83% of Highway Fatalities Linked to This 'Habit'... Check 'This Button' When Driving in Summer

Expressway Corporation Analyzes Causes of Drowsy Driving in Summer
CO₂ Levels Spike When Using Only Recirculation Mode
Decreased Concentration and Drowsiness Can Lead to Major Accidents; Caution Urged

Korea Expressway Corporation announced that fatal accidents caused by drowsy driving are concentrated on highways in July, when the rainy season coincides with the vacation period.

Car Recirculation Button. Korea Electrical Safety Corporation

According to an analysis of fatal highway accidents in July over the past three years (2023–2025) by Korea Expressway Corporation, an average of 10 people died each year due to drowsy driving and inattentiveness to the road ahead, accounting for 83% of all fatalities (12 people).

Korea Expressway Corporation identified summer air conditioner use habits as one of the causes of drowsy driving. When the windows are closed and the air conditioner is operated for an extended period in recirculation mode, carbon dioxide (CO₂) generated by the breathing of the driver and passengers accumulates. According to the corporation, if only the recirculation mode is used in a sealed vehicle, the indoor CO₂ concentration can rise from 600 ppm to 5,000 ppm within 30 minutes. If the concentration exceeds 2,000 ppm, it can lead to drowsiness, headaches, and decreased concentration.

The corporation recommended periodically opening the windows for ventilation, and advised drivers to take sufficient breaks at nearby rest areas or drowsy driving shelters if they drive continuously for more than two hours or feel fatigued. In fact, the Korea Transportation Safety Authority’s Automotive Research Institute stated in its indoor air quality management guidelines, announced earlier this year and reflecting real road driving conditions, that even when recirculation mode is maintained while driving on highways, switching to outside air mode for one to two minutes every one to two hours can significantly lower the indoor CO₂ concentration.

In July 2025, a vehicle traveling in the first lane near Daecheon Interchange on the west coast line (toward Mokpo) lost control due to drowsy driving and crashed headfirst into the impact absorption facility at the interchange exit, resulting in one death. Korea Expressway Corporation

In addition, Korea Expressway Corporation cautioned drivers about the increased risk of accidents on wet roads during the rainy season. The average rainfall in July over the past three years was 378 mm, the highest of the year, with an average of 15 days of precipitation. The number of casualties from traffic accidents on wet roads increased from a monthly average of 0.7 people in June to 1.3 in July and 3.3 in August. According to the Korea Transportation Safety Authority, there were 1,928 highway accidents on wet roads over the past five years, accounting for only 3.2% of all accidents, but the fatality rate—measured as the number of deaths per 100 accidents—was 4.7, 1.4 times higher than on clear days (3.4).

Korea Expressway Corporation explained that checking tire wear before departure and increasing tire pressure by more than 10% above normal can reduce hydroplaning and shorten braking distance. It also advised reducing speed by more than 20% on wet roads and by more than half during heavy rain, while maintaining a following distance at least twice as long as usual. When passing through areas with standing water, drivers should slow down but not stop.

Meanwhile, Korea Expressway Corporation has been operating its "Summer Disaster Response Period" from May 15 to October 10, inspecting vulnerable facilities and completing special inspections of reinforced earth retaining walls nationwide.

This content was produced with the assistance of AI translation services.