U.S. patent application number 12/285281 was filed with the patent office on 2009-02-19 for method and system for partitioning a continental roadway network for an intelligent vehicle highway system.
This patent application is currently assigned to WENSHINE TECHNOLOGY LTD.. Invention is credited to Xinyi Xu, Yiwen Xu.
Application Number | 20090048769 12/285281 |
Document ID | / |
Family ID | 39916557 |
Filed Date | 2009-02-19 |
United States Patent
Application |
20090048769 |
Kind Code |
A1 |
Xu; Yiwen ; et al. |
February 19, 2009 |
Method and system for partitioning a continental roadway network
for an intelligent vehicle highway system
Abstract
An intelligent vehicle highway system collects and provides
real-time traffic data to a vehicle traveling on a continental
roadway network. A digitized continental roadway network has nodes
interconnected by links that define a digitized representation of
the continental roadway network. To enable intelligent data
collection and navigation over large expanses of the continental
network, which would otherwise be computationally onerous, the
digitized continental roadway network is partitioned into a
plurality of digitized roadway subnetworks. The onboard vehicle
navigation device has a processor for executing an application that
instantiates a subset of the digitized roadway subnetworks in a
vicinity of a current position of the vehicle to collect and
provide relevant real-time traffic data to the vehicle in a
computationally efficient manner.
Inventors: |
Xu; Yiwen; (Brossard,
CA) ; Xu; Xinyi; (Brossard, CA) |
Correspondence
Address: |
AKERMAN SENTERFITT
801 PENNSYLVANIA AVENUE N.W., SUITE 600
WASHINGTON
DC
20004
US
|
Assignee: |
WENSHINE TECHNOLOGY LTD.
Brossard
CA
|
Family ID: |
39916557 |
Appl. No.: |
12/285281 |
Filed: |
October 1, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11778293 |
Jul 16, 2007 |
7447588 |
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12285281 |
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Current U.S.
Class: |
701/118 ;
340/988; 340/995.1; 340/995.13 |
Current CPC
Class: |
G08G 1/0104
20130101 |
Class at
Publication: |
701/118 ;
340/988; 340/995.1; 340/995.13 |
International
Class: |
G08G 1/0969 20060101
G08G001/0969; G08G 1/123 20060101 G08G001/123 |
Claims
1. A method of collecting real-time traffic data using moving
vehicles and providing the real-time traffic data to an occupant of
a vehicle traveling on a continental roadway network, the method
comprising steps of: partitioning a digitized continental roadway
network having a plurality of nodes and links that define a
digitized representation of the continental roadway network into a
plurality of contiguous digitized roadway subnetworks, each
subnetwork having its own lifeline; and instantiating a plurality
of traffic managers in an onboard vehicle navigation device wherein
at least one traffic manager is instantiated for each one of a
subset of contiguous digitized roadway subnetworks that lie in a
vicinity of a current position of the vehicle to collect traffic
data and provide relevant real-time traffic data to the occupant of
the vehicle, wherein the at least one traffic manager is
instantiated in relation to the lifelines associated with its
respective neighboring subnetworks.
2. The method as claimed in claim 1 wherein the step of
partitioning the network comprises a step of dividing the
continental roadway network into regions represented by respective
subnetworks of nodes interconnected by links, the regions being
demarcated by demarcation lines which are drawn such that no line
segment of any demarcation line coincides with a link of any of the
subnetworks.
3. The method as claimed in claim 2 wherein each demarcation line
comprises a plurality of artificially defined demarcation nodes
with which are associated an ID of an immediately adjacent
subnetwork.
4. The method as claimed in claim 3 further comprising steps of:
detecting that the vehicle has arrived at one of the demarcation
nodes; and causing a control process executing in a processor of an
onboard vehicle navigation device to hand over responsibility from
a first traffic manager that is managing the first subnetwork from
which the vehicle is departing to a second traffic manager that is
managing the adjacent subnetwork which the vehicle is entering.
5. The method as claimed in claim 1 wherein the step of
partitioning the network comprises a step of defining, as an inner
belt running along each side of each demarcation line, a joint
awareness zone comprising an awareness line having awareness nodes
along the awareness line, the awareness nodes comprising a list of
the one or more neighboring regions whose traffic managers are to
be made jointly aware of the vehicle position.
6. The method as claimed in claim 5 comprising steps of: detecting
that the vehicle has arrived at one of the awareness nodes; and
forwarding vehicle position information to one or more traffic
managers for neighboring regions to make the one or more traffic
managers jointly aware of a current position of the vehicle.
7. The method as claimed in claim 1 wherein the step of
partitioning the network comprises a step of defining, as an outer
belt running approximately parallel to each demarcation line on
each side of each demarcation line, an instantiating/terminating
threshold (ITT), the ITT comprising a plurality of lifeline nodes
each having a list of neighboring regions for instantiating traffic
managers for subnetworks corresponding to neighboring regions that
become relevant and for terminating traffic managers for
subnetworks of regions that become no longer relevant.
8. The method as claimed in claim 7 further comprising steps of:
detecting that the vehicle has arrived at one of the lifeline
nodes; determining whether the vehicle is traveling toward or away
from a demarcation line; if the vehicle is traveling toward the
demarcation, instantiating a new traffic manager for the subnetwork
which the vehicle is approaching; and if the vehicle is traveling
away from the demarcation, terminating the traffic manager for the
subnetwork from which the vehicle has departed.
9. The method as claimed in claim 1 wherein the step of
partitioning comprises steps of: defining a joint awareness zone as
an inner buffer immediately on each side of each demarcation line
that partitions one subnetwork from a neighboring subnetwork, the
joint awareness zone having a plurality of awareness nodes forming
an awareness line approximately parallel to the respective
demarcation line; and defining an instantiating/terminating
threshold (ITT) as an outer buffer immediately on each side of the
joint awareness zone, the instantiating/terminating threshold
having a plurality of lifeline nodes arranged approximately
parallel to both the awareness line and the demarcation line.
10. The method as claimed in claim 9 further comprising steps of:
instantiating a traffic manager for each of one or more neighboring
subnetworks when the vehicle arrives at a lifeline node; sharing
vehicle position information with a traffic manager responsible for
each of the one or more neighboring subnetworks when the vehicle
arrives at an awareness node; and terminating a traffic manager
corresponding to the subnetwork from which the vehicle has exited
when the vehicle, traveling away from the demarcation line, arrives
at a lifeline node on the opposite side of the
instantiating/terminating threshold.
11. The method as claimed in claim 1 wherein the step of
instantiating the subset of digitized roadway subnetworks comprises
instantiating no more than four subnetworks.
12. The method as claimed in claim 1 wherein the step of
instantiating the subset of digitized roadway subnetworks comprises
a step of instantiating exactly four subnetworks consisting of a
continental expressway subnetwork, a first regional capillary
subnetwork, and two neighboring regional capillary subnetworks.
13. An intelligent vehicle highway system for collecting and
providing real-time traffic data from and to vehicles traveling on
roadways that are part of a continental roadway network, the system
comprising: a plurality of vehicles each having an onboard vehicle
navigation device having a global positioning system (GPS) receiver
for generating real-time position data for the vehicle, a wireless
transceiver for transmitting the real-time position data and for
receiving traffic data, the onboard vehicle navigation device
having a processor that executes an application for instantiating a
plurality of traffic managers wherein at least one traffic manager
is instantiated for each of the contiguous digitized roadway
subnetworks defined by partitioning a digitized continental roadway
network representative of the roadways of a continent to form a
partitioned continental roadway network, each subnetwork having its
own lifeline which, when traversed by the vehicle, causes the
application to instantiate the at least one traffic manager for the
neighboring subnetworks associated with the lifeline being
traversed; and a traffic data center having a wireless transceiver
for receiving real-time position data from the plurality of
vehicles in the network and for transmitting to the vehicles
processed traffic data based on the real-time position data
received from the plurality of vehicles in the network.
14. The system as claimed in claim 13 wherein the application
instantiates no more than four traffic managers and executes a
control process to control each of the traffic managers.
15. The system as claimed in claim 13 wherein the partitioned
continental roadway network comprises a plurality of demarcation
lines, each demarcation line comprising artificially defined
demarcation nodes, the demarcation lines being drawn to partition
the network into subnetworks such that no line segment of any
demarcation line coincides with any link of the network.
16. The system as claimed in claim 15 wherein the partitioned
continental roadway network comprises a joint awareness zone
defining an inner buffer immediately on each side of each
demarcation line that partitions one subnetwork from a neighboring
subnetwork, the joint awareness zone having a plurality of
awareness nodes forming an awareness line approximately parallel to
a respective demarcation line whereby vehicle position data for a
vehicle located within the joint awareness zone is shared between
the traffic managers associated with the neighboring subnetworks on
either side of the demarcation line.
17. The system as claimed in claim 15 wherein the partitioned
continental roadway network comprises an instantiating/terminating
threshold (ITT) on each side of the demarcation line, the
instantiating/terminating threshold having a plurality of lifeline
nodes arranged approximately parallel to the demarcation line
whereby arrival of the vehicle at one of the lifeline nodes causes
instantiation of a new traffic manager or termination of an
existing traffic manager.
18. The system as claimed in claim 15 wherein the partitioned
continental roadway network comprises: a joint awareness zone
defining an inner buffer immediately on each side of each
demarcation line that partitions one subnetwork from a neighboring
subnetwork, the joint awareness zone having a plurality of
awareness nodes forming an awareness line approximately parallel to
the respective demarcation line whereby vehicle position data for a
vehicle located within the joint awareness zone is shared between
the traffic managers associated with the neighboring subnetworks on
either side of the demarcation line; and an
instantiating/terminating threshold (ITT) as an outer buffer
immediately on each side of the joint awareness zone, the
instantiating/terminating threshold having a plurality of lifeline
nodes arranged approximately parallel to both the awareness line
and the demarcation line whereby arrival of the vehicle at one of
the lifeline nodes causes instantiation of a new traffic manager or
termination of an existing traffic manager.
19. An onboard vehicle navigation device for collecting,
transmitting and receiving real-time traffic data and for providing
intelligent navigation to an occupant of a vehicle traveling on a
continental roadway network, the device comprising: a global
positioning system (GPS) receiver for generating a current position
of the vehicle; a wireless transceiver for transmitting the current
position of the vehicle to a traffic data center for generating
traffic data to be communicated back to the wireless transceiver; a
processor that executes an application for instantiating a
plurality of traffic managers wherein at least one traffic manager
is instantiated for each one of a plurality of partitioned
subnetworks relevant to the current position of the vehicle, the
partitioned subnetworks being defined by partitioning a digitized
continental roadway network that represents the continental roadway
network in terms of nodes interconnected by links to thus form a
partitioned continental roadway network represented by contiguous
subnetworks, each subnetwork having its own lifeline which, when
traversed by the vehicle, causes the application to instantiate the
at least one traffic manager for the neighboring subnetworks
associated with the lifeline being traversed; and a user interface
for presenting the traffic data to the occupant of the vehicle to
enable intelligent navigation through the roadway network.
20. The device as claimed in claim 19 wherein the partitioned
subnetworks are divided by demarcation lines, each demarcation line
comprising demarcation nodes, the demarcation lines being drawn to
partition the continental network into subnetworks such that no
line segment of any demarcation line coincides with any link of any
of the subnetworks and wherein the partitioned continental roadway
network comprises: a joint awareness zone defining an inner buffer
immediately on each side of each demarcation line that partitions
one subnetwork from a neighboring subnetwork, the joint awareness
zone having a plurality of awareness nodes forming an awareness
line approximately parallel to the respective demarcation line
whereby vehicle position data for a vehicle located within the
joint awareness zone is shared between the traffic managers
associated with the neighboring subnetworks on either side of the
demarcation line; and an instantiating/terminating threshold (ITT)
as an outer buffer immediately on each side of the joint awareness
zone, the instantiating/terminating threshold having a plurality of
lifeline nodes arranged approximately parallel to both the
awareness line and the demarcation line whereby arrival of the
vehicle at one of the lifeline nodes causes instantiation of a new
traffic manager or termination of an existing traffic manager.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is the first application filed for the present
invention.
TECHNICAL FIELD
[0002] The present invention relates, in general, to traffic
engineering and, more particularly, to intelligent vehicle highway
systems that collect traffic information and provide real-time
traffic information to vehicles.
BACKGROUND ART
[0003] Real-time traffic data collection is of fundamental
importance for traffic information management, road guidance, and
intelligent vehicle highway systems (IVHS).
[0004] Most techniques addressing this issue use static probes,
i.e. fixed sensors and/or cameras. Given the enormous size of a
continental roadway system, and the sheer number of roads contained
therein, it is impractical not to mention prohibitively expensive
to install sensors and/or cameras throughout the network to collect
road traffic data for each and every public road on the
continent.
[0005] U.S. Pat. No. 6,401,027 (Xu et al.) entitled "Remote Road
Traffic Data Collection and Intelligent Vehicle Highway System"
discloses a method for collecting road traffic data by using moving
vehicles as probes. As described in this patent, vehicles
subscribing to the intelligent navigation service periodically
transmit position data to a traffic data center which computes
traffic conditions and broadcasts this traffic data back to the
vehicles. In-vehicle navigation devices then display or otherwise
use the traffic information to enable the vehicle occupants to
intelligently navigate the roadways to seek the fastest route to
their destination, primarily by avoiding traffic congestion. As
taught by this above patent, each vehicle maintains only two
digitized road network maps at any time, one being the continental
expressway network map and the other being a local regional or
metropolitan roadway network map. However, even though the
foregoing technology can, in theory, cover the entire territory of
a continent, the sheer number of links and nodes needed to
represent all the roadways and intersections in a continental
roadway system is so enormously large that it is computationally
inefficient to do so.
[0006] Accordingly, there exists a need for a technology that would
enable intelligent vehicle highway systems for the entire expanse
of a continental roadway network to thereby provide
computationally-efficient and seamless intelligent navigation
services to vehicles traveling large distances from one portion of
a continental roadway network to another.
SUMMARY OF THE INVENTION
[0007] In general, this invention relates to a continental roadway
network partitioning technique for road traffic data collection and
intelligent vehicle highway systems. In particular, a system and
method is provided for dividing a continental roadway network into
a set of smaller, computationally more manageable roadway networks
for efficiently collecting real-time traffic data and providing
traffic forecasts and travel guidance to drivers of vehicles
equipped to interact with the system.
[0008] Accordingly, one aspect of the present invention entails a
method of collecting real-time traffic data using vehicles and
providing the real-time traffic data to an occupant of a vehicle
traveling on a continental roadway network. This method includes
steps of partitioning a digitized continental roadway network
having a plurality of nodes and links that define a digitized
representation of the continental roadway network into a plurality
of digitized roadway subnetworks, and instantiating one or more
traffic managers in an onboard vehicle navigation device for each
one of a subset of digitized roadway subnetworks that lie in a
vicinity of a current position of the vehicle to collect and
provide relevant real-time traffic data from and to the
vehicle.
[0009] Another aspect of the present invention entails an
intelligent vehicle highway system for collecting and providing
real-time traffic data from and to vehicles traveling on roadways
that are part of a continental roadway network. The system includes
a plurality of vehicles each having an onboard vehicle navigation
device having a global positioning system (GPS) receiver for
generating real-time position data for the vehicle, a wireless
transceiver for transmitting the real-time position data and for
receiving traffic data, the onboard vehicle navigation device
having a processor that executes an application for instantiating
one or more traffic managers for each of the digitized roadway
subnetworks defined by partitioning a digitized continental roadway
network representative of the roadways of a continent to form a
partitioned continental roadway network. The system also includes a
traffic data center having a wireless transceiver for receiving
real-time position data from the plurality of vehicles in the
network and for transmitting to the vehicles processed traffic data
based on the real-time position data received from the plurality of
vehicles in the network.
[0010] Yet a further aspect of the present invention entails an
onboard vehicle navigation device for collecting, transmitting and
receiving real-time traffic data and for providing intelligent
navigation to an occupant of a vehicle traveling on a continental
roadway network. The onboard (in-vehicle) device includes a global
positioning system (GPS) receiver for generating a current position
of the vehicle, a wireless transceiver for transmitting the current
position of the vehicle to a traffic data center for processing
traffic data to be communicated back to the wireless transceiver, a
processor that executes an application for instantiating a
plurality of partitioned subnetworks relevant to the current
position of the vehicle, the partitioned subnetworks being defined
by partitioning a digitized continental roadway network that
represents the continental roadway network in terms of nodes
interconnected by links to thus form a partitioned continental
roadway network, and a user interface for presenting the traffic
data to the occupant of the vehicle to enable intelligent
navigation through the roadway network.
[0011] This new technology facilitates what would otherwise be a
computationally onerous, if not impossible, task given the
limitations of current microprocessors, namely providing real-time
traffic data to vehicle occupants for large expanses of a
continental roadway network. Despite the limited computational
processing power of onboard vehicle navigation devices, intelligent
navigation can be provided by innovatively partitioning a
continental roadway into more computationally manageable
subnetworks. Even if processor speeds were to be dramatically
improved, this new technology would still be extremely useful in
radically augmenting computational efficiency. Traffic managers for
relevant subnetworks are instantiated to provide traffic
intelligence about the immediate vicinity without wasting
computational resources on areas or regions that are far away.
Accordingly, this technology collects traffic data and provides
intelligent navigation to vehicles even if they travel long
distances, e.g. from one metropolitan area to another, and is thus
highly useful for long-distance commuters, people on road trips,
long-distance truckers, to name but a few end-users. Nevertheless,
the traffic data that is collected from all participating vehicles
in the network is shared among all other subscribers, whether they
are traveling long distances or merely locally (short
distances).
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Further features and advantages of the present invention
will become apparent from the following detailed description, taken
in combination with the appended drawings, in which:
[0013] FIG. 1 is a schematic layout of key components of an
intelligent vehicle highway system in which the present technology
can be implemented;
[0014] FIG. 2 is a block diagram of key components of an onboard
vehicle navigation device ("in-vehicle device") in which the
present invention can be implemented;
[0015] FIG. 3 is a schematic depiction of a method of partitioning
a continental roadway network in accordance with an embodiment of
the present invention; and
[0016] FIG. 4 is a sequence diagram illustrating, by way of
example, sequential actions carried out by a Control Process (CP)
executing on a microprocessor of an onboard vehicle navigation
device in relation to an instantiated pair of interacting traffic
managers ("Digitized Road Network (DRN) Managers) that were
instantiated by the vehicle support subsystem (VSS) to manage
traffic data for Region 1 and Region 2.
[0017] It will be noted that throughout the appended drawings, like
features are identified by like reference numerals.
DETAILED DESCRIPTION
[0018] By way of general introduction, and as will be elaborated
below, an intelligent vehicle highway system collects real-time
traffic data and provides processed real-time traffic data to an
occupant (e.g. driver) of a vehicle traveling on a continental
roadway network or other large-scale roadway network. A digitized
continental roadway network represents the continental roadway
network using nodes (for intersections or highway exits or
entrances) that are interconnected by links (for each direction of
each roadway) to thus define a digitized representation of the
continental roadway network. To enable intelligent navigation over
large expanses of the continental network, which would otherwise be
computationally inefficient if the entire continental network had
to be loaded, the digitized continental roadway network is
partitioned into a plurality of digitized roadway subnetworks. The
onboard vehicle navigation device has a processor for executing a
software application that instantiates a subset of the digitized
roadway subnetworks in a vicinity of a current position of the
vehicle to collect real-time traffic data and to provide relevant,
processed real-time traffic data to the occupant of the vehicle in
a computationally efficient manner.
Method Overview
[0019] Again by way of introduction, and as will be elaborated
below in greater detail with reference to FIGS. 1-4, a method of
collecting real-time traffic data and providing processed real-time
traffic data to an occupant of a vehicle traveling on a continental
roadway network includes an initial step of partitioning a
digitized continental roadway network having a plurality of nodes
and links that define a digitized representation of the continental
roadway network into a plurality of digitized roadway subnetworks.
The step of partitioning the digitized continental roadway network
is preferably done once (with optional subsequent updates to
account for road closures and new roads) and then stored on a
server or other storage means for uploading preferably by wireless
link to the VSS onboard each vehicle. Alternatively, the
subnetworks of the partitioned network can be uploaded from a
CD-ROM, DVD or other computer-readable storage medium. Subsequent
to loading of the partitioned network, updates can be transmitted
wirelessly as over-the-air patches to update the digitized
continental roadway network to account for road closures, new roads
that are built or expanded, or for new exits or entrances, etc.
CD-ROM, DVD or computer-readable medium updates could also be
distributed at gas stations or through the American Automobile
Association (AAA) or the Canadian Automobile Association (CAA),
convenience stores, etc.
[0020] Partitioning of the continental network results in a
plurality of subnetworks, each representing a region of the
continent, such as a metropolitan area, or a expanse of territory,
etc. The partitioning is done by dividing the continental roadway
network into regions represented by respective subnetworks of nodes
interconnected by links, the regions being demarcated by enclosed
demarcation lines (i.e. virtual boundaries between subnetworks)
which are drawn to represent each region's limit such that no line
segment of any demarcation line coincides with a link of any of the
subnetworks. In other words, the demarcation lines are drawn such
that demarcation lines intersect roadways but do not overlie any
roadways. Each demarcation line includes a plurality of
artificially defined demarcation nodes with which are associated an
ID of an immediately adjacent subnetwork. Thus, artificial nodes
can be added to define virtual boundaries or limits to delimit the
distinct regions of the partitioned network.
[0021] Once the partitioning is done, the next step in the method
is instantiating one or more traffic managers (also known herein as
"digitized roadway network managers") in an onboard vehicle
navigation device for each one of a subset of digitized roadway
subnetworks that lie in a vicinity of a current position of the
vehicle to collect real-time traffic data and to provide relevant,
processed real-time traffic data to the occupant of the vehicle. A
software application executing on a processor in the onboard
vehicle navigation device should instantiate no more than four
traffic managers while executing a control process to control each
of the traffic managers.
[0022] As will be elaborated below, the partitioned continental
roadway network has a joint awareness zone (JAZ) defining an inner
buffer immediately on each side of each demarcation line that
partitions one subnetwork from a neighboring subnetwork, the joint
awareness zone having a plurality of awareness nodes forming an
awareness line approximately parallel to the respective demarcation
line whereby vehicle position data for a vehicle located within the
joint awareness zone is shared between the traffic managers
associated with the neighboring subnetworks on either side of the
demarcation line. The girth of the joint awareness zone (JAZ) is
determined by the Level of Awareness (LOA) which is a tunable
parameter that can be varied to alter the performance of the
system. The LOA will be discussed in greater detail below. The
partitioned network also has an instantiating/terminating threshold
(ITT) as an outer buffer immediately on each side of the joint
awareness zone, the instantiating/terminating threshold having a
plurality of lifeline nodes arranged approximately parallel to both
the awareness line and the demarcation line whereby arrival of the
vehicle at one of the lifeline nodes causes instantiation of a new
traffic manager or termination of an existing traffic manager.
Operation and further implementation details for this novel method
will be presented below with reference to the accompanying
drawings.
System Overview
[0023] FIG. 1 illustrates a traffic data remote collection and
intelligent vehicle roadway system (also referred to herein as an
intelligent vehicle highway system (IVHS) or an "intelligent
vehicle navigation system") which is generally designated by
reference numeral 8. A group of vehicles 20 travel a roadway system
10, which may be a metropolitan highway system, a regional highway
system, a national expressway system, a cross-continent expressway
system, rural roads, state highways, etc, or the streets, roads,
avenues and boulevards of a city, town or municipality, etc. Each
vehicle 20 is equipped with an in-vehicle device 21 (also referred
to herein as an "onboard vehicle navigation device") which receives
global positioning data from satellites 42 of a Global Positioning
System (GPS) 40 or equivalent system. The onboard vehicle
navigation device 21 converts the GPS information into respective
instantaneous positions of the respective vehicle relative to a
digitized road network map that represents the roadway system on
which the vehicle is traveling. The digitized road network map
includes a reference system (latitude and longitude) consistent
with the reference system used by the GPS 40. The in-vehicle device
21 intermittently transmits the instantaneous roadway positions of
the vehicle as radio frequency (RF) data to a communication station
50. The communication station 50, in turn, transfers the
instantaneous vehicle positions through a transfer medium 52 (i.e.
a communication link which could be a wired link such as a fiber
optic cable or a copper wire or a wireless link) to a traffic
service center 60 (hereinafter referred to simply as a "traffic
data center"). The traffic data center 60 is also connected to
External Party Data Sources (EPDS) 70 which may include information
departments of law enforcement agencies, 911 service centers and
government agencies such as weather departments, highway and
traffic administration departments, etc. The traffic data center 60
uses the instantaneous road positions of all vehicles 20 and the
information obtained from the external party data sources (EPDS) to
provide real-time road traffic conditions for the roadway system 10
and broadcasts the traffic conditions via the communication station
50. The in-vehicle device 21 on each vehicle 20 receives the
traffic conditions from traffic data center 60 and processes
information included in the traffic condition broadcasts to provide
route planning (intelligent navigation) to the driver by
recommending real-time optimum travel routes based on real-time or
forecast traffic conditions. Further implementation details
regarding this system are described in U.S. Pat. No. 6,401,027 (Xu
et al.) entitled "Remote Road Traffic Data Collection and
Intelligent Vehicle Highway System", which is hereby incorporated
by reference in its entirety.
[0024] This system is improved by providing an enhanced software
component for executing on the processor of the onboard vehicle
navigation device 21 that uses subnetworks of a partitioned
digitized continental roadway network to alleviate the
computational burden on the processor while still collecting
traffic data and providing intelligent navigation for the immediate
vicinity of the vehicle. In other words, an intelligent vehicle
navigation system in accordance with an embodiment of the present
invention collects and provides real-time traffic data from and to
vehicles traveling on roadways that are part of a continental
roadway network. This improved system includes a plurality of
vehicles each having an onboard vehicle navigation device having a
global positioning system (GPS) receiver for generating real-time
position data for the vehicle, a wireless transceiver for
transmitting the real-time position data and for receiving traffic
data, the onboard vehicle navigation device having a processor that
executes an application for instantiating one or more traffic
managers for each of the digitized roadway subnetworks defined by
partitioning a digitized continental roadway network representative
of the roadways of a continent to form a partitioned continental
roadway network. This improved system also includes a traffic data
center having a wireless transceiver for receiving real-time
position data from the plurality of vehicles in the network and for
transmitting to the vehicles processed traffic data based on the
real-time position data received from the plurality of vehicles in
the network.
Onboard Vehicle Navigation Device
[0025] As depicted in FIG. 2, an enhanced vehicle support subsystem
(VSS) 30 is provided in the onboard vehicle navigation device
(in-vehicle device) 21. The enhanced VSS 30 includes a road network
locator 32 (hereinafter simply locator 32) and a road explorer 34.
A mobile radio subsystem 24 (i.e. a wireless RF transceiver) is
provided for exchanging radio frequency data with the traffic data
center 60 via the communication station 50. Also included in the
onboard vehicle navigation device (in-vehicle device) 21 are a
computer system 26 for operating the subsystems and storing the
digitized road network map. A driver/user interface 28 includes a
microphone, data entry pad, screen display and loudspeaker to
permit drivers (or other vehicle occupants, such as a passenger who
is navigating for the driver) to interact with the onboard vehicle
navigation device (in-vehicle device) 21.
[0026] The locator 32 computes the geographical location of the
vehicle, using data received from the GPS receiver 22, and converts
it to a position on the digitized road network map and stored in
the computer system 26. From time to time, the mobile radio
subsystem 24 transmits vehicle position data processed by the
locator 32 to the communication station 50 which forwards road
traffic data reported from all vehicles 20 traveling the roadway
system 10 to the traffic data center 60 for further processing. The
processed data is used for forecasting road traffic conditions. The
mobile radio system 24 in the vehicle 20 also receives data
broadcast by the communication station 50. In addition to traffic
forecasts, the broadcast data may include one or more digitized
road network maps (that is, if such maps have not yet been uploaded
by CD, DVD, or other computer-readable storage means). The data
received by the mobile radio subsystem 24 is stored by the computer
system 26 and the road network explorer 34 uses the data in
conjunction with driver's instructions received from the driver
interface 28 to provide intelligent route guidance or "intelligent
navigation". The intelligent route guidance (intelligent
navigation), such as an optimum travel route based on real-time
traffic conditions, can be displayed on the screen display of the
driver interface 28 (or, generically, the "user interface" when the
device is used by a vehicle occupant other than the driver).
Further implementation details regarding this device are described
in U.S. Pat. No. 6,401,027.
[0027] The device presented in U.S. Pat. No. 6,401,027 is improved
by providing an enhanced software component for executing on the
processor of the onboard vehicle navigation device 21 that uses
subnetworks of a partitioned digitized continental roadway network
to alleviate the computational burden on the processor while still
providing intelligent navigation for the immediate vicinity of the
vehicle. In other words, an intelligent vehicle navigation device
in accordance with another embodiment of the present invention
provides intelligent navigation to an occupant of a vehicle
traveling on a continental roadway network. This improved device
has a global positioning system (GPS) receiver for generating a
current position of the vehicle, a wireless transceiver for
transmitting the current position of the vehicle to a traffic data
center for generating traffic data to be communicated back to the
wireless transceiver, a processor that executes an application for
instantiating a plurality of partitioned subnetworks relevant to
the current position of the vehicle, the partitioned subnetworks
being defined by partitioning a digitized continental roadway
network that represents the continental roadway network in terms of
nodes interconnected by links to thus form a partitioned
continental roadway network, and a user interface for presenting
the traffic data to the occupant of the vehicle to enable
intelligent navigation through the roadway network.
Attributes of a Digitized Continental Roadway Network
[0028] A continental roadway network can be understood as a roadway
system or network that includes all of the publicly accessible
roadways of a given continent, and thus include the network of
expressways, highways, rural roads, streets, avenues, roads and
boulevards upon which a vehicle may travel. As will be appreciated,
the continental roadway network need not strictly speaking be
"continental" in scope. In other words, the roadway network could
also be a national roadway network and therefore the present
technology can be applied equally to a national roadway network
that would include all of the public roadways of a particular
country. Indeed, persons of ordinary skill in the art will
appreciate that the present technology can be applied to any
roadway network that is too large to be computationally efficient
on a microprocessor of an onboard vehicle navigation device.
Accordingly, the expression "continental" should be construed as
referring to a large-scale roadway system or road network that is
computationally inefficient for the microprocessor of the onboard
vehicle navigation device and is thus not limited to roadway
networks that are continental in their reach. For example, this
technology could be used for the roadway network of Japan (a
national roadway) or of the USA alone (also national in scope).
Nevertheless, the main purpose of this technology is to enable
collection of traffic data and intelligent navigation over roadway
networks that are continental in scope, such as, for example, the
roadway network of North America, the roadway network of Europe, or
the roadway network of Australia.
[0029] The continental roadway network is digitized by representing
every roadway by one or more links. A link is a
directional/oriented road segment connecting two nodes, which can
be thought of as a source node and a sink node, i.e. a link
connects its source to its sink. A bidirectional (two-way) road
would be represented by two oppositely oriented links representing
each direction of travel on the bidirectional road. A one-way road
would, of course, be represented by only a single link. Nodes are
used to represent intersections, highway exits (off-ramps) or
highway entrances (on-ramps). As will be elaborated below,
artificial nodes can be artificially defined along links to
facilitate partitioning and to define buffer zones for information
management and instantiation/termination of traffic managers. A
route is thus a set of sequential links such that the first link's
sink is the second link's source, and so on. The length (or
"scale") of a route, from a starting node to a destination node, is
thus equal to the number of links. The distance from one node N1 to
another node N2 is thus defined as the scale of a shortest route
from N1 to N2. The distance from a node to the demarcation line is
the scale of a shortest route from the node to any node on the
demarcation line. The distance from a link to the demarcation is
defined as the distance from the sink of the link to the
demarcation+1. Accordingly, a link's DTD will never be zero and a
node's DTD is non-negative. Distance can also be expressed in
meters, kilometers, miles, or other units of linear measure or in
terms of a number of links. Distance can thus be represented using
scale or distance, or alternatively a combination or weighted
combination of both. Using nodes and links in the manner described
in U.S. Pat. No. 6,401,027 enables one to digitize ("discretize")
the continental roadway network into a digitized continental
roadway network that is a digitized representation of the
continental roadway network.
[0030] Each node in the network has associated data that includes a
node index, latitude, longitude, DTD and may include other data
relevant to the IVHS (Intelligent Vehicle Highway System).
Similarly, each link has associated data that includes a link
index, source, sink, length, and may include other data relevant to
the IVHS. Each subnetwork manager has a unique subnetwork
identifier. For example, subnetwork index 0 could be assigned to
the backbone expressway network; subnetwork indices 1 to 10,000
could be assigned to metropolitan subnetworks and networks indices
10,001 and higher could be assigned to other subnetworks in the
digitized continental roadway network. Each subnetwork's traffic
manager responsible for each subnetwork also has an indication of
the identification of each of its neighboring regions/subnetworks
and also contains the total number of nodes and total number of
links in the subnetwork. Each subnetwork's traffic manager also has
knowledge of the identity of each of the neighboring JAZ nodes and
links.
Partitioning the Digitized Continental Roadway Network
[0031] The continent (or other large territory) is partitioned into
discrete and distinct regions (e.g. states, provinces, counties,
metropolitan areas, or arbitrarily defined regions) by partitioning
the digitized continental roadway network into subnetworks
corresponding to each region using demarcation lines such that no
linear segment of any demarcation line overlies or coincides with
any link. In other words, the subnetworks are defined by "cleanly"
partitioning the network so that the demarcation lines intersect
links but do not coincide with any links. The resulting partitioned
continental roadway network is composed of a plurality of
subnetworks, each being represented by nodes interconnected by
links. Along each demarcation line are artificially defined
demarcation nodes that are added to facilitate the handling of
transitions from one subnetwork to another, as will be explained
below. By analogy with the techniques exposed in U.S. Pat. No.
6,401,027, vehicle location reports and traffic data received back
from the traffic data center is provided in terms of nodes and
links for one or more of the subnetworks, thus enabling route
guidance calculations and intelligent navigation through the one or
more relevant subnetworks. For the purposes of nomenclature, a
"backbone network" means a continental expressway network or
continental highway network (e.g. the network of U.S. Interstate
highways). "Capillary networks" include all other roadway networks
in the continental roadway system, including, for example, state or
provincial roadway networks, regional or rural roadway networks,
and metropolitan roadway networks. As will be appreciated, when a
vehicle is traveling along a roadway of the continental roadway
network, it is not necessary to have traffic information about
far-off locations that do not impinge on the traffic conditions or
route selection in the immediate vicinity of the vehicle.
Therefore, as will be explained below, only the traffic conditions
in certain proximate ("relevant") subnetworks of the partitioned
network need to be determined or obtained. This is the great
advantage of partitioning the continental roadway network into
smaller, more manageable subnetworks. It is important to note that
the partitioning of the continent into regions need not concord
with predetermined geographical entities such as cities, counties,
or states. In other words, demarcation lines are not necessarily
drawn along city boundaries, state lines, county lines, etc. The
continental area can be partitioned arbitrarily such that a given
region encompasses, for example, a portion of one county of one
state and a portion of a different county of another state.
Arbitrary partitioning of the continental network (without aligning
demarcations with actual geographical boundaries) ensures that
regions are optimally drawn to facilitate the smooth handover from
one traffic manager (digitized roadway network manager) to another.
Partitioning of the network is preferably done only once by a human
operator or using special software in order to provide an optimal
partitioning of the network, although partitioning could also be
performed by the enhanced VSS 30 in the onboard device 12 in each
vehicle. Once the network has been partitioned into subnetworks of
links and nodes, this "static" roadway data (the digitized roadway
network data) is uploaded to the enhanced VSS 30 in each vehicle,
e.g. by CD, DVD or wireless link. Wirelessly uploading this
digitized roadway network data is preferable since this technique
provides potentially "fresher", updated data on the network, taking
into account road closures or new roads that have been opened.
Alternatively, new versions, containing changes to the road
network, can be provided to users on CD, DVD or on another type of
computer-readable storage medium.
[0032] In operation, digitized roadway network data representing
the links and nodes of relevant subnetworks is preferably loaded to
the VSS 30 after being received over-the-air by the wireless RF
transceiver in the onboard vehicle navigation device 21 from the
traffic data center 60. As mentioned above, the preferred technique
is to partition the network first, store the resulting subnetworks,
and then upload relevant subnetworks wirelessly, which thereby
avoids the inefficiencies of having to load the digitized roadway
network data for the entire continental roadway system into the VSS
30. In this present invention, as introduced above, a continental
roadway network is partitioned into smaller subnetworks, including
a backbone network representing a continental expressway network
and a plurality of capillary roadway subnetworks. For each
subnetwork, a Digitized Roadway sub-Network (DRN) Manager (DRNM) 36
is employed to collect, manage and process traffic data for a
respective subnetwork of roadways to plot optimal routes through
the links and nodes of the subnetwork to avoid areas of congestion.
Each DRNM is implemented as a computer process in the VSS 30. For
the purpose of this specification, a DRNM shall also be known as a
"traffic manager" since it collects and then manages/processes
traffic data received from the traffic data center for a respective
subnetwork. In other words, as will be explained below, a traffic
manager (or DRNM) is instantiated as a separate computer process to
handle traffic data for each respective subnetwork of the
partitioned continental roadway network. In comparison with the
prior-art system described in U.S. Pat. No. 6,401,027, this
improved technology uses an enhanced VSS that includes a Control
Process (CP) and multiple traffic managers (i.e. multiple DRNMs) to
handle relevant subnetworks of the partitioned network.
[0033] Partitioning of the continental roadway network can be done
in such a manner that, at any location, a vehicle concerns at most
four (4) subnetworks: the continental expressway subnetwork (i.e.
the backbone network); a regional capillary subnetwork; and two
neighboring capillary subnetworks. In other words, the vehicle
might be on either the continental expressway subnetwork or a
regional capillary subnetwork, with two (2) other capillary
subnetworks serving as neighboring subnetworks. As will be readily
appreciated in view of this disclosure, more than four (or fewer
than four) subnetworks can be instantiated in other variants of
this technology. For example, in a variant, it might be useful to
instantiate five or six traffic managers for five or six respective
subnetworks in a case where the partitioning of the continental
territory into regions has a smaller granularity (i.e. smaller
regions are created by partitioning).
[0034] Preferably, and subject to the potential variation described
in the foregoing paragraph, at most four (4) DRN managers are
employed in the enhanced VSS 30. Most of the time, however, the
enhanced VSS 30 only uses two (2) DRN managers (traffic managers):
one representing the continental expressway subnetwork, and the
other representing a local capillary subnetwork on which the
vehicle is currently located. When the vehicle is approaching a
neighboring capillary network, and has approached beyond a
predetermined threshold, a DRN manager needs to be instantiated to
represent the subnetwork that the vehicle is approaching. If the
vehicle is simultaneously approaching two (2) capillary networks,
i.e. nearing the junction of three regions, then two (2) DRN
managers are instantiated to represent, respectively, the two
adjoined neighboring capillary networks. Instantiating two DRN
managers for the two capillary networks that the vehicle is
approaching is necessary to ensure that regardless which of the two
roadway subnetworks the vehicle enters, a DRN manager corresponding
to the entered subnetwork will be running.
[0035] Although there always is more than one active DRN manager in
the enhanced VSS 30, only one DRN manager (i.e. the one
corresponding to the roadway network on which the vehicle is
currently driving) plays a primary role: getting the position of
the car, through Locator 32, and reporting the car's location data
to the traffic data center 60. Each DRN manager receives and
updates real-time traffic data of its subnetwork and is effectively
on standby, i.e. ready to take over responsibilities as primary DRN
manager if the vehicle moves into its own subnetwork.
[0036] When a vehicle moves into a new subnetwork, a new traffic
manager (DRNM) is activated as the primary traffic manager (primary
DRNM). The traffic manager for the subnetwork from which the
vehicle has just departed is downgraded from "primary" to
"standby", i.e. its process remains instantiated and a decision
must also be made as to whether that existing traffic manager that
remains instantiated is still relevant or whether it should be
deactivated or terminated. Once the vehicle has gone beyond a
predetermined threshold outbound from the previous subnetwork, i.e.
has left a buffer zone or belt on the other side of the demarcation
line, the VSS no longer needs the DRN manager (traffic manager)
that handles the previous subnetwork. Thus, the DRN manager will be
terminated as being no longer required.
JAZ, ITT and Other Implementation Details
[0037] An outer buffer zone or outer belt, representing a first
threshold, is defined as an Instantiating/Terminating Threshold
(ITT). An inner buffer zone, or inner belt, representing a second
threshold, is defined as a Joint Awareness Zone (JAZ). There is
thus an inner buffer zone within an outer buffer zone (or
effectively two layers or belts on each side of the demarcation
line between adjacent regions or subnetworks). In general, when a
vehicle hits the outer buffer known as the ITT, a traffic manager
is instantiated for the subnetwork being approached. When the
vehicle approaches even closer to the demarcation line dividing one
subnetwork from its neighboring subnetwork, the vehicle hits the
awareness line of the Joint Awareness Zone (JAZ). The
active/primary traffic manager for the subnetwork in which the
vehicle is presently traveling then begins to share vehicle
position data with the traffic manager of the neighboring
subnetwork to thereby make both traffic managers for the
neighboring subnetworks aware of the vehicle position. Because of
the proximity of the vehicle to the neighboring subnetwork (and
hence the likelihood that the vehicle may in fact traverse into the
neighboring subnetwork), the traffic manager for the neighboring
subnetwork may not only receive traffic data, but may also
determine congested areas and provisionally compute optimal routes
for the vehicle in the event that the vehicle actually traverses
the demarcation line.
[0038] The Joint Awareness Zone (JAZ) runs substantially parallel
to the demarcation line, thus defining an inner belt or buffer
zone. The JAZ has a plurality of awareness nodes (some of which may
be artificially defined) arranged roughly parallel to the
demarcation line in what is referred to herein as an "awareness
line", thus constituting a predetermined threshold for triggering
the exchange of vehicle position information with the traffic
manager of an adjacent subnetwork.
[0039] Immediately outside the JAZ is the ITT
(Instantiating/Terminating Threshold) which is an outer belt or
buffer running also parallel to the awareness line and demarcation
line. The ITT is also known as a "lifeline" and includes a
plurality of lifeline nodes, some of which may be artificially
defined. In other words, a node is a "lifeline node" (in regards to
its neighboring network) if its Distance to Demarcation (DTD) or
Distance from Demarcation (DFD) is equal to the ITT. A line passing
through all lifeline nodes within a region (sub-network), as
mentioned above, is called the "lifeline". The "lifeline" is so
called because it either brings to life (instantiates) a traffic
manager (computer process) or it terminates/kills a traffic manager
(computer process). If a vehicle is driving toward a neighboring
subnetwork, then the neighboring subnetwork's manager needs to be
instantiated when the vehicle hits the lifeline. If the vehicle is
driving away from a neighboring subnetwork, then the neighboring
subnetwork's manager will be terminated when the vehicle hits the
lifeline (having, of course, traverse to the other side of the
demarcation line). From the foregoing, it should be apparent that
each region is enclosed by one or more demarcation lines
concentrically within which are the lifelines (ITT) and awareness
lines that form the outer and inner buffers, respectively, around
the periphery or boundary of each region. The lifelines and
awareness lines are each closed lines, each tracking approximately
parallel to the boundary (demarcation lines) of their respective
region.
[0040] The width of the ITT (i.e. the distance from the demarcation
to the ITT's lifeline) is chosen based on the real-time traffic
data broadcast cycle. One criterion is that the DRN manager
(traffic manager) should be instantiated such that it is given
enough time to receive a full traffic data broadcast before the
vehicle moves into its territory.
[0041] In an alternative embodiment, instead of
instantiating/terminating DRN managers, it is possible to merely
awaken/hibernate the various processes. In this implementation,
four (4) DRN managers (traffic managers) are created when the
system boots up. No DRN managers are terminated at any time.
Instead, a DRN manager is merely hibernated when it is no longer
required, and it will be awakened only when the control process
considers it necessary or expeditious to do so.)
[0042] The enhanced VSS 30 uses a Control Process 38, as depicted
schematically in FIG. 2, to instantiate and terminate a DRN manager
(i.e. traffic manager) and to coordinate operations among the
various DRN managers (traffic managers), including for example the
hand-over of primary vehicle tracking responsibility when the
vehicle crosses over from one subnetwork to an adjacent
subnetwork.
[0043] FIG. 3 depicts a part of a roadway network where a threshold
number (of the ITT)=5, and the Level of Awareness (LOA)=2. These
values are provided solely by way of example to illustrate the
operation of the present technology. The LOA ("Level of Awareness")
is a tunable parameter that can be varied to change the performance
of the navigation system. The LOA determines the placement of the
awareness line and hence the width of the joint awareness zone
(JAZ). In particular, a common LOA value is selected for all
capillary subnetworks and an LOA of zero (0) is set for the
backbone subnetwork. Setting the LOA to 0 for the backbone
subnetwork does not mean that vehicle positions when driving on the
backbone will not be shared with the traffic manager of the local
capillary subnetwork. On the contrary, vehicle positions when
driving on the backbone will always be shared with the traffic
manager of the local capillary subnetwork. Actually, the projection
of the backbone to the local capillary subnetwork is part of the
local capillary subnetwork. Therefore, when driving on the backbone
network, the vehicle is present on two (2) subnetworks: the
backbone and the local capillary subnetwork.
[0044] A higher LOA is more computationally onerous since
information is shared more frequently. A higher LOA, in theory,
provides more intelligent navigation since the occupant of the
vehicle is made aware of traffic conditions that are far from the
present location of the vehicle, thus providing better chances of
avoiding congested areas. Conversely, a lower LOA is
computationally easier but provides less "intelligence" about
traffic conditions prevailing in regions beyond the immediate
vicinity of the vehicle. In other words, when the Distance to
Demarcation (DTD) is greater than the LOA, the vehicle is outside
the joint awareness zone (JAZ), and it is probably not relevant to
make the manager for the adjoining region aware of the vehicle's
current location. However, when the DTD is less than or equal to
the LOA, then the vehicle is either at an awareness node or within
the JAZ, in which case the manager of the adjoining region needs to
know where the vehicle is currently located. In practice, however,
if the continental network is properly partitioned such that
demarcation lines are only drawn in rural areas or areas of lower
population density, then the use of a low LOA is preferable. In
other words, if metropolitan roadway networks are never partitioned
into two (2) adjoining metropolitan subnetworks, then congestion
areas will rarely, if ever, arise in close proximity to a
demarcation line. If this sort of partitioning can be achieved, a
low LOA becomes advantageous to economize computational resources
while nevertheless ensuring a smooth handover from one traffic
manager (DRNM) to another.
[0045] The area illustrated in FIG. 3 covers three (3) regions
whose respective subnetworks are separated by the demarcation lines
116. Again, it is to be understood that this diagram is presented
merely by way of example to illustrate embodiments of the
invention, and nothing in the details of this diagram should be
taken as limiting the scope of the invention defined in the
appended claims. For example, the respective sizes/widths of the
JAZ 120 and ITT 112 can be varied beyond what is illustrated in
this example.
[0046] The partitioned network includes nodes 100 and links 110.
Nodes with DTD=5 or DFD=5 are the lifeline nodes 102 along the ITT
112. Nodes with DTD=2 or DFD=2 are the awareness nodes 104 along
the awareness line 114. Nodes with DTD=0 are demarcation nodes 106
along the demarcation line 116. The lifeline 112 passes all
lifeline nodes 102 of a region and is substantially parallel to the
region's demarcation line. The awareness line 114 passes through
all awareness nodes 104 of a region and is substantially parallel
to the region's demarcation line as well. The shaded area bounded
by the awareness line 114 and the demarcation line 116 in each
region is the Joint Awareness Zone (JAZ) 120 for that region.
[0047] FIG. 4 is a sequence diagram illustrating, by way of
example, sequential actions carried out by the Control Process (CP)
and the DRN managers (traffic manager processes) as a vehicle
traveling in Region 1 hits the ITT, traverses the JAZ, and then
crosses the demarcation line to enter Region 2. Also explained are
the subsequent actions that occur in the Control Process and
traffic managers as the vehicle, heading outbound from the
demarcation line, departs the JAZ and crosses the ITT threshold of
Region 2.
[0048] The example depicted with reference to FIG. 4 assumes that a
vehicle is driving from Region 1 towards Region 2. When the vehicle
hits the lifeline 112, a DRN manager (traffic manager process)
needs to be instantiated for Region 2. When the vehicle then hits
the awareness line 114 and enters the joint awareness zone 120, the
position of the vehicle needs to be passed to the DRN Manager
(traffic manager) responsible for traffic in Region 2. When the
vehicle reaches the demarcation line 116, the DRN Manager handling
traffic for Region 2 will take over the primary role of reading GPS
data and reporting the location of the car, thus putting the Region
1 traffic manager into standby mode. Until the vehicle departs the
JAZ on the other side of the demarcation line, vehicle position
data will be shared with the manager of Region 1 even if it has
just been put into standby mode because of the possibility that the
vehicle may return to Region 1. In other words, the vehicle may
have temporarily veered into Region 2 on its way back into Region
1, thereby requiring the Region 1 manager to maintain full position
awareness. When the vehicle exits the JAZ of Region 2, then
reporting/sharing of vehicle position data to the manager of Region
1 ceases. When the vehicle reaches the lifeline of Region 2, the
DRN Manager of Region 1 is terminated by the control process. At
this point, the manager of Region 1 is no longer required for the
immediate navigation needs of the vehicle. In other words, traffic
conditions prevailing in Region 1 (and its associated subnetwork)
are no longer deemed relevant to the vehicle. Of course, if the
vehicle turns back and crosses the ITT 112 of Region 2, the manager
of Region 1 will be re-instantiated.
[0049] It is obvious for those skilled in the art that as the
technology develops the basic idea of the invention can be
implemented in various ways. The invention and the embodiments
thereof are thus not restricted to the examples described above,
but they may vary within the scope of the claims.
* * * * *