Massive Freeway Expansions
Accompany Lower than Average
Travel Increases in Phoenix

The view is often expressed that building or expanding freeways "induces" significant amounts of new highway travel, and that, as a result roadway expansion is fruitless as a strategy for reducing traffic congestion. This "building maternity wards" creates babies logic is disproven by the experience of Phoenix relative to other large urban areas.

In 1985 Phoenix had the lowest number of freeway lane miles per 1,000 population of any of the US urban areas with a population of more than 1,000,000 in 2000. Phoenix began a program of massive freeway construction, with additions to its freeway system being more than double that of second ranked Las Vegas, 7.6 and times average The rate of freeway lane addition was also 16.5 times that of Portland, Oregon, which has implemented strategies to limit freeway expansion..

The "it is fruitless to add capacity" theory would predict that this inordinate expansion of freeway capacity, roadway travel would induced an inordinate increase in roadway travel in the Phoenix area. In fact, the opposite occurred.

1. From 1985 to 2000, per capita roadway travel increased 27.1 percent in Phoenix, well below the 40 urban area average of 43.1 percent and less than one-third the 86.3 percent increase rate of Portland.

2. In 1985, per capita travel in Phoenix was above the 40 urban area average. By 2000 per capita travel in Phoenix was below average.

Adding freeway capacity does not, in and of itself, induce inordinate increases in roadway travel.

Table 1          
  Phoenix Rank Portland Rank Average
1985 0.13 40 0.50 22 0.54
2000 0.40 33 0.47 27 0.58
Change 211.3% 1 -5.2% 29 7.7%
Change in Lane Miles 390.5% 1 23.7% 30 51.5%
Phoenix Compared to Portland 16.5        
Phoenix Compared to Average 7.6        
Table 2          
  Phoenix Rank Portland Rank Average
1985 16.6 15 11.5 38 15.9
Phoenix Compared to Portland 1.45        
Phoenix Compared to Average 1.05        
2000 21.2 27 21.3 25 22.5
Phoenix Compared to Portland 0.99        
Phoenix Compared to Average 0.94        
Change 27.1% 33 86.3% 3 43.1%
Phoenix Compared to Portland 0.31        
Phoenix Compared to Average 0.63        
Calculated from Texas Transportation Institute Data      

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