U.S. patent application number 09/825959 was filed with the patent office on 2001-11-01 for vehicle safety running apparatus.
This patent application is currently assigned to Honda Giken Kogyo Kabushiki Kaisha. Invention is credited to Sekine, Hiroshi.
Application Number | 20010037173 09/825959 |
Document ID | / |
Family ID | 18638976 |
Filed Date | 2001-11-01 |
United States Patent
Application |
20010037173 |
Kind Code |
A1 |
Sekine, Hiroshi |
November 1, 2001 |
Vehicle safety running apparatus
Abstract
In a vehicle safety running apparatus, when a route guidance by
a navigation system is not in operation, a determination on
passableness is carried out as a target on a branch road of a
plurality of branch roads branched from an intersection ahead of
the subject vehicle which has lowest with respect to the degree of
difficulty in running or a branch road having a smallest
intersection angle formed by a road on which the subject vehicle is
advancing and the branch road and a curve on the branch road,
whereby an automatic deceleration control can be performed or an
alarm can be given to the driver even when the route guidance is
not in operation, and moreover the automatic deceleration control
and/or alarming the driver is prevented from being performed
unnecessarily, thereby making it possible to suppress to a minimum
level the physical disorder that the driver may feel.
Inventors: |
Sekine, Hiroshi; (Saitama,
JP) |
Correspondence
Address: |
ARENT FOX KINTNER
PLOTKIN & KAHN, PLLC
Suite 600
1050 Connecticut Aveune, N.W.,
Washington
DC
20036-5339
US
|
Assignee: |
Honda Giken Kogyo Kabushiki
Kaisha
|
Family ID: |
18638976 |
Appl. No.: |
09/825959 |
Filed: |
April 5, 2001 |
Current U.S.
Class: |
701/410 |
Current CPC
Class: |
G01C 21/3697 20130101;
G01C 21/34 20130101 |
Class at
Publication: |
701/200 ;
701/209 |
International
Class: |
G01C 021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 2000 |
JP |
P. 2000-129752 |
Claims
What is claimed is:
1. A vehicle safety running apparatus comprising: storage means
(M1) for storing road data including intersections; subject vehicle
position detecting means (M2) for detecting the position of a
subject vehicle; route setting means (M3) for setting a route to a
destination; vehicle condition detecting means (M4) for detecting a
vehicle condition of said subject vehicle including at least a
vehicle speed thereof; bend portion detecting means (M5) for
detecting curves and intersections existing along a traveling
direction of said subject vehicle based on a road data stored in
said storage means and the subject vehicle position detected by
said subject vehicle position detecting means (M2); and proper
condition determining means (M6) for calculating, based on
information on curves and intersections detected by said bend
portion detecting means (M5), proper vehicle conditions for passing
through said curves and intersections, and determining whether or
not said subject vehicle can properly pass through said curves and
intersections based on the result of a comparison of the proper
vehicle condition calculated with the vehicle condition detected by
said vehicle condition detecting means (M4); and running difficulty
determining means (M7) for determining a degree of difficulty in
running on a road on which said subject vehicle is traveling,
wherein when said bend portion detecting means (M5) detects an
intersection branching into a plurality of branch roads in a state
in which a route guidance based on a set route is not carried out,
said proper condition determining means (M6) selects a branch road
determined by said running difficulty determining means (M7) as
having a lowest degree of difficulty in running and determining
whether or not said subject vehicle can pass through said branch
road.
2. The vehicle safety running apparatus according to claim 1,
wherein said storage means (M1) is configured to store road data
through nodes and links, and wherein said running difficulty
determining means (M7) is configured to determine that a branch
road having a smaller intersecting angle formed by links
immediately before and after a node set at an intersection is lower
in the degree of difficulty in running.
3. The vehicle safety running apparatus according to claim 1,
wherein said proper condition determining means (M6) determines
whether or not a curve on a branch road selected by said proper
condition determining means can be passed along.
4. The vehicle safety running apparatus according to claim 3,
wherein said proper condition determining means (M6) cancels the
determination on whether or not said curve on said branch road
selected by said proper condition determining means can be passed
along when said subject vehicle starts to advance on a branch road
other than said branch road selected by said proper condition
determining means.
5. The vehicle safety running apparatus according to claim 1,
comprising a direction indicator unit, wherein said proper
condition determining means (M6) cancels the selection of a branch
road when said direction indicator unit indicates, before said
intersection, that said subject vehicle is advancing on a branch
road other than a branch road selected by said proper condition
determining means (M6).
6. The vehicle safety running apparatus according to claim 1,
further comprising route deviation determining means (M8) for
determining whether or not said subject vehicle deviates from a set
route by comparing a route set by said route setting means (M3)
with a position of said subject vehicle detected by said subject
vehicle position detecting means (M2), wherein said state in which
a route guidance based on a set route is not carried out involves
where a deviation from said set route is detected by said route
deviation determining means (M8).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a vehicle safety running
apparatus for a vehicle provided with a so-called navigation
system, and more particularly to a vehicle safety running apparatus
for allowing a subject vehicle to pass through intersections and
curves in front thereof exactly even when a route to a destination
is not set.
[0003] 2. Description of the Related Art
[0004] A Japanese Patent Unexamined Publication No. Hei.
8-194896(JP-A-8-194896) describes a safety running apparatus for
preventing the execution of improper automatic deceleration or
alarming the driver when the driver does not follow a route
guidance at intersections by excluding them from objects for
control in a case where vehicle speed control and/or alarming is
executed according to the shapes of curves coming up in front of a
subject vehicle along a road on which the subject vehicle is
traveling while a route guidance by a navigation system is being
carried out.
[0005] In addition, a Japanese Patent Unexamined Publication No.
Hei. 7-229745(JP-A-7-229745) discloses a safety running apparatus
for executing automatic deceleration control and alarming against a
route to be taken by a subject vehicle after the subject vehicle
deviates from its route by alarming the driver in the event that
the subject vehicle deviates from its route or a deviation of the
subject vehicle from its route is anticipated while a route
guidance by a navigation system is being carried out.
[0006] In order to execute proper automatic deceleration control
and alarming for a subject vehicle to securely pass along a road in
front thereof the driver is required to grasp the shapes of roads
based on a future route for him or her to take. To this end,
conventionally, while a route guidance by a navigation system is
being carried out and in a case where a route that will be followed
by the subject vehicle in the future can be anticipated, the
automatic deceleration control and/or alarming is carried out based
on the shapes of roads along a set route. However, there occurs a
case where the route guidance by the navigation system is not
executed on roads that are used very frequently or are known to the
driver. Alternatively, there occurs a case where the subject
vehicle deviates its route even when the route guidance is being
carried out, and in such a case, the conventional safety running
apparatus has faced a problem that it cannot execute precise
vehicle speed control and alarming .
[0007] In order to improve the safety in driving the subject
vehicle when the route guidance by the navigation system is not in
operation, it is considered to select a branch road which is the
most difficult for the subject vehicle to pass through such as a
branch road having a largest intersection angle relative to a road
on which the subject vehicle is running or a branch road having a
curve having a smallest radius of curvature and then to control the
vehicle speed or alarm the driver so that the subject vehicle can
pass through the branch road safely. However, with such a system in
operation, even in the event that the subject vehicle enters a
branch road which is not the branch road so selected, the control
or alarming is still activated and it follows that the unnecessary
control or alarming is executed. Thus, the driver may feel
uncomfortable.
SUMMARY OF THE INVENTION
[0008] The invention was made in view of these situations, and an
object thereof is to enable the precise execution of controlling
the vehicle speed and alarming the driver according to the shape of
a road ahead of the subject vehicle.
[0009] With a view to attaining the object, according to a first
aspect of the invention, there is provided a vehicle safety running
apparatus comprising a storage means for storing road data
including intersections and a subject vehicle position detecting
means for detecting the position of a subject vehicle, a route
setting means for setting a route to a destination, a vehicle
condition detecting means for detecting the vehicle condition of
the subject vehicle including at least the vehicle speed thereof, a
bend portion detecting means for detecting curves and intersections
existing along the traveling direction of the subject vehicle based
on the road data stored in the storage means and the subject
vehicle position detected by the subject vehicle position detecting
means and a proper condition determining means for calculating,
based on information on curves and intersections detected by the
bend portion detecting means proper vehicle conditions for passing
through the curves and intersections and determining whether or not
the subject vehicle can properly pass through the curves and
intersections based on the result of a comparison of the proper
vehicle condition so calculated with the vehicle condition detected
by the vehicle condition detecting means; the vehicle safety
running apparatus further comprising a running difficulty
determining means for determining the degree of difficulty in
running on a road on which the subject vehicle is traveling,
whereby when the bend portion detecting means detects an
intersection branching into a plurality of branch roads in a state
in which a route guidance based on a set route is not carried out,
the proper condition determining means selects a branch road
determined by the running difficulty determining means as having a
lowest degree of difficulty in running and determining whether or
not the subject vehicle can pass through the branch road.
[0010] According to the configuration as described above, since a
branch road of branch roads at an intersection ahead of the subject
vehicle along a road on which the subject vehicle is traveling
which has the lowest degree of difficulty in running is selected to
determine whether or not the subject vehicle can pass therethrough
in the state in which the route guidance along a set route is not
carried out, it is possible to determine whether or not the subject
vehicle can pass through the branch road even in a case where no
route to a destination is not set. Moreover, the possibility that
automatic deceleration control and/or alarming is performed
excessively can be reduced by selecting a branch road which is easy
for the subject vehicle to pass through, thereby making it possible
to suppress to a minimum level the physical disorder that the
driver feels. In addition, even in the event that the subject
vehicle happens to enter a branch road which is difficult for the
subject vehicle to pass through, since in many cases the driver
drives the vehicle without depending on the route guidance when he
or she has already been aware of the existence of an intersection
ahead of the subject vehicle or is then determined on which turn to
take at the intersection, it is most unlikely that the subject
vehicle enters the branch road which is difficult for it to pass
through with excessive vehicle speed.
[0011] Additionally, according to a second aspect of the invention,
there is provided a vehicle safety running apparatus as set forth
in the first aspect of the invention, wherein the storage means is
configured to store road data through nodes and links, and wherein
the running difficulty determining means is configured to determine
that a branch road having a smaller intersecting angle formed by
links immediately before and after a node set at an intersection is
lower in the degree of difficulty in running.
[0012] According to the configuration as described above, it is
possible to determine exactly a branch road having a lowest degree
of difficulty in running by selecting a branch road having a
smallest intersection angle formed by links located before and
after a node set at an intersection.
[0013] Furthermore, according to a third aspect of the invention,
there is provided a vehicle safety running apparatus as set forth
in the first or second aspect of the invention, wherein the proper
condition determining means determines whether or not a curve on a
branch road selected by the proper condition determining means can
be passed along.
[0014] According to the configuration as described above, since
whether or not the subject vehicle can pass through the selected
curve on the branch road is determined, it is possible to perform
an accurate automatic deceleration control and/or give an alarm to
the driver by determining whether or not a curve along which the
subject vehicle is anticipated to pass.
[0015] Moreover, according to a fourth aspect of the invention,
there is provided a vehicle safety running apparatus as set forth
in the third aspect, wherein the proper condition determining means
cancels its determination on whether or not the curve on the branch
road selected by the proper condition determining means can be
passed along when the subject vehicle starts to advance on a branch
road other than the branch road selected by the proper condition
determining means.
[0016] According to the above configuration, when the subject
vehicle advances on a branch road other than the selected branch
road, since the determination of the passableness of the selected
curve on the selected branch road is cancelled, it is possible to
prevent the execution of the automatic deceleration control and/or
alarming the driver for the curve along which the subject vehicle
is passing in no case then.
[0017] In addition, according to a fifth aspect of the invention,
there is provided a vehicle safety running apparatus as set forth
in any of the first to third aspects of the invention, wherein the
proper condition determining means cancels its selection of a
branch road when direction indicators of the subject vehicle
indicate before the intersection that the subject vehicle is
advancing on a branch road other than a branch road selected by the
proper condition determining means.
[0018] According to the above configuration, in a case where a
branch road selected by the proper condition determining means is
different from a branch road indicated by the direction indicators,
since the selection made by the proper condition determining means
is cancelled, it is possible to prevent a determination from being
made on a curve on a branch road which the subject vehicle enters
in no case.
[0019] According to a sixth aspect of the invention, there is
provided a vehicle safety running apparatus as set forth in any of
the first to fifth aspect of the invention, further comprising a
route deviation determining means for determining whether or not
the subject vehicle deviates from its set route by comparing a
route set by the route setting means with a position of the subject
vehicle detected by the subject vehicle position detecting means,
wherein the state in which a route guidance based on a set route is
not carried out involves where a deviation from the set route is
detected by the route deviation determining means.
[0020] According to the configuration as described above, whether
or not a branch road or curve can be passed through is determined
not only where no route to a destination is set but also where the
subject vehicle deviates from its set route, and moreover, the
possibility that automatic deceleration control and/or alarming the
driver is performed excessively can be reduced, thereby making it
possible to suppress to a minimum level the physical disorder that
the driver may feel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a block diagram illustrating the configuration of
a vehicle safety running apparatus;
[0022] FIG. 2 is a flowchart explaining the operation of the
apparatus;
[0023] FIG. 3 is a diagram explaining selections of branch roads at
intersections;
[0024] FIG. 4 is a diagram explaining how to determine the
passableness of curves on branch roads branched from an
intersection;
[0025] FIG. 5A and 5B are diagrams explaining the cancellation of
selections of branch roads based on the operation of a direction
indicator lever;
[0026] FIG. 6A to 6C are diagrams respectively explaining the
definition of an "intersection" and a "branch road";
[0027] FIG. 7A to 7E are diagrams respectively explaining the
definition -of a "bend portion on a road"; and
[0028] FIG. 8 is a diagram explaining the definition of an
"intersection angle of roads";
DETAILED DESCRIPTION OF THE PREFERED EMBODIMENT
[0029] A mode for carrying out the invention will be described
below based on an embodiment according to the invention illustrated
in the accompanying drawings.
[0030] First of all, terms that are used in this specification will
be defined. As shown in FIG. 6, an "intersection" used in the
specification includes not only a so-called a crossroad but also a
three-fork road (a so-called Y-shaped road) and a five-fork road.
In addition, a "branch road" used in the specification indicates
roads branched from the intersection to extend therebeyond. As
shown in FIG. 7, a "bend portion of a road" used in the
specification means a portion of the road where the driver needs to
steer the steering wheel in order to pass through the portion and
includes both curves (including a bend of an L-shaped road) and
intersections. As shown in FIG. 8, an "intersection angle of a
road" used in the specification is defined as an angle formed by
the direction a road immediately before an intersection along which
the subject vehicle is traveling and the direction of a branch road
branched the road along which the subject vehicle is traveling at
the intersection. To be more specific, road data comprises a
plurality of nodes disposed at predetermined intervals and links
constituted by lines connecting adjacent nodes, and a node is set
at an intersection in principle. Then, the "intersection angle of a
road" is defined as an angle formed by the direction of a link
immediately before the node at the intersection and the direction
of a link immediately beyond the node at the intersection.
[0031] As shown in FIG. 1, a vehicle safety running apparatus
according to the present embodiment comprises a storage means M1, a
subject vehicle position detecting means M2, a route setting means
M3, a vehicle condition detecting means M4, a bend portion
detecting means M5, a proper condition determining means M6, a
running difficulty detecting means M7 and a route deviation
determining means M8. Main portions of a navigation system are also
used, as they are, for the storage means M1, the subject vehicle
position detecting means M2 and the route setting means M3.
[0032] The storage means M1 is constituted by a storage medium such
as a CD-ROM for storing road data as a set of coordinate points of
a plurality of nodes. The subject vehicle position detecting means
M2 detects the position of the subject vehicle based on signal from
a satellite used for the global positioning system or GPS. The
route setting means M3 sets a running route to a destination for
the subject vehicle through an input operation by the driver. The
vehicle condition detecting means M4 detects the condition of the
subject vehicle based on a vehicle speed detected by a vehicle
speed sensor, a lateral acceleration detected by a lateral
acceleration sensor, a steering angle detected by a steering angle
sensor and the like. Of the respective sensors, the vehicle speed
sensor is inevitable. The bend portion detecting means 5 detects a
bend portion (that is, a curve and an intersection) of a road
existing ahead of the subject vehicle based on the road data stored
in the storage means M1 and the position of the subject vehicle
detected by the subject vehicle position detecting means M2.
[0033] The proper condition determining means M6 compares, when a
route to a destination is set by the route setting means M3, the
degree of bending (a radius of curvature and/or an intersection
angle) of a bend portion on the set route which is detected by the
bend portion detecting means M5 with the vehicle condition detected
by the vehicle condition detecting means M4 and then determines
whether or not the bend portion can be properly passed through with
the current vehicle condition being maintained. For example, the
proper condition determining means M6 compares the current vehicle
speed with a proper vehicle speed which is to be determined
according to the radius of curvature of the bend portion obtained
from the road data and determines that the bend portion is passable
by the subject vehicle if the current vehicle speed is found to be
slower than the proper vehicle speed for passing through the bend
portion. While, if the current vehicle speed is found to be faster
than the proper bend portion passing vehicle speed, the proper
condition determining means M6 determines that the bend portion is
not passable. Alternatively, the proper condition determining means
M6 compares a minimum turning radius of the subject vehicle
calculated from the current vehicle speed with the radius of
curvature of the bend portion and determines that the bend portion
is passable if the minimum turning radius so calculated is found to
be equal to or smaller than the radius of curvature of the bend
portion. While, if the minimum turning radius is found to be larger
than the radius of curvature of the bend portion, the proper
condition determining means M6 determines that the bend portion is
not passable by the subject vehicle.
[0034] Then, when the proper condition determining means M6
determines that the subject vehicle cannot pass through the bend
portion with the current vehicle speed, a vehicle speed control
means M9 comprising an automatic brake device and/or a throttle
opening reduction device is activated so as to automatically reduce
the speed of the subject vehicle to thereby allow the subject
vehicle to pass through the bend portion properly. Alternatively,
an alarming means M10 comprising a buzzer, a chime, a speaker, a
lamp or the like is activated to alarm the driver to voluntarily
reduce the vehicle speed.
[0035] Thus, while a case has been described above where the
running route of the subject vehicle to the destination is set by
the route setting means M3 and the bend portion through which the
subject vehicle is passing can be grasped in advance, in the
present embodiment, even in a case where the route setting means M3
sets no running route of the subject vehicle to the destination or
a case where while the route setting means M3 sets a running route
of the subject vehicle to the destination, the route deviation
determining means M8 determines that the subject vehicle deviates
from its set route, the running difficulty determining means M7 is
configured to then determine a branch road of branch roads branched
from an intersection ahead of the subject vehicle which is lowest
in terms of the degree of difficulty in running or a branch road
which is passable at high speed, and the proper condition
determining means M6 is configured to determine whether or not the
subject vehicle can pass through the intersection from which the
branch road is branched, as well as a curve existing on the branch
road beyond the intersection. Note that the route deviation
determining means M8 is configured to determine whether or not the
subject vehicle deviates from its set route by comparing the set
route set by the route setting means M3 and the position of the
subject vehicle detected by the subject vehicle position detecting
means M2.
[0036] Described below will be a control in a case where the route
setting means M3 sets no running route to a destination for the
subject vehicle (including a case where the subject vehicle
deviates from its set route during the route guidance).
[0037] In a case where it is determined in step S1 in a flowchart
shown in FIG. 2 that there exists no intersection ahead of the
subject vehicle within a predetermined distance, in step S2 that
there exists a curve ahead of the subject vehicle within a
predetermined distance and in step S3 that the subject vehicle
cannot pass through the curve with the current vehicle speed, then
in step S4, an automatic deceleration control is executed or an
alarm is given to the driver so that the subject vehicle can pass
through the curve. In a case where it is determined in step S1 that
there exists an intersection ahead of the subject vehicle within
the predetermined distance, in step S5, road data on each of branch
roads branched from the intersection is read, in the following step
S6, the degrees of difficulty in entering the respective branch
roads are compared, and in step S7, the branch road is selected
which is lowest with respect to the degree of difficulty in running
(FIG. 3). The lower the degrees of difficulty in entering the
respective branch roads becomes, the smaller the intersection
angles (FIG. 8) of the-branch roads becomes smaller.
[0038] In the following step S8, in a case where the traveling
course of the subject vehicle is changed to the branch road
selected at the intersection as described in the previous step,
whether or not the subject vehicle can pass through the to the
selected branch road is determined. The determination of the
passableness is effected by comparing the current vehicle speed
with a proper vehicle speed determined according to the radius of
curvature of the intersection resulting when the change in the
traveling course of the subject vehicle is so effected. In the
event that the current vehicle speed is found to be slower than the
proper vehicle speed, it is determined that the subject vehicle can
pass through the intersection, while in the event that the current
vehicle speed is found to be faster than the proper vehicle speed,
it is determined that the subject vehicle cannot pass through the
intersection. As a result, in step S9, when the passableness of the
intersection by the subject vehicle is determined negative, in step
S10, the automatic deceleration control is then executed or an
alarm is given to the driver so that the subject vehicle can pass
through the intersection as selected.
[0039] In contrast, in the event that the intersection is
determined as being passable in step S9, if there exists a curve
from where the subject vehicle is located before the intersection
to within a predetermined distance along the branch road, in step
S12, whether or not the curve can be passed through is determined
(FIG. 4). The determination is effected by comparing the current
vehicle speed with a proper vehicle speed which is determined
according to the radius of curvature of the curve. In the event
that the current vehicle speed is found to be slower than the
proper vehicle speed, then the curve is determined as being
passable, while in the event that the current vehicle speed is
found to be faster than the proper vehicle speed, the curve is
determined as being impassable. As a result, in the event that the
curve is determined as being impassable in step S13, then in step
S14, the automatic deceleration control is effected or an alarm is
given to the driver so that the subject vehicle can pass through
the curve, whereby the subject vehicle is prevented from entering
the curve existing on the branch road with the excessive vehicle
speed. The processes in steps S13 and s14 are to be continued until
the subject vehicle can pass through the intersection in step S15.
Since there exists no intersection between the subject vehicle and
the curve after the subject vehicle has passed through the
intersection, the control aimed at the curve is carried out from
step S1 to step S14.
[0040] Thus, in a case where no route guidance is carried out or a
case where the subject vehicle deviates from its set route during
the route guidance, since whether or not the subject vehicle can
pass through the intersection is determined by selecting the branch
road of the plurality of branch roads existing ahead of the subject
vehicle on the road which is lowest with respect to the degree of
difficulty in running, it is possible not only to determine on the
passableness of the intersection even when no route to the
destination is set but also to suppress, to a minimum level, the
physical disorder that the driver may feel by reducing the
possibility that the automatic deceleration control and/or alarming
the driver is performed excessively. In addition, even when the
subject vehicle enters a branch road other than the one which is
lowest with respect to the degree of difficulty in running, since
in many cases the driver drives the vehicle without depending upon
the route guidance when he or she has already been aware of the
existence of an intersection ahead of the subject vehicle or is
then determined on which direction to take at the intersection, it
is unlikely to happen that the subject vehicle enters the branch
road which is difficult to pass through with an excessive vehicle
speed being maintained.
[0041] In addition, in the event that the subject vehicle enters a
branch road other than a selected one, as soon as it occurs, the
determination on the passableness of a target curve on the selected
branch road is cancelled. Additionally, in the event that the
direction indicator lever is operated such that the direction
indicators of the subject vehicle indicate that the vehicle is
entering a branch road other than a selected one, the branch road
indicated by the direction indicators is newly selected, and any
selection made before then is cancelled (refer to FIG. 5), thereby
making it possible to prevent unnecessary determinations from being
made on the passableness of branch roads along which the subject
vehicle is most unlikely to pass.
[0042] Thus, while the embodiment of the invention has been
described in detail heretofore, the design of the invention may be
modified variously without departing from the spirit and scope
thereof.
[0043] For example, the subject vehicle position detecting means M2
is not limited to the one for detecting the position of the subject
vehicle based on signals from satellites used for GPS and may take
the form of a means for detecting the position of the subject
vehicle through a self-navigation system or a means for detecting
the position of the subject vehicle with signals from transmission
means such as beacons provided along roads.
[0044] According to the first aspect of the invention, since a
branch road of branch roads at an intersection ahead of the subject
vehicle along a road on which the subject vehicle is traveling
which has the lowest degree of difficulty in running is selected to
determine whether or not the subject vehicle can pass therethrough
in the state in which the route guidance along a set route is not
carried out, it is possible to determine whether or not the subject
vehicle can pass through the branch road even in a case where no
route to a destination is not set. Moreover, the possibility that
automatic deceleration control and/or alarming is performed
excessively can be reduced by selecting a branch road which is easy
for the subject vehicle to pass through, thereby making it possible
to suppress, to a minimum level, the physical disorder that the
driver may feel. In addition, even in the event that the subject
vehicle happens to enter a branch road which is difficult for the
subject vehicle to pass through, since in many cases the driver
drives the vehicle without depending on the route guidance when he
or she has already been aware of the existence of an intersection
ahead of the subject vehicle or is then determined on which turn to
take at the intersection, it is most unlikely that the subject
vehicle enters the branch road which is difficult for it to pass
through with excessive vehicle speed.
[0045] Additionally, according to the second aspect of the
invention, it is possible to determine exactly a branch road having
a lowest degree of difficulty in running by selecting a branch road
having a smallest intersection angle formed by links located before
and after a node set at an intersection.
[0046] Furthermore, according to the third aspect of the invention,
since whether or not the subject vehicle can pass through the
selected curve on the branch road is determined, it is possible to
perform an accurate automatic deceleration control and/or give an
alarm to the driver by determining whether or not a curve along
which the subject vehicle is anticipated to pass.
[0047] Moreover, according to the fourth aspect of the invention,
when the subject vehicle advances on a branch road other than the
selected branch road, since the determination of the passableness
of the selected curve on the selected branch road is cancelled, it
is possible to prevent the execution of the automatic deceleration
control and/or alarming the driver for the curve along which the
subject vehicle is passing in no case then.
[0048] In addition, according to the fifth aspect of the invention,
in a case where a branch road selected by the proper condition
determining means is different from a branch road indicated by the
direction indicators, since the selection made by the proper
condition determining means is cancelled, it is possible to prevent
a determination from being made on a curve on a branch road which
the subject vehicle enters in no case.
[0049] According to the sixth aspect of the invention, whether or
not a branch road or curve can be passed through is determined not
only where no route to a destination is set but also where the
subject vehicle deviates from its set route, and moreover, the
possibility that automatic deceleration control and/or alarming the
driver is performed excessively can be reduced, thereby making it
possible to suppress to a minimum level the physical disorder that
the driver may feel.
* * * * *