Method of Estimation of Traffic Information, Device of Estimation of Traffic Information and Car Navigation Device

• US 20080294331A1
• Filed: 05/22/2008
• Published: 11/27/2008
• Est. Priority Date: 05/22/2007
• Status: Active Grant

• Current Assignee: Clarion Co., Ltd. (Faurecia SA)
• Original Assignee: Xanavi Informatics Corporation (Hitachi, Ltd.)
• Inventors: Amaya, Shinichi, Yamane, Kenichiro, Kato, Manabu, FUSHIKI, Takumi
• Granted Patent: US 8,024,110 B2
• Time in Patent Office: Days
• US Class Current: 701/119
• CPC Class Codes: G08G 1/0104 Measuring and analyzing of parameters relative to traffic conditions
• CPC Class Codes: G08G 1/096827 where the route is computed onboard
• CPC Class Codes: G08G 1/096844 where the complete route is dynamically recomputed based on new data

Abstract

There is provided a method and a device for accurately estimating traffic information of a link having no traffic information even if different types of roads are mixed. The device finds a parameter characterizing a damping curve of a quantity of change of relative speed based on stored traffic information for links on a city center side on a minimum-time cost route connecting the city center and suburbs, finds a quantity of change of relative speed of the link having no observed traffic information and estimates its traffic information based on the damping curve. The device also calculates a ratio of quantities of change of relative speed of two links whose road types change as a speed change similarity ratio and estimates traffic information of the link of a second road type from known traffic information of the link of a first road type by using that ratio.

Claims

1. A traffic information estimating method of a traffic information estimating device having at least a CPU (Central Processing Unit) for executing arithmetic processing of data;

a road network information storage section for storing connection data of links composing a road network and types of roads;

a link traffic information storage section for storing observed traffic information of part of links composing the road network and for storing estimated traffic information of the links other than the part of the links;

the CPU executes steps of;

calculating a quantity of change of relative speed that is a quantity of change of link speed from a reference speed as data indicating a degree of congestion of the link based on traffic information stored in the link traffic information storage section;

calculating a damping parameter that characterizes a damping curve along which the calculated quantity of change of relative speed damps in accordance with a distance from a city center along a route from the city center to a suburb or from the suburb to the city center of the road network;

calculating a ratio of quantities of change of relative speed of two forward and following links whose road types change along the route of the road network bound for the suburb from the city center or from the suburb to the city center as a speed change similarity ratio;

estimating traffic information of a target link for which the observed traffic information is not stored in the link traffic information storage section by using the traffic information stored in the link traffic information storage section for the link on the city center side on the route of the road network bound from the city center to the suburb or from the suburb to the city center, the damping parameter calculated for the target link in the damping parameter calculating step and the speed change similarity ratio calculated for the target link in the speed change similarity ratio calculating step, and storing the estimated traffic information into the link traffic information storage section as the traffic information of the target link.

2. The traffic information estimating method according to claim 1, wherein the CPU estimates the traffic information of the target link in the traffic information estimating step based on the observed traffic information of the link on the city center side on the route and the damping parameter calculated for the target link in the damping parameter calculating step when the road type of the target link is the same with that of the link up to the target link on the city center side on the route;

and

when the road type of the target link is different from that of the link up to the target link on the city center side on the route, the CPU estimates the traffic information of the target link by estimating once the traffic information based on the observed traffic information of the link on the city center side on the route and the damping parameter calculated for the target link in the damping parameter calculating step and by multiplying the speed change similarity ratio calculated for the target link in the speed change similarity ratio calculating step with that estimated traffic information.

3. The traffic information estimating method according to claim 1, wherein the CPU estimates the traffic information of the following link of the two forward and following links whose road types change and whose observed traffic information is not stored in the link traffic information storage section based on a speed change similarity ratio calculated when observed traffic information of a following link of two forward and following links which are located near the pertinent two links and whose road types different from those of the pertinent two links change is stored in the link traffic information storage section in the speed change similarity ratio calculating step.

4. A traffic information estimating device for estimating traffic information of a link composing a road network, comprising:

a road network information storage section for storing connection data of links composing the road network and types of roads;

a link traffic information storage section for storing observed traffic information of part of links composing the road network and for storing estimated traffic information of the links other than the part of links;

a quantity of change of relative speed calculating section for calculating a quantity of change of relative speed that is a quantity of change of link speed from a reference speed as data indicating a degree of congestion of the target link based on traffic information stored in the link traffic information storage section;

a damping parameter calculating section for calculating a damping parameter that characterizes a damping curve along which the calculated quantity of change of relative speed damps in accordance with a distance from a city center along a route from the city center to a suburb or from the suburb to the city center of the road network;

a speed change similarity ratio calculating section for calculating a ratio of the quantities of change of relative speed of the two forward and following links whose road types change along the route of the road network bound for the suburb from the city center or from the suburb to the city center as a speed change similarity ratio; and

a traffic information estimating section for estimating traffic information of a link for which the observed traffic information is not stored in the link traffic information storage section by using the traffic information stored in the link traffic information storage section for the link on the city center side on the route of the road network bound from the city center to the suburb or from the suburb to the city center, the damping parameter calculated for the target link in the damping parameter calculating section and the speed change similarity ratio calculated for the target link in the speed change similarity ratio calculating section, and for storing the estimated traffic information to the link traffic information storage section as traffic information of the link.

5. The traffic information estimating device according to claim 4, wherein the traffic information estimating section estimates the traffic information of the target link based on the observed traffic information of the link on the city center side on the route and the damping parameter calculated for the target link by the damping parameter calculating section when the road type of the target link is the same with that of the link on the city center side on the route;

and

when the road type of the target link is different from that of the link to that target link on the city center side on the route, the traffic information estimating section estimates the traffic information of the target link by estimating once the traffic information based on the observed traffic information of the link on the city center side on the route and the damping parameter calculated for the target link in the damping parameter calculating step and by multiplying the speed change similarity ratio calculated for the target link in the speed change similarity ratio calculating step with that estimated traffic information.

6. The traffic information estimating device according to claim 5, wherein the speed change similarity ratio calculating section estimates the traffic information of the following link of the two forward and following links whose road types change and whose observed traffic information is not stored in the link traffic information storage section based on a speed change similarity ratio calculated when observed traffic information of a following link of two forward and following links which are located near the pertinent two links and whose road types different from those of the pertinent two links change is stored in the link traffic information storage section in the speed change similarity ratio calculating step.

7. The traffic information estimating device according to claim 4, further comprising a traffic information distributing section for distributing traffic information composed of traffic information of each link whose observed traffic information is not stored in the link traffic information storage section and estimated by the traffic information estimating section and the observed traffic information to a car navigation device mounted in a vehicle.

8. A car navigation device connected to a traffic information estimating device so that traffic information outputted out of a traffic information output section of the traffic information estimating device can be inputted to the car navigation device;

the traffic information estimating device comprising;

a road network information storage section for storing connection data of links composing the road network and types of roads;

a link traffic information storage section for storing observed traffic information of part of links composing the road network and for storing estimated traffic information of the links other than the part of links;

a quantity of change of relative speed calculating section for calculating a quantity of change of relative speed that is a quantity of change of link speed from a reference speed as data indicating a degree of congestion of that link based on traffic information stored in the link traffic information storage section;

a damping parameter calculating section for calculating a damping parameter that characterizes a damping curve along which the calculated quantity of change of relative speed damps in accordance with a distance from a city center along a route from a city center to a suburb or from the suburb to the city center of the road network;

a speed change similarity ratio calculating section for calculating a ratio of the quantities of change of relative speed of two forward and following links whose road type changes along the route of the road network bound for the suburb from the city center or from the suburb to the city center as a speed change similarity ratio;

a traffic information estimating section for estimating traffic information of a link for which the observed traffic information is not stored in the link traffic information storage section by using the traffic information stored in the link traffic information storage section for the link on the city center side on the route of the road network bound from the city center to the suburb or from the suburb to the city center, the damping parameter calculated for the target link in the damping parameter calculating section and the speed change similarity ratio calculated for the target link in the speed change similarity ratio calculating section, and for storing the estimated traffic information to the link traffic information storage section as traffic information of the target link; and

a traffic information output section for outputting the traffic information stored in the link traffic information storage section; and

the car navigation device comprising;

a traffic information input section for inputting the traffic information outputted from the traffic information output section;

a guidance route calculating section for calculating a guidance route from a current vehicle location to a destination by using the traffic information inputted from the traffic information input section, the present location information of the vehicle mounting the car navigation device and information of the destination set by a user; and

a guidance route display section for displaying the guidance route calculated by the guidance route calculating section.

9. The car navigation device according to claim 8, wherein the guidance route display section displays the guidance route so as to be discernible whether or not the guidance route has passed through the link of the estimated traffic information.

10. A navigation device, comprising:

an intersection retrieving section for retrieving an intersection connected with a road to which traffic information is added is and another road to which no traffic information is added;

a complement originator retrieving section for tracking a road connected to the intersection retrieved by the intersection retrieving section and for which traffic information is added up to a predetermined distance to specify the road within the tracked range as a complement originator of traffic information;

a complement object retrieving section for tracking a road connected to the intersection retrieved by the intersection retrieving section and for which no traffic information is added up to a predetermined distance to specify the road within the tracked range as a complement object of traffic information; and

a traffic information complementing section for complementing traffic information to the complement object specified by the complement object retrieving section based on the traffic information added to the complement originator specified by the complement originator retrieving section.

11. The navigation device according to claim 10, wherein the intersection retrieving section retrieves an intersection connected with the road to which the traffic information is added and the other road to which no traffic information is added in such directions that those roads enter the intersection;

the complement originator retrieving section tracks the road that is connected to the intersection retrieved by the intersection retrieving section in the direction of entering the intersection and to which traffic information is added in a direction opposite from the entering direction by a predetermined distance to specify the road in the tracked range as a complement originator of traffic information; and

the complement object retrieving section tracks the road that is connected to the intersection retrieved by the intersection retrieving section in the direction of entering the intersection and to which no traffic information is added in a direction opposite from the entering direction by a predetermined distance to specify the road in the tracked range as a complement object of traffic information.

12. The navigation device according to claim 10, wherein the complement object retrieving section tracks the road to which no traffic information is added by the predetermined distance while selecting a road whose connecting angular difference is least in a branch if there is the branch.

13. The navigation device according to claim 11, wherein the traffic information complementing section specifies an intersection connected with the road to be complemented and connected in the direction that the road enters the intersection, acquires an average speed of vehicles traveling through the complement originating road per complement originating road based on traffic information added to the complement originating road that enters the specified intersection, calculates a travel time of the complement object road by using the average value calculated based on the average speed per each complement originating road and complements the calculated travel time to the complement object road.

15. The navigation device according to claim 12, wherein the traffic information complementing section specifies an intersection connected with the road to be complemented and connected in the direction that the road enters the intersection, acquires an average speed of vehicles traveling through the complement originating road per complement originating road based on traffic information added to the complement originating road that enters the specified intersection, calculates a travel time of the complement object road by using the average value calculated based on the average speed per each complement originating road and complements the calculated travel time to the complement object road.

14. A traffic information estimating method of a navigation device, comprising steps of:

retrieving an intersection connected with a road to which traffic information is added and a road to which no traffic information is added;

tracking the road connected to the intersection retrieved in the intersection retrieving step and to which traffic information is added up to a predetermined distance to specify the road within the tracked range as a complement originator of traffic information;

tracking a road connected to the intersection retrieved in the intersection retrieving step and to which no traffic information is added up to a predetermined distance to specify the road within the tracked range as a complement object of traffic information; and

complementing traffic information to the complement object specified in the complement object retrieving step based on the traffic information added to the complement originator specified by the complement originator retrieving step.