Automated estimation of average stopped delay at signalized intersections

• US 7,747,041 B2
• Filed: 09/23/2004
• Issued: 06/29/2010
• Est. Priority Date: 09/24/2003
• Status: Expired due to Fees

• 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
• Primary Examiner(s): Bella; Matthew C
• Assistant Examiner(s): MACKOWEY, ANTHONY M
• Application Number:
  US10/948,104
• Publication Number:
  US 20050105773A1
• Time in Patent Office: 2,105 Days
• Field of Search: 382/103, 382/104, 382/107, 340/937, 348/148, 348/149, 701/117, 701/118, 701/119
• 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 background frame comprising a digital image of an actual traffic lane without vehicles, wherein the line of pixels extends along a path that vehicles travel down the traffic lane and wherein the line of pixels has a length that is sufficient to extend along a length of a plurality of vehicles within the traffic lane;

identifying vehicle location through measuring differences between pixel intensity values along the line of pixels between the background frame and another digital image of the actual traffic lane with vehicles;

calculating a stopped delay for each vehicle; and

calculating the average stopped delay per vehicle;

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

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 average stopped delay per vehicle comprises:

calculating a total stopped delay of all vehicles; and

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

5. 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 background frame comprising a digital image of an actual traffic lane without vehicles, wherein the line of pixels extends along a path that vehicles travel down the traffic lane and wherein the line of pixels has a length that is sufficient to extend along a length of a plurality of vehicles within the traffic lane;

identifying vehicle location through measuring differences between pixel intensity values along the line of pixels between the background frame and another digital image of the actual traffic lane with vehicles;

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

calculating the average stopped delay per vehicle;

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, determining whether a length of the vehicle is greater than a specified maximum length, 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, 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.

6. The method of claim 5, wherein calculating the average stopped delay per vehicle comprises:

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

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

7. 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 background frame comprising a digital image of an actual traffic lane without vehicles, wherein the line of pixels extends along a path that vehicles travel down the traffic lane and wherein the line of pixels has a length that is sufficient to extend along a length of a plurality of vehicles within the traffic lane;

identifying vehicle location through measuring differences between pixel intensity values along the line of pixels between the background frame and another digital image of the actual traffic lane with vehicles;

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

calculating the average stopped delay per vehicle;

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, 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, 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, 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.

8. The method of claim 7, wherein calculating the average stopped delay per vehicle comprises:

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

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

9. 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 background frame comprising a digital image of an actual traffic lane without vehicles, wherein the line of pixels extends along a path that vehicles travel down the traffic lane and wherein the line of pixels has a length that is sufficient to extend along a length of a plurality of vehicles within the traffic lane;

identifying vehicle location through measuring differences between pixel intensity values along the line of pixels between the background frame and another digital image of the actual traffic lane with vehicles;

calculating a stopped delay for each vehicle; and

calculating the average stopped delay per vehicle;

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, calculating a total stopped delay for the vehicle over consecutive frames, 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 9, wherein calculating the average stopped delay per vehicle comprises:

calculating 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; and

memory in electronic communication with the processor, wherein the memory has stored thereon executable instructions executable by the processor to;

initialize background intensities of a line of pixels in a background frame comprising a digital image of an actual traffic lane without vehicles, wherein the line of pixels extends along a path that vehicles travel down the traffic lane and wherein the line of pixels has a length that is sufficient to extend along a length of a plurality of vehicles within the traffic lane;

identify vehicle location through measuring differences between pixel intensity values along the line of pixels between the background frame and another digital image of the actual traffic lane with vehicles;

calculate a stopped delay for each vehicle; and

calculate the average stopped delay per vehicle;

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

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 average stopped delay per vehicle comprises:

calculating a total stopped delay of all vehicles; and

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

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

a processor; and

memory in electronic communication with the processor, wherein the memory has stored thereon executable instructions executable by the processor to;

initialize background intensities of a line of pixels in a background frame comprising a digital image of an actual traffic lane without vehicles, wherein the line of pixels extends along a path that vehicles travel down the traffic lane and wherein the line of pixels has a length that is sufficient to extend along a length of a plurality of vehicles within the traffic lane;

identify vehicle location through measuring differences between pixel intensity values along the line of pixels between the background frame and another digital image of the actual traffic lane with vehicles;

calculate a stopped delay for each digital image with vehicles; and

calculate the average stopped delay per vehicle;

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, determining whether a length of the vehicle is greater than a specified maximum length, 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, 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.

16. The computing device of claim 15, wherein calculating the average stopped delay per vehicle comprises:

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

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

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

a processor; and

memory in electronic communication with the processor, wherein the memory has stored thereon executable instructions executable by the processor to;

initialize background intensities of a line of pixels in a background frame comprising a digital image of an actual traffic lane without vehicles, wherein the line of pixels extends along a path that vehicles travel down the traffic lane and wherein the line of pixels has a length that is sufficient to extend along a length of a plurality of vehicles within the traffic lane;

identify vehicle location through measuring differences between pixel intensity values along the line of pixels between the background frame and another digital image of the actual traffic lane with vehicles;

calculate a stopped delay for each digital image with vehicles; and

calculate the average stopped delay per vehicle;

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, 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, 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, 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.

18. The computing device of claim 17, wherein calculating the average stopped delay per vehicle comprises:

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

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

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

a processor; and

memory in electronic communication with the processor, wherein the memory has stored thereon executable instructions executable by the processor to;

initialize background intensities of a line of pixels in a background frame comprising a digital image of an actual traffic lane without vehicles, wherein the line of pixels extends along a path that vehicles travel down the traffic lane and wherein the line of pixels has a length that is sufficient to extend along a length of a plurality of vehicles within the traffic lane;

identify vehicle location through measuring differences between pixel intensity values along the line of pixels between the background frame and another digital image of the actual traffic lane with vehicles;

calculate a stopped delay for each vehicle; and

calculate the average stopped delay per vehicle;

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, calculating a total stopped delay for the vehicle over consecutive frames, 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 19, wherein calculating the average stopped delay per vehicle comprises:

calculating 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 non-transitory computer-readable medium for estimating an average stopped delay per vehicle at a signalized intersection, the computer-readable medium comprising executable instructions for:

initializing background intensities of a line of pixels in a background frame comprising a digital image of an actual traffic lane without vehicles, wherein the line of pixels extends along a path that vehicles travel down the traffic lane and wherein the line of pixels has a length that is sufficient to extend along a length of a plurality of vehicles within the traffic lane;

identifying vehicle location through measuring differences between pixel intensity values along the line of pixels between the background frame and another digital image of the actual traffic lane with vehicles;

calculating a stopped delay for each vehicle; and

calculating the average stopped delay per vehicle;

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

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 average stopped delay per vehicle comprises:

calculating a total stopped delay of all vehicles; and

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

25. A non-transitory computer-readable medium for estimating an average stopped delay per vehicle at a signalized intersection, the computer-readable medium comprising executable instructions for:

initializing background intensities of a line of pixels in a background frame comprising a digital image of an actual traffic lane without vehicles, wherein the line of pixels extends along a path that vehicles travel down the traffic lane and wherein the line of pixels has a length that is sufficient to extend along a length of a plurality of vehicles within the traffic lane;

identifying vehicle location through measuring differences between pixel intensity values along the line of pixels between the background frame and another digital image of the actual traffic lane with vehicles;

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

calculating the average stopped delay per vehicle;

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, determining whether a length of the vehicle is greater than a specified maximum length, 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, 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.

26. The computer-readable medium of claim 25, wherein calculating the average stopped delay per vehicle comprises:

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

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

27. A non-transitory computer-readable medium for estimating an average stopped delay per vehicle at a signalized intersection, the computer-readable medium comprising executable instructions for:

initializing background intensities of a line of pixels in a background frame comprising a digital image of an actual traffic lane without vehicles, wherein the line of pixels extends along a path that vehicles travel down the traffic lane and wherein the line of pixels has a length that is sufficient to extend along a length of a plurality of vehicles within the traffic lane;

identifying vehicle location through measuring differences between pixel intensity values along the line of pixels between the background frame and another digital image of the actual traffic lane with vehicles;

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

calculating the average stopped delay per vehicle;

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, 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, 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, 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.

28. The computer-readable medium of claim 27, wherein calculating the average stopped delay per vehicle comprises:

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

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

29. A non-transitory computer-readable medium for estimating an average stopped delay per vehicle at a signalized intersection, the computer-readable medium comprising executable instructions for:

initializing background intensities of a line of pixels in a background frame comprising a digital image of an actual traffic lane without vehicles, wherein the line of pixels extends along a path that vehicles travel down the traffic lane and wherein the line of pixels has a length that is sufficient to extend along a length of a plurality of vehicles within the traffic lane;

identifying vehicle location through measuring differences between pixel intensity values along the line of pixels between the background frame and another digital image of the actual traffic lane with vehicles;

calculating a stopped delay for each vehicle; and

calculating the average stopped delay per vehicle;

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, calculating a total stopped delay for the vehicle over consecutive frames, 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 29, wherein calculating the average stopped delay per vehicle comprises:

calculating a total stopped delay of all vehicles; and

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