The Physics and Factors of Vehicular Collisions
To understand the tragic history of car crashes, it is essential to first understand the fundamental forces and factors involved. A car crash is an event of extreme energy transfer. The kinetic energy of a moving vehicle—determined by its mass and, more importantly, the square of its velocity—must be dissipated in a fraction of a second during a collision. A doubling of speed results in a quadrupling of kinetic energy, which is why speed is the single most critical factor in the severity of a crash.
Investigators and safety engineers typically categorize the causes of a crash into three main areas. Understanding these provides a framework for analyzing any collision, including those discussed in this article.
Human factors are the most common cause of accidents, accounting for over 90% of all crashes according to the National Highway Traffic Safety Administration (NHTSA). This category includes driver error, such as misjudging speed or distance; impairment from alcohol, drugs, or fatigue; distraction, such as using a mobile device; and deliberate risky behavior, like excessive speeding or aggressive driving. It also includes the critical decision of whether or not to use safety equipment like seatbelts.
Vehicle factors relate to the automobile itself. This can include mechanical failures, such as brake or tire failure, as well as design characteristics. High-performance sports cars, for example, may have challenging handling dynamics that are unforgiving of driver error. Conversely, the absence of modern safety features—such as airbags, Anti-lock Braking Systems (ABS), and Electronic Stability Control (ESC)—in older vehicles dramatically increases the risk of serious injury in a crash that might be survivable today.
Environmental factors encompass the conditions of the road and surrounding area. These include poor road design, like sharp curves or intersections with limited visibility; adverse weather conditions, such as rain or ice that reduce tire grip; and temporary hazards, like road debris or animals. The actions of other drivers or, in some cases, pedestrians, also fall within this category.
A formal investigation often involves a root cause analysis, a systematic process to identify the fundamental, underlying cause of a disaster rather than just its immediate symptoms. In a car crash, the immediate cause might be losing control on a curve, but the root causes could be a combination of excessive speed (human factor), worn tires (vehicle factor), and a poorly banked turn (environmental factor).
