The Traffic Accident Reconstruction Origin -ARnews-

Re: Speed estimates from crush

Thomas Langley (reconman@axrecon.com)
Thu, 17 Apr 1997 09:57:35 -0400 (EDT)

Tim:

Crush is arguably an approach to determining closing speeds of vehicles, thereby
providing speed shange during the collision. Several articles, papers and full symposiums
have been generated on the subject of crush. Generally, the feds have produced the CRASH III
database, software with trajectory and crash capabilities for use in determining
the speed change from crush measurements. Caveats are at the front of the CRASH III
manual about its intended use and some subsequent warnings about its misuse. Gordon
Biggs (ARSoftware), Ph.D., P.E....smart guy, has written a paper about the process
and its use and misuse. Crush generally gives an approximation of the speed change
based on the database for that particular size, wheelbase. In the RICSAC tests
that were conducted in the early days to verify the program produced as mush as 8 mph
in 30-35 mph crashes. You can research the SAE database and order the necessary papers.
As far as your questions: IPTM puts on advanced AR using microcomputers (SLAM - aka WinCrash)
, Engineering Dynamics puts on a good course (2 weeks), and I am sure that there are others,
formulaes relate to the stiffness coefficients A - B and sometimes G, though G is
currently under suspicion by the Coefficient of Restitution people, how and where to measure is taught in the courses
and covered in the papers, and tips - be careful. I published an article for TARO
earlier about the NHTSA crash database and how to extract information relative
to your investigation to minimize the ambiguities associated with 500 pound
weight classes. If you need further, you can e-mail me. Also, there are plenty of people who read and respond to these
threads that can assist you as well.
Have a great day.
Tom
Thomas Langley
reconman@axrecon.com

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