings, 1996 Annual Meeting of ITS America,
Houston, TX, April 1996, pp 82-86.

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13. Ullman, G.L., Wohlschlaeger, S.D., Dudek, C.L., and Wiles, P.B. Driver Interpretations
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14. Dudek, C.L. Changeable Message Signs. NCHRP Synthesis of Highway Practice No.
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15. Gordon, R.L., Reiss, R.A., Haenel, H., Case, E. R., French, R.L., Mohaddes, A., and
Wolcott, R. Traffic Control Systems Handbook. Report No. FHWA-SA-95-032.
FHWA, U.S. Department of Transportation, Washington, DC, February 1996.

16. Lavigne, R.C. Assessment of Changeable Message Sign Technology. Report No.
FHWA/RD-87/025. FHWA, U.S. Department of Transportation, Washington, DC,
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17. Walker, J., Alicandri, E., Sedney, C., and Roberts, K. In-vehicle Navigation Devices:
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U.S. Department of Transportation, Washington, DC, May 1990.

18. Automatic Audio Signing, Volume I: Executive Summary. Report No. FHWA/RD-
82/012. FHWA, U.S. Department of Transportation, Washington, DC, November 1981.

19. Turnage, H.C., Hawthorne, R.C., and Birdseye, M.C.L. Automatic Audio Signing,
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20. Rajendra, K., and Maki, R.E. The IVHS Strategy in Michigan. Proceedings of the IVHS
America Annual Meeting, Atlanta, GE, April 1993, pp 402-406.

21. Von Tomkewitsch, R. Dynamic Route Guidance and Interface Transport Management
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22. Dingus, T.A., Carpenter, J.T., et al. Human Factors Engineering the TravTek Driver
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23. Kiefer, R.J. A Review of Driver Performance with Head-Up Displays. Proceedings,
Third ITS World Conference, Orlando, FL, October 1996.

24. Haselkorn, M., Spyridakis, J., Gable, B., and Michalak, S. Bellevue Smart Traveler: An
Integrated Phone and Pager System for Downtown Dynamic Ride Sharing. Proceedings
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25. Starr, R.A., and Wetherby, B.C. Traffic Information on Alphanumeric Pagers: Evaluation
Results from the Genesis Project. Proceedings, Third ITS World Conference, Orlando,
FL, October 1996.

26. Schroeder, J.L., and Green, J. The Emergence of Smart Traveller Kiosk and the User
Interface Requirments for their Successful Deployment. Proceedings of the IVHS
America Annual Meeting, Atlanta, GE, April 1993, pp 831-837.

27. Pohlman, J.M., and Long, T.I. Advanced Traveler Information Project Travelink.
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28. Guiliano, G., Hall, R., and Golob, J.M. Los Angeles Smart Traveler Field Operational
Test Evaluation. Report No. UCB-ITS-RRR-95-41. California PATH Program, Institute
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29. Ullman, G.L., Tallamraju, S.S., and Trout, N.D. Visibility and Spacing of Lane Control
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Transportation Institute, College Station, TX, November 1994.

30. Tarnoff, P.J., and Batz, T. The TRANSCOM TRANSMIT Project: A Unique
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