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 Surge When Only Recirculation Mode Is Used
Decreased Concentration and Drowsiness Can Lead to Serious Accidents—Caution Advised

Korea Expressway Corporation has announced that fatal accidents caused by drowsy driving are concentrated on highways in July, when the monsoon season and vacation period overlap.

Car Recirculation Button. Korea Electrical Safety Corporation

According to an analysis by Korea Expressway Corporation of fatal accidents on highways in July over the past three years (2023–2025), the average annual number of deaths caused by drowsy driving and lack of attention to the road is 10, accounting for 83% of all fatalities (12 people) during that period.

The corporation cited summer air conditioner usage habits as one of the causes of drowsy driving. When the air conditioner is operated for a long time in recirculation mode with the windows closed, carbon dioxide (CO₂) produced by the respiration of the driver and passengers accumulates. According to Korea Expressway Corporation, if only the recirculation mode is used in a sealed vehicle, the CO₂ concentration inside can rise from 600 ppm to 5,000 ppm in just 30 minutes. When the concentration exceeds 2,000 ppm, symptoms such as drowsiness, headache, and decreased concentration may occur.

The corporation recommends opening the windows periodically to ventilate and taking sufficient breaks at a nearby rest area or drowsy driving shelter if you drive continuously for more than two hours or feel fatigued. In fact, the Korea Transportation Safety Authority’s Automobile Research Institute announced earlier this year that, according to guidelines reflecting real-road driving conditions, even if you maintain recirculation mode while driving on highways, switching to outside air mode for 1–2 minutes at intervals of 1–2 hours can significantly lower the indoor CO₂ concentration.

In July 2025, a vehicle traveling in the first lane near the Daecheon Interchange on the West Coast Expressway (toward Mokpo) lost control due to drowsy driving and collided head-on with the energy-absorbing barrier at the interchange exit, resulting in one fatality. Korea Expressway Corporation

Additionally, Korea Expressway Corporation has cautioned drivers to be mindful of the increased risk of wet-road accidents during the monsoon season. Over the past three years, the average rainfall in July was 378 mm, the highest of the year, and the average number of rainy days was recorded at 15. Injuries and fatalities from traffic accidents on wet roads increased from an average of 0.7 people in June, to 1.3 in July, and 3.3 in August. According to data from the Korea Transportation Safety Authority, there were 1,928 wet-road highway accidents over the past five years, accounting for only 3.2% of all highway accidents; however, the fatality rate per 100 accidents was 4.7 people, which is 1.4 times higher than on clear days (3.4 people).

The corporation explained that checking tire wear and increasing tire pressure by more than 10% from the usual level before departure can help reduce hydroplaning and shorten braking distances. Furthermore, when driving on wet roads, drivers should reduce their speed by more than 20% compared to normal, and by more than half during heavy rain, while maintaining at least twice the usual following distance. When passing through standing water, reduce speed but do not stop.

Meanwhile, Korea Expressway Corporation is operating a "Summer Disaster Response Period" from May 15 to October 10, during which it inspects vulnerable facilities and has completed special inspections of reinforced earth retaining walls nationwide.

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