In a recent online discussion group about congestion I posted this question:
In the face of US reports of plateauing VMT and the increase in the average age of our automobile fleet, it would seem that the demand for new lane miles would be easing. Does anyone know if this is happening? Or is the lag in demand too long to test this effect, yet? Or is the pent up demand too great for an effect to be visible. Where can I go for such data?
Another participant, Todd Litman of the Victoria Transportation Institute, provided an insightful reply that is worth sharing (with permission):
That's an interesting question, Bern. There is a growing discussion among transport planners, particularly those involved in strategic planning, about the implications of peaking VMT. During the last century, vehicle ownership and travel grew steadily so it made sense to invest significant resources to expanding roads and parking supply; there was little doubt that additional capacity would be needed, it was simply a question of how soon. The main indicator used to evaluate transport system performance, roadway level-of- service, only reflects inadequate roadway supply. Transport models that extrapolated past trends into the future were used to predict that roadways would experience "gridlock" without future expansion.
But per capita vehicle travel peaked in most developed countries about the year 2000, and total U.S. VMT peaked about 2007. This results from structural trends including aging population, rising fuel prices, improvements to alternative modes, increased urbanization, increasing health and environmental concerns, and changing consumer preferences. The research cited below indicates that in developed countries, motor vehicle travel is unlikely to grow much overall in the future; there may be modest increases in VMT in areas with significant population or industrial growth but most areas will see traffic volumes hold steady or decline in the future.
This has important implications for transport policy and planning. It indicates that traffic and parking congestion will be less important problems to address than in the past, while demand for alternatives (walking, cycling, public transit, telework and delivery services) will increase. Congestion is a problem in many urban areas, but it is unlikely to get much worse, and it is just one of many transport problems, so congestion reduction is no longer the dominant transport planning objectives. In response to the combination of these changing demands, aging roadway infrastructure and declining fuel tax revenues, transport agencies are placing more emphasis on system maintenance, operations and modal diversity, and less on system expansion.
For more information see:
Phil Goodwin (2011), "Peak Car: Evidence Indicates That Private Car Use May Have Peaked And Be On The Decline," Urban Intelligence Network (www.rudi.net/node/22123 ).
Todd Litman (2005), “Changing Travel Demand: Implications for Transport Planning,” ITE Journal, Vol. 76, No. 9, September, pp. 27-33; at www.vtpi.org/future.pdf.
Todd Litman (2012), “Optimal Transport Policy For An Uncertain Future” at http://www.planetizen.com/node/54215
David Metz (2010), “Saturation of Demand for Daily Travel,” Transport Reviews, Vol. 30, Is. 5, pp. 659 – 674; summary at www.ucl.ac.uk/news/news- articles/1006/10060306 and www.eutransportghg2050.eu/cms/assets/Metz- Brussels-2-10.pdf.
Adam Millard-Ball and Lee Schipper (2010), “Are We Reaching Peak Travel? Trends in Passenger Transport in Eight Industrialized Countries,” Transport Reviews, Vol. 30 (http://dx.doi.org/10.1080/01441647.2010.518291).
Steven E. Polzin, Xuehao Chu and Nancy McGuckin (2011), "Exploring Changing Travel Trends, presented at Using National Household Travel Survey Data for Transportation Decision Making," Transportation Research Board; at http://onlinepubs.trb.org/onlinepubs/conferences/2011/NHTS1/Polzin2.pdf.
Clark Williams-Derry (2011), "Dude, Where Are My Cars?", Sightline Institute (www.sightline.org); at http://daily.sightline.org/blog_series/dude-where-are- my-cars.