Sudden illness in real-life crashes: Drivers' pre-crash vehicle handling and signs of illness

Background Driver incapacitation due to sudden illness (e.g., cardiac arrest, seizures, diabetic events) poses a serious traffic safety concern. However, knowledge is limited regarding how such medical events manifest in drivers and affect their behavior. This study therefore aimed to investigate drivers' vehicle handling and signs of illness in crashes caused by sudden illness. Methods Crashes were identified in Volvo Cars' Internal Accident Database and the Swedish Transport Administration's register. Descriptions of drivers' vehicle handling and signs of illness were compiled from pre-crash vehicle signal recordings, mail survey responses, and in-depth crash investigations. The analysis included descriptive statistics of driver and crash characteristics, as well as an exploratory analysis of pre-crash vehicle handling and signs of illness. Results A total of 138 cases were included in the analysis. Most were single-vehicle crashes occurring in various traffic environments, with posted speed limits ranging from 30 to 110 km/h. The crashes were caused by a variety of medical conditions, typically resulting in loss of consciousness. A notable finding was that most drivers pressed the accelerator pedal after becoming ill and losing consciousness. Signs of illness varied: drivers' posture commonly collapsed, while some drivers remained upright with their hands on the steering wheel and eyes on the road despite being unconscious. Conclusion This study provides new and important insights into pre-crash driver behaviors in crashes caused by sudden illness. The findings underscore the need for multiple detection methods and rapid intervention strategies to mitigate the consequences of medical incapacitation and unintended driver actions.