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Vehicle-Miles Traveled
A more tangible measure of car use may be per capita VMT, which is the number of miles driven by the average car per day.
Statistics
The Federal Highway Administration estimates monthly national VMT with highway traffic volume counts. Presented in a monthly report called Traffic Volume Trends, these data are compiled by each state from a total of "4000 continuous traffic counting locations nationwide". [1] Changes in traffic volume are revealed by comparing traffic counts with the same month of the previous year.
The National Household Travel Survey [2], conducted roughly every 5 years, provides more specific information about VMT and Americans' driving habits.
According to the U.S. Bureau of Transportation Statistics, monthly VMT data are a good indicator of roadway use; they are used to estimate traffic congestion and air quality. In a nation so dependent on the automobile, VMT also correlate well with economic activity.
In January 2008, Americans drove a total of 226 billion miles. VMT peaks in summer and is lowest in winter. [3]
Overall Rise in Vehicle-Miles Traveled
A steady increase in VMT has been observed over the last several decades. According to the Wall Street Journal, "from 1977 to 2001, the number of miles driven every year by Americans rose by 151% -- about five times faster than the growth in population” [4].
Land use – namely sprawl development – is the main culprit. Americans are living farther from work, school, shopping and basic services. Even in higher density areas, where amenities may be closer to home, the road framework can be punishing for pedestrians. It is nearly impossible to walk in areas that cater to cars instead of people. Autocentric street design therefore forces even more cars onto roadways, which further impedes walkers and bicyclists. The vicious cycle continues and local governments turn to the only “quick fix” that they seem to know: build bigger highways (at enormous taxpayer expense) to accommodate the increased traffic.
Arguably more important than fuel efficiency, Vehicle-Miles Traveled directly affects gas consumption, emissions, and traffic patterns. A Prius owner who makes multiple, unnecessary trips and has a long work commute is no more virtuous than a Hummer driver who works close to home. Congress has addressed fuel efficiency: in December 2007, they finally mandated that CAFÉ standards be improved to 35 miles per gallon by the year 2020. This landmark legislation was achieved only after years of resistance by the automobile industry and a Democratic revolution in the 2006 mid-term elections. However, because changes in VMT have historically overtaken improvements in fuel efficiency, policymakers will need to act to reduce the number of miles that Americans drive by imposing a stiff gas tax, curtailing highway funding, heavily investing in public transit, and limiting free-for-all sprawl development.
Rising Gas Prices, Fewer Miles Driven
Highway VMT dropped from 2007 to 2008 due to high gas prices. The Department of Transportation reported a decline of 20 billion miles during the January – April period, compared to the same period in 2007. It is unlikely that the high cost of fuel alone will force a steady downward trend in VMT, but it may generate the political will needed for major changes in transportation and land use.
VMT Trivia
A survey commissioned in the 1990’s by the U.S. Department of Energy measured VMT between 1988 and 1994 [5]. Using a representative sample of vehicles, beginning-of-year and end-of-year odometer readings were noted. The data were then extrapolated to the entire national fleet.
Findings included:
- Newer cars are driven more than old cars
- Minivans were driven more than other cars
- Teenagers boost miles driven per household
- Higher income means more driving
- Older drivers cover less distance
ALSO ON THE LIVABLE STREETS NETWORK
REFERENCES
[1] Traffic Volume Trends. Federal Highway Administration. US Department of Transportation.
[2] Quick Start Guide from the National Household Travel Survey.
[3] U.S. Highway Vehicle Miles Traveled. Bureau of Transportation Statistics. US Department of Transportation.
[4] White, Joseph B. The Next Car Debate: Total Miles Driven. The Wall Street Journal February 5, 2008.
[5] Vehicle Miles Traveled. Transportation Energy Consumption Surveys. Energy Information Administration, US Department of Energy. Chapter 3.
PICTURE REFERENCES
Pictures are cited in the order they appear above. Please keep citation style consistent.
[1] US HIghway Vehicle Miles Traveled. Bureau of Transportation Statistics. US Department of Transportation. May 2008.
[2]
FURTHER READING
- Polzin, Stephen. The Case for Moderate Growth in Vehicle Miles of Travel: A Critical Juncture in U.S. Travel Behavior Trends. U.S. Department of Transportation. April 2006. Available here under Papers.
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