The basic reason is the incompatibility of strength and height specifications among these different vehicles when they get in contact. After the century in the automotive industry, this kind of tragedy, well known by everybody, continues to kill people. Safety Engineering is the science, which recognizes risks , and proposes protective measures. Safety Engineering is a science, which deals with experience, and uses the knowledge of previous negative events, as well as the deep pre-visibility analysis of further undesirable events.
Logic is therefore an essential of engineering, which is especially applicable for safety issues.
Safety Engineering is a complete exercise of human intelligence, in the defense of the life, physical integrity of the persons, and of the material properties. Not considering scientific inputs and logic in any Engineering Project is a severe mistake, which may kill people, instead of saving them. And it can simply nullify any project or investment. Active and passive safety devices require engineering efforts to achieve effective solutions. A simple example is the miscalculation of a load that a bridge must support, or the strength of a safety belt in a car.