Factors Affecting Injury Severity in Tunnel Crashes Observed over a Long Period on Korean Freeway Systems

Crashes in tunnels can be more severe than those in open road sections. In Korean freeway tunnels, despite a 0.5 % annual reduction in crash occurrences from 2013 to 2022, fatalities have increased by 6.2 % during the same period. Although various efforts have been made to analyze the injury severity of tunnel crashes in countries characterized by a high proportion of mountainous roadways, only a few such studies have been conducted in Korean freeway systems, and those used crash data over a relatively short period. Therefore, this study examines the factors affecting the injury severity in Korean freeway tunnels using an extensive 10-year dataset from 2013 to 2022. By applying a partial proportional odds model, the analysis revealed the following factors increasing the likelihood of severe injuries: crashes in spring, crashes in longer tunnels, crashes by distraction, crashes by drowsy driving, rollover after a crash, crashes including completely damaged vehicles, rear-end collisions, sideswipe collisions, and crashes by heavy vehicles, such as buses and trucks. Conversely, crashes in the interior zone were associated with a reduced likelihood of severe injuries.