According to Kyunghyang Shinmun, the pileup occurred inside a tunnel on the expressway on the 11th; one person was transported in cardiac arrest and traffic was briefly controlled.

Police and fire authorities are investigating the cause. Tunnel crashes tend to escalate because rescue access and entry control are difficult.

In tunnels, the basics are headway distance, reduced speed and headlights on; summer road trips also raise drowsy-driving risk.

The highway authority will inspect safety facilities on the section and step up warnings on signboards before tunnel entrances.