The Three Day Puzzle

| August 7th, 2008

I came across this rather interesting paper – “Terror attacks influence driving behavior in Israel” authored by Guy Stecklov and Joshua R. Goldstein (Carnegie Mellon University), which provides interesting correlations between ‘terror attacks’ and ‘traffic accidents’. Now what do ‘terror attacks’ and ‘traffic accidents’ have anything to do with some ’3 day puzzle’. Some interesting details regarding the 3-day mystery provided in the paper are as follows:

  • No day-0, day-1, or day-2 effects of terror are observed on traffic fatalities, but there is an increase of almost 35% in the rate of traffic fatalities 3 days after terror attacks.
  • The findings suggest that the third-day effect of large terror attacks is even larger, with a 69% increase in traffic fatalities.
  • Interestingly, the 3-day lag observed is similar to that found in studies on imitative suicides, in which well publicized suicides are followed 3 days after with a rise in traffic fatalities. [reference]
  • A similar 3-day spike in homicides is also found after major boxing matches. [reference]
  • Some fraction of the increase in traffic fatalities after terror attacks may be attributable to covert suicides and/or increased aggression on the road.
  • There is a notable lack of longer-term effects beyond the 3-day spike in fatal accidents. Days four and beyond have normal levels of traffic volume and accidents and suggest that the effects of terror are transient.
  • Why traffic fatalities increase on the third day after a terror attack remains a puzzle.

Possible explanations to the 3-day lag are:

  • The day-three increase in fatalities coincides with the time when those exposed to terror may try to return to their normal routines but are not yet psychologically, and perhaps physiologically, sufficiently recovered.
  • Yet another explanation for the 3-day lag is that it is a counterreaction to the collective bonding that occurs immediately after the terror event, similar to the “post-suppression rebound” found in experimental psychology.

The interesting point to look for in the graphs below is the 3rd day after the attack.

Terror attacks - Traffic accidents
Figure: Model estimates of proportional effects of terror attacks on traffic volume and accident rates by number of days after attack. (Upper) Results for all attacks. (Lower) Large attacks only.

Other similar interesting reads are in the references of the paper. I am listing a few of them below: