Weather affects driving conditions and may alter existing road conditions in a matter of minutes or seconds. Almost 1.24 million people die in traffic accidents annually throughout the world. Snowfall and rainfall reduce visibility and cause braking to be more difficult. Temperatures typically influence the frequency, mode, and purpose of motor vehicle travel.

Regardless of the weather, determining liability for a motor vehicle accident is based on the legal theory of negligence. Therefore, the main issue is whether the accident’s participating drivers observed the applicable standard of care and acted as a reasonable person would in similar circumstances.

Bad weather such as rain, fog, wind, ice or snow is usually an important factor in determining whether the driver of a motor vehicle was acting reasonably and observed the applicable and required standard of care. Failure to do so would establish negligence, or even recklessness since in bad weather scenarios, a reasonable person would slow down, perhaps even significantly depending on the conditions, and drive at a reduced rate of speed.

Other factors operate in tandem with the effects of weather to establish the applicable standard of care when an accident occurs. These include other road hazards and conditions, the condition of the car and its tires, the functionality of the windshield wipers and defogger, the functionality of the vehicle’s headlights, taillights, and brake lights, the presence of alcohol or drug use, and the driver’s familiarity with the roads and surrounding area.

According to Resources for the Future (RFF), a non-profit independent organization that conducts research in many areas, including environmental issues, the presence of warm weather increases the number of drivers on the road. The RFF evaluated 46.5 million police-reported accidents, weather reports from over 2,600 stations across America and daily travel logs of 207,455 households for the years 1990 to 2010. Initially, the researchers found that accidents increase when the weather is below freezing, or when snow or rain is present on the road. The RFF research team unexpectedly found a substantial increase in drivers when the weather was warmer than usual.

While warm weather apparently increases the number of drivers on the road, winter weather increases the danger and risk of driving. Yet, it is important to remember that the negligence of drivers often is the primary cause of accidents rather than an adverse weather condition such as ice or fog. Many young and inexperienced drivers do not adjust their speed or driving style when they encounter unfavorable road conditions caused by bad weather. RFF research indicates young drivers are most likely to have winter road accidents because they are not used to the inclement conditions, they lack driving experience, and they fail to spot hazards as quickly as those drivers that are more experienced.