JP2012247315A - Route guidance device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To guide a route to a designated destination while being reflected with an isolated crossing where there is the risk for a vehicle to be isolated without smoothly passing the crossing.SOLUTION: A risk value matrix is prepared which gives a risk value score for a crossing to become an isolated crossing for each factor feature such as a railroad crossing or a lane decreased portion of a road being existent in a leaving direction of the crossing. With respect to a search result of a route from a starting point to a destination, a route guidance device refers to the risk value matrix for each crossing on that route, determines a risk value score and extracts as an isolated crossing a crossing where the risk value score exceeds a predetermined threshold value such as a crossing 2 where a railroad crossing exists at a leaving course side. Then, a route avoiding the isolated crossing is searched and guided. Thus, a user is enabled to suppress passing the isolated crossing and a route along which the user can pass smoothly can be guided.

Description

  The present invention relates to a route guidance device that provides route guidance to a designated destination.

2. Description of the Related Art Route guidance devices that perform route guidance from a specified departure place to a destination using electronic map data are widely used. Techniques that provide support information for traffic, such as not only guiding the route but also providing information on the occurrence of traffic jams, have also been proposed.
For example, Patent Document 1 discloses a technology that evaluates whether or not the intersection is likely to make a driving mistake depending on the width or type of the intersection and provides the driver with the evaluation result.

JP-A-9-190596

At the time of route guidance, it is desired to provide guidance that can pass the route as smoothly as possible. As is clear from experience, the exit road side may be very crowded depending on the intersection, and after entering the intersection, the signal may turn red, making it impossible to move within the intersection. In this specification, an intersection that has a high possibility of being unable to move within the intersection is called an isolated intersection. Users who use the route guidance device are not necessarily familiar with the traffic conditions of the road, and if they enter the intersection without being aware of the isolated intersection and become isolated, the traffic of other vehicles is hindered and smooth. There will be obstacles in traffic.
In view of these problems, an object of the present invention is to realize route guidance in consideration of an isolated intersection.

  The present invention is a route guidance device for guiding a route to a designated destination, and is a network data that represents a road network with nodes and links, and a factor that causes a situation in which a vehicle cannot pass through an intersection and is isolated A map database storage unit for storing factor feature data related to the factor feature to be, and an exit road that is a road exiting from the intersection for an intersection existing on a candidate route based on the network data and the factor feature data Identifying the isolated feature that identifies the isolated feature that may be isolated according to the specified rules associated with the feature feature, and reflecting the specified result of the isolated intersection, A route search unit that searches for the route with reference to network data and a route guide unit that provides guidance based on the searched route It can be formed.

According to the present invention, an isolated intersection can be identified by factor features on a road other than the approach road of the intersection, and smooth traffic can be supported by reflecting this in the guidance. As a reflection method, a method of notifying the user that it is an isolated intersection when entering an intersection, a method of guiding a route that avoids an isolated intersection, and the like can be considered.
As the factor feature, the road shape of the exit road from the intersection or the feature existing on the exit road can be used. For example, the factor feature based on the road shape can include a state where the width is narrow, a state where the road is uphill, a state where the road is curved. Features on the exit path include various features that interfere with smooth traffic at intersections, such as railroad crossings, traffic lights, other intersections, tunnels, bridges, vehicle entry prohibition and other traffic restrictions.
The factorial feature data used to determine for each intersection whether or not it hits an isolated intersection does not store the factorial feature for each individual intersection. Therefore, there is no need to investigate for each intersection whether or not it hits an isolated intersection, and there is an advantage that if the situation around the intersection changes, it can be specified according to the situation of the feature after the change.
The factor features used to identify the isolated intersection are not limited to those on the exit path on which the vehicle passes. For example, for an intersection where the host vehicle goes straight, a factor feature in a direction intersecting the route may be considered, and it may be determined whether or not the vehicle is an isolated intersection for a vehicle intersecting the route of the host vehicle. This is because even if another vehicle is isolated, traffic at the intersection cannot be smoothly performed.
When specifying an isolated intersection, the factor feature to be used or the weight as the factor feature may be changed according to the time zone, the distance to the intersection to be evaluated, or the like.
Factors are not necessarily one on the exit path. When multiple factorial features exist, various methods such as a method of summarizing the whole after obtaining an evaluation of isolated intersection based on each factorial feature, a method of comprehensively evaluating multiple factorial features, etc. Can be taken.

In the present invention, the map database storage unit replaces the factor feature data with a risk value matrix in which a risk value that is an index representing a risk of causing the isolated intersection and the factor feature are associated with each other. And storing the isolated intersection specifying unit with reference to the risk value matrix to obtain a risk value corresponding to the identified factor feature and specifying the isolated intersection based on the risk value. Good.
By doing so, it is possible to easily identify an isolated intersection. The danger value matrix can take various forms. Give a basic danger value for each factor feature, and give a correction value to adjust this value according to factors such as the time of traffic, the direction of traffic such as going straight at the intersection, turning left and right, etc. Also good. Moreover, it is good also as a multidimensional matrix which gives a dangerous value according to each above-mentioned element with respect to a factor feature.
Since the risk value matrix stores the factor features in a form that associates the risk values with each other, it can also be said to be a form of factor feature data.
In the risk value matrix, the above-described elements do not necessarily have to be discrete values. The risk value matrix may be set in the form of a function that gives a risk value to the index value representing each element.

Further, in the present invention, a route search unit that searches the route to the destination by lowering the priority of the specified isolated intersection with reference to the network data, the route guide unit, The searched route may be guided.
By doing so, the possibility of passing through an isolated intersection can be suppressed. The route search can take a method of searching for a route excluding an isolated intersection, a method of searching for a route by increasing the cost of the isolated intersection, and the like. According to the method for increasing the cost of an isolated intersection, it is possible to determine a route by comparing a distance, a required time, and the like between a route that avoids the isolated intersection and a route that passes through the isolated intersection. Accordingly, it is possible to avoid such adverse effects as taking an extremely large route in order to avoid an isolated intersection.

As another aspect, the present invention can be configured as a route guidance device that searches for a route from a departure point designated by a user to a destination by reflecting an isolated intersection in the cost.
In this case, for each intersection in the predetermined area determined based on the designated starting point and destination, an isolated intersection is identified in consideration of the factor features, and a route search is performed for the identified isolated intersection. The route from the departure point to the destination can be searched with reference to the cost of the isolated intersection and the network data.
In this way, a route search with reduced priority of isolated intersections is realized. The cost of an isolated intersection can be set based on, for example, a risk value given by a risk value matrix.

  In addition to the above-described aspects, the present invention may be configured as a route guidance method for performing route guidance by a computer constituting the route guidance device, or may be configured as a computer program for causing a computer to execute such route guidance. Good. Moreover, you may comprise as a computer-readable recording medium which recorded such a computer program. Recording media include flexible disks, CD-ROMs, magneto-optical disks, IC cards, ROM cartridges, punch cards, printed matter on which codes such as bar codes are printed, computer internal storage devices (memory such as RAM and ROM), and A variety of computer-readable media such as an external storage device can be used.

It is an example of composition of a route guidance device. It is explanatory drawing which shows a route guidance example. It is explanatory drawing which shows the danger value matrix example. It is explanatory drawing which shows the example of calculation of a dangerous value score. It is explanatory drawing which shows the modification of a danger value matrix. It is a flowchart of a route search process. It is a flowchart of a detour route search process. It is a flowchart of a route guidance process. It is a flowchart of the route search process in 2nd Example. It is a flowchart of a danger value score setting process.

A. Device configuration:
As an embodiment, a configuration example as an in-vehicle route guidance device is shown. This route guidance device is a device that searches for a route from a departure point to a destination and performs route guidance in consideration of an isolated intersection on the route.
FIG. 1 is a configuration example of a route guidance device. The route guidance device is configured by connecting a terminal 100 and a server 200 via a network NE. As the terminal 100, a car navigation device, a personal computer, a mobile phone, a smartphone, a PND (Personal Navigation Device), or the like can be used. The terminal 100 and the server 200 are computers each provided with a CPU, RAM, and ROM. In this embodiment, the system is configured by software by installing a computer program that realizes each function shown in the figure.
In the embodiment, the terminal 100 and the server 200 are configured. However, the terminal 100 and the server 200 may be configured as a stand-alone operation having the functions illustrated, or may be configured as a distributed system including a larger number of computers.

The server 200 includes a map database storage unit 210, a transmission / reception unit 201, and a database management unit 202.
The transmission / reception unit 201 communicates with the terminal 100 via the network NE. The contents of communication include designation necessary for route search such as a departure point and destination, a route search result, and the like.
The database management unit 202 reads map information requested from the terminal 100 from the map database storage unit 210. The map database storage unit 210 stores feature data 211, a danger value matrix 212, and network data 213 as map information. The feature data 211 is data representing attributes such as polygons of features to be drawn on a map such as roads and buildings, and shapes of features. The risk value matrix 212 is data that provides a risk value score for determining an isolated intersection. The specific contents will be described later. The network data 213 is data that represents a road network by connection of nodes and links. The network data 213 also stores attribute data such as the type of each road, the number of lanes, the road width, and the gradient. These attribute data may be added to the feature data.

The terminal 100 includes various functional blocks that operate under the main control unit 101.
The transmission / reception unit 102 communicates with the server 200 via the network NE. Not only the server 200 but also a server that provides traffic information may be accessed to obtain traffic information.
The command input unit 103 inputs instructions from the user such as designation of a starting point and a destination for route search through the operation of the terminal 100.
The sensor input unit 104 inputs various information used for route guidance and the like from the sensor. Examples of information to be input include a current position detected by a GPS (Global Positioning System).
The map database storage unit 105 stores each data provided from the server 200. The entire map database included in the server 200 may be stored, or only a part necessary for route search and map display may be acquired and stored from the server 200 each time.
The route search unit 107 performs a route search with reference to the map database storage unit 105. The route search is performed by applying a known method such as the Dijkstra method. The searched result is provided to the route guidance unit 106 and used for route guidance.
The risk value score calculation unit 108 calculates a risk value score for specifying an isolated intersection from the intersections on the searched route. A method for calculating the risk score will be described later.
The route guidance unit 106 displays a map with reference to the map database storage unit 105 and guides the route searched by the route search unit 107. At this time, an isolated intersection identified based on the danger value score calculated by the danger value score calculation unit 108 is taken into consideration, and a route for warning the user before entering such an isolated intersection or avoiding an isolated intersection Search and guide.

B. Route guidance example:
FIG. 2 is an explanatory diagram showing an example of route guidance. This is an example of guiding a route that avoids an isolated intersection, and an example is shown in which whether or not it hits an isolated intersection changes depending on the time zone.
FIG. 2A shows an example of route guidance in the morning. As a result of the route search from the departure point to the destination, it is assumed that a route passing through the railroad crossing is obtained by turning right at the intersection A as indicated by an arrow Aa. However, since a railroad crossing becomes impossible to pass when the train passes, the railroad crossing is a feature that is generally easy to form a train, and as a result, the exit A may be blocked by the vehicle in the intersection A near the railroad crossing. Become. If you enter the intersection A casually, there is a train line on the exit road, so even if the signal turns red, you cannot leave the intersection and you may be left behind and isolated. Equivalent to. In this embodiment, the possibility of becoming an isolated intersection is represented by a risk value score. The calculation method of the danger value score will be described later, but it is assumed that the danger value score for the intersection A is a value equal to or greater than a threshold value (assuming that it is set to 3 here) determined to be an isolated intersection. ”.
When it is found that an isolated intersection exists on the planned route in this way, the route guidance device searches for another route. In the example shown in the figure, a route to turn right at the intersection B as shown by the arrow Bb can be obtained. As with the intersection A, the intersection B is also determined whether or not it hits an isolated intersection based on the risk score. In this example, it is assumed that the danger value score of the intersection B is calculated as “2”, which is a value smaller than the threshold value, and it is determined that it does not hit the isolated intersection. As a result, the route guidance device guides the route passing through the intersection B instead of the route passing through the intersection A that was originally scheduled. The route that passes through intersection A is a wide road with one lane on one side, and the route that passes through intersection B is a narrow road that does not have a central line. It is because it can be judged that can pass smoothly.

  FIG. 2B shows an example of route guidance at midnight. As a result of the route search, it is assumed that a route that turns right at the intersection A as indicated by an arrow Ab is obtained as in FIG. There are railroad crossings on the route, but trains do not operate at midnight, so railroad crossings are not a major obstacle to traffic. Therefore, it is assumed that the risk value score of the intersection A is obtained as “2” which is lower than the threshold value for determining the isolated intersection. As a result, since the intersection A is not determined to be an isolated intersection, the route guidance device guides a route that turns right at the intersection A as indicated by an arrow Ab in accordance with the initial search result. In this way, in this embodiment, since the danger value score is obtained in consideration of the time zone in which the vehicle passes, the isolated intersection also changes according to the time zone. For example, as shown in the figure, if it is determined that a road with a narrow width is difficult to pass at midnight, and a risk score “3” is obtained for the intersection B, a route passing through the intersection B is assumed in advance route search. Is obtained, a right turn at the intersection B (arrow Bb) is avoided and a route through the intersection A is guided.

C. How to identify isolated intersections:
A method for identifying an isolated intersection based on the risk score will be described below. In this embodiment, a risk value score is calculated using a risk value matrix that associates a feature that causes an isolated intersection such as a railroad crossing (hereinafter referred to as “factorial feature”) with a risk value score. I wanted it.
FIG. 3 is an explanatory diagram illustrating an example of a risk value matrix. Here, risk value scores are set for the five factor features shown.
For "railroad crossings": If there is a crossing after the left turn at the intersection (hereinafter simply referred to as “left turn”, the same applies to straight and right turns), the risk score is 0 (in the figure, meaning no setting) "-"). The risk value score is set to “1” when going straight, and the risk value score is set to “2” when turning right. A risk value score is further added to the basic values of these risk value scores according to risk factors such as the distance to the factor feature and the time zone. In the case of a left turn, the added value is 0 for any element (“−” in the figure). In the case of going straight and turning right, “2” is added if the distance from the intersection to the crossing is less than 10 m, “1” if it is less than 10 to 20 m, and “0” if it is 20 m or more. Further, “0” or “1” is added according to the time zone. The midnight time zone from 0:00 am to 5:00 is set as “0 special”. This means that for this time zone, the risk score is set to “0” regardless of the basic value and the distance from the factor feature. In such a midnight, the train is not operated, and it is a setting considering that there is no need to evaluate a railroad crossing as a factor feature.
The “intersection” means that another intersection existing ahead of the intersection that is the target of determination as to whether or not it is an isolated intersection is regarded as a factor feature. For the intersection, a basic risk score is set for each of left turn, straight ahead, and right turn, and an additional value is set according to the distance to the factor feature. The setting by time zone is “0” in this example.
The “lane decreasing” point is a point where the road becomes narrower and decreases from two lanes on one side to one lane. This is also the case when the number of lanes on the exit road is less than the approach road at the intersection. For such points as well, as in the case of the intersection, a basic risk score is set, and an added value corresponding to the distance to the factor feature is set. The setting by time zone is “0” in this example.
“The number of lanes is 1” means that the number of lanes on the exit route is 1 on the upper and lower lines, that is, the center line is not drawn. In the example of the figure, only a basic risk score is set for such a state.
“Slow uphill” means that the exit road is uphill. It is not necessarily limited to climbing hills, but includes climbing elevated roads. This is because such a gentle uphill tends to reduce the vehicle speed and increase the frequency of traffic jams. In the example of the figure, only a basic risk score is set for such a state. Aside from the “slow climb”, a setting for the factor feature “steep climb” may be provided.
In addition to this, various factor features can be set. For example, a curve, a blinking signal, a tunnel, a bridge, a vehicle entry prohibition and other traffic restrictions can be cited. Various items can be set for the risk factor. An addition value or a subtraction value may be provided according to the number of lanes of the approach road to the intersection to be evaluated. The risk value score is not limited to the setting illustrated in the figure, and various settings are possible depending on the risk of causing an isolated intersection.

FIG. 4 is an explanatory diagram illustrating an example of calculation of a risk value score. The risk score was calculated using the risk value matrix shown in FIG.
First, the road shape to be calculated will be described with reference to FIG. In this example, a risk score is calculated for intersection A where links 1 to 4 intersect. Factor features on each link are as follows: On links 1 and 2, there are intersections at points 30 m away from intersection A. On the link 3, another intersection exists at a point 18 m away from the intersection A. On the link 4, there is a crossing at a point 15m away from the intersection.
FIG. 4A shows the calculation result of the risk value score. First, consider the case of entering from link 1. When link 2 is the exit link, it corresponds to a right turn. Since the factor feature on the link 2 is another intersection, the basic risk score is obtained as “2” by the “intersection” (right turn) in FIG. Since the other intersection is at a distance of 30 m from the intersection A, the added value is “0” due to “20 m or more” in the same column. The added value according to the time zone is also “0”. Therefore, the risk score when entering from the link L1 and exiting to the link L2 is “2” regardless of the time zone.
Exiting to link 3 corresponds to straight ahead. The factor feature on link 3 is another intersection, at a point of 18m. Therefore, the basic danger value score is “1” and the added value “1” is “less than 10 to 20 m” by “intersection” and “straight ahead” in FIG. The added value according to the time zone is “0”. Therefore, the danger score when exiting to the link 3 is “2 (= 1 + 1)” regardless of the time zone.
When exiting to link 4, it corresponds to a left turn. The factor feature on link 4 is a railroad crossing, but the risk score for a left turn is “0”. Accordingly, the risk score when exiting to the link 4 is “0” regardless of the time zone.
As described above, since the risk value score varies depending on the method of traveling at the intersection and the type of factor feature on the exit side of the intersection, the risk value score is obtained for each combination of the approach link and the exit link.

Even when another link is an ingress link, the risk value score can be calculated by referring to the risk value matrix shown in FIG. 3 in the above-described manner.
When link 2 is used as the approach link, it is as follows. When link 1 is an exit link, an intersection, a left turn, and a risk value score of 20 m or more may be obtained. When link 3 is an exit link, an intersection, a right turn, and a risk score less than 10 to 20 m may be obtained. When the link 4 is the exit link, a crossing, straight ahead, and a risk value score of less than 10 to 20 m may be obtained. When a level crossing is a factor feature, the danger score is “0 special” in the midnight time zone.
When the link 3 is an approach link, it is as follows. When link 1 is used as an exit link, an intersection, a straight line, and a danger value score of 20 m or more may be obtained. When link 2 is an exit link, an intersection, a left turn, and a danger value score of 20 m or more may be obtained. When the link 4 is an exit link, a danger value score of less than 10 to 20 m may be obtained by taking a crossing, turning to the right. When a level crossing is a factor feature, the danger score is “0 special” in the midnight time zone.
The case where the link 4 is an approach link is as follows. When link 1 is an exit link, an intersection, a right turn, and a risk score of 20 m or more may be obtained. When link 2 is used as an exit link, an intersection, straight ahead, and a danger value score of 20 m or more may be obtained. When link 3 is an exit link, an intersection, a left turn, and a risk score of less than 10 to 20 m may be obtained.
The risk score shown in FIG. 4 (a) may be calculated in advance for each intersection according to the combination of the approach link and the exit link, but in this embodiment, at the time of route guidance, Calculated.

The danger value matrix can be set in various forms. In FIG. 3, the case where it set in the form which gives the addition value according to a risk factor with respect to the basic risk score was illustrated. On the other hand, the risk value matrix may be configured as a multidimensional matrix corresponding to the type of factor feature and the risk factor.
FIG. 5 is an explanatory diagram illustrating a modified example of the risk value matrix. This is an example of a three-dimensional matrix in which a risk value score is stored in each lattice point in a three-dimensional space determined according to the distance to a factor feature, a time zone, and a route (traveling direction). For example, if it is less than 20 m to the factorial feature and it is a daytime zone, three grid points shown in the figure correspond to three routes of right turn, straight ahead, and left turn. A risk score is set for each grid point. In the embodiment of FIG. 3, it is necessary to divide and set the influence of the risk factor for each element. However, in the case of a multi-dimensional matrix, it is more realistic by taking into account the synergistic effect of the risk factor. There is an advantage that a risk score can be set accordingly.
In the example of FIG. 5, the distance to the factor feature, the time zone, the route, and the like have been described as taking discrete values, but each of these elements may take a continuous value. For example, “Distance” is used as the distance to the factor feature, “Time” is used as the time zone, and the continuous direction angle is 0 degree for the route, −90 degrees for the right turn, and +90 degrees for the left turn. It is expressed as The risk score is given as a multidimensional function. In this way, each element can be reflected in the calculation of the risk score in a more realistic manner such as “the course in the diagonally right direction” (−45 degrees).

D. Route search / guidance processing:
The contents of the route search and route guidance processing using the risk value score described above will be described next. Here, after searching for a route from the departure point to the destination by a normal method without considering the danger value score, an isolated intersection on the route is identified based on the danger value score, and its detour is shown. Is a process of searching.

D1. Route search process:
FIG. 6 is a flowchart of route search processing. This process is mainly executed by the route search unit 107 and is executed by the CPU of the terminal 100 in terms of hardware.
When the process is started, the CPU inputs a starting point and a destination based on a user operation (step S11). The departure point may be the current position or may be specified by the user. Next, the CPU searches for a route from the designated departure place to the destination (step S12). The route search can be performed by a known method such as the Dijkstra method with reference to the network data 213. With the above processing, a normal route that does not consider the risk value score can be obtained.
The CPU sequentially calculates a danger value score for the intersections on the route, and extracts an intersection where the danger value score is larger than the threshold value Th as an isolated intersection (step S13). In the figure, an example of isolated intersection extraction processing is shown. As shown in the figure, there are intersections 1 to 3 on the route from the departure point to the destination, and the risk score of these intersections is “0” for intersections 1 and 3 and “3” for intersection 2. To do. The calculation method of the risk score is as described with reference to FIGS. Since the danger value score varies depending on the traffic time zone (see FIGS. 3 and 4), it is necessary to specify the time for passing the route in the process of step S13. Since it is normal to drive immediately after the route search, the time during the route search may be used as the passage time zone. If the searched route is long, the passage time of each intersection may be predicted according to the route from the departure place, and used for risk value cost calculation. Further, when a route search is performed prior to traveling, the user may specify the scheduled passage time, or the process of step S13 may be performed immediately before the start of traveling.
After obtaining the risk value score of each intersection, an isolated intersection is extracted by comparison with the threshold Th. If the threshold Th is set to “2”, the intersection 2 is extracted as an isolated intersection because “danger value score (= 3)> threshold Th (= 2)”. When the threshold value Th is set to “3” or more, the intersection 2 is not an isolated intersection.
When the isolated intersection can be extracted in this way, the CPU executes a detour route search process (step S20). This is a process of searching for a route by lowering the priority of an isolated intersection. Details of the process will be described later.
When a route considering the risk score is obtained by the above processing, the CPU stores the search result (step S40) and ends the route search processing.

FIG. 7 is a flowchart of a detour route search process. This is a process of searching for a route by lowering the priority of an isolated intersection, and corresponds to the process in step S20 of the route search process (FIG. 6). For convenience of explanation, the route obtained in steps S11 and S12 in FIG. 6 is referred to as an existing route.
The CPU identifies nodes before and after the isolated intersection, and searches for alternative route candidates as virtual departure and destination points, respectively (step S21). Then, the risk value score of the isolated intersection is reflected in the cost for route search, and the cost of the existing route and the alternative route candidate is compared (step S22).
The processing example of steps S21 and S22 is shown on the right side of the figure. Assume that the existing routes are links L1, L2, L3, and L4 (route A with solid arrows in the figure), and that the node N2 is extracted as an isolated intersection. In step S21, the node N1 located in front of the node N2 is set as the virtual departure point, and the node N3 located behind the node N2 is set as the virtual destination. In the case where the node N1 or the node N3 hits an isolated intersection, a node existing one before or after the existing route may be used. When a virtual departure point and a virtual destination are set, a route search is performed between them. In the example in the figure, it is assumed that a broken line path (path B in the figure) is obtained. This is a detour route candidate.
Next, the cost is calculated for the existing route and the alternative route candidate. In this example, it is assumed that the cost of each link is all “3”. Further, the risk value score of each intersection is used as the cost of the node as it is.
The existing route (route A in the figure) is as follows. Since the node N1 turns left and passes, the danger value score is “0” (see FIG. 3). It is assumed that the node N2 corresponds to an isolated intersection and the danger score is “5”. Since the node N3 passes straight through, the danger score is “1” (see FIG. 3). When the risk score of each of these nodes and the costs of the links L2 and L3 are added, the total cost for the route A is “12” (= 0 + 3 + 5 + 3 + 1).
The alternative route candidate (route B in the figure) is as follows. Since the node N1 turns right and passes, the danger value score is “2” (see FIG. 3). Since the nodes N4 and N5 turn left, the risk score is “0”. Since the node N3 is a right turn, the danger score is “2” (see FIG. 3). When the risk score of each of these nodes and the costs of the links L5, L6, and L7 are added, the total cost for the route B is “10” (= 2 + 3 + 3 + 3 + 2).
When the costs of the existing route and the alternative route candidate are calculated, the CPU selects a route with a low cost as the guidance route (step S23). In the example described above, the alternative route candidate (route B) is selected instead of the existing route (route A). When the cost of the existing route (route A) is lower, the route guidance is to be performed using the existing route (route A) even when an isolated intersection is included. This is because when a detour candidate route (route B) is taken, the existing route is considered to be more advantageous in consideration of the existence of an isolated intersection of the route and the possibility of a large turn.
In this way, for existing routes and bypass candidate routes, by selecting a route that reflects the risk score in the cost, a route that becomes extremely large or includes an isolated intersection is selected as a bypass route. You can avoid that. Steps S22 and S23 may be omitted, and the alternative route candidate obtained in step S21 may be used as it is. In this method, it is possible to provide a route that reliably avoids the isolated intersection extracted by the existing route.

D2. Route guidance process:
FIG. 8 is a flowchart of route guidance processing. This process is mainly executed by the route guide unit 106, and is executed by the CPU of the terminal 100 in terms of hardware.
First, the CPU reads the route obtained by the route search process (step S51). Then, the current position of the user is detected (step S52).
Also, traffic jam information is acquired (step S53). The traffic jam information may be acquired from a server that provides traffic information via the network. Then, an isolated intersection is extracted based on the traffic jam information (step S54). An example of isolated intersection extraction is shown in the figure. It is assumed that a traffic jam occurs on the link L2 when a route passing through the intersection 1 and the intersection 2 is obtained. Since the traffic jam location is a factor that hinders smooth traffic like the factor features shown in FIG. 3 and the like, the intersection 2 in front of the traffic jam location can be an isolated intersection. Since there is no traffic jam on the link L1, the intersection 1 is not an isolated intersection. The risk value score due to traffic jam can be obtained, for example, by setting a function or a risk value matrix that gives a risk value score based on the distance of traffic jam and the traffic time of the traffic jam location. Similar to the risk value matrix of FIG. 3, the risk value score may be added according to the distance from the intersection to the traffic jam location.
Thus, when an isolated intersection is extracted by considering the traffic jam (step S55), the CPU executes a detour route search process (step S20). This processing is as described in FIG. By doing so, it is possible to search for a route that can avoid a traffic jam location while avoiding the danger of becoming a route that becomes extremely large or a route that includes a new isolated intersection. If there is no isolated intersection due to a traffic jam location, this process may be skipped (step S55). Further, all the processes (steps S53 to S55, S20) taking into account the traffic information may be omitted.
Based on the above processing, the CPU performs route guidance according to the current position (step S60). The route may be displayed on the map and guided by voice output or the like. In the route guidance process, this process is repeatedly executed until it arrives at the destination (step S61).

  In this embodiment, in the detour route search process, if the cost of a detour route candidate is high, an existing route may be selected. Therefore, in the route guidance process, a route passing through the isolated intersection is guided. In such a case, in step S60, the CPU preferably notifies the user that the vehicle is an isolated intersection with a display, a voice, or the like before entering the isolated intersection. By doing so, the user carefully enters the intersection and can avoid being isolated in the intersection.

  According to the route guidance device of the first embodiment described above, route search and route guidance considering an isolated intersection can be realized, and smooth traffic can be realized.

E. Route search process:
Next, a second embodiment will be described. The route guidance apparatus of the second embodiment has the same configuration as that of the first embodiment (FIG. 1), and uses the same risk value matrix (see FIGS. 3 to 5). In the second embodiment, the contents of the route search process are different from those in the first embodiment. That is, in the second embodiment, an example is shown in which the route search from the departure point to the destination is performed in consideration of the risk score of each intersection in advance.
FIG. 9 is a flowchart of route search processing in the second embodiment. This process is mainly executed by the route search unit 107 and is executed by the CPU of the terminal 100 in terms of hardware.
The CPU inputs a departure point and a destination (step S71), and executes a risk value score setting process (step S80). The risk value score setting process is a process for calculating a risk value score for each intersection in consideration of all traffic directions as shown in FIG. The processing content will be described later.
The CPU searches for a route by reflecting this risk value score in the cost (step S91). The risk value score may be used as the cost as it is, or may be converted into the cost by a predetermined function according to the risk value score. The CPU stores the search result thus obtained (step S92), and ends the route search process.

FIG. 10 is a flowchart of the risk value score setting process. This is a process corresponding to step S80 of the route search process (FIG. 9). This process is mainly executed by the risk value score calculation unit 108, and is executed by the CPU of the terminal 100 in terms of hardware.
The CPU first sets a processing target area (step S81). The target region can be, for example, a rectangular region having a half width W with the starting point and destination as the symmetry axis. The value of the half width W can be arbitrarily set within a range that can include the route search result. The shape of the target area is not limited to a rectangle. In addition, the entire target area may be the target area without providing the limited target area.
The CPU selects an intersection of three or more roads within the target area as the target intersection (step S82). Then, for the target intersection, as shown in FIG. 4A, the risk value score is calculated in the following procedure for all combinations of the approach link and the exit link.
Specifically, first, any exit link is selected (step S83), and it is determined whether or not there is a factor feature ahead (step S84). If there is a factor feature, a risk score is calculated for each approach link (step S85). An example of calculation is shown in the figure. When the link L14 is an exit link, the risk score is calculated while sequentially changing the approach link to L11, L12, and L13. In this example, the route toward the exit link L14 is a left turn for the approach link L11, a straight turn for the approach link L12, and a right turn for the approach link L13. The risk value score can be calculated by referring to 3) and obtaining an addition value corresponding to the basic value and the risk factor. Of the risk factors, the time zone may be calculated based on the time when the route search is performed, the time specified by the user, or the like. If there is no factor feature, the process of calculating the risk score is skipped.
This process is repeatedly executed for all exit links and entry link combinations for the target intersection (step S86), and is repeatedly executed for all intersections (step S87).
Through the above processing, the risk score for all the traveling directions is obtained for the intersection of the target area. In the route search process (FIG. 9), the route search considering the risk value score can be realized by using the risk value score for each intersection.

  In the second embodiment (FIGS. 9 and 10), an example is shown in which a risk value score is calculated in advance for each intersection, but each time a next route is selected from the intersection during the route search, the risk value is calculated. A method of calculating a score may be used.

F. Effects and variations:
According to the route guidance apparatus described in the first embodiment and the second embodiment, it is possible to identify an isolated intersection by a factor feature on a road other than the approach road of the intersection, and reflect this in the guidance. , Can support smooth traffic.
Also, instead of preparing for each individual intersection, a risk value matrix is set as a generalized rule, and an isolated intersection is identified using this, so it is necessary to investigate whether or not it is an isolated intersection for each intersection In addition, even when the situation around the intersection changes, there is an advantage that it can be specified according to the situation of the feature after the change.

The present invention is not limited to having all the various features described in the embodiments, and various modifications can be made.
(1) In the embodiment, the case where there is one factor feature on the exit road side is illustrated, but when judging an isolated intersection, a plurality of factor features may be judged comprehensively. For example, a method of adding a risk value score for each factor feature, a method of separately setting a risk value score when a plurality of factor features exist, and the like can be employed. When adding, a weight corresponding to the distance from the intersection to each factor feature may be applied.
(2) You may consider the length of the green light of the advancing direction in an intersection as one of a factor feature or a risk factor. This is because the shorter the green light, the higher the possibility of becoming an isolated intersection. The length of the green light may be prepared in advance as a database for each intersection, or may be estimated from the previous traffic state if the route has passed many times. For example, at the time of route guidance, the time when the vehicle stopped by a red light at each intersection and the probability of passing without stopping are accumulated as a log, and if the maximum value of this stop time is taken, the time of the red light can be estimated. it can. Further, the time of the green light can be estimated so that the ratio of the time of the red light (time to stop) and the time of the green light (time allowed to pass) matches the probability of being able to pass.
(3) In the embodiment, the processing when the user's own route hits an isolated intersection is illustrated. The identification of the isolated intersection may take into account factor features other than the exit route on the route through which the user passes. For example, regarding an intersection where the user goes straight, a factor feature in a direction that intersects the route may be considered, and it may be determined whether or not the vehicle is an isolated intersection for a vehicle that intersects the user's route. This is because even if another vehicle is isolated, traffic at the intersection cannot be smoothly performed.
When making such a determination, for example, the risk value score in all directions may be calculated for the intersection on the route by the processes in steps S82 to S86 in the risk value score setting process (FIG. 10) of the second embodiment. .
(4) The risk value score may be calculated without using the risk value matrix shown in FIGS. For example, a method of defining a function for calculating a risk score according to various factor features, risk factors and the like listed in FIGS.
(5) In addition, the part processed in software in the embodiment can be realized in hardware and vice versa.

  The present invention can be used for route guidance to a specified destination in consideration of an isolated intersection.

DESCRIPTION OF SYMBOLS 100 ... Terminal 101 ... Main control part 102 ... Transmission / reception part 103 ... Command input part 104 ... Sensor input part 105 ... Map database memory | storage part 106 ... Route guidance part 107 ... Route search part 108 ... Risk value score calculation part 200 ... Server 201 ... Transmission / reception unit 202 ... Database management unit 210 ... Map database storage unit 211 ... Feature data 212 ... Danger value matrix 213 ... Network data

Claims (2)

A route guidance device for guiding a route to a specified destination,
Network data representing the road network as nodes and links, a map database storage unit for storing factor feature data relating to factor features that cause a situation in which the vehicle cannot pass through the intersection and is isolated, and
Based on the network data and factor feature data, the factor feature on the exit road that is a road exiting from the intersection is identified for the intersection existing on the candidate route, and the identification corresponding to the factor feature An isolated intersection identifying unit that identifies an isolated intersection that may be isolated according to a rule;
A route search unit that searches for the route with reference to the network data, reflecting the identification result of the isolated intersection,
A route guidance device comprising: a route guidance unit that performs guidance based on a searched route. The route guidance device according to claim 1,
The map database storage unit stores, in place of the factor feature data, a risk value matrix that associates the factor feature with a risk value that is an index representing the risk of causing the isolated intersection,
The isolated intersection specifying unit refers to the danger value matrix, obtains a danger value corresponding to the identified factor feature, and identifies the isolated intersection based on the danger value.

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