Civil Engineering Reference
In-Depth Information
by the impacted communities is strong, environmental regulations limiting the
scope of highway improvement projects, and last but not least, a lack of funding
sources.
6.2 Causes of VMT Growth
Metro area VMT growth has been driven by population and household growth, by a
decreasing population density; a higher labor force participation rate, higher per
capita income, and higher car ownership.
6.2.1 City Versus Suburban Population Growth
In 1950 the US population was 151.3 million, with 84.9 million living in metro-
politan areas
59 % in central cities and 41 % in suburbs.
The US population grew to 281.4 million in 2000, with 226.0 million living in
metropolitan areas
—
—
38 % in central cities, and 62 % in suburbs (Table
6.2
).
During this period, metropolitan areas grew by 141.1 million people with the
suburbs receiving 75 % (105.4 million) of this growth, and central cities the
remaining 25 % (35.7 million).
The additional 35.7 million people in central cities live in a higher density
environment (with the density of large cities being the higher than that of smaller
cities) where they can choose from a variety of mobility options available to them
(e.g., car, transit, walking, biking). However the additional 105.4 million people
who chose the suburbs, rely mainly on the automobile for daily mobility needs.
These location choices and conditions have fundamental consequences on how and
where people travel (Table
6.3
).
During the 1950
2000 period, metropolitan areas have grown in area as well as
-
in population
with area growth far exceeding population growth (for example, see
Table
6.4
). Therefore, population densities in the suburbs have remained low,
despite their population increase.
—
Table 6.2 US population trends: 1950
-
2000 millions
1950
2000
Change
All US
153.1
281.4
+128.3 (84 %)
Metro areas
84.9 (100 %)
226.0 (100 %)
+141.1 (166 %)
- Central cities
49.7 (59 %)
85.4 (38 %)
+35.7 (25 %)
- Suburbs
35.2 (41 %)
140.6 (62 %)
+105.4 (299 %)
Source
Calculated from Reference [
3
], Table 2-13, p. 27
