#43 Daylight Saving and Road Safety

Research has examined the relationship between serious and fatal road crashes and daylight saving time (DST), focusing mostly on the Spring and Autumn transitions to/from standard time to DST to identify road safety impacts. Internationally, DST is currently used in many countries and in Australia, it is implemented in the ACT, New South Wales, South Australia, Tasmania and Victoria. Multiple trials of DST in other jurisdictions, including Queensland and Western Australia, and associated referendums, have led to those states rejecting DST.

Factors that may influence crash frequency and severity as result of DST include the obvious changes in ambient light conditions relative to time-of-day, as well as changes in the sleep patterns of road users. European research identifies that people tend to sleep less during DST, and particularly during the Spring transition to DST from standard time[1]. Separating ambient light conditions from sleep deprivation as alternative explanatory factors, this study points to the former as being more influential on crash frequencies and outcomes. The transition to DST was found not to affect total and minor crash frequencies, but was found to reduce serious crashes in the evening period. While some differences were found regarding different categories of crashes by severity, the study concluded that, overall, DST has ‘rather small effects on the realisation of car crashes’.

Other recent research examined the effects of DST on road crashes in Australia[2]. Similar to the European research cited above, this study also used sleep and ambient light as the key explanatory factors. The study found no evidence of sleep mechanisms impacting road crashes in association with DST. It was found, however, that the distribution of crashes by time-of-day differed for DST and non-DST periods, indicating some potential influence of an ambient light mechanism. According to the author (James, 2023), similar to Laliotis et al. (2023), there is a reduction of crashes in the 6pm – 9pm evening period. However, this reduction is not clearly countered by an increase in morning period crashes, but by a seemingly random increase across all hours. Overall, the results do not suggest that ‘DST has a negative impact on fatal crashes in the long run’.

[1] Laliotis, I., Moscelli, G., & Monastiriotis, V. (2023). Summertime and the drivin’ is easy? Daylight saving time and vehicle accidents. Health Economics, 1–XXX. https://doi.org/10.1002/hec.4715

[2] James, J. (2023) Let there be light: daylight saving time and road traffic collisions. Economic Inquiry, 61(3), 523–545. Available from: https://doi.org/10.1111/ecin.13130