NAVIGATION: Journal of The Institute ofNauigatz'on
Vol, 34, No. 3, Fall 1987
Printed in USA.
The Evolving Roles of Vehicular
Navigation
ROBERT L. FRENCH
R. L. French and Associates, Fort Worth. Texas
Received June 1987
ABSTRACT
This paper examines existing and potential applications ofnavigation technology
to motor vehicles that operate primarily upon streets and highways. Applications
are described and representative systems approaches are outlined in three broad
categories; driver information, traffic management, and fleet management. Driver
information systems include those that develop and present navigation information
in various forms to aid the driver in reaching the desired destination. The traffic
management category includes navigation systems that consider real-time traffic
conditions in determining optimum routes and, consequently, contribute to the
overall improvement of traffic flow. Fleet management applications include automatic vehicle location monitoring systems (which do not necessarily provide navigation information to vehicle drivers) as well as systems which provide routing or
step-by-step route guidance. The most comprehensive fleet management applications of vehicular navigation may also include command and control functions.
INTRODUCTION
Motor vehicle navigation has traditionally been accomplished by reference
to external road signs and landmarks while traveling over routes constrained
(unlike sea, air and space navigation) to finite networks of streets and roads.
Commonly used in-vehicle navigation aids have essentially been limited to
road maps, the odometer, and an occasional magnetic compass} Except for a
brief flirtation with mechanical route guides starting around 1910,” automobile
navigation received little attention until the late 1960s, when the Federal
Highway Administration’s short—1ived Electronic Route Guidance System (ERGS)
project3 presaged a wave of research on similar proximity-beacon route guidance and information systems which spread to Japan and Europe during the
1970’s.4 The 1980s have brought extensive development work on a new generation of automobile navigation systems based upon dead reckoning, radio
location and map matching, in addition to further development of proximitybeacon systems.5
Advances in microelectronics, computer, space, and cartographic technologies permit the development of vehicular navigation systems with unprecedented capabilities. Figure 1 shows improvements in position accuracy achieved
by radio location as compiled by Luse and Mallaf‘ Although not strictly comparable because their accuracies are expressed relative to digitized maps rather
than absolute location, the accuracies of ARCS and Etak dead reckoning aug212
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EXHIBIT 1010
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French: Vehicular Navigation
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mented by map matching are included in Figure 1.” While each of the accuracy
values plotted in Figure 1 is subject to qualifications and exceptions, the overall
trend is inescapable——we are entering an era in which vehicle location may be
pin-pointed to individual streets and intersections.
The navigation technologies available, or that are in the process of becoming
available, support the development of vehicular systems for performing such a
wide variety of useful functions that the taxonomy of systems applications is
not yet well established. However, the following broad categories provide a
useful framework for examining some of the more important functional roles
that are evolving, and for outlining examples of various systems approaches to
vehicular navigation that are applicable to these roles.
10000
-_
CELESTIAI.
--O-- RADIO LOCATION
A MAP MATCHING
1000
(mAPCOeSUtIRTrsYN)
100
TRANSIT
NNSS
.
10
1940
1960
YEAR
1960
2000
Fig. 1—Improvements in Position Accuracy.
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DRIVER INFORMATION
This category includes systems that develop and present to the driver various
forms of navigation information useful in determining how to reach the desired
destination. This may range from minimal information regarding the direction
and line-of-sight distance to a specified destination, to real—time step—by—step
route guidance instructions for reaching the destination. Intermediate levels
of driver information systems may provide a complete plan and position indication on a map display.
Use of conventional road maps as a navigation aid requires several cumbersome and error—prone steps. Users must first identify their location and destination on the map. A reasonable route between these two points must then be
determined by inspection. Finally, the user must be able to successfully follow
the planned route. Research indicates that 64 percent of the general population
has difficulty in reading maps, and that navigation aids that replace conventional map reading and following processes by voice instructions are the most
effective?
The wide range of vehicular navigation aids in the driver information category is illustrated by the following systems, some of which are already on the
market.
VDO City Pilot
A dead-reckoning system called “City Pilot” is currently on the European
market. Developed by VDO Adolf Schindling AG, it uses an earth magnetic
field sensor and an odometer distance sensor.“ Like virtually all other dead-
reckoning processes included in vehicular navigation systems, City Pilot integrates measured increments of travel with corresponding heading measurements to continuosly estimate the vehicle’s coordinates relative to an initial
location.
Prior to a journey, the driver uses a light pen to read bar—coded starting and
destination coordinates on a special map. Using the sensor inputs and destination coordinates, a microcomputer continuously calculates and displays the
direction and line-of-sight distance to the destination. LCD arrows show the
driver which general direction to take, while numerals indicate the remaining
distance. Test results reveal that drivers using the system reach their desti-
nations with an accuracy of 97 percent (i.e., within 3 percent of the distance
traveled).
Etak Navigator”
The first commercially available automobile navigation system based on dead
reckoning augmented by map matching is the Etak Navigator” now marketed
in California. Map matching applies artificial—inte11igence pattern recognition
concepts to correlate measured vehicle paths with road maps which are digitized
and stored in computer memory. With map matching, sensed mathematical
features of the vehicle path are continuously associated with those of roads
encoded in a map data base, just as a driver associates observed landmarks and
road features with those depicted on a paper map to recognize position.5 Deadreckoning errors are thus removed by automatic reinitialization at each turn.
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The Etak system uses a flux-gate magnetic compass as well as differential
odometer for dead reckoning. The differential odometer is essentially a pair of
odometers, one each for the wheels at opposite ends of a common axle. When
the vehicle changes heading, the outer wheel travels farther than the inner
wheel by an amount (AD) that is equal to the product of the change in heading
(Ada) and the vehicle’s width (W): AD = WAd>. Thus, by real-time analysis of
the differential travel of opposite wheels, a vehicle’s path and heading relative
to its starting point may be computed using algorithms based on the above
equation.”
The Etak system uses 3.5-MByte tape cassettes to store digital map data
approximately equivalent to two paper street maps? The vehicle’s location
relative to its surroundings is continuously displayed on a monochrome CRT
map presentation which may be zoomed to different scales. A fixed symbol
below the center of the CRT represents the vehicle position, and points to the
top of the display indicating vehicle heading as indicated in Figure 2. As the
vehicle is driven, the map rotates and shifts about the vehicle symbol to maintain an orientation corresponding with the driver’s view through the windshield.
A simplified push button arrangement allows destinations to be input by
street number and name, or by street name and nearby cross street. The current
destination is shown on the Etak screen as a flashing star. When off the
Fig. 2—Etak Navigator” Display.
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displayed map scale, the direction and distance to the destination is shown on
the margin of the screen. Up to 16 destinations may be stored for sorting and
quick recall.
Blaupunkt EVA
Bosch-Blaupunkt has developed a map-matching system called “EVA” which
uses a differential odometer and includes route-search software to generate an
optimum route to input destinations.“ Turns at intersections, lane changes,
etc. are specified on an LCD in the form of simplified diagrams which show
lane boundaries and displays arrows to indicate the path to be taken. Synthesized voice capability is included, and is used to confirm destination entries as
well as to articulate turn-by—turn, real-time route guidance instructions.
The first version of EVA (Figure 3), which has been tested and demonstrated
since 1983, has a digital map of the test site (the small city of Hildesheim in
West Germany) stored in EPROM with a capacity of approximately 109 KBytes.
Like the Etak system and most others that use digital maps, the EVA map
represents streets by straight segments that connect node points whose coordinates correspond to intersections. Intermediate nodes, known as shape points,
are used to approximate street curvature between intersections. Since optimum
routes are determined by algorithm, the EVA map data must also define traffic
attributes such as one—way streets and turn restrictions.
An enhanced version of EVA which is slated for testing late this year has
been designed to use CD-ROM for storing map data. Since CD-ROM has a
storage capacity of approximately 550 MBytes, one compact disc could accom—
modate all streets and roads in West Germany plus extensive “yellow pages”
and other directory features.
Navstar GPS
The Navstar Global Positioning System (GPS), which is being implemented
by the Department of Defense, has been investigated as a basis for automobile
navigation systems by General Motors,” and was the basis for CLASS, the
Chrysler Laser Atlas and Satellite System, a concept displayed at the 1984
World’s Fair in New Orleans.” CLASS included a nationwide set of maps stored
wuce outpyl
Mass memory lo: caty map
Inpul at destmaloon
DISDIIY
Home search
Location
Nawonlion
wheel sensors tor
locating Signals
Fig. 3—Bla.upunkt EVA System Concept.
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in image form on a video disc, and software for automatically selecting and
displaying on a color CRT the map area incorporating the vehicle’s current
location. Like most proposed automotive navigation systems based on Navstar
GPS, CLASS shows vehicle location by positioning a curser on the map display.
Still in the implementation stage, the Navstar GPS system will be completed
in the early 1990s when the last of 18 satellites are orbited. The 18 satellites
are being spaced in 12-hour orbits such that at least four will always be in
range from any point on earth. Using precisely timed signals from four satellites, the GPS receiver’s computer automatically solves a system of four
simultaneous equations for its three position coordinates and a time bias signal
for synchronizing the receiver’s quartz clock with the satellites’ precise atomic
clocks.
Although GPS has great potential accuracy and will provide continuous
coverage when the satellite constellation is complete, auxiliary dead reckoning
is required in automobile applications to compensate for signal aberrations due
to shadowing by buildings, bridges, foliage, etc. A recent evaluation of GPS for
land vehicles notes that, because of differing ellipsoidal reference systems, the
task of melding GPS location with local maps is formidable.“ Hence mapmatching technologies may be useful with GPS as well as with dead reckoning.
TRAFFIC MANAG EMENT
The potential of on-board route guidance systems for improved traffic man-
agement has long been recognized and, in fact, was the major thrust behind
the Federal Highway Administration’s ERGS project of the late 1960s.3 Although
the pursuit of this objective has, until recently, been essentially dormant in the
United States, it has been the basis for extensive public sector involvement in
the development of navigation and route guidance systems in Japan and Europe.
A recent economic assessment” of the potential for improved motorist routefollowing in the United States found that recoverable navigation waste amounts
to 6.4 percent of all distance traveled by non-commercial vehicles and 12.0
percent of all time spent in such travel. The annual cost to individuals and to
society of this excess travel was estimated at $45.7 billion considering only
vehicle operating and accident costs and the value of time. It follows that if a
significant fraction of vehicles were outfitted with effective navigation aids,
their diminished demands on roadway capacity would contribute to improved
traffic conditions as well as great economic savings.
Automobile navigation systems with routing or guidance functions are even
more effective if current information on traffic conditions is available for consideration in routing. It is estimated that the potential savings by eliminating
navigation wastes increases to $73.6 billion annually if real-time traffic information is available to on-board route guidance systems.” Traffic flow would
also be enhanced by route guidance systems that responded dynamically to
current conditions to avoid congested areas, thus contributing to balanced
traffic management.
Philips CARIN
Self-contained automobile navigation route guidance systems such as the
EVA system outlined above may be adapted to receive real-time traffic infor-
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mation over a suitable data communication link, and to take this information
into account in providing guidance over routes optimized for minimal travel
time under the prevailing traffic conditions. This concept is included by Philips
in the design of CARIN, another automobile navigation and information system
under development in Europe. Figure 4 shows a functional block diagram of
CARIN .17
The vehicle location subsystem of the CARIN test and demonstration system
employs dead reckoning augmented by map matching, and future versions may
include a GPS receiver as well. CARIN is the first system to use the compact
disc (CD-ROM) for storage of digital map data. The system includes a routesearch algorithm and provides step-by-step route guidance. A color CRT map
display shows vehicle location relative to the surroundings, and synthesized
voice instructions prompt the driver when operating in the route guidance
mode.
The CARIN car radio data link for traffic information has not been implemented because standards have not yet been set and the infrastructure for
collecting and communicating traffic data is not fully in place. However, several
different approaches for communicating traffic data are being considered in
Europe.“ One approach, called RDS (radio data system), uses a sub—carrier
(SCA) to piggyback traffic data on commerical FM broadcast transmissions.
Such data could be detected by a special feature or attachment to the regular
VEHICLE
COMPACT
LOCATOR
DISC
USUAL
INFORHATION
AUTOMOTIVE
PROCESSOR
FUNCTIONS
USER
INTERFACE
DRIVER
Fig. 4—CARIN Functional Block Diagram.
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car radio and relayed to the navigation system. A precedent for this approach
is Blaupunkt’s ARI system which receives voice traffic bulletins over an FM
sub-carrier.”
U.K. Autoguide
In 1986, the U.K. Department of Transport proposed Autoguide (Figure 5),
a multi-step project starting with an early demonstration of interactive route
guidance and traffic management in London.“ Autoguide is a system for helping drivers find their way through the primary road network. A route computer
is mounted in the vehicle and the driver enters the destination. Either visually
or using synthesized speech, the computer then gives easy-to—follow instructions
during the journey.
Unlike CARIN, which has autonomous navigation and route guidance functions that are useful even in the absence of infrastructure support, Autoguide
operation is dependent upon proximity beacons. The Autoguide computer communicates with beacons, near main junctions, which act as “electronic signposts.” As an equipped vehicle passes each beacon, it transmits its destination,
type and, possibly, preference for the type of route—-the driver might want the
quickest, or the shortest (the two are not necessarily the same), or have some
other requirement such as “no motorways.” The beacon immediately transmits
back to the vehicle details of the directions to be taken at the junction, and the
route computer translates them into simple instructions for the driver.
The Autoguide beacons are themselves small computers which store the
electronic signpost information as a form of list, which is frequently updated
by a larger computer in a control center. The control center continuously
recalculates routes on the basis of current traffic conditions. Drivers can therefore be given guidance based on up—to-date information about the entire urban
area.
While it is to be implemented with microelectronics and other advanced
technologies that were not available 20 years ago, the Autoguide concept is
virtually identical to that of the Federal Highway Administration’s ERGS
project of the late 19605.3
F.R.G. ALI-SCOUT
A major new development in route guidance systems is ALI-SCOUT, a joint
project of the Federal Republic of Germany, Siemens, Volkswagen, Blaupunkt
and others.“ ALI-SCOUT combines certain characteristics of both CARIN and
Autoguide in that, while dependent upon proximity beacons like Autoguide,
the in-vehicle equipment includes dead reckoning and map matching features
that permit autonomous navigation between beacons which, consequently, may
be spaced at greater intervals.
The ALI-SCOUT vehicular equipment receives approximately 8 KBytes of
area road network data and recommended route data when passing strategically-located infrared beacons. Simplified graphic driving directions to the
input destination are presented in real time on a dashboard LCD. The operating
principle and major system elements of ALI-SCOUT are illustrated by Figure 6.
An unusual feature of ALI-SCOUT is that, as an equipped Vehicle passed
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Fall 1987
0 Dullnulon
ROAD SIDE
EQUIPMENT
o VIhldelYP°
ELECTRONIC
SIGNPOST
Fig. 5—-A utoguide System Concept.
each beacon, it transmits to the beacon stored data on its travel history since
passing the last beacon. The equipped automobiles thus serve, in effect, as their
own traffic sensors. ALI-SCOUT will be subjected to large-scale field testing in
West Berlin starting in 1988. Beacons will be installed at 20 percent of the
traffic lights, and 1000 automobiles will be equipped.
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P:
Position-finding device with
magnetic field sensor MS and
wheel pulsor WP
N: Navigation device
0: Operation board with keyboard
direction indicator and
destination store DS
MT: Measuring device
lo! travelling time
IT: Infrared transmitter
Travel time
IR:
Infrared receiver
per mad section
Traffic-dependent
route
recommendations
TGC: Traffic guidance
computer
TC: Traflic light
controller
BE: Beacon electronics
BR: IR beacon receiver
ET: IR beacon transmitter
Fig. 6—ALI-SCOUT Operating Principle.
CALTRANS Initiative
Between 1970, when Congress failed to appropriate funds for continuation
of the ERGS project, and 1987, U.S. public sector research on Vehicular route
guidance was essentially limited to a few paper studies.“’15 Although a number
of private organizations have pursued the development of vehicular navigation
systems that can operate autonomously, public sector involvement is required
for dynamic traffic-responsive route guidance systems because of its responsibilities in traffic management and the collection of traffic data.
Due largely to a CALTRANS conference on “Technology Options for Highway
Transportation Operations” held in Sacramento, California, October 28-31,
198622 which served as a catalyst, a coalition including the FHWA, CALTRANS
and the transportation departments of other key states, and private industry,
is now actively developing a plan for demonstrating the traffic management
advantages of providing real—time traffic information to on—board navigation
systems. This planning effort is still in the formative stages, and is expected to
lead to an initial procurement action in October 1987 to select a systems
integrator for the demonstration.
Concepts under consideration for the demonstration center on the Etak Navigator”, the only automobile navigation system already available in the U.S.
While the Etak system does not provide route guidance per se, software modifications would permit the system to superimpose real—time traffic information
on the map display (see Figure 2) in a manner such that the driver could take
it into account in route planning. Traffic data already collected by conventional
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means for traffic signal control would be augmented and communicated to
Etak—equipped vehicles via cellular telephone. Consideration is also being given
to communicating the recent travel experience of some Etak-equipped vehicles
to the traffic data center for additional information on current traffic conditions.
FLEET MANAGEMENT
Various systems for remotely monitoring the location and status of individual
vehicles have been used as fleet management tools for years, particularly for
transit bus schedule control and police car dispatching.” The location information thus developed aboard fleet vehicles is almost invariably communicated
via radio link to the dispatch center rather than presented to the driver as in
the case of a vehicular navigation system.
In the past, such systems have primarily used electronic signposts, dead
reckoning or, especially in recent years, Loran-C. Now, several technologies
offer fleet managers wider choices for obtaining continuous updated position
readings for their vehicles, whether locally or anywhere in the country.“
The technologies employed for automatic vehicle location (AVL) monitoring
and for vehicular navigation tend to overlap, and some integrated systems
which serve both functions are now beginning to appear. In addition, valuable
fleet management functions may be performed by systems which have navigation features alone, or navigation in conjunction with command and control
features, regardless of whether vehicle location information is automatically
communicated to a central dispatch station.
Loran—C AVL
Although Loran—C has been used for decades for marine and aircraft navigation, and has often been considered as a possible basis for AVL systems,”
dependable cost-effective Loran—C receivers designed specifically for the hostile
electromagnetic environment encountered by land vehicles have become available only in the last few years.25’2“’27
Loran—C AVL systems, unlike the obsolescent electronic signpost approach
to AVL, have the advantage of not requiring infrastructure support other than
the existing Loran—C transmitter chains operated by the U.S. Coast Guard
which is now installing mid-continent chains to complete nationwide coverage.
Each chain of 3 to 5 stations transmits time—synchronized signals at approximately 100 KHz in the form of groups of pulses. The time difference of arrival
of pulses between the master and each of the secondary stations describes a
line of position. A Loran—C receiver measures the time difference of two or more
master-secondary pairs, and the intersection of the described lines of position
defines the receiver’s location. In most cases the time differences are transmitted from the vehicle to the monitoring dispatch office for conversion to location
coordinates which, in turn, are used to show vehicle location on a CRT map
display. Most systems include driver—operated switches for reporting status as
well as location.
Land mobile radios, which many fleet operaters already have installed for
voice communications, are often fitted with modems to transmit vehicle location
data to the dispatch office. However, at least one Loran—C based AVL system
uses cellular telephone.”
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With the availability of high—performance Loran-C receivers at moderate
cost, the types and number of AVL installations have proliferated. In addition
to traditional transit bus and police fleet monitoring, Loran-C AVL applications
now include public utilities, waste management, security, and general trucking
applications. Although Loran-C has not yet been seriously pursued as a basis
for automobile navigation, the experience base being acquired through AVL,
along with the completion of nationwide coverage in 1989, make it probable
that Loran-C automobile navigation systems will also be developed Within the
next few years. However, like Navstar GPS systems, dead-reckoning backup
and possibly map-matching augmentation may be required.
Geostar Positioning
The Geostar Satellite System will be the world’s first commercial network
that provides fleet managers with nationwide radio location and two-way digital communications from the same set of user equipment.” Major system
elements include a control and central processing center (ground station), two
or more geosynchronous relay satellites, and user transceivers. Except for very
large-scale fleets which might justify operating their own ground stations,
Geostar AVL operates as a service requiring additional communications links
between the control and central processing center and the dispatch centers of
individual user fleets.
When complete, two Geostar satellites will be used in a triangulation process
to determine vehicle location. The process starts at the base station with an
interrogation code that addresses the message to one or a group of vehicles,
plus a digital notation indicating the time the signal was sent. One satellite
relays the signal to the vehicle’s transceiver where it is retransmitted to both
satellites which, in turn, relay it back to the ground station. Recognizing its
original time notation, the base-station computer calculates the time it took
the vehicle’s retransmission to reach the separate satellites. Since the satellites’
positions are known, the computer can determine the vehicle’s distance from
each and pinpoint the location. The computer then uses digital map data to
translate position coordinates into a real-world location and transmits it to the
fleet terminal.
Full-scale Geostar service is scheduled for 1989. In the meantime, location
service is provided by using a single Geostar satellite to relay Loran-C determined vehicle locations to the ground station.“
Etak Dispatch System
The Etak Navigator” described above serves as the location sensor of an
AVL and dispatch management system that has been introduced by Etak, Inc.”
As shown schematically in Figure 7, a modem is used to interface the onboard
navigation system to a conventional land mobile radio for data communications
with the dispatch center.
Reports from the navigation system that are sent to the dispatch center
consist of the vehicle’s latitude, longitude, heading, speed, status, and other
pertinent data for special applications. Heading is necessary to orient the
vehicle symbol on the dispatcher’s map display, and speed is useful for man-
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BASE
STAHUN
Fall 1987
DISPATCH
MANAGED!
Fig. 7-Etak AVL System.
agement purposes. Status codes may be selected by the driver through button
entry.
The Etak dispatch system includes an interactive map display workstation
designed to enable dispatchers to monitor location and dispatch vehicles. The
workstation comprises an IBM PC/AT (or equivalent) with keyboard, mouse,
full color monitor and local area network interface. Resident on disk at each
workstation is a map database corresponding to the digital maps used by the
on-board navigation system. The map is displayed on the monitor with different
colors representing different street categories (e.g. residential, arterial, freeway). Items from several categories of interest may be superimposed on the
map display, including vehicles, landmarks and destinations.
Each vehicle appears as a color coded symbol on the map display. The color
and symbol shape may be used to designate type of vehicle (e.g. ambulance,
hook and ladder, police, etc.), and status (e.g. available, enroute, emergency).
The position and orientation of the symbol indicates last reported position and
heading. Each vehicle has associated with it an identification number, status,
vehicle type, position, heading, speed, report time, driver name, and dispatch
assignment, if active. Any one of these attributes may be used to label the
vehicles on screen.
In addition to conventional AVL and dispatch functions, the Etak dispatch
management system may be used to communicate destinations directly to the
on-board navigation system. Once received, the destination appears on the
screen as a flashing star. Because of the heading—up format, the direction to
the destination is immediately obvious. The distance to go and direction to the
destination are also displayed at the top of the CRT screen so that if the driver
selects a map scale which does not include the destination, positive orientation
is maintained. The dispatcher may also send a message with each new destination to instruct the driver on dispatch details.
Routeware” ARCS
A further extension offleet management applications of vehicular navigation
systems is illustrated by the Automatic Route Control System (ARCS) which
provided command and control functions in addition to real-time route guidance
over programmed newspaper delivery routes.7 The routes were programmed on
tape cartridges in the form of digital maps which included the location of each
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individual street address. The route data tapes could be prepared from central
computer files, or by driving a route with an equipped vehicle to “record” the
route.
ARCS pioneered the application of map matching to vehicular navigation.
An on-board computer analyzed differential odometer signals, deduced the
vehicle’s path and correlated it with the programmed path to maintain high
accuracy, to identify locations for issuing route guidance instructions to the
driver, and for prompting the throwing of newspapers to individual subscriber
houses included on the route tapes. Route guidance was initially accomplished
by automatically activating prerecorded voice messages as each turn was
approached. A subsequent version used a plasma panel to display graphic
instructions and explanatory text as shown in Figure 8.3°
This system was in daily revenue service during a one-year test by the Fort
Worth Star Telegram in the 19705.3‘ While technically successful, and even
marginally cost—effective in spite of the relatively expensive electronics at that
time, ARCS’ patented technology was subsequently put on the shelf until labor
and management were more receptive to highly automated forms of fleet management. The author and a group of associates are currently developing an
enhanced version of ARCS which will be applicable to a variety of fleet route
operations.
CONCLUSIONS
The most fundamental task of a vehicular navigation system is to continuously maintain accurate track of the vehicle’s location. This may be accomplished by a number of means, but practical systems require two or more
navigation technologies for continuously effective operation. Dead reckoning
appears as the common element in virtually every systems approach. Dead
Fig. 8——ARCS Route Guidance Instruction.
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reckoning is necessary to augment radio-location systems under poor signal
conditions, and to keep track of position between proximity beacons. Dead
reckoning is also used in combination with artificial—intelligence map matching
in autonomous systems to maintain accurate information on a vehicle’s location
relative to an on-board digital map.
However, except for fleet management AVL applications, vehicular navigation systems must do much more than accurately track a vehicle’s location in
order to be highly useful. In particular, a navigation system must also provide
information to help the driver reach particular destinations. Such information
takes several forms depending upon the sophistication of the system. The
simplest systems merely indicate the direction and distance to a destination.
Intermediate systems facilitate route selection by providing map displays showing both vehicle and destination location relative to the road network. The
most advanced systems select routes automatically and prompt the driver turnby-turn to reach a destination. Although such systems use digital maps, the
maps are not necessarily displayed to the driver.
Advanced vehicular navigation systems have significant potential for helping
individual drivers cope with traffic congestion as well as for helping balance
the overall flow of traffic in urban areas. However, these roles require the
systematic collection and communication of real—time traffic data to the onboard systems, a task requiring public sector involvement which is only beginning to emerge in the United States.
In addition to traditional AVL functions, vehicular navigation has many
potentially important roles in fleet management. These include assistance in
navigating among destinations that may be assigned either before dispatch or
destinations communicated in digital form directly to the navigation unit while
the vehicle is in the field. The most advanced fleet management applications
of vehicular navigation provide automated command and control along with
step—by-step route guidance to aid the driver in performing route functions.
The various technologies required for future automobile navigation and route
guidance systems that will relieve drivers from the tedium of planning routes
and finding the way over them have already been developed, or are within
reach. The main developments yet to come are in the information and institu-
tional areas. In particular, comprehensive digital map databases must be developed and maintained, and public sector organizations must coordinate the
collection, standardization and communication of real-time information on
traffic and road conditions.
REFERENCES
1. French, R. L., In-Vehicle Route Guidance in the United States: 1910-1985,
Proceedings of the IEE International Conference on Road Traffic Control, pp. 6-9,
London, England, April 15-18, 1986.
2. French, R. L., Historical Overview ofAutomobile Navigation Technology,
Proceedings of the 36th IEEE Vehicular Technology Conference, pp. 350-358,
Dallas, Texas, May 20-22, 1986.
3. Rosen, D. A., Mammano, F. J ., and Favout, R., An Electronic Route Guidance
System for Highway Vehicles, IEEE Transactions on Vehicular Technology, Vol.
VT-19, pp. 143-152 (1970).
4. Gordon, R. L., Soicher, B. and Donaldson, E., Study of the Feasibility and Design
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