Confidence limits for motorcycle speed from slide distance

Abstract

In many motorcycle accidents, the motorcycle falls to the ground and slides to rest following impact or loss of control. The determination of the motorcycle speed just prior to ‘fall-over’ is important for biomechanics research and for litigation. This paper presents a new model of motorcycle fall-over and slide, which accounts for the loss of horizontal momentum resulting from the initial motorcycle-to-ground impact and the subsequent slide to rest. The model includes cases involving motorcycle fall-over owing to loss of control as well as impact. The models represent both the mean and variation present in the available experimental data for dry roads very well and are used to develop confidence limits for accident reconstruction purposes, in cases where only the motorcycle slide distance along the ground is known. Previously proposed confidence limit criteria are applied to predicting motorcycle speed ranges from slide distance, and it is shown that the level of prediction uncertainty can be substantially reduced in cases where additional information specific to the vehicle and road configurations is available.

Deceleration of sliding motorcycles (mainly scooters) in accident reconstructions

“…From the above results, it emerges that drag tests can be applied as an efficient method to evaluate the average deceleration rate at a given place where a road accident occurred. This coefficient allows the side speed when the motorcycle falls over to be estimated in an optimal way when calculated from equation (2) proposed by Wood et al 11 For practical application of the method, it is sufficient to put the crashed motorcycle on the side of interest and to tow it with appropriate instrumentation.…”

“…where V c is the vertical impact velocity defined by Wood et al 11 as a function of the height h cg of the centre of gravity, the motorcycle frame width f w and the roll radius k r of gyration. In this work, motorcycle accidents (where the term motorcycles includes scooters) are investigated to determine the speed at which the motorcycle falls over.…”

“…The sliding phase is characterized by motions which are not always easy to model, and it is not always possible to evaluate easily the kinetic energy dissipated. According to Wood et al, 11 when a motorcycle falls to the ground, typically three distinct phases of motion can be identified: in the first phase, loss of control; in the second phase, impact with the ground and rebound; in the third phase, stabilized sliding.…”

“…In the paper by Wood et al, 11 the evaluation of the speed of the motorcycle when it falls over was optimized. The equation defined by Wood et al 11 considers the impact with the ground and μ is defined as the coefficient of retardation of the stabilized sliding according to…”

“…where V c is the vertical impact velocity defined by Wood et al 11 as a function of the height h cg of the centre of gravity, the motorcycle frame width f w and the roll radius k r of gyration.…”