Automated estimation of average stopped delay at signalized intersections

• US 20050105773A1
• Filed: 09/23/2004
• Published: 05/19/2005
• Est. Priority Date: 09/24/2003
• Status: Active Grant

• Current Assignee: Brigham Young University (The Church of Jesus Christ of Latter-Day Saints)
• Original Assignee: Brigham Young University (The Church of Jesus Christ of Latter-Day Saints)
• Inventors: Saito, Mitsuru, Hereth, William R. Jr., Zundel, Alan
• Granted Patent: US 7,747,041 B2
• Time in Patent Office: Days
• US Class Current: 382/104
• CPC Class Codes: G08G 1/0104 Measuring and analyzing of parameters relative to traffic conditions
• CPC Class Codes: G08G 1/04 using optical or ultrasonic detectors

Abstract

A system and method for automated estimation of average stopped delay at signalized intersections using digitized still image analysis of actual traffic flow is disclosed. The system and method includes digitizing images of an intersection and creating a line of pixels that acts as a virtual sensor in a traffic lane of interest. Background intensities of the pixel line on the traffic lane without vehicles are compared to pixel intensities on images with traffic. Once vehicles are identified, the present method and system provides for three alternative embodiments of methods for determining the stopped delay for an entire image or for a particular vehicle. Once the stopped delay for all relevant images or for all relevant vehicles is determined, the average stopped delay per vehicle is estimated.

Claims

1. A method for estimating an average stopped delay per vehicle at a signalized intersection, comprising:

initializing background intensities of a line of pixels in a digital image of an actual traffic lane without vehicles;

identifying vehicle location through measuring intensities of the line of pixels in another digital image of the actual traffic lane with vehicles;

calculating a stopped delay for each vehicle or digital image with vehicles; and

calculating the average stopped delay per vehicle.

2. The method of claim 1, wherein initializing background intensities comprises:

digitizing an image of the actual traffic lane without vehicles;

establishing the line of pixels on the digital image of the traffic lane without vehicles, such that the line of pixels extends upstream into the traffic lane;

assigning a length value to each pixel in the line of pixels; and

reading and storing the intensities of each pixel in the line of pixels.

3. The method of claim 2, wherein identifying vehicle location comprises:

measuring the intensities of each pixel in the line of pixels on the digital image of the actual traffic lane with vehicles;

calculating the difference between the pixel intensities of the line of pixels on the digital image of the traffic lane without vehicles and the pixel intensities of the line of pixels on the digital image of the traffic lane with vehicles; and

identifying a group of consecutive pixels where the difference between pixel intensity is outside of a specified threshold.

4. The method of claim 1, wherein calculating the stopped delay for each digital image with vehicles comprises:

calculating a distance between vehicles on the digital image with vehicles;

determining whether a vehicle is stopped if the distance between vehicles is below a specified gap distance;

adding together a total number of vehicles stopped in the digital image with vehicles; and

multiplying the total number of vehicles stopped by a time interval between each digital image with vehicles.

5. The method of claim 4, wherein calculating the stopped delay for each digital image with vehicles further comprises:

determining whether a length of the vehicle is greater than a specified maximum length; and

dividing the vehicle into multiple stopped vehicles based on a specified average vehicle length if the length of the vehicle is greater than the specified maximum length.

6. The method of claim 4, wherein calculating the stopped delay for each digital image with vehicles further comprises:

identifying a vehicle with a length greater than a specified maximum length;

determining a number and length of vehicles in a previous frame in a substantially similar location as the vehicle with the length greater than the specified maximum length; and

dividing the vehicle with the length greater than the specified maximum length into multiple stopped vehicles based on the number and length of vehicles in the previous frame in the substantially similar location.

7. The method of claim 1, wherein calculating the stopped delay for each vehicle comprises:

monitoring a location of a front and rear of a vehicle between consecutive frames;

calculating a speed and future position of the vehicle;

determining the vehicle is stopped if the speed is below a specified stopping speed; and

calculating a total stopped delay for the vehicle over consecutive frames.

8. The method of claim 7, wherein calculating the stopped delay for each vehicle further comprises:

determining whether the vehicle overlaps another vehicle; and

maintaining a division between the vehicles through a ratio of vehicle lengths before the vehicles were viewed as overlapping.

9. The method of claim 7, wherein calculating the stopped delay for each vehicle further comprises:

determining if the vehicle becomes longer than an allowed vehicle length growth percentage when entering the intersection; and

separating the rear of the vehicle from a front of a following vehicle such that the vehicle does not become longer than the allowed vehicle length growth percentage.

10. The method of claim 1, wherein calculating the average stopped delay per vehicle comprises:

calculating a total stopped delay of all digital images with vehicles or a total stopped delay of all vehicles; and

dividing the total stopped delay by a total number of vehicles that entered the intersection.

11. A computing device configured for estimating an average stopped delay per vehicle at a signalized intersection, the computing device comprising:

a processor;

memory in electronic communication with the processor; and

executable instructions executable by the processor, wherein the executable instructions are configured to implement a method comprising;

initializing background intensities of a line of pixels in a digital image of an actual traffic lane without vehicles;

identifying vehicle location by measuring intensities of the line of pixels in another digital image of the actual traffic lane with vehicles;

calculating a stopped delay for each vehicle or digital image with vehicles; and

calculating the average stopped delay per vehicle.

12. The computing device of claim 11, wherein initializing background intensities comprises:

digitizing an image of the actual traffic lane without vehicles;

establishing the line of pixels on the digital image of the traffic lane without vehicles, such that the line of pixels extends upstream into the traffic lane;

assigning a length value to each pixel in the line of pixels; and

reading and storing the intensities of each pixel in the line of pixels.

13. The computing device of claim 12, wherein identifying vehicle location comprises:

measuring the intensities of each pixel in the line of pixels on the digital image of the actual traffic lane with vehicles;

calculating the difference between the pixel intensities of the line of pixels on the digital image of the traffic lane without vehicles and the pixel intensities of the line of pixels on the digital image of the traffic lane with vehicles; and

identifying a group of consecutive pixels where the difference between pixel intensity is outside of a specified threshold.

14. The computing device of claim 11, wherein calculating the stopped delay for each digital image with vehicles comprises:

calculating a distance between vehicles on the digital image with vehicles;

determining whether a vehicle is stopped if the distance between vehicles is below a specified gap distance;

adding together a total number of vehicles stopped in the digital image with vehicles; and

multiplying the total number of vehicles stopped by a time interval between each digital image with vehicles.

15. The computing device of claim 14, wherein calculating the stopped delay for each digital image with vehicles further comprises:

determining whether a length of the vehicle is greater than a specified maximum length; and

dividing the vehicle into multiple stopped vehicles based on a specified average vehicle length if the length of the vehicle is greater than the specified maximum length.

16. The computing device of claim 14, wherein calculating the stopped delay for each digital image with vehicles further comprises:

identifying a vehicle with a length greater than a specified maximum length;

determining a number and length of vehicles in a previous frame in a substantially similar location as the vehicle with the length greater than the specified maximum length; and

dividing the vehicle with the length greater than the specified maximum length into multiple stopped vehicles based on the number and length of vehicles in the previous frame in the substantially similar location.

17. The computing device of claim 11, wherein calculating the stopped delay for each vehicle comprises:

monitoring a location of a front and rear of a vehicle between consecutive frames;

calculating a speed and future position of the vehicle;

determining the vehicle is stopped if the speed is below a specified stopping speed; and

calculating a total stopped delay for the vehicle over consecutive frames.

18. The computing device of claim 17, wherein calculating the stopped delay for each vehicle further comprises:

determining whether the vehicle overlaps another vehicle; and

maintaining a division between the vehicles through a ratio of vehicle lengths before the vehicles were viewed as overlapping.

19. The computing device of claim 17, wherein calculating the stopped delay for each vehicle further comprises:

determining if the vehicle becomes longer than an allowed vehicle length growth percentage when entering the intersection; and

separating the rear of the vehicle from a front of a following vehicle such that the vehicle does not become longer than the allowed vehicle length growth percentage.

20. The computing device of claim 11, wherein calculating the average stopped delay per vehicle comprises:

calculating a total stopped delay of all digital images with vehicles or a total stopped delay of all vehicles; and

dividing the total stopped delay by a total number of vehicles that entered the intersection.

21. A computer-readable medium for storing program data, wherein the program data comprises executable instructions for implementing a method in a computing device for estimating an average stopped delay per vehicle at a signalized intersection, the method comprising:

initializing background intensities of a line of pixels in a digital image of an actual traffic lane without vehicles;

identifying vehicle location by measuring intensities of the line of pixels in another digital image of the actual traffic lane with vehicles;

calculating a stopped delay for each vehicle or digital image with vehicles; and

calculating the average stopped delay per vehicle.

22. The computer-readable medium of claim 21, wherein initializing background intensities comprises:

digitizing an image of the actual traffic lane without vehicles;

establishing the line of pixels on the digital image of the traffic lane without vehicles, such that the line of pixels extends upstream into the traffic lane;

assigning a length value to each pixel in the line of pixels; and

reading and storing the intensities of each pixel in the line of pixels.

23. The computer-readable medium of claim 22, wherein identifying vehicle location comprises:

measuring the intensities of each pixel in the line of pixels on the digital image of the actual traffic lane with vehicles;

calculating the difference between the pixel intensities of the line of pixels on the digital image of the traffic lane without vehicles and the pixel intensities of the line of pixels on the digital image of the traffic lane with vehicles; and

identifying a group of consecutive pixels where the difference between pixel intensity is outside of a specified threshold.

24. The computer-readable medium of claim 21, wherein calculating the stopped delay for each digital image with vehicles comprises:

calculating a distance between vehicles on the digital image with vehicles;

determining whether a vehicle is stopped if the distance between vehicles is below a specified gap distance;

adding together a total number of vehicles stopped in the digital image with vehicles; and

multiplying the total number of vehicles stopped by a time interval between each digital image with vehicles.

25. The computer-readable medium of claim 24, wherein calculating the stopped delay for each digital image with vehicles further comprises:

determining whether a length of the vehicle is greater than a specified maximum length; and

dividing the vehicle into multiple stopped vehicles based on a specified average vehicle length if the length of the vehicle is greater than the specified maximum length.

26. The computer-readable medium of claim 24, wherein calculating the stopped delay for each digital image with vehicles further comprises:

identifying a vehicle with a length greater than a specified maximum length;

determining a number and length of vehicles in a previous frame in a substantially similar location as the vehicle with the length greater than the specified maximum length; and

dividing the vehicle with the length greater than the specified maximum length into multiple stopped vehicles based on the number and length of vehicles in the previous frame in the substantially similar location.

27. The computer-readable medium of claim 21, wherein calculating the stopped delay for each vehicle comprises:

monitoring a location of a front and rear of a vehicle between consecutive frames;

calculating a speed and future position of the vehicle;

determining the vehicle is stopped if the speed is below a specified stopping speed; and

calculating a total stopped delay for the vehicle over consecutive frames.

28. The computer-readable medium of claim 27, wherein calculating the stopped delay for each vehicle further comprises:

determining whether the vehicle overlaps another vehicle; and

maintaining a division between the vehicles through a ratio of vehicle lengths before the vehicles were viewed as overlapping.

29. The computer-readable medium of claim 27, wherein calculating the stopped delay for each vehicle further comprises:

determining if the vehicle becomes longer than an allowed vehicle length growth percentage when entering the intersection; and

separating the rear of the vehicle from a front of a following vehicle such that the vehicle does not become longer than the allowed vehicle length growth percentage.

30. The computer-readable medium of claim 21, wherein calculating the average stopped delay per vehicle comprises:

calculating a total stopped delay of all digital images with vehicles or a total stopped delay of all vehicles; and

dividing the total stopped delay by a total number of vehicles that entered the intersection.