Fig. 4

Probability of multiple casualties with a high likelihood of a life-threatening condition before and after system introduction. The probability of multiple casualties with a high likelihood of life-threatening conditions before and after system introduction was not significantly different during daytime weekday hours (before vs. after, 10.0% vs. 15.1%, P = 0.062) (a). However, during nights or weekends, the probability of multiple casualties with a high likelihood of life-threatening conditions after system introduction was significantly higher compared to before system introduction (before vs. after [nights or weekends], 4.8% vs. 12.9%, P < 0.0001) (b), as well as in the overall time period (before vs. after, 6.2% vs. 13.6%, P < 0.0001) (c). P value was calculated using a chi-square test