As we saw in “The respective gain, dip in light-duty vehicle travel miles, fuel-economy in America and what’s driving the change” post of Jan. 13, 2021 here on the Air Quality Matters blog, there were increases in aggregate light-duty vehicle (LDV) road-travel miles (VMT) 2019 versus 2018, and adding injury to insult was the notion that LDV fuel-efficiency values had worsened – they retreated from 25.1 miles per gallon (mpg) in Model Year (MY) 2018 to 24.9 mpg in MY 2019 LDVs, a difference of -0.2 mpg or -0.8 percent.
It was also seen how with the worsening average LDV fuel-economy values, there was an increase in carbon dioxide produced as a result that was released into the atmosphere on account of that. The amount of CO2 released into the air increased by 19.244 million tons, a gain of 1.694 percent.
In today’s thread looked at are the U.S. 2018 and 2019 average per-vehicle VMT-related stats. No surprise that those numbers climbed too, though, historically, that has not always been the case. There have been past situations where with increases in aggregate VMT, per-vehicle VMT figures actually fell. Explaining this phenomenon could be more people driving which would account for the aggregate rise but the overall distance each of those drivers drove was less one year to the next.
So, just how many more U.S. average per-vehicle VMT were logged in 2019 over that which was registered in 2018?
To find that information, the U.S. Department of Transportation, Federal Highway Administration’s “Annual Vehicle Distance Traveled in Miles and Related Data – 2019 by Highway Category and Vehicle Type” table was referenced.
It should be noted also that in this particular table, the class of light-duty vehicles was subdivided into two groups based on the length of their wheelbases. There are the LDVs with short wheelbases (less than or equal to 121 inches) and those with long wheelbases (more than 121 inches). For purposes of this discussion, this evaluation concerns itself with the short-wheelbase LDVs – passenger cars, light trucks, vans and sport utility vehicles (SUVs).
So, for the short wheelbase LDV sub-class the average per-vehicle VMT are 11,576 and 11,599 for years 2018 and 2019, respectively, a jump of 23 VMT. This is a difference of +0.199 percent.
But this does not tell us all we need to know. It is important to compare the stats for the two sub-classes.
For the long wheelbase LDV class, the per-vehicle VMT values were flipped. The numbers regarding average per-vehicle VMT were 11,486 (2018) versus 11,263 (2019), a decrease of 223 VMT or -1.942 percent. Long-wheelbase LDVs, incidentally, are comprised of large passenger cars, pickup trucks, vans and SUVs. Interesting to note is there are a little above three times more short-wheelbase (swb) light-duty vehicles on the road than there are long-wheelbase (lwb) LDVs (194,348,815 swb versus 59,465,369 lwb and 192,856,211 swb versus 57,853,842 lwb in 2019 and 2018, respectively). What’s surprising here is that while average per-vehicle VMT among the lwb group 2018 to 2019 retreated, for the swb group it was the opposite.
And, what does this mean regarding gas consumption and consequent swb LDV tailpipe-produced atmospheric carbon dioxide releases? For these, we must look at the per-vehicle average fuel consumption – in 2018 this was 475 gallons compared to 2019’s 481 gallons. It should be noted according to this same source that fuel economy in 2018 was 24.4 mpg while it was 24.1 mpg in 2019 – a -0.3 mpg or -1.23 percent change 2018 to 2019.
Meanwhile, regarding the number of gallons of gasoline consumed per vehicle, for the swb LDVs this was 91,585,334,000 in 2018 and 93,420,373,000 in 2019. And, being that for each gallon of gasoline burned and emitted into the air is 19.64 pounds of CO2, emitted were 1.799 trillion pounds (~900 million tons) and 1.835 trillion pounds (~917 million tons) of CO2 into the air in years 2018 and 2019, respectively. This is a difference of ~36.04 billion pounds (~+18 million tons) or a change of ~+2 percent. (Disclaimer: Due to rounding, the mathematically determined totals disagree slightly).
You’ll notice that today’s CO2 release figures of 18 million tons (2 percent) differ from those determined on Jan. 13, 2021 of 19.244 million tons (1.694 percent). No doubt accounting for the differences is the fact that in today’s post looked at were light-duty vehicles with short wheelbases while in the earlier post considered was light-duty vehicles as a whole.
Image above: U.S. Census Bureau
This post was last revised on Jan. 16, 2021 @ 3:43 p.m. Pacific Standard Time.
Published by Alan Kandel