When will we reach peak road?

We have possibly reached peak vehicle, and peak travel in the US.

Peak Road? Source: Table 1-4: Public Road and Street Mileage in the United States by Type of Surface(a) (Thousands of miles) http://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/national_transportation_statistics/html/table_01_04.html
Peak Road? Source: Table 1-4: Public Road and Street Mileage in the United States by Type of Surface(a) (Thousands of miles) http://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/national_transportation_statistics/html/table_01_04.html

Have we reached peak road?

Noodling about USDOT statistics I see Table 1-4: Public Road and Street Mileage in the United States by Type of Surface (Bureau of Transportation Statistics), which suggests we reached peak road sometime between 2008 and 2011.

Unpaved mileage has been generally declining for years, as unpaved roads were paved. But paved miles (and the total) have generally been increasing, until between 2008 and 2011 that is. Some of this is likely to be statistical noise (either reporting errors on the part of one or a few states, some changes in definitions), but some of it is real, as states and localities begin to gravelize. We see that about half of the decline in paved roads is compensated for by an increase in unpaved roads.

In the railroad sector, miles of track peaked around 1920, though freight traffic continued to increase, and there is more traffic and especially more productivity (traffic per worker, traffic per mile) today then ever before. Using that as a model suggests the issues are complex.

Clearly we have overbuilt much of the road network. We can think about a number peaks, which will not likely occur simultaneously:

  • Peak Freeway Centerline Miles
  • Peak Freeway Lane Miles
  • Peak Freeway Surface Area
  • Peak Non-Freeway Centerline Miles
  • Peak Non-Freeway Lane Miles
  • Peak Paved Surface Area

Lane miles may continue to increase well after centerline miles have decreased, as some roads are abandoned (faster than new routes are built), and others continue to be widened.

The processes that govern this, in order of the immediate significance, I posit as follow:

  • Rural depaving (gravelization)
  • Removing urban freeways
  • Complete streets/road diets
  • Bus lanes
  • Skinny cars and automation
  • Flying cars

While freeway centerline miles are almost done, and overall centerline miles quite possibly are done, lane miles still have a lot of potential capacity. The transportation-industrial complex doesn’t care much whether it is paving a new link or widening an existing link (though clearly some prefer one over the other). It will be saddened and disheartened to see total capacity decreasing however.

3 thoughts on “When will we reach peak road?”

  1. Your x-axis is scaled differently for the different time periods, which misrepresents the slopes in data that you show.

      1. True. But when a rate of change is the subject of the chart, comparing two sets of data that are not scaled the same, on the same chart, can be accidentally misleading.

        Interesting stuff though.

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