Travel Safety: Time versus Distance

Many references to travel safety, especially in regards to aviation, often refer to fatalities per passenger mile or kilometer. It will be argued here that a better measure for transportation safety analysis would be to measure fatalities per passenger hour instead of per passenger mile or kilometer. Note that fatalities differ for larger vehicles wherein a fatality in a car may be associated with a fewer fatalities per vehicle whereas for airlines or rail it may be associated with a higher number of fellow fatalities per vehicle. The major thrust of this article is to consider the extreme cases of not traveling at all versus traveling at a very high speed and thus a greater distance. In not traveling at all, one might incur an otherwise actuarial fatality with an hourly computation here being finite but with the mileage computation dividing by zero and creating a nominally infinite fatality rate! Likewise in an opposite case for a fast but dangerous travel (like the Space Shuttle) would result in a lower fatality rate with a distance based rate, but not in terms of a time based rate! Indeed, I suspect that distance traveled rates are promoted in that a more favorable comparison results for air travel