Research Article

A Method of Estimating the Distance and Relative Speed of an Object when a Vehicle Hits It, as Indicated in the Black Box Image Created at the Moment of Impact

Myung Cheol Park*, Jong Hyuk Kim, Won Taek Oh and Sang Hyun Lim

Traffic Accident Analysis Division, National Forensic Service, Republic of Korea

Submission:April 1, 2020; Published:April 13, 2020

*Corresponding author:Myung cheol Park, Traffic Accident Analysis Division, National Forensic Service, Republic of Korea

How to cite this article:Myung Cheol P, Jong Hyuk K, Won Taek O, Sang Hyun L. A Method of Estimating the Distance and Relative Speed of an Object when a Vehicle Hits It, as Indicated in the Black Box Image Created at the Moment of Impact. J Forensic Sci & Criminal Inves. 2020; 13(5): 555873. DOI: 10.19080/JFSCI.2020.13.555873.

Abstract

This paper proposes a method by which the distance and relative speed of a vehicle vis-à-vis the object it hit are measured using the phenomenon in which when a vehicle impacts another vehicle, a pedestrian, or another object, if the object is n times distant from the black box, its image looks about n times smaller

Keywords:Forensic video; Car black box; Vehicle speed; Pixel; Distance; Relative speed; Impact; Collision

Method of Measuring the Distance and Relative Speed of an Object Hit by a Vehicle from the Images Createdby the Vehicle’s Black Box

a) Method of measuring the object filmed by the vehicle’s black box

Figure 1 shows the method of measuring the distance of a tree filmed by a black box. The tree with 3 length was expected to be located 30 from the black box The aforementioned can be attributed to the fact that resembles , and as such, DODEAOAB=resembles ÄDOFand ÄAOCThus,//DOAOFOCO=. Therefore, //DEABFOCO=, so3//10hhFOm=, and FO is 30m. Figure 2 shows the method of measuring the distance of a stick filmed by the black box. At ()0ttt=−Δtime, the reference stick was moved so that its distance from the black box could be assumed as00dns=, and the reference stick was extended so that its extended length could be assumed as0hhnh=, with the top and bottom of the imaginary stick touching the imaginary lines. Then, 000hdnsns=and 0hhnh= 00hdsh∴ was expected. In the above expression, can be attributed to the fact that the black box image magnification may vary according to the distance, and to the possibility of magnification may vary according to the distance, and to the possibility of distortion [1-4]. In addition, it was assumed that after the black box image was captured at , the pixel of 0h would be 0p. Next, it was assumed that the pixel of captured from the black box image at was , and that the pixel of 0h was p, and 0pnp=.

Then, 00hdsh, 00phhp, and 0pnp=.

The distance d of the reference stick moved from the black box was estimated using the expression below.

b) Method of Measuring the Distance and Relative speed of a Pedestrian and the Vehicle ahead Filmed by the Black Box

Figure 3 & 4 shows the method of measuring the distance and relative speed of a pedestrian filmed by the black box. If the pedestrian’s distance from the black box is and the distance between the vehicle and the pedestrian is , then 0sds=−. Therefore, the distance is expected [5-9].

Further, if, at , the relative speed of the vehicle and the pedestrian is , is expected in the expression below

Conclusion

This study proposed the following [10-14]. If, at the time when a vehicle hits an object, the horizontal distance from the vehicle black box to the part of the object that was hit is assumed as reference distance ; the pixel length of the part of the object that was hit is assumed as ; and at the time of rewinding the black box, the part of the object that was hit is assumed as , the expression

and correction factor are proposed for measuring the distance from the vehicle to the object, and

and correction factor for measuring the relative speed of the vehicle and the object are proposed. In the experiment in this study, while the Hyundai Veracruz SUV was travelling, its installed black box filmed the dummy. Then the Veracruz black box filmed the rear side of the Sonata when it faced the front, when it turned, and when the Sonata offset it. Then the proposed method measured the distance from the black box images. The image distortion correction factor was applied to the expression

. ªThis confirmed a greater accuracy in distance. Thus, the correction factor for correcting the two said situations was applied to the expression

, and this confirmed a greater accuracy in speed. In the experiment, the four black boxes filmed various impact experiments, and in the consequent impact images, the correction factor of 1.1 was unilaterally applied to the expression

. As such, the vehicle’s pedestrian impact speed average error was determined to be 4.1%, and the maximum error, 3.1 km/h (7.9%), at about 40 km/h. The vehicle’s vehicle impact speed average error was measured as 3.1%, and the maximum error was measured as 2.1 km/h (5.3%), at about 40 km/h. This confirmed that the measured speed error was not big. Therefore, in this study, in the general case of a sedan hitting another sedan, a universal correction factor 1.1 was estimated. In this study, we proposed

and correction factor for the measurement of the relative velocity between the vehicle and the object. In order to reduce the error that occurs in a remarkably complicated situation, only the correction factor is introduced. However, many experiments have confirmed that the error is not large. This equation is very simple and can be used conveniently in actual situations. Thus, this study confirmed that the proposed method can estimate the distance from a vehicle to the object it hit in a traffic accident, and the relative speed of the object compared to that of the vehicle that hit it, using the images created by the vehicle’s black box. In addition, this method is expected to be further verified and supplemented by widespread use in actual traffic accidents. For this method, the relative speed estimation will be further studied in cases where the black box is rotated and the vehicle is offset. The method will be used in the development of programs that are specially designed to calculate the relative speed in real time.

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