In facts traffic collisions are the leading cause of preventable deaths in our country. Thus it is important to have an understanding as to the leading factors contributing to car accidents. A list of the leading causes of traffic accidents in provided below. 1. Speeding While Driving and Reckless Driving: Failing to follow the speed limit is the most common cause of traffic accidents in the United States. 2. Use of Mobile Phone – Texting While Driving: The proliferation of mobile phone use has resulted an increased level of danger on our roads.