LPSISRL wrote:
That's exactly the piece of data left out. 150 million more miles driven in 2015 than in 2013. Sounds like a lot and it supports your hypothesis. But maybe not. In 2015 there were 7.8 million more cars registered than in 2013. (263.6 vs 255.8) Assuming, (making an ass of you and me) 12K miles on the average per year for those additional cars, that's 93.6 million additional miles driven simply by the increase in the number of cars. Now you spread the real difference of 56.4 million miles between the other 255.8 million cars and the increase does not look very significant. That's .2 miles per car. What if the average number of miles driven was 15K or 18K? At 18K per year, the number of additional miles driven is about totally wiped out by the additional cars. BUT... How many more drivers were there? How many were actually on the roads and not sitting in driveways and dealer lots? That's the problem with statistics.
"In 2015 there were 7.8 million more cars registered than in 2013."
You're right that in the grand scheme of nationwide statistics for the United States, 7.8 million is really a nominal number. While this does suggest an addition of millions of cars, you also have to account for the number of cars that were junked, totaled beyond repair, and rendered inoperable between that time. Much like with birth statistics and population numbers, you have to examine death statistics. In come the new, but out go the old.
That being said, the number is by registration which doesn't exclude older cars on the road and the 7.8 million is a difference, meaning growth in number in this case. However, that seems to actually support my main argument: cheaper gas prices causing more people to drive. The additional registration figures during the time when gas is cheap actually seem to reflect that more people bought cars and drove due to lower gas prices than alternatives such as carpooling, public transportation, cycling, etc. It's likely that the lower gas prices positively affected car sales and increased registration numbers which then meant more cars and more drivers at any given time in 2015 than in 2013. This then made accidents and motor vehicle deaths more likely.
The statistics reminds me of someone I know who used to ride the Metro (the subway system) in DC to work. When gas prices got so low, it made less and less sense for her to take over twice the amount of time to ride the Metro in to work. She then got a Prius and started driving herself. The low gas prices in this case added another car on the road. While empirical data is the weakest in any argument, I can't help but to note the increase in traffic I observed in my commute when the gas prices plummeted. It really did seem like more people were driving.
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