Supercommuters garner supersized attention far beyond their numbers. A supercommuter has a travel time between their nominal place of residence and nominal place of work that is far above the average (about 25 minutes each way in the US). The press loves the anecdote of someone who lives on Mars and commutes to Venus via spaceship, but they tend to leave out the point that they don’t do it every day. At the extreme, if someone has a 4-hour one way commute, they would be in motion 8 hours a day if they traveled every day, leaving no time for anything other than work and sleep. This seems unlikely because it is.
The Census, which is as official as it gets, gives the following definitions.
- Extreme Commuting: Traveling 90 or more minutes to work.
- Long-distance Commuting: Traveling 50 or more miles to work.
- Mega Commuting: Traveling 90 or more minutes and 50 or more miles to work.
This notably does not get at frequency, which Census data does not collect. Of the 71 million commuters, 587 thousand are considered mega commuters according to this Census study.
|Mean Time (Minutes)||Mean Distance (Miles)||Number (thousands)||Drove Alone (%)||Transit (%)||Share of Total Distance**||Share of Total Minutes**||Share of total Trips**|
Note: * this was what the Census reported, see text for discussion; ** Transportist calculations.
Immediately, to the transport analyst something seems wrong. The Mean time for long distance commuters is 61 minutes, but the mean distance is 247 miles. Distance over time equals speed. Damn, those long distance commuters drive fast at 240MPH). No, that’s not what’s going on. It’s that time is reported by the respondent, but distance is computed based on place of residence and place of work. The commute is not always from their “place of residence”, but some other place (a second home, a cousin’s couch, a hotel). To not realize this is to miss at least half the story.
Certainly, people who have commutes between 25 minutes and 4 hours are potentially interesting, not least because even if their numbers are small, their share of work vehicle miles traveled would be larger if they commuted as frequently. To illustrate with a numeric example, if 99% of the people have an average 1 hour (round-trip) commute and 1% have an average 4 hour (round-trip) commute, the average is now 1.03 hours, 3% higher. The 1% of supercommuters presumably cover at least 4% of total home-to-work distance, probably more since they are likely to be on faster links. So their influence is supersized, but still relatively small, and not as outsized as implied by the table above.
A recent PLOS One article: Nash, Rae (2016) An Economic Geography of the United States: From Commutes to Megaregions uses supercommuters to derive economic regions. While the results in the paper look perfectly plausible as economic regions, for the reasons above, I am suspicious of using Census Mega commuter data.
Another paper, Simini, Filippo; Marta C. Gonzales; Amos Maritan; Albert-László Barabási (2012). “A universal model for mobility and migration patterns” (PDF). Nature. 7392. 484: 96–100. doi:10.1038/nature10856 also pivots on the Census definition of commutes.
The claims in this paper are too great (a “universal” model is a bit presumptuous for a curve fitting exercise which assumes no differences in individual preferences). But they spend a lot of effort showing how their model explains what are either data errors, misinterpretations, or non-daily commutes in the same frame as daily commutes. The outliers (supercommuters) who commute once a week or have multiple residences of course exhibit different behavior than daily commuters.
What is commuting? In general terms, it is something that is done on a regular basis, but most commonly it refers to daily, rather than weekly commutes. The term “commuter” derives from the discounts (commuted fares, just like commuted sentences) that railroads gave to their suburban riders.
The distance between the primary residence and work for someone staying in a hotel or with a Pied-à-terre as a secondary residence, or commuting once a week, is qualitatively different from someone with a single residence and a daily commute.
So when you see articles about super-commuters, mega-commuters, long distance commuters, and the like, please arch an eyebrow.
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