[0] https://en.wikipedia.org/wiki/Aviation_safety#Transport_comp...
Since I'm unlikely to fly my 20 mile commute to work, logging those miles under the "drive car" category isn't comparable, but is likely how I'd be in a car accident since that's something like 75% of my driving life. It seems you should only compare flights of 3 hrs vs car trips of 3 hours, or similar.
Comparing flying for an hour vs driving for an hour isn’t a comparison between two substitute goods, unless the purpose of my trip was “to kill an hour”, making those valid substitutes.
You'd need to set some minimum trip distance for which flying is a viable alternative, like say 300 or 500 miles. Then throw out all the driving data for under that. Now, how would you expect this to shift the deaths/mile of driving?
In order to reduce it, driving short trips would have to be more dangerous per mile than driving long trips. I think this is unlikely to be true. Long trips often take place on highways at higher speeds and thus accidents have higher consequences. Drivers are more likely to be fatigued on longer trips. Drivers are less likely to be familiar with the roads on longer trips.
You've probably also got to throw out all flights for which driving is not a possibility. Like transcontinental trips. That may make flying appear safer since flights over oceans are more dangerous since there arent as many emergency landing opportunities.
High speed delta to predominant flow is the more accurate metric.
Your fatigue comment is well received, but not a given either. A person may feel driving in a fatigued state is more acceptable for a short trip, but enforce more rigid limits on behavior for a long trip from home.
I would be shocked to find that short trips were safer (per-mile) than long trips, as my intuition is that interstate highways are likely to be by far the safest type of roadway on a per-mile basis.
So I did some digging. It was surprisingly hard to find data that broke it down by roadway type, but I eventually found an article[1] that also linked to data[2].
Taking the most recent year available [2004], and converting to the typical airline standard (deaths per 10 billion miles travelled), urban interstates have a death rate of 57 deaths/10Bmi, urban collector roads 85 deaths/10Bmi, urban local roads 128 d/10Bmi, and rural local roads 315 d/10Bmi.
Airline figures for comparison are about 0.2 deaths per 10Bmi for scheduled commercial airline travel (Delta, United, Southwest, American, etc; not charter, not corporate, not general aviation), yet people are much more fearful of airplanes than automobiles on average.
[1] - http://freakonomics.com/2010/01/29/the-irony-of-road-fear/
[2] - https://www.bts.gov/archive/publications/national_transporta...
This isn't actually true for recreational travelers. People roughly spend the same amount of time traveling as before commercial flight, they just go further.
To put it differently, people generally have the same vacation time available to them. They're also generally willing to burn roughly the same fraction of their vacation on the travel portion.
Commercial air travel has just enabled people to travel further in the same amount of time, while also burning more fuel doing so vs. the alternatives (road, rail...)
Short haul flights are right around 100 miles per gallon per passenger seat: https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft#Short...
For a couple considering an airline flight vs a car, they'd need to be driving a 50mpg car to achieve the same fuel efficiency as the airline.
This is obviously not the case.
Trying to compare the two "per pax mile" ignores the fact that the convenience of air travel created more travel than it ever saved in fuel efficiency as a bulk mover. It covers longer distances in generally less time and more comfort, it created a new class of travel in an additive fashion, it didn't strictly replace the alternatives.
If we're actually debating fuel and emissions on a large scale, this is a major part of the larger picture.
Furthermore, since the primary dimension which matters to individuals is time and cost not distance, when you'd compare a vacation by automobile to flight, the automobile vacation would likely be to a nearer destination. So one shouldn't even be comparing equal distances if attempting such a comparison, it's just not comfortable and/or worthwhile for most people to drive across the country for a weekend trip - many will do that flight without batting an eye.
Fortunately modern vehicles, especially the likes of Teslas and supercharger networks completely destroy even your disingenuous comparison.
If someone invents a plane which has the same probability of death flying between point A and point B, but gets there in half the time, it's not really less safe.