A traffic collision, also called a motor vehicle collision (MVC) among other terms, occurs when a vehicle collides with another vehicle, pedestrian, animal, road debris, or other stationary obstruction, such as a tree, pole or building. Traffic collisions often result in injury, death, and property damage. A number of factors contribute to the risk of collision, including vehicle design, speed of operation, road design, road environment, and driver skill, impairment due to alcohol or drugs, and behavior, notably speeding and street racing. Worldwide, motor vehicle collisions lead to death and disability as well as financial costs to both society and the individuals involved. In 2013, 54 million people sustained injuries from traffic collisions. This resulted in 1.4 million deaths in 2013, up from 1.1 million deaths in 1990. About 68,000 of these occurred in children less than five years old. Almost all high-income countries have decreasing death rates, while the majority of low-income countries have increasing death rates due to traffic collisions. Middle-income countries have the highest rate with 20 deaths per 100,000 inhabitants, 80% of all road fatalities by only 52% of all vehicles. While the death rate in Africa is the highest (24.1 per 100,000 inhabitants), the lowest rate is to be found in Europe (10.3 per 100,000 inhabitants). Traffic collisions can be classified by general type. Types of collision include head-on, road departure, rear-end, side collisions, and rollovers. Many different terms are commonly used to describe vehicle collisions. The World Health Organization use the term road traffic injury,while the U.S. Census Bureau uses the term motor vehicle accidents (MVA), and Transport Canada uses the term motor vehicle traffic collision (MVTC).Other common terms include auto accident, car accident, car crash, car smash, car wreck, motor vehicle collision(MVC), personal injury collision (PIC), road accident, road traffic accident (RTA), road traffic collision (RTC), road traffic incident (RTI), road traffic accident and road traffic collision, as well as more unofficial terms including smash-up, pile-up, and fender bender. Some organizations have begun to avoid the term accident. Although auto collisions are rare in terms of the number of vehicles on the road and the distance they travel, addressing the contributing factors can reduce their likelihood. For example, proper signage can decrease driver error and thereby reduce crash frequency by a third or more. That is why these organizations prefer the term collision to accident. In the UK the term incident is displacing accident in official and quasi-official use. Historically in the United States, use of terms other than accidents had been criticized for holding back safety improvements, based on the idea that a culture of blame may discourage the involved parties from fully disclosing the facts, and thus frustrate attempts to address the real root causes. Road injuries resulted in 1.4 million deaths in 2013 up from 1.1 million deaths in 1990. This is about 2.5% of all deaths. In 2004 50 million more were injured in motor vehicle collisions. India recorded 105,000 traffic deaths in a year, followed by China with over 96,000 deaths. This makes motor vehicle collisions the leading cause of injury and death among children worldwide 10 – 19 years old (260,000 children die a year, 10 million are injured) and the sixth leading preventable cause of death in the United States (45,800 people died and 2.4 million were injured in 2005). In the state of Texas alone, there were a total of 415,892 traffic collisions, including 3,005 fatal crashes in 2012. In Canada they are the cause of 48% of severe injuries.

Crash rates

The safety performance of roadways is almost always reported as a rate. That is, some measure of harm (deaths, injuries, or number of crashes) divided by some measure of exposure to the risk of this harm. Rates are used so the safety performance of different locations can be compared, and to prioritize safety improvements. Common rates related to road traffic fatalities include the number of deaths per capita, per registered vehicle, per licensed driver, or per vehicle mile or kilometer traveled. Simple counts are almost never used. The annual count of fatalities is a rate, namely, the number of fatalities per year. There is no one rate that is superior to others in any general sense. The rate to be selected depends on the question being asked – and often also on what data are available. What is important is to specify exactly what rate is measured and how it relates to the problem being addressed. Some agencies concentrate on crashes per total vehicle distance traveled. Others combine rates. The U.S. state of Iowa, for example, selects high collision locations based on a combination of crashes per million miles traveled, crashes per mile per year, and value loss (crash severity).