Chapter 13 – Information
Page 2 of 3
13.2.7 Highway Advisory Radio
Although not as widely used as CMS, Highway Advisory Radio (HAR) is another
means of providing highway users with information in their vehicles. Traditionally,
information is relayed to highway users through the AM radio receiver
in their vehicles. Upstream of the HAR signal, users are instructed to
tune their vehicle radios to a specific frequency via roadside or overhead
signs. Usually, the information is relayed to the users by a prerecorded
message, although live messages can also be broadcast.
Highway advisory radio (HAR) is an effective tool for providing timely
traffic and travel condition information to the public. It has various
advantages and disadvantages. It's most important advantage is that it
can reach more travelers, or potential travelers, than Changeable Message
Signs (CMS). While CMS's reach only those motorists at a particular point,
and can only convey a short message, HAR has the advantage of being able
to communicate with any persons in their broadcast range. Further, the
amount of information that can be conveyed is much greater. Its primary
disadvantages are that it is restricted to low power, and this leads quite
often to poor signal quality (since it affected by many outside forces
such as weather), and it requires the driver to take an action (i.e.,
turn on the radio or change the station or both). This can lead to poor
HAR is an element of the Federal Communication Commission's (FCC) Traveler
Information Systems designation. They are permitted under strict FCC guidelines
and regulations associated with technology and operations. They are licensed
as a secondary user, which means simply that they cannot interfere with
a primary user, i.e., a commercial broadcast station. As a secondary user,
HAR broadcasts are restricted in signal strength, a level that limits
their transmission range to no more three or four miles from the transmitter.
A number of technologies are available for HAR transmission, using both
AM and FM bands.
Typically, HAR has been implemented using 10-watt AM transmitters. This
is because, beginning in 1977, it was the only technology permitted by
the FCC for traveler information. As such, this technology implementation
has also proven to be the most effective. Other means involve very-low
power AM transmission, where multiple transmitters are spaced closely
together to form a large area of coverage. This application, however,
has not proven very successful. As late as 2000, the FCC ruled to allow
the use of low-power FM transmission for TIS. This technology has limited
Urban areas typically present a unique set of challenges to HAR application.
Tall buildings present an obstacle to uniform transmission since the FCC
restricts antenna height to approximately fifty (50) feet. High-power
electric lines can incur noise on the transmission that negatively impacts
Messages are broadcast in the field from transmitters that play stored
messages. These messages are transmitted to the field from a "central"
location, which can be a traffic control center or any telephone. In its
simplest form, no central system is needed, only an analog phone line
to the transmitter so that an operator can record a message in the transmitter
for broadcast. This is labor intensive if an agency maintains a number
of transmitters, and traffic conditions change throughout the day. Its
advantage is that it is inexpensive, and message can be sent to a transmitter
from anywhere a phone exists, even from a cell phone. Alternatively, a
central message distribution system is used to record new messages, store
pre-recorded messages, and distribute messages to the transmitters (simultaneous
if necessary). This is typically a PC-based system with security access
184.108.40.206 Field System
Figure 13-5: Highway Advisory Radio Station Along Freeway
The transmitters and other broadcast components are located in the field.
(Figure 13-5) There are multiple
technologies available for HAR application.
10-Watt AM Transmission (FCC Licensed)
This is the most common HAR application. When properly maintained and
installed, 10-watt transmitters have a broadcast radius of approximately
3–5 miles depending on topography, atmospheric conditions, and the time
of day. Frequencies used are generally located at the extreme ends of
the AM band using specific frequencies based upon the availability of "holes" in the spectrum left by government and commercial stations. New
FCC rules permit HAR to be broadcast on any frequency between 530 kHz
and 1710 kHz provided an FCC license is obtained. The FCC rulings have
also opened up the former dedicated HAR frequencies, 530 kHz and 1610
kHz, to commercial broadcasting, thereby increasing the potential for
interference or possibly the loss of a license.
The characteristics of the broadcast are also affected by the frequency
used. The lower ranges of the band (e.g., 530 kHz) are adversely affected
by power lines (because of its long wavelength). It also has problems
with signal fade, which causes distorted transmission for a reasonable
distance along the outer (fringe) areas of the coverage area. Because
of this, it is uncommon to find any commercial broadcasters on this end,
which is an advantage. On the other end of the spectrum, power lines have
less impact on the signal, and a crisper fringe transmission.
Digital Highway Advisory Radio
Digital HAR eliminates many limitations of traditional dial-up systems,
and improve quality of messages being broadcast to the traveling public.
While dial-up systems typically operate over analog phone lines, advanced
computer-controlled systems use digital signal processing to optimize
Compared to traditional dial-up systems, "digital HAR" offers increased
speed of message updating, centralized management of multiple stations,
enhanced reliability, superior audio quality, ease of operation, and automated
event logging. The time required for an operator to update audio at a
remote site from the central control unit can be as little as two seconds.
This can be accomplished through a simple "drag & drop" operation
using a specialized Windows program. A Windows environment also easily
allows for control of multiple HAR stations from a single central location.
Digital control provides closed loop operation assuring that messages
and commands are received exactly as downloaded. There is no guessing
about what is occurring at the remote sites. Analog phone lines typically
limit audio bandwidth to about 2.5 kHz reducing the quality of the audio
motorists receive on their vehicle radios. If desired, digital messages
can be downloaded to remote HAR sites at CD quality provided that FCC
imposed bandwidth limitations are satisfied.
Low-Power AM Transmission (No FCC License Required)
Low-power HAR has been developed as a means of tightly controlling the
broadcast zone and thereby limiting interference from adjacent zones.
Low power HAR differs from the previously discussed 10-watt HAR in that
its broadcast radius (per transmitter) is generally limited to 500 feet
to 1500 feet. By FCC regulation, each transmitter is limited to a maximum
0.1 watt power input to the final frequency stage, and the total length
of the transmission line, antenna, and ground lead can not exceed 3 meters.
Whereas this limits its broadcast range, it also provides for a reasonably
well-defined area of influence, which, through an inter-connection and
synchronizing process, permits upwards of 100 transmitters to be coordinated
into larger and well-defined saturation zones. Once a car leaves this
broadcast area, the signal quality becomes too weak to be heard. This
permits a second zonal configuration to be established nearby, transmitting
a different message on the same frequency.
By using this concept, a series of zones all operating on the same frequency,
may be established whereby unique site-specific messages may be transmitted
to provide condition updates in advance of decision points. Aside from
the flexibility provided in establishing multiple message zones, low-power
HAR may also broadcast over any available AM radio frequency without the
need to obtain additional FCC licensing approval. Though the ability to
install a system without FCC approval provides the user with great flexibility
in installing a system wherever desired, there is no guarantee that once
installed, it will not be interfered with by some future more powerful
The relatively low signal strength must compete with a variety of obstacles,
including overpowering commercial broadcasts, signal skip (particularly
at night), and poor signal propagation. These difficulties can be overcome
by saturating an area (zone) with multiple transmitters and synchronizing
their broadcasts. However, this concept is relatively new and, very expensive
as the number of transmitters required is large.
Low-Power FM Transmission (FCC License Required)
LPFM service is available to noncommercial educational entities and Travelers'
Information Station entities, but not commercial operations or individuals.
Maximum effective radiated power for these stations is 100 watts, and
the LPFM stations will not be protected from interference caused by full
service stations that make changes to their operations. A construction
permit or license is required before construction or operation of a LPFM
station can be initiated.
Low-power 100-watt FM transmitters, when installed properly, have a broadcast
radius of approximately 3-5 miles depending on topography and atmospheric
conditions. 10-watt transmitters have an effective range of 1-2 miles
in radius. At present, LPFM licenses are not being issued for HAR. The
FCC only opened the application process for frequencies for a short time
period. The FCC is non-committal about if and when this technology will
again be available for HAR.
220.127.116.11 Deployment Strategies
HAR can be broadcast in two ways: Point or Wide-Area coverage.
- In Point broadcast, a single transmitter is used to broadcast over
a given area. This is typically used at diversion points of areas of
recurring congestion to notify motorists of queues and congestion. This
type of implementation is popular with travelers because the information
is specific to them. This is the most common application for HAR, and
typically utilizes 10-Watt transmitters. It is the simplest to manage
in terms of equipment to maintain.
- Wide Area Broadcast transmits a signal to a larger coverage area using
multiple synchronized transmitters. This is an effective strategy when
a single message is applicable to a large coverage area, and the coverage
area is sufficiently large for a motorist to hear the longer message
length. The fact that a long single message, that is pertinent to specific
travelers for only a part of the message is indeed a disadvantage. Studies
have shown that travelers want brief, specific information, pertinent
to their location and situation. They are not likely to listen for long
periods of time until their information is broadcast. Technically, synchronization
is difficult to accomplish between transmitters because both the time
and repeated voice signal must be in sync.
18.104.22.168 Portable and Mobile Systems
Figure 13-6: Portable Highway Advisory Radio Station
Portable systems permanently installed on trailers and mobile systems
installed on service or maintenance vehicles can be of value in providing
timely dissemination of information to motorists during short-term deviations
from normal highway conditions. This is particularly true in areas where
there is limited or no normal coverage or the permanent transmitter site
has failed. These systems can be solar powered, generator powered, or
battery powered. (Figure 13-6). Portable / mobile systems can be set up at decision points where a route
guidance system directs motorist to an alternate route. This will increase
motorist comfort level by reinforcing their confidence that they are following
the alternate route instructions correctly.
22.214.171.124 Message Distribution
A number of decisions pertaining to the message distribution must be
made. One alternative is centralized recording, storage, and playback
of messages where transmission lines for audio connectivity and time synchronization
with selected transmitters need to be considered. In this alternative,
messages are created and stored at a central operations center. The audio
is typically retrieved from a digital recorder system and is transmitted
via a distribution network to the appropriate HAR controller for radio
broadcast. Distribution circuits/lines of this type are commonly referred
to as transmission lines because they transmit the actual audio signal
to the transmitter. However, the bandwidth on these transmission lines
is limited, thereby affecting the quality of the audio signal once it
reaches the transmitter site. This quality is further degraded by bandwidth
limitations on AM channels. This can be partially corrected by the installation
of audio compensation equipment at each transmitter site. In addition
to the audio transmission, separate circuits or functionality must be
used to control the remote transmitter. This architecture is also subject
to single point failures at the central operations center.
A second alternative is distributed recording, storage, and playback
where all system functionality is remote to the field HAR station. In
this case, data circuits would be used to select the message to be transmitted,
control the transmitter, and provide the timing synchronization, if required.
A library of standard messages, phrases, and/or individual words are created
at, or under the supervision of, a central operations center. The audio
information for these "canned" messages is either downloaded
into message storage at the HAR site or is transported there and installed
in the station's recorder/player. As with central site storage, an ITS
central processor could be used to create or select the appropriate message,
phrase, or word combinations. Message selection for broadcast, and control
of the transmitter controller and digital recorder/player are all done
via remote commands from the central site. The type of distribution circuits
/ lines used are commonly referred to as control circuits because they
"control" the remote equipment. Because they must be capable
of sending a live message to a transmitter from the central operations
center, these lines must also function as transmission circuits when necessary.
A distributed storage system is inherently more robust and less vulnerable
to single point failures than a centralized system.
126.96.36.199 HAR Signing
HAR signs, indicating the frequency at which traffic information is available,
are typically installed throughout each zone. These signs usually include
flashing beacons that are activated only when a message of some predetermined
level of importance is being broadcast and a legend reading (or similar)
"TRAFFIC ALERT WHEN FLASHING." (Figure
13-7) This technique permits the system to continuously broadcast "default" messages in each zone during non-congestion periods, while alerting
the motorist to an urgent/emergency message by turning on the flashing
beacons, thus preventing motorists from tuning to the HAR frequency only
to hear the default message time and time again – situations that could
negatively impact system credibility. CMS can also be used to alert the
motorist to the broadcast of a message of the utmost importance.
Figure 13-7: Highway Advisory Radio Sign
These signs can be controlled through phone lines, or with cellular or
paging technology, and can be solar powered with battery back up. They
offer a great deal of flexibility, by allowing only the pertinent signs
to be activated. For instance, while two signs (one in each direction)
may be associated with a particular transmitter, only one would be activated
for a downstream incident, thereby eliminating any loss in credibility
by notifying traffic in both directions, one of which, the information
188.8.131.52 Automatic Highway Advisory Radio (AHAR)
Automatic highway advisory radio (AHAR) provides a method to overcome
the need for HAR signing and manual tuning to the HAR frequency. The traveler
information is the same as traditional HAR; the automatic part of the
system is tuning the radio to the HAR frequency. The AHAR transmitter
sends out a leading message, which is picked up by a special in-vehicle
receiver when the vehicle enters the AHAR zone. The message automatically
tunes the radio to the AHAR station and mutes any regular radio broadcast
until the AHAR transmission is complete.
A form of AHAR has been implemented in Europe via the "Radio Data System
[RDS] Traffic Management Channel [TMC]". This system relies on a silent
data channel broadcast via FM from existing radio stations.
13.2.8 Telephone-based Traveler Information
An in-vehicle communication technology that has seen dramatic growth
in the past few years is cellular telephones, which gives the motorist
the ability to call special "hotline" systems for traffic information
from within their vehicle. Originally, these systems allowed motorists
and transit users to call for information to assist in pre-trip decisions
from their homes. Information can now be accessed en route via cellular
telephone, and decisions can be made whether to alter travel routes. The
creation of call-in systems has been a popular traffic impact mitigation
strategy for many major urban freeway reconstruction projects in recent
This type of in-vehicle communication has the advantage over HAR of giving
the motorist some control over the type and amount of information he/she
wants to obtain through the touch-tone menus. In addition, it is also
possible to generate two-way communication between the motorist and the
Recommendations for establishing cellular telephone-based systems include
- The caller should only be charged for airtime according to his or
her cellular calling plan. No additional fees should be charged.
- The telephone number must be easy to remember and dial.
- The information must be concise.
- If a menu system is used, a long and tedious menu selection process
should be avoided.
- A sufficient number of telephone lines should be provided to prevent
the majority of users from receiving a busy signal.
- If a system is going to be used to gather information from users,
there must be a method of ensuring the accuracy of the incoming information.
- "Official" use of tipster information should include procedures for
verifying that information.
- If incident information is to be received, a human operator is recommended
so that secondary questions can be asked to clarify confusing or unclear
As with HAR systems, this technology also requires action by the motorist
to access information. Depending on the users calling plan, there may
also be significant operating costs associated with this technology, (as
any calls made using cellular telephones must be paid for by either the
motorist, or a public agency, or else absorbed by the corporation providing
cellular telephone communication capabilities in the region). Finally,
there is some concern that cellular telephone usage while driving may
degrade motorist attention and operating capabilities. Manufacturers have
developed "hands-free" telephones (typically with headsets) that allow
motorists to listen and talk without holding the telephone receiver. Moreover,
some states (e.g., New York) have adopted a hands-free law requiring operators
of motor vehicles to use hands-free assistance when using a mobile phone.
Nevertheless, the need to push the telephone buttons to go through a menu
of information operations can defeat the "safety" purpose behind hands-free
devices, unless the telephone service has voice recognition capability
(i.e., saying a number instead of pushing the keypad button).
Understanding the importance of consistence and simplicity in providing
telephone-based traveler information, in1999, the U.S. Department of Transportation
(USDOT) petitioned the Federal Communications Commission (FCC) to designate
a nationwide three-digit telephone number for traveler information. This
petition was formally supported by 17 State DOTs, 32 transit operators,
and 23 Metropolitan Planning Organizations and local agencies. On July
21, 2000 the FCC designated "511" as the national traveler information
Simply put, 511 is an abbreviated three-digit dialing code; a short cut
to a ten-digit telephone number for obtaining traveler information from
a telephone. In petitioning the FCC, USDOT had to demonstrate the need
and benefits for such a number. To that end, the USDOT identified the
- Over 300 telephone traveler information systems in the U.S. could
benefit from one such number
- Demonstrated value of traveler information services to the public
- 72% call volume increase N11 vs. easy 7-digit number
- 10-digit dialing makes numbers harder to remember
- Area code expansion making 7-digit numbers less plausible
Further benefits are realized. 511 puts a "face" on ITS and transportation
operations, while increasing attention on the potential for traveler information
services. With 511, transportation agencies can offer easier access to
information via telephone, and have the same number work in multiple places.
It is not uncommon for traveler information numbers to change across jurisdictional
boundaries, creating confusion among motorists.
A number of issues must be addressed when implementing a 511 service.
The following system considerations are taken from the 511 Deployment
Coalition's, "511 America's Travel Information Number, Implementation
Guidelines for Launching 511 Services", version 1.1, June 2002 (Reference
- System Access Quality: The ability of the telephone system to reliably
and quickly answer calls.
- Hours of System Operation: The days and hours that 511 service should
be available to callers.
- ADA Implementation: Complying with accessibility laws and regulations.
- Environmental Justice: The relationship of 511 and environmental justice
principles that prevent discrimination against minority and low-income
- Standards: 511 and National ITS standards.
- Privacy: Privacy protections for callers.
- 911 Linkage: Relationship of 511 services to 911 services.
- 511 Branding: The creation of a brand identity for 511 services to
manage consumer expectations.
- Number Allocation and Service Coordination: Organizing and coordinating
transportation agencies in a given region to determine what 511 services
will be offered, by whom and in what geographic area(s).
- Inter-regional Interoperability: How 511 services interconnect.
To reduce the potential for service confusion and inconsistency, the
511 Deployment Coalition offers other guidelines for implementing 511
services. The guidelines include: (12)
- Content guidelines that focus on defining the information
that should be provided by a basic 511 service. The guidelines recommend
that every 511 system deployed in the United States provide at minimum
the basic content as defined in the document. It is this basic content
that callers will associate with the core of 511. A summary of some
possible optional content categories also is provided.
- Consistency guidelines that address steps that implementers
can take increase the degree of uniformity and consistency of 511 service
across the country. The consistency guidelines cover 15 separate issues,
such as user interface, and time stamping of information.
As of the end of 2002, 32 "511" programs have been, or are readying to
be, implemented in 27 states. In December 2002, a total of 741,841 "511"
calls were received totally over 978,000 minutes of usage. (11).
These systems differ greatly, from simplified versions where a live operator
answers and responds to all calls of all nature to automated systems where
the caller is routed through a menu system to obtain information specific
to their travel location. An example is shown in Figure
Additional information on 511 is available from "Resource 511", a repository
of information for the 511 deployment community (e.g., marketing ideals,
implementation guidelines, evaluation), available at http://www.deploy511.org.
An example of a 511 scheme is "CARS-511". CARS-511 is a road reporting
system that utilizes information, which was created within the CARS multi-state
database of highway events. CARS-511 provides timely information to travelers
who can access this information via a telephone by simply dialing "5-1-1"
on the touch pad. Authorized staff use CARS to input construction, accidents,
delays, and other roadway, weather and tourism information into state-wide
databases, using standard web browser software. CARS servers also support
routine DOT dispatch, press release and emergency response activities.
The information entered into CARS is then continuously updated to the
CARS-511 system. CARS-511 provides traveler information through a variety
of categories including urgent reports, routine reports, road weather
and it also provides transfers to outside phone numbers that provide transit-related
information. Eight of the ten CARS Pooled Fund States have elected to
participate in the CARS-511 initiative. These States are Alaska, Iowa,
Kentucky, Maine, Minnesota, New Hampshire, New Mexico, and Vermont. CARS-511
was first launched with the Minnesota DOT on June 30, 2002.
13.2.9 In-Vehicle Devices
184.108.40.206 Commercial Radio
The public has learned to depend upon the media to provide them with
"almost" real-time traffic information. Commercial radio has proven to
be a good means of providing travelers with traffic information both in
and out of their vehicles. Traffic and roadway condition reports have
become standard programming items on many commercial radio stations. Commercial
radio has the best potential of reaching the greatest number of commuters,
since most of them have radios (and listen to them) in the vehicles they
drive to and from work.
The primary disadvantage of using commercial radio relates to the accuracy
of the information and the level of detail provided. Traffic reports often
are transmitted only when normal scheduling permits. Most major metropolitan
areas have stations that report traffic every 10 minutes; but the available
time is limited, meaning that only the worst situations are reported.
Moreover, with other stations, there may be considerable time delays between
when an incident occurs and when it is reported. The accuracy of the information
provided by commercial radio is a function of the time between the broadcaster's
last communication with the incident reporting source and the number of
incidents that have occurred and/or have been cleared during that time.
Some transportation agencies have made substantial efforts to improve
coordination and cooperation between themselves and the media traffic
reporters. For example, some agencies allow private traffic reporting
agencies to place personnel in the traffic management center to obtain
information on traffic conditions and expected agency responses in an
accurate and timely manner. Others means of working with the media include
proving the media with real time data feeds, congestion maps, and video
220.127.116.11 Video Display Terminals
A video display terminal (VDT) mounted in the dashboard, with wireless
communications, is another form for providing information to motorists
in their vehicles. This is primarily a private sector industry, which
has not been used widely for information distribution. These systems can
be used to provide motorists with route guidance and navigational information
in one of two different formats. One approach is to present the driver
navigation and route guidance information in the form of maps or equivalent
displays. With these systems, a global picture of the traffic network
can be provided. Recommended routes can be highlighted on the video map
display as well. In another approach, simple symbolic signals (e.g., arrows,
text instructions, or a combination of both) guide the driver along a
recommended route. Some systems use a variety of displays depending upon
whether or not the vehicle is in motion, the functions selected, and level
of informational and navigational displays available.
In-vehicle VDTs offer a number of advantages over available technologies
in providing information to motorists while driving. These include the
- Travel information is more readily accessible to the driver (providing
continuous access to current position, routing, and navigational information).
- Computer-generated navigational maps and displays are logical extensions
of traditional forms of providing drivers with route guidance and navigation
- Information can be displayed in text, graphics, or both and tailored
to the needs and desires of each motorist.
There are also limitations to in-vehicle VDTs. These include the following:
- Drivers have to take their eyes off the roadway in order to receive
- In-vehicle VDTs present the driver with complex maps and diagrams
that may create a potential to overload the driver with too much information.
- VDTs may also add to the visual clutter already inside the vehicle.
As technology continues to improve, the Head-Up Display (HUD) has become
another alternative to in-vehicle VDTs for presenting visual navigational
and route guidance information to motorists. Although originally developed
for the aviation industry, several automobile manufacturers are beginning
to develop HUDs for presenting vehicle status and navigational information
to drivers. A wide variety of options for displaying information may be
available using HUDs. Through both icons and alphanumeric text, navigation
and route guidance information may be projected directly into the driver's
field of view. This is expected to reduce the need for visual scanning
between two information sources (the inside instrument panel and the outside
environment), and the associated visual accommodation time.
18.104.22.168 Subscription Services
A number of private providers supply traveler information services on-demand
as a subscription. Most notably, General Motors' (GM) OnStar is a 24 hours
a day, 7 days a week motorist assistance system installed in the vehicle.
It provides a wide range of services to the driver including concierge
service, telephone service, remote unlocking of the car, notification
of air-bag deployment just to name a few. Another feature it provides
is route guidance to motorists.
The motorist initiates a call from a button installed in the car, and
is connected to a live Onstar operator, and asks for directions. The operator
knows the vehicle's location through OnStar's automated vehicle location
system, and provides directions for the fasted route. OnStar currently
uses third-party wireless analog networks, and is moving to a digital
technology, which will allow the service to be expanded to handheld devices
as well. 53 current (2003) vehicle models are offered with OnStar, and
GM intends to expand to 60 models by the end of 2003. Routing assistance
is the most utilized services, and OnStar reports that it handles more
than 220,000 routing call per month.
Internet subscription services are addressed in the following section.
13.2.10 Other Methods
Television (together with radio) was one of the first off-roadway motorist
information technologies available to motorists. Even today, commercial
television stations in most major cities provide traffic reports to viewers
as part of their morning programs to indicate incident locations, closures,
and other traffic "hotspots." These locations are usually shown on some
type of wall-mounted or computer-generated map display, often coupled
with video images from planes / helicopters, a privately-owned network
of cameras, video images from FMS cameras, or some combination. In some
instances, the TV reports are broadcast directly from the TMC. Another
option is for the cable TV franchise to allow the DOT to provide continuous
traffic coverage (e.g., cycling through real time video feeds) during
peak periods or throughout the day.
22.214.171.124 Personal Data Assistants (PDAs)
Personal Data Assistants (PDAs) are the next higher level of sophistication
in both off and on-roadway information dissemination technology. PDAs
are computer products that have enough power to support applications such
as time management and handwriting recognition. By adding radio frequency
(RF) communications technology, PDAs allow users to interact directly
with travel information systems. This interaction allows users to obtain
route planning assistance, traffic information broadcasts, and other pertinent
information. Through keypad entry, the user can log on to the information
system, request pertinent information, and then log off. PDAs offer the
user increased communication and information transmission/receiving power
over alphanumeric pagers.
126.96.36.199 Computers (Internet & Web Sites)
On-Line services to access the Internet represent an additional means
to disseminate pre-trip traveler information. The Internet's effectiveness
as a fast and flexible communication medium has spurred explosive growth
in all sectors of society. The network is now in daily use by people in
Most state and many local DOT's have web sites that include traffic information
(Note: In general, these can be found at either www.dot.state.xx.us, or
www.dot.xx.gov, where "xx" is the state abbreviation, and then clicking
on the traffic / construction information links.), with the freeway management
system often providing much of the information (e.g., data, maps, video).
Several private Information Service Providers also have web sites providing
similar information for multiple cities. Many of these sites provide:
- Real-time traffic flow information via color-coded maps
- Road closure information (e.g., for construction or maintenance)
- Real time video images (still captures or streaming video)
- Camera selection.
- Travel advisory information for route planning
- Links to other web sites
- News and weather.
Examples are provided in Figures 13-9 through 13-11. It is worth
noting the different legends that are used to describe states of traffic
flow and levels of congestion to the traveling public.
Figure 13-9: Examples of Traveler Information Websites
Figure 13-10: Examples of Traveler Information Websites
Figure 13-11: Example of Traveler Information Websites
(CCTV Selection and Viewing)
Some of the more sophisticated sites provide pre-trip and en-route traveler
information with a subscription service (either free, or for a fee, depending
on the service) for automated travel advisories via e-mail, pagers / PDAs,
or cell phones. When they sign up for the service, subscribers input a
travel profile (e.g., primary / alternative routes, times of day) and
their choice of device(s) for receiving information. They are then alerted
whenever there is an incident or other travel problem on these routes
during their travel schedule.