The new energy bill will give us an extra hour of daylight savings time for parts of both March and November. But is this a good idea? Is daylight savings time at all a good idea? I don’t know, but here is a new argument I never heard before:
“Springing forward” is tantamount to imposing a mild case of jet lag throughout the country, with potentially unhappy consequences.
Might that mean more traffic accidents?
…following the spring shift to Daylight Savings Time (when one hour of sleep is lost) there is a measurable increase in the number of traffic accidents that result in fatalities. Furthermore, it replicates the absence of any “rebound” reduction of accidents following the fall shift to DST (when the opportunity is present for an additional hour of sleep).
Of the two competing hypotheses for this increase in accidents, namely the one that suggests that it is the increased sleep deficit that causes the change in accident rate, versus notions based upon reduced illumination levels when driving to work, or suppositions that people forget the DST time change, fail to adjust their clocks, and find themselves rushing to work to avoid being late, the sleep hypothesis seems to be the most tenable. Hypotheses based upon haste and dim morning light both predict the bulk of the increased accidents to be confined to the morning hours. The sleep loss hypothesis would predict that individuals become more tired as the day wears on and hence the bulk of the accidents will appear later in the day. It is, of course, this latter pattern which appears with most of the accident fatality increase confined to the period after noon.
If the sleep loss hypothesis is correct, then why isn’t there a reduction in the number of traffic accidents in the fall, when the shift back to standard time provides an extra hour for sleep? Although this was the pattern observed in one study (Coren, 1996b) it has not replicated in other studies. The failure of the “safety rebound” may simply have to do with human nature. Just because a person has the opportunity to sleep for an addition hour does not mean that people actually will go to sleep on time. Many may spend that extra hour socializing or watching television. In some instances, where individuals do go to bed at the appropriate time, their usual circadian rhythm may still wake them after 7 or 8 hours in response internal signals or the external morning increase in illumination. Contrast this to what happens in the spring, where an individual’s work schedule will enforce the person’s awakening on the new DST time in order to meet job commitments.
Here is a blog post (with further discussion) on the topic, here is the underlying study, the original tip is from Eric Rasmusen. I have yet to see data on whether Indiana — which does not adopt Daylight Savings Time — is in fact a safer place to drive, at least for a part of each year.