Table 4 The estimated impact of the terrorist attack on ED inflow for increasing distances from the epicenter of the attack. The Table shows that the effect no longer becomes significant over 10 km distance. Note that the maximum distance in the data is 28.5 km and that the results cannot be extrapolated beyond this point due to the linearity assumption

From: The effect of a terrorist attack on emergency department inflow: an observation study using difference-in-differences methodology