Question: It is the year 2,500 and there are regular space flights around the galaxy. The space ship travels at 60,000 km/hour. The fatality rate is 10 per billion kilometers traveled? Each ship holds five people and when a crash occurs everyone dies. What is the fatality rate per hour traveled? Is travel to Jupiter feasible?
In your view, what is the better measure of the risk of travel -- fatalities per mile or fatalities per hour?
What are the ramifications of this finding towards the argument that air travel is extremely safe because deaths per mile traveled are low?
Answer: At 60,000 km/hour it would take 1.67x104 hours (1.0 x 109)/6.0x104) hours to fly one billion miles. This means there would on average be 10 deaths per 16,700 hours or 6 deaths in 10,000 hours.
The distance between earth and Jupiter varies. When they are closest together the distance is 628 million kilometers. The fatality rates indicate that travel between earth and Jupiter is not feasible.
A death rate of 10 deaths per billion kilometers is safer than the death rate for travel by cars in the United States.
Fatalities per mile clearly understate the risk of space (or air) travel.
An interesting discussion of the difference in the two fatality rates and the ramification for the safety of travel by plane can be found in the link below.