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 n analysis
of the respected Texas Transportation Institute's (TTI) annual
report on metropolitan congestion shows that the most common
congestion-fighting strategy road-building has had virtually
no impact on the growth of traffic congestion in major urban
areas in the last 15 years.
 The
analysis, by STPP, was prompted by a number of recent studies
questioning whether building new roads reduces congestion. Using
TTI data, STPP compared metro areas that added significant new
capacity with those that did not and found that while the first
group spent roughly $22 billion more on construction, the average
of TTI's "roadway congestion index" for each of the
two groups was almost identical."
Widening
roads to ease traffic congestion is ineffective and expensive,"
says Roy Kienitz, executive director of STPP. "It's like
trying to cure obesity by loosening your belt."
The
TTI study also projects the increase in lane miles needed to
keep up with traffic growth. STPP's analysis of the data estimates
that most urban areas would have to spend thousands of dollars
per family each year to build new roads, ranging up to $3,243
in Nashville, Tennessee.
The
STPP report says the problem may be partially explained by the
phenomenon of "induced traffic." Several recent studies
have documented that new roads actually encourage more driving.
A University
of California study of 30 urban counties in the state found that
every 1 percent increase in lane miles generates a 0.9 percent
increase in traffic within five years, negating any congestion-easing
effect.
The
report did not control for other factors that might influence
congestion, such as economic activity or population growth. But
the large size of the data set (70 metropolitan areas) and long
duration of the study (15 years) make it likely that any relationships
between road-building and congestion would emerge.
The
study concludes that given the enormous costs of roadway construction,
officials need to investigate a broader menu of measures that
include other transportation modes, new technology, pricing,
land use and other strategies.
View
the report at www.transact.org;
TTI's study is at http://mobility.tamu.edu.
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