The three major causes of collisions are distracted driving, speeding, and impaired driving. Together, these three behaviors account for the vast majority of preventable traffic deaths in the United States, where an estimated 39,345 people died in crashes in 2024 alone. All three are forms of human error, which is responsible for over 90% of all crashes on the road.
Distracted Driving
Distracted driving means anything that pulls your attention away from the road: texting, adjusting navigation, eating, talking to passengers, or even daydreaming. In 2023, distracted driving was linked to 3,275 motor vehicle fatalities nationwide, roughly 8% of all traffic deaths that year. That number almost certainly undercounts the real toll, since distraction is harder to prove after a crash than alcohol or speed.
What makes distraction so dangerous is the time gap it creates. At highway speed, looking at your phone for five seconds means traveling the length of a football field essentially blind. Your brain also needs a moment to re-engage with the driving task after a distraction ends, so the risk extends beyond the seconds your eyes are off the road. For teen drivers, distraction is an especially prominent factor because inexperience already demands more of their attention. The CDC lists distracted driving alongside inexperience, nighttime driving, and reckless driving as leading causes of teen crashes.
Speeding
Speeding has been involved in approximately one-third of all motor vehicle fatalities for more than two decades. In 2023, it killed 11,775 people and was a contributing factor in 29% of all traffic deaths, according to the National Highway Traffic Safety Administration.
Speed affects a crash in two ways: it makes the crash more likely to happen, and it makes the crash more severe when it does. At higher speeds, you need more distance to stop after spotting a hazard. A car traveling at 60 mph needs significantly more stopping distance than one at 40 mph, and the difference is not proportional. Doubling your speed roughly quadruples the force of impact, which is why crashes at higher speeds produce dramatically worse injuries.
Speeding doesn’t only mean exceeding the posted limit. Driving at the speed limit during heavy rain, on a poorly lit road, or through a construction zone can still be “too fast for conditions.” Reduced tire grip, limited visibility, and narrowed lanes all shrink your margin of safety, even if you’re technically legal. The physics don’t care about the speed limit sign.
Impaired Driving
Alcohol and drug impairment is the deadliest of the three causes in terms of raw fatality numbers. In 2022, 13,524 people were killed in crashes involving alcohol-impaired drivers, accounting for 32% of all traffic-related deaths in the United States. A study across seven trauma centers found that 54% of drivers who were seriously injured in crashes tested positive for alcohol, drugs, or both.
Alcohol is the most well-known impairment, but it’s far from the only one. In that same trauma center study, 25% of injured drivers tested positive for cannabis, 10% for stimulants, 9% for opioids, and 8% for sedatives. Many drivers tested positive for more than one substance. Impairment slows reaction time, distorts judgment about speed and distance, and reduces the coordination needed to steer, brake, and make split-second decisions. Even at levels below the legal limit, alcohol measurably degrades driving ability.
How These Three Causes Overlap
These categories are not always separate. A driver who has been drinking is also more likely to speed and less likely to notice distractions. Someone texting while driving may also drift above the speed limit without realizing it. Crash reports often list multiple contributing factors, which means the individual percentages for distraction, speed, and impairment don’t add up neatly. The real-world picture is messier than any single statistic suggests.
The World Health Organization identifies the same core risk factors globally: excessive speed and drink-driving top the list, alongside failures to use seat belts and helmets. Only about 15% of countries have laws that meet evidence-based standards for addressing these risks, which helps explain why road traffic injuries remain a leading cause of death worldwide.
Other Contributing Factors
While distraction, speed, and impairment are the “big three,” several other factors contribute to a significant number of crashes. Drowsy driving may be involved in as many as 7,500 fatal crashes per year in the U.S., roughly 25% of the total. Fatigue affects the brain in ways similar to alcohol: slower reactions, poor judgment, and the risk of briefly falling asleep at the wheel.
Weather plays a smaller but real role. An analysis of over 125,000 fatal crashes found that about 7.7% occurred during active precipitation, compared to a baseline expectation of 5.8% based on how often it actually rains or snows. That gap confirms that wet or icy roads increase crash risk, but the effect is modest compared to human behavior. Rain doesn’t cause crashes on its own. It raises the stakes for drivers who are already speeding, distracted, or impaired.
For newer drivers, inexperience is itself a major risk factor. Teens face elevated crash rates not just because of risky choices but because they haven’t yet developed the automatic scanning habits, hazard recognition, and vehicle control that come with years of practice. Nighttime driving and having teen passengers in the car further increase their risk.