Relationship Between Daylight Saving Time and Traffic Crashes in Florida

Abstract

The objective of this study was to examine the effect of transitions between daylight saving time (DST) and standard time (ST) on traffic crashes in Florida. The study was conducted using 37 years of crash data from Florida from 1983 to 2019. The analysis was based on crashes that occurred during the week before and the week following the time change. The paired Wilcoxon rank test implemented using a Bayesian approach was used to compare the difference in crash frequency following the clock shift to DST. The analysis showed that the time shift has a significant effect on traffic crashes. More specifically, the beginning of DST in the spring, when the clock moves forward by one hour, was associated with a higher frequency of fatal and nighttime crashes. The shift at the end of DST in the fall, when the clock moves back by one hour, resulted in a significant increase in all, no injury, morning peak hours, afternoon off-peak hours, two-vehicle, and multiple-vehicle crashes. Crashes during evening peak hours decreased in the week immediately following the time change. These findings were particularly significant on the Sunday when the shift occurred and the following Monday and Tuesday. It can be inferred from these findings that the impact of DST on safety may be attributed to the disruption of circadian rhythms as well as to the one-hour loss in the spring and one-hour gain in the fall. The study findings could assist researchers and practitioners in understanding the impacts of DST on roadway safety.