Wind-Drag Estimation in a Traffic Accident Involving a Motor Scooter and a Tractor-Trailer

Abstract

This case report describes a noncontact traffic accident involving a motor scooter and a tractor-trailer with a focus on the wind-drag effect. We used load cells to measure the drag force acting on a substantially similar motor scooter when a substantially similar tractor-trailer passes by it, taking into consideration various speeds of the tractor-trailer and distances between the two vehicles. A three-dimensional steady-state flow analysis was also performed by using the CFX program for computational fluid dynamics to examine the streamlines and the pressure distribution around the tractor-trailer at various speeds. From the experiment, for a separation distance of 1.0m (3.28ft) and a speed of 90km/h (55.9mph), the maximum resultant drag force is 124.5N (28lb); this constitutes a degree of force that could abruptly disrupt the stability in maneuvering by an operator who is unaware of the approaching tractor-trailer. In addition, a single equation that relates the tractor-trailer speed to the drag force that acts on the motor scooter was derived on the basis of the Reynolds number (Re) and the wind-drag coefficient (C d): C d=1.298×10 -7 Re. © 2012 American Academy of Forensic Sciences.