Multiplex communications – Pathfinding or routing
Reexamination Certificate
1998-03-23
2001-04-24
Ton, Dang (Department: 2661)
Multiplex communications
Pathfinding or routing
Reexamination Certificate
active
06222836
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a route searching device, and more specifically to a dynamic route guidance system (DRGS) for searching a route to a destination based on traffic information obtained from outside facilities.
2. Description of the Related Art
Heretofore, there has been proposed a dynamic route guidance system (DRGS) which searches a route to reach a destination in the shortest period of time based on traffic information, such as a link travelling time, obtained from an information center using a vehicle information communication system (VICS), and then informs a driver of the route. In such a system, traffic information of all the links should ideally be obtained. However, in actual situations, there are usually many links where a beacon cannot be installed or where traffic information can not be obtained due to nonconformity of the beacon installed. Therefore, it is very important to deal with such links in the search of the optimum route.
Taking into account the real word situation described above, in Japanese Patent Laid-Open Publication No. Hei 7-129893, the applicant of the present invention disclosed an art for finding a route by estimating a travelling time of a link for which the travelling time cannot be obtained, based on the travelling time of surrounding links. More specifically, average car speed is found from the travelling time and link length of links which are in front of and behind the link concerned. Then, the travelling time of the link is estimated on the assumption that the link can travel at the average car speed, on the assumption that an average travelling time of links which are parallel to the link on right and left will be the travelling time of the link. Thus, accuracy in the search of the optimum route can be improved in comparison with the case that there is no traffic information whatsoever.
However, the aforementioned art is only effective when at least one link whose traffic information can be obtained is adjacent to a link whose traffic information can not be obtained and it will be difficult to accurately estimate the traffic information of a link whose traffic information cannot be obtained if the link is far from a link or links whose traffic information can be obtained. Therefore, the aforementioned art has a certain limit ineffectively utilizing the dynamic route searching system.
SUMMARY OF THE INVENTION
The present invention is made in consideration of the problems of the art described above. It is directed to provide a device capable of increasing accuracy in the search of the optimum route by estimating, in a wider area than previously, traffic information for a link for which traffic information, such as a travelling time, can not be obtained.
In order to achieve the object mentioned above, the present invention includes arithmetic means for computing traffic information of the aforementioned second link by carrying out weighting of the traffic information of the aforementioned first link according to a difference in direction and distance between the first link and the second link when the route to a destination is searched by using a first link with its traffic information and a second link without its traffic information. Correlation between the traffic information of the first and second links differs depending on the direction and distance between the first link and the second link. In other words, if the first link and the second link are in the nearly same direction and close to each other, the traffic information of the first link will be very correlative to the second link. However, if the two links are in the same direction, but not near to each other, or if the two links adjoin, but are in a different direction, the traffic information of the first link will have less of a correlation with the second link. Therefore, if weighting of the traffic information of the first link is performed, in other word, the correlation is determined according to how the two links differ in direction and distance, traffic information of the second link will be estimated in a wider area than used was possible before.
Further, the present invention detects a change of the aforementioned traffic information of the first link with the passage of time, and the aforementioned arithmetic means perform weighting of the traffic information based on the aforementioned change. If the traffic information changes with the passage of time, circumstances of the second link will also change with the passage of time. For example, if traffic congestion of the first link tends to become worse, traffic congestion of the second link will also have a general tendency to worsen. Therefore, by determining weight of the traffic information of the first link at the time of estimating the traffic information of the second link in consideration of a change of the traffic information of the first link with the passage of time, accuracy in the search of a route can further be increased.
Further, computing means of the present invention perform weighting based on statistical traffic information. If there is some statistical traffic information, it will be utilized for the second link whose traffic information cannot be obtained. More specifically, by weighting such that an estimation value coincides with a statistical value, accuracy of estimation can be increased.
REFERENCES:
patent: 5042027 (1991-08-01), Takase et al.
patent: 5170353 (1992-12-01), Verstraete
patent: 5257023 (1993-10-01), Furuya
patent: 5265092 (1993-11-01), Solouay et al.
patent: 5428545 (1995-06-01), Maegawa et al.
patent: 02 017407 (1990-01-01), None
patent: 7-83680 (1995-03-01), None
patent: 7-129893 (1995-05-01), None
patent: 8-313285 (1996-11-01), None
patent: 08 293094 (1996-11-01), None
Sekiyama Hiroaki
Sugimoto Hironobu
Pillsbury & Winthrop LLP
Ton Dang
Toyota Jidosha & Kabushiki Kaisha
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