As mentioned above, the approach of physical models and equations must be accompanied by the search for evidence to raise a first work hypothesis of how a particular collision occurred. This hypothesis should be analyzed without passion and according to the progress of the investigations, it can be discarded or modified until the answer, that best represents the case under analysis, is reached. It is not the intention of these notes to describe the multiple techniques of research and reconstruction, however, we will briefly mention some tools (Work Hypothesis computer software, roadway markings and vehicles inspection that may be helpful in solving crash cases, taking as an example a real collision investigated by the author Related with the computer software, the book includes the software “Two dimensional Collision Dynamics” from the author, developed using the equations contained in this book. This software is extremely useful first of all, because allow to test multiple situations avoiding the complexities that arise when calculations are done by hand.