Environmental Engineering Reference
In-Depth Information
portation Alliance, a group that favors more state investment in road
and rail projects, said that a 10 cent increase in the gas tax would cost
each Virginia motorist an average of $60 a year, much less than the poor
roads are costing them.
The rate of road deterioration depends not only on the number of
vehicles it services, but also on the weight of the vehicles. This means
that heavy trucks are disproportionately responsible for highway damage.
The average American or Japanese car weighs about 3,000 pounds;
trailer trucks can weigh more than 100,000 pounds. According to the
Department of Transportation (DOT), combination trucks weighing
80,000 to 100,000 pounds pay just 50 percent of the cost of the damage
they cause to the highway system. Trucks weighing more than 100,000
pounds pay only 40 percent. 38 The DOT has pointed out that this violates
a tenet of highway taxation, dating back to the creation of the Highway
Trust Fund, that “different vehicle classes should be charged in propor-
tion to their contribution to highway investment requirements.” Drivers
of automobiles are subsidizing the trucking industry.
Collapsing Bridges
A 2000 report by the Federal Highway Administration (FHA) indicated
that an average of about 2,500 new and well-constructed bridges are
built each year. But there are 594,709 bridges longer than twenty feet
in the United States. Their average age is forty-three years, seven years
shy of the maximum age for which most are designed. Twenty percent
are more than fi fty years old. The FHA reported in 2006 that 25.8
percent were “structurally defi cient” (12.4 percent) or “functionally
obsolete” (13.4 percent). 39 The percentage of defi cient bridges was
highest in the District of Columbia (52.2 percent) and lowest in South
Dakota (4.4 percent). “Structurally defi cient” generally means the bridge
cannot carry the traffi c it was designed to accommodate. Functionally
obsolete bridges also have major design problems that diminish their
load-carrying capacity.
In its most recent report card on the nation's infrastructure, in 2009,
the American Society of Civil Engineers gave the nation's bridges a grade
of C. About one-quarter of our bridges are in trouble. A $17 billion
annual investment is needed to substantially improve current bridge
conditions. Total bridge expenditures by all levels of government for
system preservation and expansion are $10.5 billion.
Many of the inadequate bridges were built between the 1930s and
1960s, when designers did not fully understand the effects of metal
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