Most people do, in fact, have specific travel time expectations for specific kinds of trips. Going away for a long weekend? Probably you're thinking 1-5 hours,

Most people do, in fact, have specific travel time expectations for specific kinds of trips. Going away for a long weekend? Probably you're thinking 1-5 hours, whether you're driving or flying. A week or two? Maybe 5-10 hours. Going to the store? 5-15 minutes. Physical distance doesn't matter at all, because it's abstracted away by the transportation technology. All we care about is cost (time and money), availability of destinations, and risk; and since distance doesn't matter, it really can't be risk per distance that we care about. In practice, no mode of transportation anywhere near as risky per time or per trip as my Mars example is ever going to become mainstream. The point of it is to demonstrate how absurd risk per distance is as a way of getting at a practical and meaningful assessment of travel risk, and we have to go outside of existing mainstream transportation options to see that absurdity because all the existing options must be extremely low risk by any measure or they wouldn't exist. The majority of consumers won't tolerate 1 in 10, 1 in 100, or even 1 in 1000 odds of death per trip.