One of the primary reasons snow leads to car crashes is the significant reduction in traction. Traction is the friction between a car's tires and the road surface, providing the necessary grip for acceleration, steering, and braking. Snow-covered roads decrease this friction, making it harder for tires to maintain contact with the pavement. As a result, vehicles have a higher likelihood of skidding, particularly during deceleration and cornering. Even with modern technologies like ABS (Anti-lock Braking System) and ESC (Electronic Stability Control), cars can still experience loss of grip on snowy surfaces, causing drivers to lose control.

Additionally, when snow compacts into ice, the issue is exacerbated. Ice provides even less traction than snow, presenting a serious danger. Drivers may find their vehicles shifting unpredictably or spinning out, especially at higher velocities or when sudden maneuvers are necessary. Winter tires, designed to perform better in snowy and icy conditions, have deeper treads and softer rubber compounds that provide better grip. However, even with the best tires, drivers must adapt their behavior to the reduced traction conditions that snow imposes.

Decreased Visibility

Heavy snowfall can severely impair visibility, which is crucial for safe driving. When visibility drops, it's harder for drivers to spot critical elements such as traffic signals, stop signs, road markings, and other vehicles. Further complicating matters, accumulating snow can cover the windshield, side windows, and mirrors, obstructing the driver's view. This layer requires constant effort to keep clear, often reducing the driver's attention to the road.

Another factor contributing to visibility issues is the bright glare from snowfall, which can be blinding, especially when coupled with the reflection from headlights and taillights during nighttime driving. Reduced visibility forces drivers to slow down, yet even at lower speeds, reaction times to unexpected obstacles are hampered. The visual cues normally relied upon for spatial awareness and speed judgment become unreliable, increasing the risk of collisions and off-road accidents.

Longer Stopping Distances

Snow and ice significantly increase the distance required for a vehicle to come to a complete stop. Under normal conditions, a car's braking distance is a straightforward function of speed, vehicle weight, and tire-road friction. In snowy conditions, however, the braking distance can be multiplied several times. This elongated stopping distance poses a challenge for all drivers but is particularly treacherous in areas with frequent stops and starts, such as intersections or congested roads.

Drivers may misjudge the time needed to halt their vehicle, leading to rear-end collisions. Snow compacts under braking force and can become a thin layer of ice, further increasing stopping distances. This phenomenon is particularly dangerous downhill or when attempting to avoid unexpected obstacles. Traffic accidents can also arise from panic braking, where sudden force applied to brakes could result in loss of control, skidding, or drifting into adjacent lanes.

Hidden Hazards

Snow can conceal hidden hazards on the road, such as ice patches (commonly referred to as black ice due to their near-invisible nature), potholes, uneven surfaces, curbs, and debris. Often forming on bridges, overpasses, and shaded areas, black ice appears as a thin, transparent layer of ice that blends in with the road, making it indistinguishable to drivers. Vehicles that hit black ice can instantly lose traction, leading to sudden skidding and potential crashes.

Patches of snow can also hide substantial road defects like potholes that, when driven over, can cause tire blowouts, control loss, or vehicle damage requiring abrupt forceful maneuvers. Thus, even experienced drivers familiar with their daily routes may find themselves caught off guard by these disguised perils.

Inexperienced or Unprepared Drivers

In areas unaccustomed to significant snowfall, many drivers may lack experience or confidence in driving under such conditions. Without proper knowledge of winter driving techniques—such as increasing following distances, using gentle braking, and making controlled instead of reactive steering adjustments—drivers are more prone to accidents. For instance, driving on snow requires different behavior compared to other conditions, such as brake tapping instead of slamming to maintain control and manage slips.

Many drivers fail to prepare their vehicles adequately for snowy conditions. Essential winter safety features, like snow tires and windshield wiper fluid resistant to freezing temperatures, can make a considerable difference. Insufficiently cleared cars can lead to ice and snow dislodging while in transit, posing risks to both the driver and other road users. Thus, preparedness plays a substantial role in mitigating the risks associated with driving in snowy conditions.

Immediate Compounding Factors

The presence of snow often introduces a chain reaction of hazardous circumstances that further raises the likelihood of accidents.

• Temperature Fluctuations: During winter, rapid changes in temperature can lead to alternating phases of melting and refreezing snow and ice, creating treacherous driving conditions. Morning commutes, for example, are particularly vulnerable to these shifts as melted snow from the previous day refreezes overnight, forming black ice.

• Mood and Behavior Adjustments: Snow can also alter driver behavior based on interpretations of conditions. Drivers might overcompensate by driving too slowly, creating traffic backups and increasing the chances of fender-benders. Conversely, overconfidence in handling winter conditions can lead to excessive speeds and reckless driving, particularly among drivers with four-wheel or all-wheel drive vehicles who believe these features make their cars invulnerable to lose traction.