**3. Causes and prevention methods of collisions**

Involuntary emerged incidents by the humans, vehicles, and environmental effects may cause accidents randomly. Sometimes, the reasons are known and the sufficient prevention methods can be created for the safety of the vehicles or the occupants or the both of the occupants and the vehicles. Although the vehicle is UAV, the opponents or the other vehicles could be driven by the humans. Thus, the human existence should be considered evermore, while the robust‐ ness of the vehicles is acceptable. With reference to known conversant reasons of the collisions, inaccurate parts of the mechanical, electronical, or software-based problems could be adjusted. However, the human originated mistakes which can differ from one being to another are much harder to fix with straightforward solution approaches. The psychological, physiological, behavioral potential, capability, and carefulness of the humans will alter the results of the happenings. Sometimes, the reasons are known, but it is not able be figured out by anything else the events like the several natural disasters. Otherwise, if the reasons are not specified or estimated for the collisions, the new methodologies must be evaluated to diminish the odds of failures for both humans and the vehicles.

Considering the vehicle, which is not a UAV, can be also investigated for the safety of the pedestrians, occupants, regular vehicles, and the autonomous vehicles. The idea of preventive driving technique or expert skills will come into the minds for the human driver. Initially, validity of this opinion could be reasonable with the existence of the natural aptitude alongside the education of the preventive driving. Although the careful driving is very important, the reflex of a human body is a prominent factor of the innate talent effecting throughout the trip. Sometimes, this gained time in milliseconds can save lives when the human body reacts against an unexpected incident. Reflexes can be improved with the help of the practice, while we can assume this, as a learned or educated reflex.

Otherwise, if the reflex response is not satisfying the sudden handling situations, preventive driving education avails to avert the collisions during or before the accidents. This education covers primarily the calm driving in contrast with the aggressive and fast driving, refraining from the instantaneous movements of the steering wheel conducts the vehicle, sudden acceleration and decelerations in particular in tough weather and environmental conditions. To ensure a safe trip, an admissible space between the vehicles is a necessary approach to acquiring an enough time along the duration of the collision. Subsequently, scanning all around the vehicle with eyes and computerized systems for every single threat is the key factor for a reliable trip, like a radar system to perceive the risky ventures which could be possibly induced by anything else.

Afterward, the driver will face with the most critical phase: *Decision*! And the worst scenario is *Uncertainty* as an opposite situation signifying that "the worst decision is better than a hesitant behaviour." If we consider the options for the decision:


If there is no chance avoiding from the accident, try to be in the safe zone or select the least hazardous way via changing the speed and maneuvering the vehicle to save the lives and minimize the collision effects. Doing nothing and being petrified is not an option, it is just an ambivalent condition eventuating with an undesirable result.

Considering the hassle of the situation during collisions, these types of behaviors and appli‐ cations are so difficult for a human to apply and need some expertise. It is not for everyone! Thus, if the computerized UAV system is capable to handle all of these situations at the same time, except some uncommon incidents, it will be much more robust and reliable for everyone, although we consider that sometimes human mind and body can create metaphysical and exceptional solutions.
