“You can't build your way out of congestion.” – Or can you?

Abstract

The phenomenon of induced traffic was recognized (if rarely measured) even before the automotive age. Its existence calls into question the effectiveness of road construction as a solution to traffic congestion. Why, then, has it rarely been factored into highway investment decisions? An examination of references to induced traffic suggests that it posed an inconvenient complication to a consensus that had emerged by the 1920s. That consensus endorsed automotive mobility along with a commitment to keep building road space as long as traffic grew to fill it. Recent research challenges the factual assumptions underlying that consensus, but has not yet overturned the deeper beliefs upon which it rests.

Notes

McClintock (1925): 25 (both quotations). In more recent definitions, it is a reduction in speed caused by the presence of other vehicles, see Dargay and Goodwin (1998): “… the impedance vehicles impose on each other, due to the speedflow relationship, in conditions where the use of a transport system approaches its capacity.”

Brown (2006): 13. On recent use of similar calculations: see Dargay and Goodwin (1998): 163–166.

See Metz (2008a) and Cortwright's (2010) criticism that the widely cited Texas Transportation Institute statistics on US urban congestion assume that the ideal is highway speed rather than accessibility.

Proceedings of the Eighth National Conference on City Planning (1916): 75. Other early examples are cited by Vanderbilt (2008): 155 (from 1900) and Barrett (1983): 46 (from 1907).

George Baker Anderson, quoted in A. Brilliant (1989): 144.

Bartholomew in American Society of Civil Engineers, Transactions 88 (1925): 238–239. For other examples, see Fogelson (2001): 259–260, 267–268, 274; Norton (2008): 336, note 49. What Bartholomew describes is induced traffic as I am using the term, including travel diverted in time and route as well as new travel generated by a transportation improvement.

Asphalt 17 (1) (Jan. 1965): 2, 17 (4) (Oct. 1965): 2, and 18 (2) (Apr. 1966): 1.

See the argument against using the term “latent demand” in Gorham 2009: 4–5.

For further examples, see Ladd (2008): 121.

For other British references to US induced traffic, see Foster (1963): 18.

On engineers' dominance of transportation planning, see Rose (2003): 217, and Seely (1987). On the freeway revolts, see Ladd (2008): 103–129.

Meier (1989) is an early German-language example.

Recent studies (the first two include literature reviews) include Noland (2007), Weis and Axhausen (2009), and Duranton and Turner (2011).

Handy (2008) concludes that congestion relief measures still drive the planning process in the US. Næss et al. (2012): 294–295 points to several European states' policies that ignore induced traffic. Bayliss (2008): 13–16 accepts its existence, even while pushing for new road construction.

Recent scholarship on measuring accessibility: Axhausen (2008); Grengs et al. (2010). On integrating land-use and transportation planning: Straatemeier and Bertolini (2008); Zöllig and Axhausen (2011).

Additional information

Notes on contributors

Brian Ladd

Brian Ladd is a Research Associate in history at the University at Albany, State University of New York, and the author of books on German urban history as well as Autophobia: Love and Hate in the Automotive Age (University of Chicago Press, 2008).