Balancing Collision Forces in Crush/Energy Analysis

Balancing Collision Forces in Crush/Energy Analysis

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Balancing Collision Forces in Crush / Energy Analyses
by Nathan Shigemura and Andrew Rich

Crush/energy analysis continues to remain an important tool for the reconstructionist. It provides another method of resolving a traffic crash where other methods may not be available or appropriate. For any reconstructionist who is faced with the task of performing this analysis, this article may help take the mystery out of the process of solving for the stiffness coefficients of a particular crash.

Mr. Shigemura and Mr. Rich show you how appropriate stiffness coefficients can be determined by performing an analysis where collision forces are balanced and new stiffness coefficients are calculated. These values can be obtained when published values are not available or not applicable. By determining the proper stiffness coefficient, you will be able to calculate equivalent barrier speeds (EBS), delta-V’s and impact speeds of colliding vehicles.

An appendix at the end of the article shows you an example of the process of balancing collision forces and calculating new stiffness coefficients for one vehicle, when the value is known for the other.


Nathan Shigemura retired in 2002 as a sergeant from the Illinois State Police, where his duties included crash investigation instructor, traffic crash reconstructionist and supervisor of the statewide Traffic Crash Reconstruction Unit. As co-owner of the Traffic Safety Group, LLC, a traffic crash reconstruction and analysis company based in Illinois, he remains active as a reconstructionist. Since 1989, Mr. Shigemura has been an adjunct faculty member of IPTM, for whom he continues to teach courses nationwide in all levels of traffic crash investigation and reconstruction. He is the author of Mathematics for the Traffic Accident Investigator and Reconstrucitonists, published by IPTM in 1996 and co-author with John Daily of Fundamentals of Applied Physics for Traffic Accident Investigators, published by IPTM in 1997, and co-author with John Daily and Jeremy Daily of Fundamentals of Traffic Crash Reconstruction, published by IPTM in 2006. Mr. Shigemura received in 1975 a BS degree in Electrical and Electronic Engineering (BSEE) from the University of Illinois, Chicago. He is accredited by the Accreditation Commission for Traffic Accident Reconstruction (ACTAR).

Andrew Rich began his career in law enforcement in 1988 with the Palisades Interstate Parkway Police (PIP) in Northeastern New Jersey. After seven years of service, he was promoted to sergeant and became the officer in charge of the Accident Investigation Unit and the Search and Rescue Unit. Additionally, he programmed the department’s computer systems applications. He was also a part-time investigator for the Bergen County (NJ) Prosecutor’s Office Fatal Accident Investigation Unit (FAIU). In 1999 Sergeant Rich left the PIP to become a detective for the Bergen County Prosecutor’s Office (FAIU), where he is presently assigned to investigate and reconstruct serious and fatal collisions on a county-wide basis. Andrew Rich is a member of IPTM’s adjunct faculty, is ACTAR accredited, and is currently completing the last classes necessary for a degree in mechanical engineering at the New Jersey Institute of Technology.

Specifications: 24 pages; 8-1/2”x11”; saddle stitched; Publisher: IPTM (April 2008)

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