The use of vector sum
analysis plays a very important role in accident reconstruction.
To understand vectors and their components is to understand
momentum. A vector diagram is a way to draw a visual
representation of the dynamics of the collision. It
also allows you to calculate the impact speeds. You
may be asking yourself, "If I can solve it mathematically,
why bother with this?" Remember, you may have to explain
how you came about your conclusions to a jury. I am
sure that a fair percentage of any jury would be comprised
of "visual learners". There have been a few notable
trials in recent years where the jury has returned a
notguilty verdict, possibly because the scientific
evidence was not understood. Now imagine spending over
an hour explaining to a jury how you mathematically
calculated the impact speeds for two vehicles and what
sine and cosine mean. Do you think that you may lose
the interest of a few of your jurors? To be honest,
when you have to explain some of this stuff to people,
it can get pretty boring. Vector diagramming is a way
that allows you to visually represent the collision
and easily explain it to jury.
In addition, the vector diagram will help you determine
what the deltaV
(change in velocity) and the principal
direction of force (PDOF) are. This "change in velocity"
experienced by the vehicle, and its occupants, is what
determines the severity of the collision and will act
along the PDOF. The deltaV correlates well with serious
injury and fatality collisions. Emergency room doctors
are very interested in the deltaV experienced by their
patient. They know if the deltaV is high enough they
can expect to see life threatening injuries. The deltaV
can be calculated mathematically and through a vector
diagram.
