Introduction: Driving with warning lights and sirens is highly demanding for ambulance drivers, and the crash risk is much higher than that during normal driving. In this study our goals were to establish a coding protocol to observe how often and how long potentially critical driving situations (PCDS) occur during "blue-light" driving (driving with emergency response lights) and to describe traffic and environmental conditions preceding and accompanying the PCDS.
Methods: We collected randomly drawn video data of real ambulance driving between 2014-2017 in two German federal states. A coding protocol was developed to categorize PCDS into four types ("right of way," "crosswalks," "overtaking" [passing], and "other") and to describe them within the context of road characteristics, incident type, traffic, weather conditions, and driving style.
Results: A total of 172 videos of 71 different drivers were chosen randomly covering 1125 minutes of driving with warning lights and sirens. The drivers had a mean age of 33.7 years, and 25.4% were female. A total of 2048 PCDS occurred with a mean duration of five seconds (range of 1-66), amounting to one PCDS every 33 seconds. Twenty percent of the driving time involved PCDS. The rapid driving style (10.5%) showed more PCDS (one every 28.5 seconds), and the defensive driving style showed fewer PCDS (one every 49.6 seconds). Of all detected PCDS, "right of way" situations (57.5%) were most frequent, followed by "overtaking" [passing] maneuvers (30.2%).
Conclusion: This study used a detailed coding protocol to describe driving with warning lights and sirens. The PCDS occurred less frequently than anticipated, although they were still common events when driving an ambulance, representing significant potential for crashes or near-crashes. These results can be used for insight training programs to raise ambulance drivers' awareness of typical PCDS and associated potential crash risk.