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Video based Vehicle Speed Computation (HAWK)

United States Patent

“Homography-Based Passive Vehicle Speed Measuring”
Shah et al.
Patent No.: US 8,238,610 B2
Issued: Aug. 7, 2012

The goal of this project is to measure vehicle speeds on US highways by processing the video of moving vehicles captured through a digital video camera. The system was designed to be able to satisfy the following requirements:

  • Real-time system
  • Use limited resources: (1) Quality of the camera (2) Power of the processing unit
  • Robust and accurate
  • Exploit existing infrastructure: (1) Bridges over highway (2) Traffic monitoring cameras

Results – Output from the HAWK system

Top View Videos
Side View Videos


Our video based speed computation system has following advantages over conventional systems:

  • Monitors multiple lanes simultaneously – with a single camera
  • Uses existing infrastructure – bridges, poles etc
  • Passive monitoring – effective against radar detectors and laser jammers
  • Low Cost – Cameras cheaper than radar or laser technology

The initial development version of the speed computation system has been developed. It is written in C++ and processes either the recorded video or live video captured via a USB webcam. The system runs on a Windows based Desktop or Laptop running Windows XP or higher. Apart from the GUI (which uses the MFC library), maximum adherence to the ANSI C++ specification has been attempted.

(a) (b)

(a) The main modules of our speed computation system (b) The software components of the HAWK system

The system runs real time on a 2GHz laptop computer, while processing 320×240 resolution video at 15 fps. Under these conditions the system is able to identify and compute speeds for 99% of the vehicles travelling on the highway (including trucks, buses and motorcycles). The accuracy of the system was determined by comparing the speeds with those obtained from a commercially available radar-based speed gun. The mean difference between the speeds was 0.86 mph with a standard deviation of 0.89 mph. This difference was negligible considering the fact that speed gun computes instantaneous speeds while our system computes average speeds.



(a) (b)

(a) The main dialog box of the HAWK application (b) The parameters dialog box of the HAWK system