Speed Determination Using Audio of Dash Camera Video from Commercial Vehicle Tires Frequencies for Vehicle Accident Reconstruction

Prior research has validated a reliable method for determining vehicle speed using audio recorded by cameras mounted in vehicles, specifically for rolling passenger vehicle tires. Passenger vehicle tires produce a frequency component directly correlated to vehicle speed when traveling on concrete roadways. However, prior research has not been conducted on audio for rolling commercial vehicle tires, which differ in construction from passenger vehicle tires and therefore produce audio signals on roadway surfaces that passenger vehicles tires did not when tested in the prior study. The current research concluded that commercial vehicle tires rolling on various roadway surfaces also generated a frequency that varied with vehicle speed. The purpose of this study was to outline, test, and confirm the source of the speed-dependent frequency and to develop a validated method for use in forensic applications. A modified version of the passenger vehicle tire equation from prior research was developed to account for the difference in construction associated with commercial vehicle tires, which takes into account the center tire blocks whereas the passenger vehicle equation did not. Data collection included a commercially available dash camera, a GoPro camera, and a pair of remote microphones to identify the source of the speed-dependent frequency. A baseline speed was captured using GPS data from a Racelogic VBOX Sport. iZotope RX was used to identify and compare the speed-dependent frequencies of interest with the baseline speed. The proposed audio analysis method is similar to the prior audio analysis method(s) to determine vehicle speed. The proposed method can be useful in addition to other critical events of a vehicle for accident reconstruction analysis.