It was found that the likelihood of death in a traffic crash on a rainy day is 1.4 times higher than on a clear day. On wet roads, the braking distance for passenger cars (the distance traveled from the moment the driver presses the brake pedal until the vehicle comes to a stop) nearly doubles compared with usual conditions, making collisions harder to avoid. The Korea Expressway Corporation advised reducing speed by more than 20% when driving in the rain.

The Korea Expressway Corporation (KEC) announced on the 9th, citing data from the Korea Road Traffic Authority, that an analysis of highway crash fatality rates over the past five years (2021~2025) showed 4.7 deaths per 100 crashes on rainy days, about 1.4 times higher than 3.4 on clear days.

Specifically, over the five years there were 1928 wet-road crashes on highways, with 90 fatalities. On clear days, there were 22226 crashes, resulting in 747 deaths.

The difference was also clear when expanded to all roads, including general national highways. On rainy days, there were 1058 deaths out of 60649 crashes, for a fatality rate of 1.7 per 100 crashes. On clear days, there were 11023 deaths out of 875935 crashes, or 1.3 per 100. In other words, the likelihood of death in a wet-road crash was 1.3 times higher.

KEC cites the ‘hydroplaning’ phenomenon that occurs on wet roads as a main cause. This refers to a situation in which, while driving in the rain, the tires fail to make proper contact with the road surface and move as if floating on water. In such cases, steering and braking are more likely to deviate from what the driver intends.

In fact, according to test results released last year by the Korea Transportation Safety Authority, the wet-road braking distance for passenger cars was 18.1ｍ, which was 1.8 times longer than 9.9ｍ on a dry surface. Because trucks and buses are heavier, their braking distances are longer than those of passenger cars. On wet roads, braking distances were 24.3ｍ for trucks and 28.9ｍ for buses.

KEC said, “When it rains, it is necessary to slow down by more than 20%, and when there is a downpour, by more than 50%,” adding, “On wet roads, the risk of rear-end collisions increases, so you should secure at least twice the usual following distance.” In particular, KEC explained that vehicles with taller bodies, such as trucks and buses, are more likely to sway in rain accompanied by wind, which raises crash risk, so drivers should be especially careful with steering.

KEC designated the period from May 15 to October 15 as the ‘summer flood and storm countermeasure period’ and formed a task force (TF) to inspect rain-vulnerable areas such as slopes, drainage facilities, and underpasses. It has also built and is operating a smart disaster management system that monitors river levels 24 hours a day to detect warning signs.

An official at KEC said, “Safety during the monsoon can be protected only when individual drivers comply with safety rules along with the response posture of relevant agencies,” and added, “Please pay attention to information provided via traffic broadcasts and other channels while driving.”