WO2012036050A1

WO2012036050A1 - Driving support device, driving support method, and computer program

Info

Publication number: WO2012036050A1
Application number: PCT/JP2011/070421
Authority: WO
Inventors: Masatoshi Takahara; Tomoki Kodan; Kuniaki Tanaka; Motohiro Nakamura; Yuya Higuchi; Kiyoshi Tsurumi
Original assignee: Aisin Aw Co., Ltd.; Toyota Jidosha Kabushiki Kaisha; Denso Corporation
Priority date: 2010-09-17
Filing date: 2011-09-01
Publication date: 2012-03-22
Also published as: JP2012064121A; CN103052865B; JP5291683B2; CN103052865A

Abstract

A tolerance for lateral acceleration generated in a vehicle (lateral acceleration tolerance) is set at which the vehicle can safely perform a U-turn without applying a load to vehicle occupants while the vehicle performs the U-turn. Based on the set lateral acceleration tolerance and a width curvature radius, a "maximum U-turn speed of the vehicle for the road" is set. If the vehicle performs turning that may be a U-turn while traveling in a one-way zone and a turning speed at such time is equal to or less than the "maximum U-turn speed of the vehicle for the road", it is determined that the vehicle performed a U-turn. The vehicle is thus recognized as in a wrong-way travel situation due to performing the U-turn, and a warning of the vehicle traveling in the wrong direction is made.

Description

DESCRIPTION

DRIVING SUPPORT DEVICE, DRIVING SUPPORT METHOD, AND

COMPUTER PROGRAM

TECHNICAL FIELD

[0001] The present invention relates to a driving support device, a driving support method, and a computer program that support the driving of a vehicle. BACKGROUND ART

[0001] Some roads where high speed travel is possible such as expressways, city expressways, motorways, general toll roads and national roads, as well as general roads with a narrow road width, are divided by the direction of travel and have zones configured to allow a vehicle to travel in only a predetermined direction. However, when the direction of travel is not clearly indicated, a so-called wrong-way travel situation may occur in which a vehicle mistakes the direction of travel and travels in the reverse direction of the traveling direction established in a travel zone. The following case illustrates a possible cause behind why a vehicle may end up traveling in the wrong direction.

[0002] For example, as shown in FIG. 6, when a vehicle 101 travels on a one-way road with multiple lanes, the driver may mistakenly believe that the right lane is an oncoming vehicle lane. In such case, the vehicle 101 may perform a U-turn with an intent to travel in the oncoming vehicle lane. But as a result of traveling in the right lane, the vehicle ends up traveling in the reverse direction of the direction of travel established for the road, thus traveling in the wrong direction.

[0003] In order to promptly stop wrong-way travel if the vehicle is found to be in a wrong-way travel situation, it is important to accurately detect on the vehicle side that the vehicle performed a U-turn. With accurate detection, the driver can be warned and a vehicle control can be performed to stop the vehicle traveling in the wrong direction. To this end, Japanese Patent Application Publication No. JP-A-2008-96141 (pages 6 and 7, FIG. 3) describes art that, when turning of the vehicle is detected, compares a turn curvature radius of the turn performed and a width curvature radius calculated based on the road width. If the rum curvature radius is smaller than the width curvature radius, the art determines that the vehicle performed a U-turn.

[0004] However, there are some cases in which the art described in JP-A-2008-96141 cannot accurately determine that the vehicle performed a U-turn. For example, if the vehicle performs a sharp turn in order to avoid an obstacle on a road with a relatively wide road width, the turn curvature radius is smaller than the width curvature radius. Consequently, it may be wrongly determined that the vehicle performed a U-turn regardless of the fact that the vehicle did not perform a U-turn. In such case, warning of wrong-way travel could interfere with the driving operations of the driver and cause confusion as to the current traveling direction of the vehicle.

DISCLOSURE OF THE INVENTION

[0005] The present invention was devised in order to solve problems in the related art, and it is an object of the present invention to provide a driving support device, a driving support method, and a computer program that are capable of accurately determining that a vehicle performed a U-turn.

[0006] In order to achieve the above object, a driving support device according to a first aspect of the present application is characterized by including: a road width acquisition unit that acquires a road width of a road traveled by a vehicle; a maximum speed setting unit that sets a maximum U-turn speed of the vehicle for the road based on the road width acquired by the road width acquisition unit; a vehicle behavior acquisition unit that acquires a behavior of the vehicle; and a U-turn determination unit that determines whether the vehicle performed a U-turn on the road by determining whether the vehicle performed turning that satisfies a condition under which the vehicle can perform a U-turn on the road at equal to or less than the maximum U-turn speed, based on the road width acquired by the road width acquisition unit and the behavior of the vehicle acquired by the vehicle behavior acquisition unit.

Note that "turning that satisfies a condition under which the vehicle can perform a U-turn on the road" refers to turning that satisfies a fixed condition such as a turn direction, a turn curvature radius, a turn angle, or a surrounding road condition. [0007] In the driving support device according to a second aspect of the present invention, the maximum speed setting unit sets, as the maximum U-turn speed, an upper limit of speed at which a lateral acceleration generated in the vehicle while the vehicle performs a U-turn on the road is equal to or less than a predetermined acceleration.

[0008] The driving support device according to a third aspect of the present invention further includes a warning unit that, if the road traveled by the vehicle is a one-way zone and the U-turn determination unit determines that the vehicle performed a U-turn on the road, warns of the vehicle traveling in a wrong direction.

[0009] A driving support method according to a fourth aspect of the present invention is characterized by including the steps of: acquiring a road width of a road traveled by a vehicle; setting a maximum U-turn speed of the vehicle for the road based on the road width acquired at the road width acquisition step; acquiring a behavior of the vehicle; and determining whether the vehicle performed a U-turn on the road by determining whether the vehicle performed turning that satisfies a condition under which the vehicle can perform a U-turn on the road at equal to or less than the maximum U-turn speed, based on the road width acquired at the road width acquisition step and the behavior of the vehicle acquired at the vehicle behavior acquisition step.

[0010] A computer program according to a fifth aspect of the present invention is characterized by performing in a computer the functions of: acquiring a road width of a road traveled by a vehicle; setting a maximum U-tum speed of the vehicle for the road based on the road width acquired by the road width acquisition function; acquiring a behavior of the vehicle; and determining whether the vehicle performed a U-turn on the road by determining whether the vehicle performed turning that satisfies a condition under which the vehicle can perform a U-turn on the road at equal to or less than the maximum U-turn speed, based on the road width acquired by the road width acquisition function and the behavior of the vehicle acquired by the vehicle behavior acquisition function.

[0011] According to the thus configured driving support device described the first aspect, a maximum U-turn speed of the vehicle for the road is set, and whether the vehicle performed a U-turn is determined based on the set maximum U-turn speed. Therefore, it is possible to accurately determine that the vehicle performed a U-turn. Consequently, a wrong-way travel situation of the vehicle can be accurately and promptly recognized. By warning the driver or performing a vehicle control, for example, travel in the wrong direction can thus be stopped.

[0012] According to the driving support device described in the second aspect, it is possible to accurately determine that the vehicle performed a U-turn by considering safety and a load applied to vehicle occupants during a U-turn.

[0013] According to the driving support device described in the third aspect, if it is determined that the vehicle performed a U-turn while traveling in a one-way zone, a warning of the vehicle traveling in the wrong direction is made.

Therefore, if the vehicle is in a wrong-way travel situation due to performing a

U-turn, such wrong- way travel can be promptly stopped.

[0014] According to the driving support method described the fourth aspect, a maximum U-turn speed of the vehicle for the road is set, and whether the vehicle performed a U-turn is determined based on the set maximum U-turn speed.

Therefore, it is possible to accurately determine that the vehicle performed a U-turn.

Consequently, a wrong-way travel situation of the vehicle can be accurately and promptly recognized. By warning the driver or performing a vehicle control, for example, travel in the wrong direction can thus be stopped.

[0015] According to the computer program described the fifth aspect, a maximum U-turn speed of the vehicle for the road is set, and whether the vehicle performed a U-turn is determined based on the set maximum U-turn speed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is a block diagram that shows a navigation device according to an embodiment;

FIG 2 is a diagram that shows the constitution of a navigation

ECU;

FIG. 3 is a flowchart of a wrong-way travel warning processing program according to the embodiment;

FIG. 4 is a flowchart of a sub-processing program for a U-turn detection process;

FIG. 5 is a diagram that shows a lateral acceleration of a vehicle during turning by turn curvature radius; and

FIG. 6 is a diagram that shows an example of a wrong-way travel situation caused by the vehicle making a U-turn.

BEST MODES FOR CARRYING OUT THE INVENTION

[0017] A specific embodiment of a driving support device according to the present invention that is realized in a navigation device will be described in detail below with reference to the drawings. First, an overall configuration of a navigation device 1 according to the present embodiment will be explained using FIG. 1. FIG. 1 is a block diagram that shows the navigation device 1 according to the present embodiment.

[0018] As shown in FIG. 1, the navigation device 1 according to the present embodiment is configured from a current position detection unit 11 that detects a current position of a vehicle, a data storage unit 12 that stores various types of data, a navigation ECU 13 that performs various types of computational processing based on input information, an operation portion 14 that receives an operation from a user, a liquid crystal display 15 that displays a map and a guidance route to a destination for the user, a speaker 16 that outputs voice guidance related to route guidance, a DVD drive 17 that reads a DVD serving as a storage medium that stores programs, and a communication module 18 that performs communication with an information center such as a traffic information center.

[0019] Each of the configuring elements of the navigation device 1 will be explained in order below.

The current position detection unit 11 includes a GPS 21, a vehicle speed sensor 22, a steering sensor 23, a gyroscopic sensor 24, a G-force sensor 25, an altimeter (not shown in the drawing), and is capable of detecting the current vehicle position, heading, vehicle running speed, and the like. The vehicle speed sensor 22, in particular, is a sensor for detecting the vehicle's speed and distance traveled. The vehicle speed sensor 22 generates a pulse in response to the rotation of the vehicle's wheels and outputs a pulse signal to the navigation ECU 13. The navigation ECU 13 counts the generated pulses to compute the revolution speed of the wheels and the distance traveled. Note that it is not necessary for the navigation device 1 to be provided with all of the five types of sensors described above, and it is acceptable for the navigation device 1 to be provided with only one or a plurality among the five types of sensors.

[0020] The data storage unit 12 includes a hard disk (not shown in the drawing) serving as an external storage device and recording medium, and a read/write head (not shown in the drawing) serving as a drive for reading a map information database 31, predetermined programs, and so on from the hard disk and writing predetermined data to the hard disk.

[0021] The map information database 31 stores various types of map data that are necessary for route guidance, traffic information guidance, and map displays.

Specifically, the map data includes link data 32 that pertains to the shapes of roads (links), node data 33 that pertains to node points, POI data that is information pertaining to points such as facilities, intersection data that pertains to various intersections, search data for finding routes, search data for finding geographical points, and image drawing data for drawing images of maps, roads, traffic information, and the like on the liquid crystal display 15. In particular, information that pertains to link road types (e.g., expressway, city expressway, motorway, general toll road, service road, and general road), information that pertains to road widths, information that pertains to whether a one-way zone is set, and the like is stored as the link data 32.

Note that the map information database 31 is updated based on update data provided through a storage medium (such as a DVD or a memory card) or update data distributed from a map distribution center or the like.

[0022] The navigation ECU 13 is an electronic control unit that performs an overall control of the navigation device 1, and as shown in FIG. 2 includes: a guidance route setting unit 41 that sets a guidance route from a place of departure to a destination if a destination is selected; a road width acquisition unit 42 that acquires the road width of the road traveled by the vehicle; a maximum speed setting unit 43 that sets a maximum U-turn speed of the vehicle for the road based on the acquired road width; a vehicle behavior acquisition unit 44 that acquires a vehicle behavior; a U-turn determination unit 45 that, based on the acquired road width and the vehicle behavior, determines the vehicle performed a U-turn on the road if the vehicle performed turning that satisfies a condition under which the vehicle can perform a U-turn on the road at equal to or less than the maximum U-turn speed; and a warning unit 46 that warns of wrong-way travel of the vehicle if the road traveled by the vehicle is a one-way zone and the U-turn determination unit 45 determines that the vehicle performed a U-turn on the road. The navigation ECU 13 also includes: a CPU 51 that serves as a computational device and a control device; a RAM 52 that is used as a working memory when the CPU 51 performs various types of computational processing, and also stores route data and the like when a route has been found; a ROM 53 that stores control programs as well as a wrong- way travel warning processing program (see FIG. 3); and an internal storage device such as a flash memory 54 that stores programs read from the ROM 53.

[0023] The operation unit 14 is operated at times such as when a place of departure is input as a travel start point and a destination is input as a travel end point, and includes a plurality of operation switches (not shown in the drawing), such as various types of keys, buttons, and the like. Based on switch signals that are output by operating the various operation switches, such as by pressing or the like, the navigation ECU 13 controls the various types of corresponding operations that are executed. Note that the operation unit 14 can also be configured as a touch panel that is provided on the front surface of the liquid crystal display 15.

[0024] The liquid crystal display 15 displays a map image that includes roads, traffic information, operation guidance, an operation menu, key guidance, a guidance route from the place of departure to the destination, guidance information along the guidance route, news, a weather forecast, the time, e-mail, a television program, and the like. If it is determined that the vehicle performed a U-turn while traveling in a one-way zone, a wrong-way travel situation is assumed and the liquid crystal display 15 displays a warning against traveling in the wrong direction.

[0025] The speaker 16 outputs traffic information guidance and voice guidance for guiding travel along the guidance route on the basis of an instruction from the navigation ECU 13. If it is determined that the vehicle performed a U-turn while traveling in a one-way zone, a wrong-way travel situation is assumed and the speaker 16 outputs a warning sound against traveling in the wrong direction.

[0026] The DVD drive 17 is a drive capable of reading data stored on a recording medium such as a DVD or a CD. The map information database 31 is updated and the like based on the data that is read.

[0027] The communication module 18 is a communication device, such as a mobile telephone or a DCM, for example, that receives traffic information that is transmitted from a traffic information center, such as the Vehicle Information and Communication System (VICS (registered trademark)) center, a probe center, or the like, for example. The traffic information includes various types of information, such as congestion information, regulatory information, and traffic accident information.

[0028] Next, the wrong-way travel warning processing program that is executed in the navigation device 1 having the above configuration will be explained based on FIG. 3. FIG. 3 is a flowchart of the wrong-way travel warning processing program according to the present embodiment. Here, the wrong-way travel warning processing program is a program executed after the vehicle power is turned on, and determines whether the vehicle performed a U-turn while traveling in a one-way zone and issues a warning against wrong-way travel based on the determination result. Note that the programs below shown in the flowcharts of FIGS. 3 and 4 are stored in the RAM 52, the ROM 53, or the like provided in the navigation ECU 13, and executed by the CPU 51.

[0029] In the wrong-way travel warning processing program, first, the CPU 51 performs a fail determination process at step (hereinafter abbreviated to "S") 1. In the fail determination process, the CPU 51 determines whether various components such as the GPS 21, the vehicle speed sensor 22, the steering sensor 23, the gyroscopic sensor 24, and the G-force sensor 25 are operating properly.

[0030] If a fail state is determined in the processing at SI (S2: Yes), the wrong-way travel warning processing program is ended. However, if no fail state is determined (S2: No), the CPU 51 proceeds to S3.

[0031] At S3, the CPU 51 performs a matching state determination process. In the matching state determination process, the CPU 51 uses map matching processing to determine whether the current position of the vehicle is correctly specified on (matched to) a link in a map. Note that the G-force sensor 25 may also be used in addition to the GPS 21 to specify the current position of the vehicle on a link. Specifically, in the case of roads that were built vertically overlapping, the road on which the vehicle is traveling is specified by using the G-force sensor 25 to detect the acceleration generated in the vehicle.

[0032] If a matching state is determined in the processing at S3 (S4: Yes), the CPU 51 proceeds to S5. However, if no matching state is determined (S4: No), the wrong-way travel warning processing program is ended.

[0033] At S5, the CPU 51 acquires from the map information database 31 information (such as road type and restriction information) that pertains to a travel zone of the road traveled by the vehicle. More specifically, this is performed by specifying the link currently traveled by the vehicle and acquiring the link data 32 of the link from the map information database 31.

[0034] Next, at S6, the CPU 51 determines whether the zone traveled by the vehicle is a one-way zone based on the information acquired at S5. More specifically, the CPU 51 makes this determination based on the link data 32 of the link currently traveled by the vehicle. Note that the one-way zone is a zone configured to allow the vehicle to travel in only a predetermined direction, and is set in some roads where high speed travel is possible such as expressways, city expressways, motorways, general toll roads and national roads, as well as general roads with a narrow road width.

[0035] If it is determined that the zone traveled by the vehicle is a one-way zone (S6: Yes), the CPU 51 proceeds to S7. However, if it is determined that the zone traveled by the vehicle is not a one-way zone (S6: No), the wrong- way travel warning processing program is ended.

[0036] At S7, the CPU 1 performs a U-turn detection process described later (FIG. 4). Note that the U-turn detection process detects that the vehicle performed a U-turn when a U-turn is performed by the vehicle. Also, in the U-turn detection process, a U-turn flag stored in the RAM 52 is turned on when it is detected that the vehicle performed a U-turn as described later.

[0037] Next, at S8, the CPU 51 reads the U-turn flag stored in the RAM

52 and determines whether the U-turn flag is turned on, that is, whether the vehicle performed a U-turn. Note that the U-turn flag is set to off in an initial state.

[0038] If it is determined that the U-turn flag is turned on, that is, the vehicle performed a U-turn (S8: Yes), the CPU 51 assumes that performing the U-turn put the vehicle in a wrong-way travel situation (a situation in which the vehicle travels in a direction opposite the direction of travel set for the road) and the CPU 51 proceeds to S9. However, if it is determined that the U-turn flag is turned off, that is, the vehicle did not perform a U-turn (S8: No), it is assumed that the vehicle is not in a wrong-way travel situation and the wrong-way travel warning processing program is ended without issuing a warning.

[0039] At S9, the CPU 1 performs a warning process that warns of the vehicle traveling in the wrong direction. More specifically, the message "Warning: the vehicle is traveling in the wrong direction" is displayed on the liquid crystal display 15, and the same content is output by voice from the speaker 16.

[0040] Next, sub-processing for the U-turn detection process at S7 will be described based on FIG. 4. FIG. 4 is a flowchart of a sub-processing program for the U-turn detection process.

[0041] First, at S 11 , the CPU 51 acquires a detection value detected by the gyroscopic sensor 24. Note that the acquired detection value is used to determine at S16 described later whether the vehicle performed turning that may be a U-tum.

[0042] Next, at SI 2, the CPU 51 acquires the current vehicle speed based on the detection result of the vehicle speed sensor 22.

[0043] At SI 3, the CPU 51 then sets a tolerance for lateral acceleration generated in the vehicle (referred to as a "lateral acceleration tolerance" below) up to which the vehicle can safely perform a U-tum without applying a load to vehicle occupants while the vehicle performs the U-tum.

Here, lateral acceleration is generated in the vehicle by centrifugal force when the vehicle turns. The lateral acceleration increases in accordance with a faster vehicle speed during turning and a smaller turn curvature radius. If the lateral acceleration becomes excessively large, a load may be applied to vehicle occupants or cause slipping. Accordingly, for the vehicle to safely perform a U-tum without applying a load to vehicle occupants while the vehicle performs the U-tum, the lateral acceleration generated in the vehicle must be equal to or less than a predetermined value. This predetermined value is set as the lateral acceleration tolerance.

Note that, in the present embodiment, the lateral acceleration tolerance is set to 0.8 G (9.81 kg.m/sec²). The lateral acceleration tolerance may also be set depending on the vehicle model, weather, number and age of vehicle occupants, and lateral acceleration generated during past U-turns.

[0044] Next, at SI 4, the CPU 51 acquires a width curvature radius. Note that the width curvature radius is the maximum turn curvature radius at which a U-turn can be performed on the road currently traveled by the vehicle, and is equal to half the road width. More specifically, the width of the road currently traveled by the vehicle is acquired from the map information database 31 , and the width curvature radius is acquired by calculating the length of half the acquired road width.

[0045] Next, at SI 5, the CPU 51 sets a "maximum U-turn speed of the vehicle for the road" based on the lateral acceleration tolerance acquired at S13 and the width curvature radius acquired at S14. Here, the "maximum U-turn speed of the vehicle for the road" is an upper limit of speed up to which the vehicle can safely perform a U-turn without applying a load to vehicle occupants if the vehicle makes a U-turn on the road currently traveled by the vehicle. More specifically, the lateral acceleration generated in the vehicle if the vehicle turns at the width curvature radius acquired at S14 is the upper limit of speed and equal to the lateral acceleration tolerance acquired at SI 3.

[0046] A setting process of the "maximum U-turn speed of the vehicle for the road" at S 15 will be described in detail below.

A lateral acceleration k generated in the vehicle during turning is shown in Equation (1) below, where k is the lateral acceleration generated in the vehicle during turning, V is the vehicle speed during turning, R is the turn curvature radius, and g is the gravitational acceleration. k = V² / (R x g) (1)

FIG. 5 is a diagram that shows changes in the lateral acceleration k generated in the vehicle during turning with respect to the vehicle speed V when the turn curvature radius R is 4 meters, 5.5 meters, and 10 meters, respectively.

[0047] As shown in FIG. 5, the lateral acceleration generated in the vehicle during turning increases in accordance with a faster vehicle speed during turning and a smaller turn curvature radius. If the lateral acceleration tolerance is 0.8 G, a "maximum U-turn speed Vmax of the vehicle for the road" is shown in Equation (2) below. Vmax = (0.8 x R x g) (2)

At SI 5, based on Equation (2), the "maximum U-turn speed of the vehicle for the road" is calculated and set. For example, on the road with a turn curvature radius of 4 meters, the "maximum U-turn speed of the vehicle for the road" is 20.2 km/h. On the road with a turn curvature radius of 5.5 meters, the "maximum U-turn speed of the vehicle for the road" is 23.7 km/h. On the road with a turn curvature radius of 10 meters, the "maximum U-turn speed of the vehicle for the road" is 31.9 km/h.

[0048] Next, at SI 6, the CPU 51 determines whether the vehicle performed turning that satisfies a condition under a U-turn can be made. Here, turning that satisfies a condition under which a U-turn can be made is turning where the turn direction or the turn curvature radius satisfies a condition, e.g., turning that is in the right direction and at a turn curvature radius that is smaller than the width curvature radius. Note that the turn direction and turn curvature radius are calculated using the detection value of the gyroscopic sensor 24 acquired at SI. Further note that, instead of or in addition to the turn direction and the turn curvature radius, a turn angle, surrounding road conditions, and the like may also be used in the determination.

[0049] If it is determined that the vehicle performed turning that may be a U-turn (SI 6: Yes), the CPU 51 proceeds to SI 7. However, if it is determined that the vehicle did not perform turning that may be a U-turn (SI 6: No), the CPU 1 determines that the vehicle did not perform a U-turn, after which the CPU 51 ends the sub-processing program for the U-turn detection process and proceeds to S8.

[0050] At S 17, the CPU 51 determines whether the current vehicle speed acquired at S 12 (i.e., vehicle turning speed) is equal to or less than the "maximum U-turn speed of the vehicle for the road" set at S I 5.

[0051] If it is determined that the vehicle turning speed is equal to or less than the "maximum U-turn speed of the vehicle for the road" (SI 7: Yes), the CPU 51 determines that the vehicle performed a U-turn and proceeds to SI 8. However, if it is determined that the vehicle turning speed is faster than the "maximum U-turn speed of the vehicle for the road" (SI 7: No), the vehicle is likely performing a spin or sharp turn to avoid an obstacle. The CPU 51 thus determines that the vehicle did not perform a U-turn, after which the CPU 51 ends the sub-processing program for the U-turn detection process and proceeds to S8.

In other words, by determining whether the vehicle performed turning that satisfies a condition under which the vehicle can perform a U-turn on the road at equal to or less than the maximum U-turn speed, the CPU 51 determines whether the vehicle performed a U-turn on the road. If it is then determined that the vehicle performed turning that satisfies a condition under which the vehicle can perform a U-turn on the road at equal to or less than the maximum U-turn speed, the CPU 51 determines that the vehicle performed a U-turn on the road.

[0052] At SI 8, the CPU 51 reads the U-turn flag from the RAM 52 and sets the U-turn flag to on. The CPU 51 subsequently proceeds to S8. Thereafter, the CPU 51 performs a warning process that warns of the vehicle traveling in the wrong direction (S9).

[0053] As described in detail above, in the navigation device 1 according to the present embodiment, a tolerance for lateral acceleration generated in the vehicle (lateral acceleration tolerance) is set at which the vehicle can safely perform a U-turn without applying a load to vehicle occupants while the vehicle performs the U-turn (SI 3). Based on the set lateral acceleration tolerance and the width curvature radius, the "maximum U-turn speed of the vehicle for the road" is set (S14). If the vehicle performs turning that may be a U-turn while traveling in a one-way zone and the turning speed at such time is equal to or less than the "maximum U-turn speed of the vehicle for the road", it is determined that the vehicle performed a U-turn. The vehicle is thus recognized as in a wrong-way travel situation due to performing the U-turn, and a warning of the vehicle traveling in the wrong direction is made (S9). Therefore, it is possible to accurately determine that the vehicle performed a U-turn. Further, if the vehicle is in a wrong-way travel situation due to performing a U-turn, such wrong-way travel can be promptly stopped.

Moreover, the maximum U-turn speed is set as the upper limit of speed at which the lateral acceleration generated in the vehicle while the vehicle performs a U-turn on the road is equal to or less than a predetermined acceleration. Therefore, it is possible to accurately determine that the vehicle performed a U-turn by considering safety and the load acting on vehicle occupants during a U-turn.

[0054] Note that the present invention is not limited to the embodiment described above, and may of course be subjected to various improvements and modifications within a scope that does not depart from the spirit of the present invention.

For example, in the present embodiment, the "maximum U-turn speed of the vehicle for the road" is an upper limit of speed at which the lateral acceleration generated in the vehicle when the vehicle turns at the width curvature radius acquired at S 14 is equal to or less than the lateral acceleration tolerance acquired at SI 3. However, instead of the width curvature radius, the minimum turn curvature radius of the vehicle may be used. The actual turn curvature radius at which the vehicle turned may also be detected, and the detected turn curvature radius used instead of the width curvature radius.

[0055] The lateral acceleration tolerance is set to 0.8 G (9.81 kg.m/sec²) in the present embodiment, but another value may be used. The lateral acceleration tolerance may also be changed depending on the vehicle model, weather, number and age of vehicle occupants, and lateral acceleration generated during past U-turns.

Claims

1. A driving support device, characterized by comprising:

a road width acquisition unit that acquires a road width of a road traveled by a vehicle;

a maximum speed setting unit that sets a maximum U-turn speed of the vehicle for the road based on the road width acquired by the road width acquisition unit;

a vehicle behavior acquisition unit that acquires a behavior of the vehicle; and

a U-turn determination unit that determines whether the vehicle performed a U-turn on the road by determining whether the vehicle performed turning that satisfies a condition under which the vehicle can perform a U-turn on the road at equal to or less than the maximum U-turn speed, based on the road width acquired by the road width acquisition unit and the behavior of the vehicle acquired by the vehicle behavior acquisition unit.

2. The driving support device according to claim 1, wherein

the maximum speed setting unit sets, as the maximum U-turn speed, an upper limit of speed at which a lateral acceleration generated in the vehicle while the vehicle performs a U-turn on the road is equal to or less than a predetermined acceleration.

3. The driving support device according to claim 1 or 2, further comprising: a warning unit that, if the road traveled by the vehicle is a one-way zone and the U-tum determination unit determines that the vehicle performed a U-turn on the road, warns of the vehicle traveling in a wrong direction.

4. A driving support method, characterized by comprising the steps of:

acquiring a road width of a road traveled by a vehicle;

setting a maximum U-turn speed of the vehicle for the road based on the road width acquired at the road width acquisition step;

acquiring a behavior of the vehicle; and determining whether the vehicle performed a U-turn on the road by determining whether the vehicle performed turning that satisfies a condition under which the vehicle can perform a U-turn on the road at equal to or less than the maximum U-turn speed, based on the road width acquired at the road width acquisition step and the behavior of the vehicle acquired at the vehicle behavior acquisition step.

5. A computer program, characterized by performing in a computer the functions of:

acquiring a road width of a road traveled by a vehicle;

setting a maximum U-turn speed of the vehicle for the road based on the road width acquired by the road width acquisition function;

acquiring a behavior of the vehicle; and

determining whether the vehicle performed a U-turn on the road by determining whether the vehicle performed turning that satisfies a condition under which the vehicle can perform a U-turn on the road at equal to or less than the maximum U-turn speed, based on the road width acquired by the road width acquisition function and the behavior of the vehicle acquired by the vehicle behavior acquisition function.