Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2000-09-28
2002-01-08
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C340S990000, C340S995190, C701S211000
Reexamination Certificate
active
06338021
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to route selection systems and, more specifically, to a system for automatically selecting an optimal route between a starting point and a destination designated on a map.
2. Description of the Background Art
Recently, with the progression of electronic technology, car navigation systems became popular with great speed. Some conventional car navigation systems are equipped with a route selection system so that an optimal route (e.g., shortest, fastest) between a starting point and a destination is automatically selected.
Applied in such conventional route selection system is exemplarily a method disclosed in Japanese Patent Laid-Open Publication No. 59-105113 (84-105113). This method makes use of Dijkstra method, for example, to determine an optimal route between a starting point and a destination utilizing data representing road connection. The theory of the Dijkstra method is found in “Data Structures and Algorithms”, written by A. V. Aho, et al., and translated by Yoshio Ono, Baifu-kan, 1990, pp. 179-183.
Another method for determining an optimal route is exemplarily a route search method disclosed in Japanese Patent Laid-Open Publication No. 4-204881 (92-204881). In this method, the route search is simultaneously made in a bi-directional manner, both a search from a starting point and a search from a destination. With such bi-directional search, searching time is shortened.
Still another method for determining an optimal route is disclosed in Japanese Patent Laid-Open Publication No. 4-372985 (92-372985) titled “Recommended Route Guiding Device”, for example. The method is for calculating cost of right-turns and left-turns at intersections and adding the calculated cost to an evaluation value for an optimal route.
In such conventional methods, however, no consideration is given for stops at traffic lights and consequences to be caused thereby, including delay in a vehicle's reaching its destination due to acceleration and deceleration before and after the stops. Therefore, any optimal route determined by such conventional methods cannot bring the vehicle to its destination within the estimated time.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a route selection method and system for searching for an optimal route while taking stops at traffic lights on the way into consideration.
In order to attain the object above, a first aspect of the present invention is directed to a route selection method for selecting an optimal route on a map, road network data representing an intersection and a road, and route selecting data including a traffic light flag to indicate whether the intersection has a traffic light or not are previously stored, the method comprising: a first step of determining, during a route search process for selecting an optimal route between a designated starting point and a destination, whether a target intersection has a traffic light by referring to the traffic light flag included in the route selecting data; and a second step of calculating, based on the determination made in the first step, a passage cost for passing the target intersection, wherein the passage cost calculated in the second step is based on to select the optimal route.
In the first aspect, the route selecting data including the traffic light flag which indicates presence or absence of traffic light at intersections is previously stored. In the second step, during the route search process based on the route selecting data, the passage cost is calculated depending on whether the target intersection has any traffic light. In this manner, the passage cost calculated in the second step can accordingly vary. Therefore, it becomes possible to find an optimal route under careful consideration for stops at traffic lights and consequences to be caused thereby, including delay in a vehicle's reaching its destination due to acceleration and deceleration before and after the stops, for example
According to a second aspect, in the first aspect, in the second step, when the target intersection is determined as having the traffic light in the first step, a traffic light cost relevant to a waiting time due to the traffic light is calculated, and based on the calculated traffic light cost, the passage cost is calculated for the target intersection.
In the second aspect, the traffic light cost is calculated only when the target intersection has any traffic light. In this manner, in the route search process, it becomes possible to find an optimal route under careful consideration for a waiting time due to traffic lights and consequences to be caused thereby.
According to a third aspect, in the first aspect, the route selecting data further includes road type information for specifying a road by type, and in the second step, when the target intersection is determined as having the traffic light in the first step, the road type information for a road connected to the target intersection is referred to for calculating the traffic light cost relevant to the waiting time due to the traffic light, and based on the calculated traffic light cost, the passage cost is calculated for the target intersection.
In the third aspect, the traffic light cost is calculated based on a road type of roads connected to the intersection. In this manner, the traffic light cost thus calculated can vary depending on whether the road leading to the intersection has a higher priority over the others. Therefore, in the route search process, it becomes possible to find an optimal route in a manner reflecting any influence caused by a waiting time at intersections, for example.
According to a fourth aspect, in the first aspect, the route selection data further includes road width information for specifying a road by width, in the second step, when the target intersection is determined as having the traffic light in the first step, the road width information for a road connected to the target intersection is referred to for calculating the traffic light cost relevant to the waiting time due to the traffic light, and based on the calculated traffic light cost, the passage cost is calculated for the target intersection.
According to a fifth aspect, in the first aspect, the route selection data further includes lane information for specifying a road by the number of lanes, in the second step, when the target intersection is determined as having the traffic light in the first step, the lane information for a road connected to the target intersection is referred to for calculating the traffic light cost relevant to the waiting time due to the traffic light, and based on the calculated traffic light cost, the passage cost is calculated for the target intersection.
In the fourth and fifth aspects, the traffic light cost is calculated by referring to the width or the number of lanes of a road connected to an intersection. In this manner, the traffic light cost thus calculated can vary depending on whether the road leading to the intersection has a higher priority over the others. Further, in the fourth and fifth aspects, the roads connected to the intersection are compared with one another in width (or the number of lanes). In this manner, the traffic light cost thus calculated can vary depending on whether the road leading to the intersection has a higher priority over the others. Therefore, in the route search process, it becomes possible to find an optimal route in a manner reflecting any influence caused by a waiting time at intersections, for example.
According to a sixth aspect, in the first aspect, the route selecting data includes a predetermined reference waiting time cost, and a ratio of waiting time on the load leading to an intersection having a traffic light to the reference waiting time, and in the second step, when the target intersection is determined as having the traffic light in the first step, the reference waiting time cost and the waiting time ratio on the road leading to the target intersection a
Fushimi Makoto
Ueyama Yoshiki
Yagyu Takeshi
Cuchlinski Jr. William A.
Hernandez Olga
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