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2009 ARC-CSI Crash Conference Presentation
Estimation of Vehicle Speed and Trajectory
Based on Video from a Vehicle-Mounted Camera
Presented By: Dan T. Horak
Time: 1 Hour
The use of vehicle-mounted video cameras, such as DriveCam, is on the increase. They can be seen on buses, trucks, taxis and trains all over the country. The primary purpose of such cameras is to enforce safe driving by allowing safety supervisors to view unsafe driving events caused by drivers and provide training that reduces such events in the future.
NTSB developed a method for estimating vehicle speed and trajectory based on video from such vehicle-mounted cameras. When a vehicle is involved in an accident, an acceleration-based trigger initiates storage of driver’s view video frames from several seconds prior to the trigger to several seconds after it. These frames include landmarks such as lane markings, guardrails, Jersey walls, reflectors, signs, buildings and trees.
The developed method utilizes a survey of the accident scene, or available aerial photographs, or video of the scene taken after the accident to generate a 3D map of these landmarks. It then uses a calibrated model of the camera optics to synthesize video frames with the landmark locations marked on them. The locations of the landmarks in the synthesized frames depend on the unknown locations and orientations of the camera. A computer-aided iterative process is then used to move and rotate the vehicle (and the camera attached to it) on a map of the accident scene shown on the display. When the landmark locations in a synthesized frame coincide with their location in a stored video frame, the vehicle location when that frame was acquired by the camera is the vehicle location shown on the computer display.
Typically, about twenty such locations will be identified and, since the camera frame rate is known, this information can be used to estimate the trajectory and speed of the vehicle just prior to the accident. In a typical highway accident, the location estimation accuracy is a fraction of a foot and the speed estimation accuracy is about ±2 mph.
An example will be used to illustrate the use of the method for estimating the speed and trajectory of a highway vehicle.
About Dan T. Horak
Dan joined the National Transportation Safety Board (NTSB) in 2007 as a vehicle dynamicist in the Office of Research and Engineering in Washington, DC. His interests and activities include accident reconstruction, vehicle trajectory simulation and estimation, stability control systems and intelligent safety systems. While most of his work involves ground vehicles, occasionally he is also involved in reconstruction of aircraft and railroad accidents. Before joining NTSB, he spent twenty six years in private industry conducting research and development on vehicle and aircraft dynamics, monitoring and control.
Dan holds B.S. and M.S. degrees in mechanical engineering from The Ohio State University and Ph.D. in mechanical engineering, specializing in vehicle dynamics, from MIT. He published eight papers in refereed engineering journals, over twenty conference papers, and he holds four US patents.
