Civil Engineering Reference
In-Depth Information
additional indirect costs on other projects the city might want to undertake.
Once the bridge is built, the new traffic patterns have chain reactions along
the road network, speeding up traffic near the downtown, reducing gridlock
miles away and lessening travel time from the city to suburbs. These are
indirect positive impacts. More city residents frequent the suburban mall
while others move to outlying suburban houses, imposing negative impact on
city business and housing. As users can now get around in less time, some
choose additional paid work in the city, positively impacting their wages,
and eat more while downtown, positively affecting restaurants. Trucks more
easily supply city businesses and carry products from city manufacturers to
the rest of the world, increasing business revenues.
These secondary effects in turn generate tertiary waves of cost and
benefit, to those who build the additional house in the suburb or to the
wholesaler selling additional food to the downtown restaurant. To ever
more minuscule extents, these waves spread out, to the nation as a whole.
Researchers who model such effects use giant interindustry charts in which
changes in one sector, say trucking, are examined for their impacts on all
other sectors, whether housing construction or restaurants, according to a
procedure called input-output analysis. A detailed economic impact analysis
would try to capture these effects. Some believe that studies with complete
national and regional input-output charts can give the fullest answer to the
question of bridge economic impact.
That being said, there are critics who question whether economic
impact studies truly capture the full range of infrastructure effects. One
set of critics focuses on neighborhood effects, here meant literally as the
neighborhoods near the foot of the bridge. Residents near the landings may
resent the added traffic that the bridge sends though their streets. The traffic
causes extra noise, endangers the children walking to school, and adds to
local air pollution, which some believe increases asthma rates. If the area
under the bridge becomes derelict, it may also become a meeting place for
vagrants, increasing crime, or just residents' fear of crime. Then again, the
formerly abandoned railway yard (let's say that's what was there before the
bridge) is turned into a fine landscaped park accessible to the public. Traffic
is elevated overhead, removing some exhaust from the residents. Drivers who
would formerly zip through the area now stop to patronize local businesses,
increasing employment and incomes. The critics point out that it is difficult
to accurately measure these varied effects.
Other critics points out that the market economy is dynamic and flex-
ible. Recessions and growth spurts occur, businesses expand or contract, new
products lines open up using new technologies, and businesses are started or
closed. Workers shift to new work sites, suppliers to new buyers, truckers to
new customers, tourists to new destinations. Mobility is essential to all these
