Risk factors affecting the severity of traffic accidents at Shanghai river-crossing tunnel.

<bold>Objective: </bold>With increasing traffic volume and urban development, increasing numbers of underground tunnels have been constructed to relieve conflict between strained land and heavy traffic. However, as more long tunnels are constructed, tunnel traffic safety is becoming increasingly serious. Thus, it is necessary to acquire their implications and impacts. This study examined 4,539 traffic accidents that have occurred in 14 Shanghai river-crossing tunnels for the period 2011-2012 and analyze the correlation between potential factors and accident injury severity.<bold>Methods: </bold>An ordered logit model was developed to examine the correlation between potential factors and accident injury severity.<bold>Results: </bold>Results show that increased injury severity is associated with male drivers, drivers aged 65 years or older, accident time from midnight to dawn, weekends, wet road surface, goods vehicles, 3 or more vehicles, 4 or more lanes, middle speed limits (50-79 km/h), zone 3, extra-long tunnels (over 3,000 m), and maximum longitudinal gradient.<bold>Conclusions: </bold>This article aims to provide useful information for engineers to develop interventions and countermeasures to improve tunnel safety in China. [ABSTRACT FROM AUTHOR]