Traffic flow monitor apparatus

• US 5,999,877 A
• Filed: 04/30/1997
• Issued: 12/07/1999
• Est. Priority Date: 05/15/1996
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Satoh, Yoshiyuki, Takahashi, Kazuya, Kitamura, Tadaaki
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Hernandez, Olga
• Application Number:
  US08/841,402
• Time in Patent Office: 951 Days
• Field of Search: 701/117, 340/905, 340/916, 340/942, 340/995, 364/438, 364/436, 348/149
• US Class Current: 701/117
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/30236 Traffic on road, railway or crossing
• CPC Class Codes: G06T 7/248 involving reference images or patches
• CPC Class Codes: G06V 20/54 of traffic, e.g. cars on the road, trains or boats
• CPC Class Codes: G08G 1/01 Detecting movement of traffic to be counted or controlled G08G1/07 - G08G1/14 take precedence
• CPC Class Codes: G08G 1/04 using optical or ultrasonic detectors

Abstract

A traffic flow monitor apparatus which can monitor a traffic flow at high precision over a wide range from the position near a TV camera to the distant position regardless of traffic conditions. An image analysis area crossing a road of an overlooked road image received every predetermined cycle is analyzed, the characteristic portion of the front (rear) portion of the vehicle is registered as a template, the vehicle is tracked by a pattern-matching process while updating the template, and the size of the template is reduced (enlarge) depending on a change in apparent width of a lane during template updating. Since the characteristic portion of the front (rear) portion of the vehicle is registered, and the vehicle is tracked by the pattern-matching process, no reference image of a road portion on which no vehicle exists is required, and influence of approaching or overlapping of another vehicle can be reduced. A traffic flow can be monitored at high precision regardless of deserted traffic or crowded traffic. Since the size is reduced (enlarged) during template updating, a vehicle can be stably tracked by using a template having an appropriate size in the range from the near position to the distant position.

Claims

1. A traffic flow monitor apparatus comprising:

image-pickup means for photographing a road in an overlooking manner;

means for analyzing a luminance distribution of an image analysis area crossing a road of overlooked road images received every predetermined cycle;

means for performing template registration to a luminance pattern of a part or whole of a vehicle in the image analysis area as a characteristic portion of the vehicle;

tracking means for calculating the degree of similarity between the template and the luminance pattern of the overlooked road image by correlation calculation to track a luminance pattern having a high degree of similarity as a vehicle which is subjected to template registration; and

monitor means for monitoring zigzag running, a sudden change in speed, excessively low-speed running and excessively high-speed running, and on the basis of a change in vehicle position in the overlooked road images received every predetermined cycle.

2. A traffic flow monitor apparatus according to claim 1, comprising

means for calculating, on the basis of a movement distance of a vehicle moving between two images having a time difference not shorter than a predetermined period of time of the overlooked road images received every predetermined cycle, an instantaneous speed of the vehicle;

wherein said monitor means is monitor means for monitoring a suddenly change in speed, excessively low-speed running, and excessively high-speed running, on the basis of the instantaneous speed.

3. A traffic flow monitor apparatus according to claim 1

wherein said means for performing template registration to the characteristic portion of the vehicle has a plurality of templates corresponding to the number of vehicles to be monitored;

and

said tracking means is tracking means for s imultaneously tracking a plurality of vehicles which differently move by using the plurality of templates.

4. A traffic flow monitor apparatus according to claim 3,

wherein said tracking means has a tracking management table for each template, independently registers templates in columns of each tracking management table, independently adds or erases information to independently track different movements of the respective vehicles.

5. A traffic flow monitor apparatus according to claim 1, comprising:

means for holding a lane division line as a primary approximate expression or a polynomial approximate expression, means for calculating a lane to which the vehicle belongs by using a vehicle position in the overlooked road image received every predetermined cycle and the primary approximate expression or the polynomial approximate expression, and means for determining a change in lane by the change of the belonging lane.

6. A traffic flow monitor apparatus according to claim 1, comprising:

means for calculating a lane width on a screen at a position where a template is subjected to initial registration by using the primary approximate expression or the polynomial approximate expression to define the lane width as a reference lane width, calculating a lane width on a screen at a position after the template has moved by using the primary approximate expression or the polynomial approximate expression to define the lane width as a detection position lane width, and enlarging or reducing the size of the template in the initial registration such that a ratio of the detection position lane width to the reference lane width is equal to a ratio of the size of the template in initial registration to the size of the template after the template has moved, thereby determining the size of the template after the template has moved.

7. A traffic flow monitor apparatus according to claim 1, comprising:

means for forming a measurement zone crossing the road of the overlooked road images received every predetermined cycle, counting vehicles passing through the measurement zone for each lane, and measuring an average speed of each vehicle passing through the measurement zone.

8. A traffic flow monitor apparatus according to claim 1, comprising:

means for arranging at least one road surface luminance pattern collation area for each lane on a road surface of the overlooked road images received every predetermined cycle, evaluating the degree of similarity between the road surface luminance pattern of the collation area which is held as a template in advance and an actual luminance pattern on the basis of correlation calculation between the road surface luminance pattern and the actual luminance pattern, determining that no vehicle exist in the collation area when the degree of similarity is high, and determining that a vehicle exists in the collation area when the degree of similarity is low.

9. A traffic flow monitor apparatus according to claim 8, comprising:

means for measuring the length of the vehicle on the basis of relative positions of the collation area and the front and rear portions of the vehicle when the vehicle passes through the collation area.

11. A traffic flow monitor system in which a traffic flow monitor apparatus according to claim 1 receives the overlooked road image through a video distributor to process the image, stores a traffic event or a traffic index such as an instantaneous speed or change in lane in a traffic event accumulation means, transmits the traffic event or the traffic index to a control room through traffic event communication means, and, on the control room side, video overlapping means overlaps the traffic event obtained through said traffic event communication means and an overlooked road image obtained through said video distributor to display the resultant image on display means,

wherein said traffic flow monitor apparatus monitors an instantaneous speed and a change in existence lane for each vehicle and transmits data such as detection time, detection position, and contents of a change in lane according to avoidance running or zigzag running of the vehicle and excessively low-speed or high-speed running of the vehicle to said control room to accumulate the data in a storage unit in said control room.

12. A traffic flow monitor system according to claim 11,

wherein said image-pickup means is a color TV camera;

said traffic flow monitor apparatus receives the overlooked road image as a monochrome image; and

said display means in said control room is means for overlap-displaying a color image from said image-pickup means and monochrome monitor data generated by said traffic flow monitor apparatus on the basis of the monochrome image.

10. A traffic flow monitor apparatus comprising a keyboard, a man-machine interface such as a display unit, a CPU having a main memory, image input means which receives an overlooked road image from image-pickup means under the control of said CPU to convert the image into a digital value, image processing means for processing the converted digital image under the control of said CPU, and an image memory for the digital image,

wherein said image processing means is means for analyzing a luminance distribution in an image analysis area crossing a road of overlooked road images received every predetermined cycle, and

said CPU serves as means for performing template registration to a luminance pattern of a part or whole of a vehicle in the image analysis area as a characteristic portion of the vehicle;

tracking means for recognizing at least initial registration coordinates, initial registration time, latest image input time, a vehicle existence position in the latest image, a lane number in the vehicle in the latest image exists, time at which images are input in a plurality of cycles, a position of a vehicle pattern in the image input in the plurality of cycles for each vehicle and calculating the degree of similarity between the template and the luminance pattern of the overlooked road image by correlation calculation to track a luminance pattern having a high degree of similarity as a vehicle which is subjected to template registration; and

monitor means for monitoring abnormal running such as zigzag running, a suddenly change in speed, excessively low-speed running, or excessively high-speed running, on the basis of a change in vehicle position in the overlooked road images received every predetermined cycle, recording time and position of occurrence of abnormal running and contents of the abnormal running, and informing of the time, position, and contents of the abnormal running.

13. A traffic flow monitor apparatus comprising:

means for digitally processing a road image received every predetermined cycle to track passing vehicles;

means for measuring an instantaneous speed of the passing vehicles;

means for dividing the road image into small areas by lanes and distances and calculating a small-area speed representing average speeds of the passing vehicles for each small area; and

means for determining the presence/absence of traffic jam and/or the degree of traffic jam for each small area on the basis of the magnitude of the small-area speed.

14. A traffic flow monitor apparatus according to claim 13,

wherein said passing vehicle tracking means is means for tracking a characteristic portion such as a portion having a large change in luminance of the passing vehicle by shading pattern matching.

15. A traffic flow monitor apparatus according to claim 13,

wherein said passing vehicle tracking means is means, having a plurality of templates, for simultaneously tracking a plurality of vehicles which differently move by using the plurality of templates.

16. A traffic flow monitor apparatus according to claim 13,

wherein said instantaneous speed measurement means is means for calculating an instantaneous speed of the vehicle on the basis of the vehicle moves between two images, having time different not longer than a predetermined period of time, of the road images received every predetermined cycles.

17. A traffic flow monitor apparatus according to claim 13,

wherein said small-area speed calculation means is means for holding a line division line as a primary approximate expression or a polynomial approximate expression, applying the primary approximate expression or the polynomial approximate expression to a vehicle position in the road images received every predetermined cycles, and calculating a lane to which the vehicle belongs.

18. A traffic flow monitor apparatus according to claim 13,

wherein tracking management tables are arranged for templates, the templates are independently registered on columns of the tracking management tables, information is added or erased from each column, and different movements of respective vehicles are independently monitored.

19. A traffic flow monitor apparatus according to claim 18,

wherein said passing vehicle tracking means is means for calculating a lane width on a screen at a position where a template is subjected to initial registration by using the primary approximate expression or the polynomial approximate expression to define the lane width as a reference lane width, calculating a lane width on a screen at a position after the template has moved by using the primary approximate expression or the polynomial approximate expression to define the lane width as a detection position lane width, enlarging or reducing the size of the template in the initial registration such that a ratio of the detection position lane width to the reference lane width is equal to a ratio of the size of the template in initial registration to the size of the template after the template has moved, thereby determining the size of the template after the template has moved.

20. A traffic flow monitor apparatus according to claim 13,

wherein said traffic jam determination means is means for calculating an average value of instantaneous speeds of all vehicles existing in the small area within a predetermined period of time to define the average value as a small-area speed, and determining the presence/absence of traffic jam or the degree of traffic jam for each small area on the basis of the magnitude of the small-area speed.

21. A traffic flow monitor apparatus according to claim 13,

wherein said traffic jam determination means is means for performing a smoothing process to the instantaneous speeds of vehicles existing in the small area within the predetermined period of time by using a filter, calculating an average value to define the average value as a small-area speed, and determining the presence/absence of traffic jam or the degree of traffic jam for each small area on the basis of the magnitude of the small-area speed.

22. A traffic flow monitor apparatus according to claim 20,

wherein said traffic jam determination means is means for calculating a weighting average value for giving a weight which is proportional to the newness of measurement time to the instantaneous speed to define the average value as a small-area speed, and determining the presence/absence of traffic jam or the degree of traffic jam for each small area on the basis of the magnitude of the small-area speed.

23. A traffic flow monitor apparatus according to claim 13,

wherein said traffic jam determination means is means for, when areas which are determined as traffic jam areas with respect to lanes are adjacent to each other, measuring the length of the connected traffic jam areas to define the length as the length of traffic jam.

24. A traffic flow monitor apparatus comprising a keyboard, a man-machine interface such as a display unit, a CPU having a main memory, image input means which receives an overlooked road image from image-pickup means under the control of said CPU to convert the image into a digital value, image processing means for processing the converted digital image under the control of said CPU, and an image memory for the digital image,

wherein said image processing means is means for arranging at least one image analysis area crossing a road of the road image received every predetermined cycle, and analyzing a luminance distribution in the image analysis area, and

said CPU serves as means for performing template registration to a luminance pattern of a front portion or a rear portion of a vehicle in the image analysis area or a luminance pattern of a part or whole of the vehicle in the image analysis area as a characteristic portion of the vehicle;

passing vehicle tracking means for searching the vehicle pattern from an image received in a next cycle by a pattern matching process by using the template, updating the vehicle pattern as a new template, and recognizing at least initial registration coordinates, initial registration time, latest image input time, a vehicle existence position in the latest image, a lane number in which the vehicle in the latest image exists, time at which images are input in a plurality of cycles, a position of a vehicle pattern in the image input in the plurality of cycles for each vehicle;

instantaneous speed measurement means for calculating an instantaneous speed of each vehicle; and

means for arranging small areas divided by lanes and distances from a camera in the road, smoothing instantaneous speeds of vehicles existing in the small areas within a predetermined period of time by using a filter, calculating a weighted means value of loads which are proportional to the newness of the instantaneous speeds according to measurement time of the instantaneous speeds as small-area speeds of the small areas, and determining the presence/absence of traffic jam in each small area on the basis of the magnitude of the small-area speeds.

25. A traffic flow monitor apparatus according to claim 24,

wherein said display unit is means for displaying the arrangement of the small areas to overlap the arrangement and the road image and a schematic view, and changing a small area portion determined as a small area portion having traffic jam in luminance or color to display a traffic jam length or a traffic jam end.

26. A traffic flow monitor apparatus comprising:

template registration means for holding a luminance pattern of a front portion or a rear portion of a vehicle existing in road images received by image-pickup means every predetermined cycle as a template of the vehicle;

tracking means for performing a pattern matching process to the template and the luminance pattern to track the vehicle;

instantaneous speed measurement means for measuring an instantaneous speed of the vehicle on the basis of a reception interval between the road images and a movement distance of the vehicle between the road images; and

overlapping measurement correction means for, when at least two vehicles pass, calculating a passing time difference and a speed difference between the two vehicles, determining that different portions of one vehicle are tracked by a plurality of templates when the passing time difference is not larger than a predetermined time difference and when the speed difference is not smaller than a predetermined speed difference, and making only one template related to the vehicle valid and the other templates invalid.

27. A traffic flow monitor apparatus according to claim 26,

wherein said overlapping measurement correction means is means for making, of the plurality of templates, only a template in which the instantaneous speed is the lowest speed valid, and the other templates invalid.

28. A traffic flow monitor apparatus according to claim 26,

wherein the predetermined time difference and the predetermined speed difference are proportional to the instantaneous speed.

29. A traffic flow monitor apparatus according to claim 26, comprising:

means for arranging a belt-like measurement zone crossing a road of the overlooked road image and counting vehicles for each lane to which the vehicle in tracking belongs when the vehicle passes through the measurement zone;

means for measuring a zone speed of the vehicle on the basis of a difference between time at which the vehicle flows into the measurement zone and time at which the vehicle flows our of the measurement zone;

a buffer for recording flow-out times and zone speeds of the vehicle in order of flowing of the vehicle into a lane in which the vehicle flows out of the measurement zone;

means for recording, in said buffer, the flow-out time and zone speed of the vehicle, and a difference between flow-in time of a vehicle which is previously recorded by one in the same lane as that of the above vehicle and flow-out time of the vehicle as a "time difference"; and

means for recording, in said buffer, a difference between the zone speed of the vehicle and a zone speed of a vehicle which is previously recorded by one in the same lane as that of the above vehicle as a "speed difference".

30. A traffic flow monitor apparatus according to claim 29,

wherein the flow-out time and zone speed of the vehicle, a time difference, a speed difference, and a 1-bit invalid flag are stored in said buffer;

and

the invalid flag is turned on when the time difference is small and the speed difference is large, and the invalid flag is turned off except when the time difference is small and the speed difference is large.

31. A traffic flow monitor apparatus according to claim 29, comprising:

means for erasing vehicle information recorded on said buffer in order of oldness, counting passing vehicles, recording the number of passing vehicles and the zone speed on a recording unit, and/or transmitting the number of passing vehicles and the zone speed to a control room.

32. A traffic flow monitor apparatus according to claim 29, comprising:

means for, of vehicles having the small time difference and the large speed difference, making only a vehicle having the lowest zone speed valid, and making the other vehicles invalid to except the other vehicles from measurement targets.

33. A traffic flow monitor apparatus according to claim 30, comprising:

means for calculating passing vehicles leaving from a near position on the overlooked road image except for a vehicle preceding a vehicle having the invalid flag which is ON in said buffer, recording the number of passing vehicles and the zone speed on said recording unit, and/or transmitting the number of passing vehicles and the zone speed to said control room.

34. A traffic flow monitor apparatus according to claim 30, comprising:

means for calculating passing vehicles approaching a near position on the overlooked road image except for a vehicle having the invalid flag which is ON in said buffer, recording the number of passing vehicles and the zone speed on said recording unit, and/or transmitting the number of passing vehicles and the zone speed to said control room.

35. A traffic flow monitor apparatus according to claim 26, comprising:

means for recording a lane number to which the vehicle belongs during the vehicle tracking on the tracking management table;

means for comparing a past belonging lane number and a present belonging lane number with each other;

means for determining that a change in lane is made when the lane numbers are different from each other;

means for determining a low-speed running vehicle when the instantaneous speed obtained by said instantaneous speed measurement means is not higher than a predetermined speed; and

means for determining an avoidance-running vehicle when a low-speed running vehicle makes a change in line.