Patent Publication Number: US-2021191418-A1

Title: Method, apparatus, and program product for localizing center of intersection

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based on and claims the benefit of priority from Japanese Patent Application No. 2019-232554 filed on Dec. 24, 2019, the entire disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to methods, apparatuses, and program products for localizing the center of an intersection, and also to methods and apparatuses for identifying the type of a lane where an own vehicle is located, the lane being a part of an intersection. 
     BACKGROUND 
     In recent years, driving assistance technologies of vehicles, in particular, autonomous driving technologies of vehicles, have been widely researched and developed. 
     SUMMARY 
     An exemplary aspect of the present disclosure provides an apparatus for localizing a center of an intersection. The apparatus is configured to detect an intersection point between a location of a center of a road identified by a road center identifier and a line connecting between at least two traffic light devices detected by a traffic light detector, thus localizing the detected intersection point as a center of an intersection. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other aspects of the present disclosure will become apparent from the following description of embodiments with reference to the accompanying drawings in which: 
         FIG. 1  is a block diagram schematically illustrating an example of the overall structure of an intersection lane identification apparatus according to the first embodiment of the present disclosure; 
         FIG. 2  is a view schematically illustrating a frame image showing a forward directional view of a vehicle; 
         FIG. 3  is a schematic view of a target intersection where two traffic light devices are located; 
         FIG. 4  is a schematic view of a target intersection whose situation is different from the target intersection illustrated in  FIG. 3 ; 
         FIG. 5  is a flowchart schematically illustrating the sequence of an intersection center localizing routine; 
         FIG. 6  is a flowchart schematically illustrating the sequence of a road center identification subroutine in the intersection center localizing routine; 
         FIG. 7  is a flowchart schematically illustrating the sequence of a lane identification routine; 
         FIG. 8  is a block diagram schematically illustrating an example of the overall structure of an intersection lane identification apparatus according to the second embodiment of the present disclosure; 
         FIG. 9  is a schematic view of a target intersection where two traffic light devices are located, which is used to show how to identify a right-turn-only lane according to the second embodiment; and 
         FIG. 10  is a flowchart schematically illustrating the sequence of a lane identification routine according to the second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENT 
     Japanese Patent Application publication No. 2019-18827 discloses a technology that assists the driving of a vehicle at an intersection without using road-to-vehicle communications. Specifically, the above known patent publication discloses a method of determining a target point in an intersection when a vehicle turns right in the intersection, creating, based on the target point, a traveling route in the intersection, and assisting the right turn of the vehicle in accordance with the created traveling route. 
     The method disclosed in the known patent publication detects the center of the intersection, and determines the target point in the intersection based on the detected center of the intersection. 
     The known patent publication discloses various approaches of detecting the center of an intersection (see paragraphs [0046] to [0050] thereof). 
     Advanced driving assist technologies and autonomous driving technologies need to detect (i) the configuration of an intersection, and (ii) a lane-junction relationship indicative of how the intersection joins to lanes for permitting a vehicle to reliably pass through the intersection. For detecting the configuration and lane-junction relationship of an intersection, these technologies can use (i) a first measure of using high definition maps for autonomous driving, and (ii) a second measure of estimating the configuration and lane-junction relationship of the intersection using autonomous sensors. 
     The first measure requires preparation of high definition maps for many general roads, resulting in high costs for the preparation of the high definition maps. This therefore may make it difficult for the advanced driving assist technologies and autonomous driving technologies to use the first measure for detecting the configuration of an intersection. 
     Regarding the second measure, the autonomous sensors have difficulty in recognizing complicated configurations of intersections. 
     More specifically, the second measure, which is likely to be more feasible in cost than the first measure, may have difficulty in 
     1. Estimating the configuration of an intersection due to the paucity of clues, such as information about lane markers and road edges, associated with the intersection 
     2. Recognizing the lane-junction relationship of the intersection 
     The present disclosure aims to solve at least part of the issues described above. 
     According to a first exemplary aspect of the present disclosure, there is provided an apparatus for localizing a center of an intersection. The apparatus includes a data obtainer configured to obtain, from a surrounding monitor that monitors a surrounding situation around a vehicle traveling on a road, data indicative of the surrounding situation monitored by the surrounding monitor. The apparatus includes a road center identifier configured to identify a location of a center of the road based on the data indicative of the surrounding situation around the vehicle. The apparatus includes a traffic light detector configured to detect, based on the data indicative of the surrounding situation around the vehicle, at least two traffic light devices located in an intersection to which the road joins. The apparatus includes a center localization unit configured to detect an intersection point between the location of the center of the road identified by the road center identifier and a line connecting between the at least two traffic light devices detected by the traffic light detector, thus localizing the detected intersection point as a center of the intersection. 
     According to a second exemplary aspect of the present disclosure, there is provided an intersection lane identification apparatus. The intersection lane identification apparatus includes an intersection center localization apparatus. The intersection center localization apparatus includes a data obtainer configured to obtain, from a surrounding monitor that monitors a surrounding situation around a vehicle traveling on a road, data indicative of the surrounding situation monitored by the surrounding monitor. The intersection lane identification apparatus includes a road center identifier configured to identify a location of a center of the road based on the data indicative of the surrounding situation around the vehicle. The intersection lane identification apparatus includes a traffic light detector configured to detect, based on the data indicative of the surrounding situation around the vehicle, at least two traffic light devices located in an intersection to which the road joins. The intersection lane identification apparatus includes a center localization unit configured to detect an intersection point between the location of the center of the road identified by the road center identifier and a line connecting between the at least two traffic light devices detected by the traffic light detector, thus localizing the detected intersection point as a center of the intersection. 
     The intersection lane identification apparatus includes a lane identifier. The lane identifier is configured to 
     (i) Obtain, based on the localized center of the intersection, a minimum distance of a traveling position of the vehicle from the localized center of the intersection in a width direction of the road 
     (ii) Determine whether the obtained minimum distance is longer than or equal to a predetermined threshold distance 
     (iii) Identify that the vehicle is located at a left turnable lane upon determining that the obtained minimum distance is longer than or equal to the predetermined threshold distance 
     (iv) Identify that the vehicle is located at a right turnable lane upon determining that the obtained minimum distance is shorter than the predetermined threshold distance 
     According to a third exemplary aspect of the present disclosure, there is provided a method of localizing a center of an intersection. The method includes 
     (1) Obtaining, from a surrounding monitor that monitors a surrounding situation around a vehicle traveling on a road, data indicative of the surrounding situation monitored by the surrounding monitor 
     (2) Identifying a location of a center of the road based on the data indicative of the surrounding situation around the vehicle 
     (3) Detecting, based on the data indicative of the surrounding situation around the vehicle, at least two traffic light devices located in an intersection to which the road joins 
     (4) Detecting an intersection point between the location of the center of the road and a line connecting between the at least two traffic light devices, thus localizing the detected intersection point as a center of the intersection 
     According to a fourth exemplary aspect of the present disclosure, there is provided a method of localizing a center of an intersection. The method includes a computer-readable program product. The computer-readable program product includes a non-transitory computer-readable storage medium, and a set of computer program instructions stored in the computer-readable storage medium, the instructions causing a computer to 
     1. Obtain, from a surrounding monitor that monitors a surrounding situation around a vehicle traveling on a road, data indicative of the surrounding situation monitored by the surrounding monitor 
     2. Identify a location of a center of the road based on the data indicative of the surrounding situation around the vehicle 
     3. Detect, based on the data indicative of the surrounding situation around the vehicle, at least two traffic light devices located in an intersection to which the road joins 
     4. Detect an intersection point between the location of the center of the road and a line connecting between the at least two traffic light devices, thus localizing the detected intersection point as a center of the intersection. 
     EMBODIMENTS 
     The following describes exemplary embodiments of the present disclosure with reference to the accompanying drawings. In the exemplary embodiments and their modifications, like parts between the exemplary embodiments and their modifications are omitted or simplified to avoid redundant description. 
     First Embodiment 
       FIG. 1  schematically illustrates an intersection lane identification apparatus  1 , which includes an intersection center localization apparatus  10 , according to the first embodiment. The intersection lane identification apparatus  1  is for example installed in a vehicle V that is traveling on a lane, and is configured to identify the lane where the vehicle V is traveling. 
     The intersection lane identification apparatus  1  is communicable with a surrounding monitor  20  for monitoring a surrounding situation around the vehicle V. Specifically, the intersection lane identification apparatus  1  is adapted to cyclically obtain, from the surrounding monitor  20 , data, which will be referred to as surrounding situation data; the data represents the surrounding situation around, i.e. the environment of, the vehicle V. 
     The intersection lane identification apparatus  1  is also adapted to identify, based on the obtained data, a lane where the vehicle V is traveling. 
     The surrounding monitor  20  includes, for example, one or more cameras and/or one or more millimeter-wave radars installed in the vehicle V for monitoring the surrounding situation around the vehicle V. The surrounding monitor  20  can include another type of sensors for monitoring the surrounding situation around the vehicle V. 
     For example, each of the cameras is configured to successively capture frame images around the vehicle V as video data, and output the video data comprised of the successively captured frame images to the intersection lane identification apparatus  1 . 
     Each of the millimeter wave sensors is configured to emit millimeter waves around the vehicle V, receive echo millimeter waves resulting from reflection of the emitted radio waves by one or more objects located around the vehicle V, and generate, based on the received echo millimeter waves, surrounding situation information indicative of the situation around the vehicle V. 
     The intersection lane identification apparatus  1  includes the intersection center localization apparatus  10  and a lane identifier  17 . 
     For example, the intersection lane identification apparatus  1  is comprised of at least one microcomputer comprised of a CPU  1   a , a memory  1   b  comprised of, for example, a RAM, a ROM, and/or a hard disk drive, and a communication interface (CI)  1   c . The intersection lane identification apparatus  1  can include a display device and an input device. 
     The CPU  1   a  is configured to cyclically obtain the surrounding situation data to accordingly store the obtained surrounding situation data in, for example, the RAM of the memory  1   b , and run one or more programs stored in, for example, the ROM of the memory  1   b , thus implementing various functions corresponding to the one or more programs in accordance with the surrounding situation data stored in the RAM of the memory  1   b.    
     That is, the memory  1   b  serves as, for example, a non-transitory storage medium storing one or more programs. In other words, the CPU  1   a  runs one or more programs stored in the memory  1   b , thus carrying out various methods corresponding to the one or more programs in accordance with the surrounding situation data stored in the memory  1   b.    
     Note that the non-transitory storage medium is defined as a storage medium without transitory media, such as electromagnetic waves. 
     The intersection center localization apparatus  10  and the lane identifier  17  can be implemented by the CPU  1   a  of the intersection lane identification apparatus  1 . 
     Referring to  FIG. 1 , the intersection center localization apparatus  10  functionally includes, for example, a data obtainer  11 , a traffic light detector  12 , a pair selector  13 , a road center identifier  14 , a center localization unit  15 , and an output unit  16 ; these functional units  11  to  16  cooperatively localize the center of an intersection. 
     The data obtainer  11  is configured to cyclically obtain, from the surrounding monitor  20 , surrounding situation data indicative of the surrounding situation around the vehicle V. The surrounding monitor  20  according to the first embodiment includes cameras, each of which is configured to successively capture frame images around the vehicle V as video data, and output the video data comprised of the successively captured frame images to the intersection lane identification apparatus  1 . Then, the data obtainer  11  cyclically receives the video data from the surrounding monitor  20  as the surrounding situation data. 
     The road center identifier  14  is configured to identify the location of the center of the road on which the vehicle V is traveling; the road on which the vehicle V is traveling will be referred to as a current travel road. Note that the center of the road is defined as an imaginary line of the current travel road, which is equidistant from both edges of the current travel road. The defined center of the current travel road is based on the above concept, which is different from the concept of a center line based on the traffic regulations, but the defined center of the road can be in agreement with the center line based on the traffic regulations. 
     Specifically, the road center identifier  14  is configured to detect, based on the video data obtained from at least one of the cameras, the left and right edges of the current travel road, and identify the location of an imaginary line that is equidistant from the detected left and right edges as the center of the current travel road. 
     If the road center identifier  14  cannot identify the left edge of the current travel road due to one or more other vehicles located on the left side of the vehicle V in a lateral direction that is perpendicular to the longitudinal direction of the current travel road to block the view from the vehicle V to the left edge of the current travel road, the road center identifier  14  can perform an estimation approach that 
     1. Counts the number of one or more other vehicles located on the left side of the vehicle V in the lateral direction, which blocks the view from the vehicle V to the left edge of the vehicle V 
     2. Estimates, based on the counted number of one or more other vehicles, the minimum distance to the left edge of the current travel road from a predetermined reference point of the vehicle V 
     3. Identifies, based on the detected right edge and the estimated minimum distance to the left edge of the current travel road from the predetermined reference point of the vehicle V, the location of the center of the current travel road 
     Specifically, the road center identifier  14  can suppose the counted number of one or more other vehicles located on the left side of the vehicle V in the lateral direction to block the view from the vehicle V to the left edge of the current travel road as the number of one or more left-side lanes, and multiply the counted number by a predetermined width of one lane of the current travel road, such as 3.5 m, thus measuring the minimum distance from the predetermined reference point of the vehicle V to the left edge of the current travel road. Then, the road center identifier  14  can identify the location of the center of the current travel road in accordance with the detected right edge and the measured minimum distance from the predetermined reference point of the vehicle V to the left edge. 
     Similarly, if the road center identifier  14  cannot identify the right edge of the current travel road due to one or more other vehicles traveling on one or more right-side lanes of the current travel road, the road center identifier  14  can be configured to 
     1. Estimate the minimum distance from the predetermined reference point of the vehicle V to the right edge in the same manner as the measurement of the minimum distance from the predetermined reference point of vehicle V to the left edge 
     2. Identify, based on the detected left edge and the estimated minimum distance to the right edge of the current travel road from the predetermined reference point of vehicle V, the location of the center of the current travel road 
     If the road center identifier  14  cannot identify the left edge of the current travel road due to one or more other vehicles traveling on one or more left-side lanes of the current travel road, and cannot detect the right edge of the current travel road due to one or more other vehicles traveling on one or more right-side lanes of the current travel road, the road center identifier  14  can identify the location of the center of the current travel road in accordance with the estimated minimum distance from the predetermined reference point of the vehicle V to the left edge and the estimated minimum distance from the predetermined reference point of the vehicle V to the right edge. 
     If the road center identifier  14  estimates the center of the current travel road based on the number of one or more other vehicles, the road center identifier  14  can be configured to 
     1. Calculate an absolute difference between the estimated minimum distance from the predetermined reference point of the vehicle V to the left edge or right edge of the current travel road and a lateral distance between at least two traffic light devices described later 
     2. Determine whether the calculated absolute difference is greater or equal to a predetermined threshold 
     3. Estimate the minimum distance from the predetermined reference point of vehicle V to the left or right edge of the current travel road again upon determining that the calculated absolute difference is greater or equal to the predetermined threshold to accordingly determine that there may be a mistake in measurement of the minimum distance from the predetermined reference point of the vehicle V to the left or right edge of the current travel road 
     The traffic light detector  12  is configured to detect, based on the surrounding situation data obtained by the data obtainer  11 , at least two traffic light devices located in a target intersection around the vehicle V. Specifically, the traffic light detector  12  analyzes the video data using, for example, template pattern images of light traffic devices to accordingly detect at least two traffic light devices, and localizes each of the at least two traffic light devices located in the target intersection. 
     Note that the target intersection to be detected by the traffic light detector  12  is a junction where the current travel road of the vehicle V crosses at least one other road. 
       FIG. 2  schematically illustrates one frame image I 1  in the video data, which shows a forward directional view of the vehicle V. As illustrated in  FIG. 2 , in the frame image I 1 , two traffic light devices S 01  and S 02  located in a target intersection IN 0 , are included. Each of the traffic light devices S 01  and S 02  includes, for example, an emitting mechanism EM for emitting at least a red-light signal and a blue-light signal, and a pole P for supporting the emitting mechanism EM. 
     When detecting the at least two traffic light devices (for example, the traffic light devices S 01  and S 02 ), the traffic light detector  12  identifies the position of the pole P of the traffic light device S 01  as a position of the traffic light device S 01 , and the position of the pole P of the traffic light device S 02  as a position of the traffic light device S 02 . 
     The pair selector  13  is configured to select a pair of traffic light devices from at least three traffic light devices when the traffic light detector  12  detects the at least three traffic light devices. 
       FIG. 3  schematically illustrates a target intersection IN 1  where a traffic light device S 1  and a traffic light device S 2  are located. That is, in the intersection IN 1  illustrated in  FIG. 3 , the traffic light device S 1  is located at a near-right corner of the target intersection IN 1 , and the traffic light device S 2  is located at a far-left corner of the target intersection IN 1  when viewed from the vehicle V. 
     A longitudinal distance VD between the traffic light devices S 1  and S 2  represents a minimum distance between the traffic light devices S 1  and S 2  along a direction parallel to the traveling direction of the vehicle V. A lateral distance LD between the traffic light devices S 1  and S 2  represents a minimum distance between the traffic light devices S 1  and S 2  along a direction perpendicular to the traveling direction of the vehicle V. 
     Specifically, the pair selector  13  calculates each of a value of the longitudinal distance VD and a value of the lateral distance LD between each adjacent pair of the at least three traffic light devices detected by the traffic light detector  12  to accordingly select, from the at least three traffic light devices, at least one adjacent pair of traffic light devices that have the value of the longitudinal distance VD and the value of the lateral distance LD; these values of the respective longitudinal and lateral distances VD and LD are each longer than or equal to a width (see reference character “W” in  FIG. 3 ) of the current travel road of the vehicle V. 
     Let us assume that there are 
     (1) A first pair of traffic light devices having a value of each of the longitudinal and lateral distances VD and LD being longer than or equal to the width of the current travel road 
     (2) A second pair of traffic light devices having a value of each of the longitudinal and lateral distances VD and LD being longer than or equal to the width of the current travel road 
     In this assumption, the pair selector  13  selects one of the first pair of traffic light devices and the second pair of traffic light devices which have a larger longitudinal distance VD therebetween. 
     The center localization unit  15  is configured to detect an intersection point between the center of the current travel road of the vehicle V and a line connecting between the pair of traffic light devices selected by the pair selector  13 , thus localizing the detected intersection point as a center of the target intersection. If the traffic light detector  12  detects two traffic light devices, the center localization unit  15  is configured to localize an intersection point between the center of the current travel road of the vehicle V and a line connecting between the two traffic light devices detected by the traffic light detector  12 , thus recognizing the detected intersection point as a center of the target intersection. 
     For example, for the target intersection IN 1  illustrated in  FIG. 3 , the center localization unit  15  localizes, as the center of the intersection IN 1 , an intersection point C between the center (see reference character “L” in  FIG. 3 ) of the current travel road of the vehicle V and the line (reference character “SD” in  FIG. 3 ) connecting between the traffic light devices S 1  and S 2  of the selected pair. 
     The output unit  16  is configured to output, to the lane identifier  17 , data indicative of the center of the target intersection localized by the center localization unit  15 ; this data indicative of the center of the target intersection localized by the center localization unit  15  will be referred to as intersection center data. 
     The lane identifier  17  is configured to identify a lane where the vehicle V is traveling in accordance with the surrounding situation data obtained from the surrounding monitor  20  and the intersection center data outputted from the output unit  16 . 
     Specifically, the lane identifier  17  is configured to obtain, based on the intersection center data, a minimum distance of the traveling position of the vehicle V from the center of the target intersection in the width direction of the current travel road. Then, the lane identifier  17  is configured to 
     1. Determine whether the obtained minimum distance is longer than or equal to a predetermined threshold distance of, for example, 3 meters 
     2. Identify that the vehicle V is located at a left turnable lane, i.e. a lane where the vehicle V can turn left, upon determining that the obtained minimum distance is longer than or equal to the predetermined threshold distance 
     3. Identify that the vehicle V is located at a right turnable lane, i.e. a lane where the vehicle V can turn right, upon determining that the obtained minimum distance is shorter than the predetermined threshold distance 
     Note that the left turnable lane represents a lane where a vehicle located at the lane can turn left, and the right turnable lane represents a lane where a vehicle located at the lane can turn right. 
     Additionally, the lane identifier  17  is configured to detect, based on the surrounding situation data, a division center line of a traveling-directional road across the target intersection to accordingly obtain a deviation Z of an extending line of the division center line from the center of the target intersection. Then, the lane identifier  17  is configured to determine whether the obtained deviation Z is larger than or equal to a predetermined threshold length of, for example, 0.5 meters, and determine that the target intersection includes a right-turn-only lane upon determining that the obtained deviation Z is larger than or equal to the predetermined threshold length. 
       FIG. 4  illustrates a target intersection IN 2 , whose situation is different from that of the target intersection IN 1 . Specifically, a typical intersection, which has a right-turn-only lane, is configured such that the right-turn-only lane is located to be adjacent to the center of a road, resulting in the division center line of the road being deviated from the center of the typical intersection. This therefore makes it possible for the lane identifier  17  to determine that the target intersection has a right-turn-only lane upon determining that the obtained deviation Z is larger than or equal to the predetermined threshold length. 
     Additionally, the lane identifier  17  is configured to obtain, based on the surrounding situation data, a width of a crossing road constituting the target intersection and crossing to the current travel road, and determine whether the width of the crossing road is shorter than or equal to a predetermined threshold width of, for example, 5 meters. Specifically, the lane identifier  17  determines that the vehicle V is capable of only going straight ahead upon determining that the width of the crossing road is shorter than or equal to the predetermined threshold width. 
     Moreover, the lane identifier  17  is configured to determine, based on the surrounding situation data, whether there is a road across the target intersection along the traveling direction of the vehicle V, and determine that the vehicle V is capable of only turning right or left in the target intersection upon determining that there is not a road across the target intersection along the traveling direction of the vehicle V. 
     Next, the following describes, with reference to the flowchart of  FIG. 5 , the sequence of an intersection center localizing routine, which will be referred to as a localizing routine, periodically carried out by the intersection lane identification apparatus  1 . One localizing routine carried out by the intersection lane identification apparatus  1  will also be referred to as a cycle. 
     When starting the intersection center localizing routine, the intersection center localization apparatus  10  of the intersection lane identification apparatus  1  serves as, for example, the data obtainer  11  to receive surrounding situation data monitored by and sent from the surrounding monitor  20  in step S 10 . 
     Next, the intersection center localization apparatus  10  serves as, for example, the traffic light detector  12  to detect, based on the surrounding situation data, at least one traffic light in step S 11 . 
     In step S 12 , the intersection center localization apparatus  10  serves as, for example, the traffic light detector  12  to determine whether at least two traffic light devices located in an intersection are detected in step S 11 . 
     Upon determining that at least two traffic light devices are not detected in step S 11  (NO in step S 12 ), the intersection center localization apparatus  10  returns to the operation in step S 10 . Then, the intersection center localization apparatus  10  repeats the localizing routine from the operation in step S 10  based on surrounding situation data each time of receiving the surrounding situation data monitored by and sent from the surrounding monitor  20  until the determination in step S 12  is affirmative. 
     Otherwise, upon determining that at least two traffic light devices are detected in an intersection (YES in step S 12 ), the intersection center localization apparatus  10  serves as, for example, the pair selector  13  to calculate, based on the surrounding situation data monitored by and sent from the surrounding monitor  20 , a value of the longitudinal distance VD and a value of the lateral distance LD between each adjacent pair of the at least two traffic light devices detected in step S 11  in step S 13 . Note that the intersection in which at least two traffic light devices are detected will also be referred to as a target intersection. The target intersection is defined as a junction where the current travel road of the vehicle V crosses at least one other road. 
     Next, the intersection center localization apparatus  10  serves as, for example, the road center identifier  14  to perform a road center identification subroutine in step S 14 . 
     The following describes the road center identification subroutine in step S 14  with reference to a flowchart of  FIG. 6 . 
     The intersection center localization apparatus  10  serves as, for example, the road center identifier  14  to perform, based on video data obtained from at least one of the cameras and included in the surrounding situation data used in step S 13 , determination of the left edge of the current travel road in step S 20  to thereby determine whether determination of the left edge of the current travel road has succeeded in step S 21 . 
     When determination of the left edge of the current travel road is determined to have succeeded (YES in step S 21 ), the road center identification subroutine proceeds to step S 24 . 
     Otherwise, determination of the left edge of the current travel road is determined to have not succeeded (NO in step S 21 ), the road center identification subroutine proceeds to step S 22 . 
     In step S 22 , the intersection center localization apparatus  10  serves as, for example, the road center identifier  14  to determine whether there are one or more other vehicles located on the left side of the vehicle V in the lateral direction to block the view from the vehicle V to the left edge of the current. 
     When it is determined that there are no other vehicles located on the left side of the vehicle V in the lateral direction (NO in step S 22 ), the intersection center localization apparatus  10  returns to step S 20 . Then, the intersection center localization apparatus  10  serves as, for example, the road center identifier  14  to repeat the operations in steps S 20  to S 22  in accordance with video data obtained from at least one of the cameras and included in surrounding situation data monitored by and sent from the surrounding monitor  20 ; the video data monitored by and sent from the surrounding monitor  20  is, for example, newer than the immediately previous affirmative determination in step S 22 . If there are no affirmative determinations before this cycle of the localizing routine, the road center identifier  14  can repeat the operations in steps S 20  to S 22  in accordance with video data obtained by and sent from the surrounding monitor  20  after the negative determination in step S 22  of this cycle of the localizing routine. The repetition of the operations in step S 20  to S 22  until the determination in step S 22  is affirmative. 
     Otherwise, when it is determined that there are one or more other vehicles located on the left side of the vehicle V in the lateral direction (YES in step S 22 ), the intersection center localization apparatus  10  counts the number of one or more other vehicles located on the left side of the vehicle V in the lateral direction in step S 23 . 
     Following the operation in step S 23 , the intersection center localization apparatus  10  serves as, for example, the road center identifier  14  to perform, based on video data obtained from at least one of the cameras and included in the surrounding situation data used in step S 13 , determination of the right edge of the current travel road in step S 24  to thereby determine whether determination of the right edge of the current travel road has succeeded in step S 25 . 
     When determination of the right edge of the current travel road is determined to have succeeded (YES in step S 25 ), and the road center identification subroutine proceeds to step S 28 . 
     Otherwise, determination of the right edge of the current travel road is determined to have not succeeded (NO in step S 25 ), and the road center identification subroutine proceeds to step S 26 . 
     In step S 26 , the intersection center localization apparatus  10  serves as, for example, the road center identifier  14  to determine whether there are one or more other vehicles located on the right side of the vehicle V in the lateral direction to block the view from the vehicle V to the right edge of the current. 
     When it is determined that there are no other vehicles located on the right side of the vehicle V in the lateral direction (NO in step S 26 ), the intersection center localization apparatus  10  returns to step S 24 . Then, the intersection center localization apparatus  10  serves as, for example, the road center identifier  14  to repeat the operations in steps S 24  to S 26  in accordance with video data obtained from at least one of the cameras and included in surrounding situation data monitored by and sent from the surrounding monitor  20  in response to negative determination in step S 26 ; the video data monitored by and sent from the surrounding monitor  20  is, for example, newer than the immediately previous affirmative determination in step S 26 . If there are no affirmative determinations before this cycle of the localizing routine, the road center identifier  14  can repeat the operations in steps S 24  to S 26  in accordance with video data obtained by and sent from the surrounding monitor  20  after the negative determination in step S 26  of this cycle of the localizing routine. The repetition of the operations in step S 24  to S 26  until the determination in step S 26  is affirmative. 
     Otherwise, when it is determined that there are one or more other vehicles located on the right side of the vehicle V in the lateral direction (YES in step S 26 ), the intersection center localization apparatus  10  counts the number of one or more other vehicles located on the right side of the vehicle V in the lateral direction in step S 27 . 
     Following the affirmative determination in step S 25  or the operation in step S 27 , the intersection center localization apparatus  10  serves as, for example, the road center identifier  14  to determine, in step S 28 , the width of the current travel road in accordance with one of 
     I. The detected left and right edges of the current travel road 
     II. The detected left edge of the current travel road and the counted number of one or more other vehicles located on the right side of the vehicle V in the lateral direction 
     III. The detected right edge of the current travel road and the counted number of one or more other vehicles located on the left side of the vehicle V in the lateral direction 
     IV. The counted number of one or more other vehicles located on the left side of the vehicle V in the lateral direction and the counted number of one or more other vehicles located on the left side of the vehicle V in the lateral direction 
     For example, for the second case II, i.e. for the case of NO in step S 25 , the road center identifier  14  estimates, based on the counted number of one or more other vehicles located on the right side of the vehicle V in the lateral direction, the minimum distance to the right edge of the current travel road from the predetermined reference point of the vehicle V. Then, the road center identifier  14  determines the width of the current travel road based on the detected left edge of the current travel road and the estimated minimum distance to the right edge of the current travel road from the predetermined reference point of the vehicle V. 
     For the third case III, i.e. for the case of NO in step S 21 , the road center identifier  14  estimates, based on the counted number of one or more other vehicles located on the left side of the vehicle V in the lateral direction, the minimum distance to the left edge of the current travel road from the predetermined reference point of the vehicle V. Then, the road center identifier  14  determines the width of the current travel road based on the detected right edge of the current travel road and the estimated minimum distance to the left edge of the current travel road from the predetermined reference point of the vehicle V. 
     For the fourth case IV, i.e. for the case of NO in each of steps S 21  and S 25 , the road center identifier  14  estimates, based on the counted number of one or more other vehicles located on the left side of the vehicle V in the lateral direction, the minimum distance to the left edge of the current travel road from the predetermined reference point of the vehicle V. Additionally, the road center identifier  14  estimates, based on the counted number of one or more other vehicles located on the right side of the vehicle V in the lateral direction, the minimum distance to the right edge of the current travel road from the predetermined reference point of the vehicle V. 
     Then, the road center identifier  14  determines the width of the current travel road based on the estimated minimum distance to each of the left and right edges of the current travel road from the predetermined reference point of the vehicle V. 
     Following the operation in step S 28 , the intersection center localization apparatus  10  serves as, for example, the road center identifier  14  to identify, based on the determined width of the current travel road, the location of an imaginary line of the current travel road, which is equidistant from both the left and right edges of the current travel road, to accordingly calculate the center of the current travel road based on the identified imaginary line in step S 29 . This terminates the road center identification subroutine in S 14 , so that execution of the road center identification subroutine proceeds to step S 15  of the main routine, i.e. the localizing routine. 
     In response to the termination of the road center identification subroutine in S 14 , the intersection center localization apparatus  10  serves as, for example, the pair selector  13  to perform a traffic-light pair selection task in step S 15 . 
     Specifically, the traffic-light pair selection task in step S 15  determines whether there is at least one pair of traffic light devices in the at least two traffic light devices detected by the operation in step S 12 ; the values of the longitudinal and lateral distances VD and LD of the at least one pair of traffic light devices are each longer than or equal to the width of the vehicle V. 
     We consider a first case where it is determined that there are no pairs of traffic light devices in the at least two traffic light devices detected by the operation in step S 12 ; the values of the longitudinal and lateral distances VD and LD of each pair of traffic light devices are each shorter than the width of the vehicle V (NO in step S 15 ). In response to the negative determination in step S 15 , the intersection center localization apparatus  10  returns to the operation in step S 10 . Then, the intersection center localization apparatus  10  repeats the localizing routine from the operation in step S 10  based on surrounding situation data each time of receiving the surrounding situation data monitored by and sent from the surrounding monitor  20 . 
     Otherwise, we consider a second case where it is determined that there is at least one pair of traffic light devices in the at least two traffic light devices detected by the operation in step S 12 ; the values of the longitudinal and lateral distances VD and LD of the at least one pair of traffic light devices are each longer than or equal to the width of the vehicle V (YES in step S 15 ). 
     In response to the affirmative determination in step S 15 , the intersection center localization apparatus  10  serves as, for example, the pair selector  13  to determine whether there are at least two pairs of traffic light devices in the at least two traffic light devices detected by the operation in step S 12 ; values of the longitudinal and lateral distances VD and LD of each of the at least two pairs of traffic light devices are each longer than or equal to the width of the vehicle V in step S 16 . The number of at least one pair of traffic light devices, the value of each of the longitudinal and lateral distances VD and LD of which is longer than or equal to the width of the vehicle V, will also be referred to as a pair number. 
     That is, the determination in step S 16  is determination of whether the pair number is more than or equal to 2. 
     We consider a first case where it is determined that there are at least two pairs of traffic light devices in the at least two traffic light devices detected by the operation in step S 12 ; values of the longitudinal and lateral distances VD and LD of each of the at least two pairs of traffic light devices are each longer than or equal to the width of the vehicle V (YES in step S 16 ). 
     In response to the affirmative determination in step S 16 , the intersection center localization apparatus  10  serves as, for example, the pair selector  13  to select one pair of traffic light devices in the at least two pairs of traffic light devices; the value of the longitudinal distance VD of the selected pair of traffic light devices is longest in the at least two pairs of traffic light devices in step S 17 . 
     Following the negative determination in step S 16  or the operation in step S 17 , the intersection center localization apparatus  10  serves as, for example, the center localization unit  15  to localize an intersection point, i.e. identify the location of the intersection point, between the center of the current travel road of the vehicle V and a line connecting between the pair of traffic light devices selected in step S 15  or S 17 , thus recognizing the localized intersection point as a center of the target intersection in step S 18 . 
     Then, the intersection center localization apparatus  10  serves as, for example, the output unit  16  to output intersection center data indicative of the center of the target intersection to the lane identifier  17  in step S 18 . 
     The following describes a lane identification routine carried out by the load identifier  17  of the intersection lane identification apparatus  1  in response to, for example, receiving the intersection center data with reference to a flowchart of  FIG. 7 . 
     When starting the lane identification routine, the lane identifier  17  obtains the width of the at least one other road crossing the current travel road of the vehicle V in accordance with the surrounding situation data obtained in step S 10  or the surrounding situation data currently obtained from the surrounding monitor  20  in step S 30 . Then, the lane identifier  17  determines whether the obtained width of the at least one other road crossing the current travel road is smaller than or equal to the predetermined threshold width in step S 30 . 
     Upon determining that the obtained width of the at least one other road crossing the current travel road is smaller than or equal to the predetermined threshold width (YES in step S 30 ), the lane identifier  17  determines that the at least one other road crossing the current travel road is a narrow road where it is difficult for vehicles to travel, thus determining that a lane where the vehicle V is traveling included in the current travel road is a straight only lane where the vehicle V is able to only go straight in step S 36 . The lane where the vehicle V is traveling will also be referred to as a current travel lane. Thereafter, the lane identifier  17  terminates lane identification routine. 
     Otherwise, when it is determined that the obtained width of the at least one other road crossing the current travel road is larger than or equal to the predetermined threshold width (NO in step S 30 ), the lane identification routine proceeds to step S 31 . 
     In step S 31 , the lane identifier  17  calculates, based on the intersection center data, a minimum distance of the traveling position of the vehicle V from the center of the target intersection in the width direction of the current travel road. Then, the lane identifier  17  determines whether the obtained minimum distance is longer than or equal to the predetermined threshold distance of, for example, 3 meters in step S 32 . 
     Upon determining that the obtained minimum distance is longer than or equal to the predetermined threshold distance (YES in step S 32 ), the lane identifier  17  determines whether there is a road across the target intersection along the traveling direction of the vehicle V in step S 33 . 
     Upon determining that there is not a road across the target intersection along the traveling direction of the vehicle V (NO in step S 33 ), the lane identifier  17  determines that the current travel lane is a left-turn-only lane where the vehicle V is capable of only turning left in the target intersection in step S 37 . Thereafter, the lane identifier  17  terminates lane identification routine. 
     Otherwise, upon determining that there is a road crossing across the target intersection along the traveling direction of the vehicle V (YES in step S 33 ), the lane identifier  17  determines that the current travel lane is a lane where the vehicle V is capable of going straight across the target intersection or turning left in the target intersection in step S 38 . Thereafter, the lane identifier  17  terminates lane identification routine. 
     On the other hand, upon determining that the obtained minimum distance is smaller than the predetermined threshold distance (NO in step S 32 ), the lane identifier  17  detects a division center line of a traveling-directional road across the target intersection in accordance with the surrounding situation data obtained in step S 10  or the surrounding situation data currently obtained from the surrounding monitor  20  to accordingly obtain the deviation Z of the extending line of the division center line from the center of the target intersection in step S 34 . 
     Then, in step S 34 , the lane identifier  17  determines whether the obtained deviation Z is larger than or equal to the predetermined threshold length of, for example, 0.5 meters. 
     Upon determining that the obtained deviation Z is larger than or equal to the predetermined threshold length (YES in step S 34 ), the lane identifier  17  determines that the current travel lane is a right-turn-only lane where the vehicle V is capable of only turning right in the target intersection in step S 39   a . Thereafter, the lane identifier  17  terminates lane identification routine. 
     Otherwise, upon determining that the obtained deviation Z is smaller than the predetermined threshold length (NO in step S 34 ), the lane identifier  17  determines whether there is a road across the target intersection along the traveling direction of the vehicle V in step S 35 . 
     Upon determining that there is not a road across the target intersection along the traveling direction of the vehicle V (NO in step S 35 ), the lane identifier  17  determines that the current travel lane is a right-turn-only lane where the vehicle V is capable of only turning right in the target intersection in step S 39   a . Thereafter, the lane identifier  17  terminates lane identification routine. 
     Otherwise, upon determining that there is a road across the target intersection along the traveling direction of the vehicle V (YES in step S 35 ), the lane identifier  17  determines that the current travel lane is a lane where the vehicle V is capable of going straight across the target intersection and turning right in the target intersection in step S 39   b . Thereafter, the lane identifier  17  terminates lane identification routine. 
     As described above, the intersection center localization apparatus  10  of the intersection lane identification apparatus  1  is configured to localize the center of the target intersection where the vehicle V is going to enter in accordance with the identified location of at least one pair of light traffic devices located in the target intersection. 
     This configuration therefore makes it possible to localize the center of the target intersection more easily than the other measures described in the above known patent publication, thus easily estimating the configuration of the intersection in accordance with the localized center of the intersection, and the identified location of each of the light traffic devices of the at least one pair. This is because a typical intersection has at least one pair of light traffic devices located diagonally opposite to each other at respective near and far corners of the intersection. 
     The intersection lane identification apparatus  1  is configured to identify how the current travel lane of the vehicle V joins to the target intersection that constitutes a part of the target intersection more easily based on the localized center of the target intersection. 
     Second Embodiment 
     The following describes an intersection lane identification apparatus  2  according to the second embodiment. To one or more components of the intersection lane identification apparatus  2  according to the second embodiment, which are identical to those of the intersection lane identification apparatus  1  according to the first embodiment, identical reference characters are respectively assigned, so that detailed descriptions of the one or more components are omitted. 
     Like the first embodiment, the intersection lane identification apparatus  2  is comprised of at least one microcomputer comprised of a CPU  2   a , a memory  2   b  comprised of, for example, a RAM, a ROM, and/or a hard disk drive, and a communication interface (CI)  2   c . The intersection lane identification apparatus  2  can include a display device and an input device. 
     The intersection lane identification apparatus  2  is for example installed in a vehicle V that is traveling on a lane, and is configured to identify the lane where the vehicle V is traveling. 
     Referring to  FIG. 8 , the intersection lane identification apparatus  2  functionally includes, for example, a data obtainer  30 , a road center identifier  31 , and a lane identifier  32 . 
     The data obtainer  30  is configured to cyclically obtain, from the surrounding monitor  20 , surrounding situation data indicative of the surrounding situation around the vehicle V. The surrounding monitor  20  according to the second embodiment includes cameras, each of which is configured to successively capture frame images around the vehicle V as video data, and output the video data comprised of the successively captured frame images to the intersection lane identification apparatus  2 . Then, the data obtainer  30  cyclically receives the video data from the surrounding monitor  20  as the surrounding situation data. 
     The road center identifier  31  is configured to identify the location of the center of the current travel road of the vehicle V. Note that the center of the road is defined as an imaginary line of the current travel road, which is equidistant from both edges of the current travel road. The defined center of the current travel road is based on the above concept, which is different from the concept of a center line based on the traffic regulations, but the defined center of the road can be in agreement with the center line based on the traffic regulations. 
     Specifically, the road center identifier  31  is configured to identify, based on the video data obtained from at least one of the cameras, the left and right edges of the current travel road, and identify the location of an imaginary line that is equidistant from the detected left and right edges as the center of the current travel road. 
     If the road center identifier  31  cannot identify the left edge of the current travel road due to one or more other vehicles located on the left side of the vehicle V in a lateral direction that is perpendicular to the longitudinal direction of the current travel road to block the view from the vehicle V to the left edge of the current travel road, the road center identifier  31  can perform an estimation approach that 
     1. Counts the number of one or more other vehicles located on the left side of the vehicle V in the lateral direction to block the view from the vehicle V to the left edge of the vehicle V 
     2. Estimates, based on the counted number of one or more other vehicles, the minimum distance to the left edge of the current travel road from a predetermined reference point of the vehicle V 
     3. Identifies, based on the detected right edge and the estimated minimum distance to the left edge of the current travel road from the predetermined reference point of the vehicle V, the location of the current travel road of the vehicle V 
     Specifically, the road center identifier  31  can estimate the counted number of one or more other vehicles located on the left side of the vehicle V in the lateral direction which block the view from the vehicle V to the left edge of the current travel road as the number of one or more left-side lanes, and multiply the counted number by a predetermined width of one lane of the current travel road, such as 3.5 m, thus measuring the minimum distance from the predetermined reference point of the vehicle V to the left edge of the current travel road. Then, the road center identifier  31  can identify the location of the center of the current travel road in accordance with the detected right edge and the measured minimum distance from the predetermined reference point of the vehicle V to the left edge. 
     Similarly, if the road center identifier  31  cannot identify the right edge of the current travel road due to one or more other vehicles traveling on one or more right-side lanes of the current travel road, the road center identifier  31  can be configured to 
     1. Estimate the minimum distance from the predetermined reference point of the vehicle V to the right edge in the same manner as the measurement of the minimum distance from the predetermined reference point of vehicle V to the left edge 
     2. Identify, based on the detected left edge and the estimated minimum distance to the right edge of the current travel road from the predetermined reference point of vehicle V, the location of the center of the current travel road 
     If the road center identifier  31  cannot identify the left edge of the current travel road due to one or more other vehicles traveling on one or more left-side lanes of the current travel road, and cannot detect the right edge of the current travel road due to one or more other vehicles traveling on one or more right-side lanes of the current travel road, the road center identifier  31  can identify the location of the center of the current travel road in accordance with the estimated minimum distance from the predetermined reference point of the vehicle V to the left edge and the estimated minimum distance from the predetermined reference point of the vehicle V to the right edge. 
     The road center identifier  31  is further configured to output, to the lane identifier  32 , data indicative of the location of the center of the current travel road; this data indicative of the location of the center of the current travel road will be referred to as road center data. 
     That is, the configuration and functions of the road center identifier  31  are substantially identical to those of the road center identifier  14 . 
     The lane identifier  32  is configured to identify a lane where the vehicle V is traveling in accordance with the surrounding situation data obtained from the surrounding monitor  20  and the lane center data outputted from the road center identifier  31 . 
     Specifically, the lane identifier  32  is configured to obtain, based on the intersection center data, a deviated distance of the traveling position of the vehicle V from the center of the current travel road in the width direction of the current travel road. Then, the lane identifier  32  is configured to 
     1. Determine whether the obtained deviated distance is longer than or equal to a predetermined threshold distance of, for example, 3 meters 
     2. Identify that the vehicle V is located at a left turnable lane upon determining that the obtained deviated distance is longer than or equal to the predetermined threshold distance 
     3. Identify that the vehicle V is located at a right turnable lane upon determining that the obtained deviated distance is shorter than the predetermined threshold distance 
     Additionally, the lane identifier  32  is configured to detect, based on the surrounding situation data, a division center line of a traveling-directional road across the target intersection to accordingly obtain a minimum distance Z 1  of an extending line of the division center line from the center of the current travel road. Then, the lane identifier  32  is configured to determine whether the obtained minimum distance Z 1  is larger than or equal to a predetermined threshold length of, for example, 0.5 meters, and determine that the target intersection includes a right-turn-only lane upon determining that the obtained minimum distance Z 1  is larger than or equal to the predetermined threshold length. 
       FIG. 9  illustrates a target intersection IN 3 , whose situation is different from that of the target intersection IN 1 . Specifically, a typical intersection, which has a right-turn-only lane, is configured such that the right-turn-only lane is located to be adjacent to the center of the current travel road of the vehicle V, resulting in the division center line of the current travel road being deviated from the center of the current travel road. This therefore makes it possible for the lane identifier  32  to determine that the target intersection has a right-turn-only lane upon determining that the obtained minimum distance Z 1  is larger than or equal to the predetermined threshold length. 
     Additionally, the lane identifier  32  is configured to obtain, based on the surrounding situation data, a width of a crossing road constituting the target intersection and crossing to the current travel road, and determine whether the width of the crossing road is shorter than or equal to a predetermined threshold width of, for example, 5 meters. Specifically, the lane identifier  32  determines that the vehicle V is capable of only going straight ahead upon determining that the width of the crossing road is shorter than or equal to the predetermined threshold width. 
     Moreover, the lane identifier  32  is configured to determine, based on the surrounding situation data, whether there is a road across the target intersection along the traveling direction of the vehicle V, and determine that the vehicle V is capable of only turning right or left in the target intersection upon determining that there is not a road across the target intersection along the traveling direction of the vehicle V. 
     Next, the following describes, with reference to the flowchart of  FIG. 10 , the sequence of a lane identification routine periodically carried out by the load identifier  32  of the intersection lane identification apparatus  2 . One lane identification routine carried out by the intersection lane identification apparatus  2  will also be referred to as a cycle. 
     When starting the intersection lane identification routine, the intersection lane identification apparatus  2  serves as, for example, the data obtainer  30  to receive surrounding situation data monitored by and sent from the surrounding monitor  20  in step S 40 . 
     Next, the intersection lane identification apparatus  2  serves as, for example, the road center identifier  31  to perform a road center identification subroutine in step S 41 , which is the same as the road center identification subroutine illustrated in  FIG. 6 . 
     In response to the termination of the road center identification subroutine in S 41 , the intersection lane identification apparatus  2  serves as, for example, the lane identifier  32  obtains the width of the at least one other road crossing the current travel road of the vehicle V in accordance with the surrounding situation data obtained in step S 40  or the surrounding situation data currently obtained from the surrounding monitor  20  in step S 42 . Then, the lane identifier  32  determines whether the obtained width of the at least one other road crossing the current travel road is smaller than or equal to the predetermined threshold width in step S 42 . 
     Upon determining that the obtained width of the at least one other road crossing the current travel road is smaller than or equal to the predetermined threshold width (YES in step S 42 ), the lane identifier  32  determines that the at least one other road crossing the current travel road is a narrow road where it is difficult for vehicles to travel, thus determining that a lane where the vehicle V is traveling included in the current travel road is a straight only lane where the vehicle V is able to only go straight in step S 48 . The lane where the vehicle V is traveling will also be referred to as a current travel lane. Thereafter, the lane identifier  32  terminates lane identification routine. 
     Otherwise, when it is determined that the obtained width of the at least one other road crossing the current travel road is larger than or equal to the predetermined threshold width (NO in step S 42 ), the lane identification routine proceeds to step S 43 . 
     In step S 43 , the lane identifier  32  calculates, based on the road center data obtained by the road center identifier  31 , a minimum distance of the traveling position of the vehicle V from the center of the current travel road in the width direction of the current travel road. Then, the lane identifier  32  determines whether the obtained minimum distance is longer than or equal to the predetermined threshold distance of, for example, 3 meters in step S 44 . 
     Upon determining that the obtained minimum distance is longer than or equal to the predetermined threshold distance (YES in step S 44 ), the lane identifier  32  determines whether there is a road across the target intersection along the traveling direction of the vehicle V in step S 45 . 
     Upon determining that there is not a road across the target intersection along the traveling direction of the vehicle V (NO in step S 45 ), the lane identifier  32  determines that the current travel lane is a lane where the vehicle V is capable of only turning left in the target intersection in step S 49 . Thereafter, the lane identifier  32  terminates lane identification routine. 
     Otherwise, upon determining that there is a road across the target intersection along the traveling direction of the vehicle V (YES in step S 45 ), the lane identifier  32  determines that the current travel lane is a lane where the vehicle V is capable of going straight across the target intersection or turning left in the target intersection in step S 50 . Thereafter, the lane identifier  32  terminates lane identification routine. 
     On the other hand, upon determining that the obtained minimum distance is smaller than the predetermined threshold distance (NO in step S 44 ), the lane identifier  32  detects a division center line of a traveling-directional road across the target intersection in accordance with the surrounding situation data obtained in step S 40  or the surrounding situation data currently obtained from the surrounding monitor  20  to accordingly obtain the minimum distance Z 1  of the extending line of the division center line from the center of the current travel road in step S 46 . 
     Then, in step S 46 , the lane identifier  32  determines whether the obtained minimum distance Z 1  is larger than or equal to the predetermined threshold length of, for example, 0.5 meters. 
     Upon determining that the obtained minimum distance Z 1  is larger than or equal to the predetermined threshold length (YES in step S 46 ), the lane identifier  32  determines that the current travel lane is a right-turn-only lane where the vehicle V is capable of only turning right in the target intersection in step S 51 . Thereafter, the lane identifier  32  terminates lane identification routine. 
     Otherwise, upon determining that the obtained minimum distance Z 1  is smaller than the predetermined threshold length (NO in step S 46 ), the lane identifier  32  determines whether there is a road across the target intersection along the traveling direction of the vehicle V in step S 47 . 
     Upon determining that there is not a road across the target intersection along the traveling direction of the vehicle V (NO in step S 47 ), the lane identifier  32  determines that the current travel lane is a right-turn-only lane where the vehicle V is capable of only turning right in the target intersection in step S 51 . Thereafter, the lane identifier  32  terminates lane identification routine. 
     Otherwise, upon determining that there is a road across the target intersection along the traveling direction of the vehicle V (YES in step S 47 ), the lane identifier  32  determines that the current travel lane is a lane where the vehicle V is capable of going straight across the target intersection or turning right in the target intersection in step S 52 . Thereafter, the lane identifier  32  terminates lane identification routine. 
     As described above, the intersection lane identification apparatus  2  is configured to identify how the current travel lane of the vehicle V joins to the target intersection that constitutes a part of the intersection more easily based on the identified location of the center of the current travel road. 
     Modifications 
     At least part of all functions provided by the apparatus  1  or  2  can be implemented by at least one processor; the at least one processor can be comprised of 
     (1) The combination of at least one programmed processing unit, i.e. at least one programmed logic circuit, and at least one memory including software that causes the at least one programed logic circuit to implement all the functions 
     (2) At least one hardwired logic circuit that implements all the functions 
     (3) At least one hardwired-logic and programmed-logic hybrid circuit that implements all the functions 
     An intersection lane identification apparatus according to a first exemplary aspect of the second embodiment includes a data obtainer configured to obtain, from a surrounding monitor that monitors a surrounding situation around a vehicle traveling on a road, data indicative of the surrounding situation monitored by the surrounding monitor. The intersection lane identification apparatus includes a road center identifier configured to identify a location of a center of the road based on the data indicative of the surrounding situation around the vehicle, and a lane identifier. 
     The lane identifier is configured to
         (i) Obtain, based on the identified location of the center of the road, a minimum distance of a traveling position of the vehicle from the identified location of the center of the road   (ii) Determine whether the obtained minimum distance is longer than or equal to a predetermined threshold distance   (iii) Identify that the vehicle is located at a left turnable lane upon determining that the obtained minimum distance is longer than or equal to the predetermined threshold distance   (iv) Identify that the vehicle is located at a right turnable lane upon determining that the obtained minimum distance is shorter than the predetermined threshold distance       

     The lane identifier according to a second exemplary aspect of the second embodiment is configured to
         1. Detect, based on the data indicative of the surrounding situation around the vehicle, a division center line of a traveling directional road across the intersection   2. Obtain a deviation of the division center line from the identified location of the center of the road   3. Determine whether the obtained deviation is larger than or equal to a predetermined threshold length   4. Identify that the intersection has a right-turn-only lane upon determining that the obtained deviation is larger than or equal to the predetermined threshold length       

     The lane identifier according to a third exemplary aspect of the second embodiment is configured to
         (1) Detect, based on the data indicative of the surrounding situation around the vehicle, a width of a crossing road constituting the intersection and crossing to the road;   (2) Determine whether the width of the crossing road is shorter or equal to a predetermined threshold width; and   (3) Determine that the vehicle is capable of only going straight ahead upon determining that the width of the crossing road is shorter than or equal to the predetermined threshold width       

     The lane identifier according to a fourth exemplary aspect of the second embodiment is further configured to
         1. Determine, based on the data indicative of the surrounding situation around the vehicle, whether there is a road across the intersection along a traveling direction of the vehicle; and   2. Determine that the vehicle is capable of only turning right or left in the intersection upon determining that there is not a road across the target intersection along the traveling direction of the vehicle.       

     An intersection lane identification method according to a fifth exemplary aspect of the second embodiment includes
         1. Obtaining, from a surrounding monitor that monitors a surrounding situation around a vehicle traveling on a road, data indicative of the surrounding situation monitored by the surrounding monitor   2. Identifying a location of a center of the road based on the data indicative of the surrounding situation around the vehicle   3. Obtaining, based on the identified location of the center of the road, a minimum distance of a traveling position of the vehicle from the identified location of the center of the road   4. Determining whether the obtained minimum distance is longer than or equal to a predetermined threshold distance   5. Identifying that the vehicle is located at a left turnable lane upon determining that the obtained minimum distance is longer than or equal to the predetermined threshold distance   6. Identifying that the vehicle is located at a right turnable lane upon determining that the obtained minimum distance is shorter than the predetermined threshold distance       

     A computer-readable program product according to a sixth exemplary aspect of the second embodiment includes a non-transitory computer-readable storage medium, and a set of computer program instructions stored in the computer-readable storage medium, the instructions causing a computer to
         1. Obtain, from a surrounding monitor that monitors a surrounding situation around a vehicle traveling on a road, data indicative of the surrounding situation monitored by the surrounding monitor   2. Identify a location of a center of the road based on the data indicative of the surrounding situation around the vehicle   3. Obtain, based on the identified location of the center of the road, a minimum distance of a traveling position of the vehicle from the identified location of the center of the road   4. Determine whether the obtained minimum distance is longer than or equal to a predetermined threshold distance   5. Identify that the vehicle is located at a left turnable lane upon determining that the obtained minimum distance is longer than or equal to the predetermined threshold distance   6. Identify that the vehicle is located at a right turnable lane upon determining that the obtained minimum distance is shorter than the predetermined threshold distance       

     While illustrative embodiments of the present disclosure have been described herein, the present disclosure is not limited to the embodiments and their modifications described herein, but includes any and all embodiments having modifications, omissions, combinations (e.g., of aspects across various embodiments), adaptations and/or alterations as would be appreciated by those in the art based on the present disclosure within the scope of the present disclosure. 
     For example, each of the technical features described in each embodiment and its modifications can be replaced with a known structure having the same function as the corresponding technical feature. Each of the technical features described in each embodiment and its modifications can also be combined with at least one of the other technical features. At least one of the technical features described in each embodiment and its modifications can further be eliminated unless the at least one of the technical features is described as an essential element in the present specification. 
     The functions of each of the apparatuses  1  and  2  according to the first and second embodiments can be implemented by various embodiments; the various embodiments include apparatuses and systems, programs for serving a computer as the functions, storage media, such as non-transitory media, storing the programs, and autonomous driving control methods.