Kick Scooter Speed Test Results

Accident Reconstruction Journal, Volume 27, No. 2, March/April, 2017 Author: Jonathan Balasa

Kick scooters or two-wheeled scooters (similar to the “Razor” scooters) are a popular mode of transportation for young children. When these scooters are operated on or near active roadways, there is the potential for collision. As a result of those crashes, an accident reconstructionist may be called upon to estimate the speed of the child on the scooter or to perform some type of time-distance analysis in order to determine how the motor vehicle and the scooter moved relative to each other in the moments before the crash.

Developing a Crush Profile Estimate by Balancing Impact Forces

SAE Paper No. 970942 Authors: Wesley D. Grimes, Ronald Heusser, John Hunter, and James A. Neptune

There are many collisions in which the "standard" analysis methods are not sufficient to complete an analysis. Many times the points of rest for the vehicles are not documented or the vehicles were "driven" to the points of rest. There are also cases in which one of the vehicles is repaired prior to being documented. In these cases, there is a method that can be used to establish the approximated speed change of the vehicles. This method involves using the crush profile of one of the vehicles and balancing the opposing forces across the crush profile to determine an equivalent crush depth on the undocumented vehicle. Using this "balanced forces" method requires a detailed crush profile of one of the vehicles and good stiffness data for both vehicles. The method is not as accurate as standard methods because of the unknowns, but does yield reasonable results for the speed change severity for the vehicles involved. This paper will discuss the theory of this method and present two (2) example cases.

Programming Fortran Applications for HVE

SAE Paper No. 960889 Author: Wesley D. Grimes

The Human Vehicle Environment (HVE) program, developed by Engineering Dynamics Corporation, combines the vehicle parameters, physics and graphics into a single computer system for use in analyzing motor vehicle collisions, handling issues, studying occupant motion, etc. One of the most valuable assets of the HVE program is the open architecture that allows easy access to the data and graphics capabilities from an independent computer program. Thus, virtually any program that can be recompiled on the Silicon Graphics system can be set up to utilize the HVE tools. HVE is written in two computer languages known as C and C++ (pronounced "C plus plus"), this aids in the graphics processing. Unfortunately, FORTRAN programs do not automatically interface with C or C++ programs. These programs must be modified to allow a two-way data path to and from HVE. This paper will briefly review the concepts of interfacing programs and then give specific examples of combining FORTRAN programs with the HVE environment.

Error Analysis of Center-Of-Gravity Measurement Techniques

SAE Paper No. 950027 Authors: Steven C. Shapiro, Stephen M. Arndt, Gregory A. Mowry, Charles P. Dickerson, and Mark W. Arndt

The height of a vehicle's center-of-gravity (CG) is one factor that influences its handling characteristics. A number of height methods are used to measure CG within the automotive industry. This research determined which method has the greatest potential to produce accurate CG height measurements, given anticipated measurement tolerances. Several techniques for measuring vehicle CG height were analyzed mathematically. The contributions of various parameters to total error were determined and the total error inherent in each method was then compared.

Evaluation of Vehicle Velocity Predictions Using the Critical Speed Formula

SAE Paper No. 950137 Authors: Charles P. Dickerson, Mark W. Arndt, Stephen M. Arndt, and Gregory A. Mowry

Tire marks left by the vehicle prior to impact, rollover, or other event, are important forensic evidence reconstruction of motor vehicle accidents. Often these tire marks have some curvature that is measured and used to calculate the speed of vehicles prior to the event. This calculation is based on the coefficient of friction of the tire/road interface and the radius of curvature of the vehicle center of gravity (c.g.) path. There is controversy about the validity of this approach. To explore this theory, a test vehicle was driven through a series of maneuvers that produced yaw marks for direct comparison of actual vehicle velocity to the velocity calculated by the critical speed formula. Test results show the critical speed formula is inaccurate for most circumstances and does not correctly describe vehicle limit performance behavior.