Daylight Savings Time

Our paper on The effects of daylight saving time on vehicle crashes in Minnesota, which has just been accepted to the Journal of Safety Research was discussed on today’s John Hines show on WCCO radio.

Daylight saving time (DST), implemented as an energy saving policy, impacts many other aspects of life; one is road safety. Based on vehicle crash data in Minnesota from
2001 to 2007, this paper evaluates long- and short-term e ffects of DST on daily vehicle
crashes. To provide evidence to explain the causes of more/fewer crashes in DST, we
examine the impact of DST on crashes in four periods of a day: 3 am-9 am, 9 am-3 pm,
3 pm-9 pm, 9 pm-12 pm. The eff ects of risk and exposure to traffic are also separated.
Our statistical models not only include weather conditions and dummy variables for
days in DST as independent variables, but also consider traffic volumes on major roads
in di fferent periods of a day. Our major fi nding is that the short-term eff ect of DST
on crashes on the morning of the first DST is not statistically signi ficant. Moreover, it
is interesting to notice that while DST per se is associated with fewer crashes during
dusk, this is in part off set because it is also associated with more traffic on roads (and
hence more crashes). Our path analysis shows that overall DST reduces crashes.