McHenry Forum - Crash Reconstruction & Simulation

Q: October 21, 2012: If you have a moment can you help me understand angle theta reference the crush magnification factor (1 + tangent theta2)? For example, if my PDOF is 150-degrees (right, passenger side) would the magnification factor theta be tangent 30? (Example: 150-90=60 degrees and since 60 is larger than 45-degrees, subtract it from 90-degrees resulting in 30). I can think fine out to a PDOF of 135 because that does exceed a 45-degree theta (which I know we can’t exceed the limit of magnification factor of 2). But what about theta angles greater than 45-degrees?

A: The 'Magnification Factor' and 'Theta' angle apparently are from Daily book 'Fundamentals of Traffic Crash Reconstruction'.
For some reason Daily changed

• 'Energy Correction factor' from the CRASH program to 'Magnification factor'
• The angle Alpha from CRASH to Theta.

No biggie except this can add to confusion surrounding such questions since one would have to know that these are the same terms and that Daily merely changed them from the 1970's CRASH related documentation by Raymond R McHenry

• see What is CRASH? for more information on CRASH.

The inquiry seems to be simply a request for the definition of the angle alpha (which is called 'theta' by Daily).
Further information:

• See forum topic What is the CRASH Energy Correction Factor (ECF)?.
  • That cited forum thread includes reference to topic Energy Correction Factor(ECF) from our book McHenry Accident Reconstruction.