Car speed estimation based on image scale factor

• Published in: Forensic science international Vol. 310; p. 110229
• Main Authors: Costa, Luciano R., Rauen, Michelle S., Fronza, Andressa B.
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01.05.2020; Elsevier Limited
• Subjects: Cameras; Digital cameras; Forensic science; Forensic sciences; Mathematical analysis; Methods; Photogrammetry; Traffic accidents; Traffic accidents & safety; Traffic speed; Vehicle speed; Vehicles; Velocity; Video analysis; Vehicle speed; Forensic science; Video analysis; Photogrammetry
• ISSN: 0379-0738; 1872-6283
• DOI: 10.1016/j.forsciint.2020.110229

•Video analysis of traffic accidents is an important part of the legal process.•ISF-based method allows speed estimates to be made even without reference markers in the scene.•ISF-based method can produce reliable vehicle speed estimates.•ISF-based method is a speed estimation approach applicable to forensic science. Speed estimation by video analysis has been an increasingly common method for obtaining the speed of vehicles involved in traffic accidents. Generally, the estimate is based on reference measurements obtained on site or on measurements calculated by photogrammetric techniques. In this work, we proposed an alternative method for estimating the speed of a vehicle with longitudinal trajectory relative to the camera, either approaching it or moving away from it. The method uses the “image scale factor in pixels” to calculate the distance from the vehicle to the camera in different video frames, thus allowing the estimation of a vehicle’s average speed. The results were verified by means of a simulation, with a vehicle moving at known speeds. The small deviation obtained supports the forensic use of the method in speed estimation by video analysis.