As in any technical problem, common sense plays a fundamental role in the reconstruction of the facts, even more in collision problems, in which several of the variables involved are usually unknown. Numbers should be prevented from devouring us and clouding our common sense and good judgment, which, unfortunately every day becomes a sad nightmare, with the complex computer programs available for the collision and other technical analysis, not enough understood by the users and sometimes by the developers. The great Master of Engineering, Professor Hardy Cross, in his book “Engineers and Ivory Towers” wrote: “There has not been a falser point of view than the one that visualizes the engineers inevitably reaching a single solution to their problems through mathematics or laboratory procedures because their solutions are rarely unique. Engineering is not a mathematical science, but it does take advantage of many of the mathematical procedures.”