Civil Engineering Reference
In-Depth Information
shifts, most of which cannot be predicted, since investors themselves have a
hard time predicting what they will do next year. It follows, the critics say,
that this kind of dynamic economy depends heavily on the existence of a
high-quality transportation network, one that provides lots of choices for
users. The usual cost-benefit analytical procedure, which assumes fixed pres-
ent resources, will tend to
underinvest
in infrastructure, because it will tend to
underappreciate the range of alternative possibilities to which future invest-
ment will respond and underestimate the degree to which future economic
development (to which the bridge contributes) will expand the resources
available. These critics would say that, with the bridge in existence, the
city will enjoy an increased flow of resources by which to pay for bridges
and other future projects.
Another group of critics argues, by contrast, that road transportation
poses environmental harms that ordinary cost-benefit analysis leaves out.
The former railroad land on which our bridge is built could have been
put to other use; in our cost-benefit analysis we attributed to it no cost
because the city owned it, but perhaps we should have valued it, since it
could have been put to use as a wildlife preserve. What's more, building a
new bridge increases dependence on automobiles rather than public transit.
As the bridge initially reduces travel times, people can move farther from
each other, as can businesses from customers and suppliers, imposing greater
distances on travelers, forcing still more people to rely on cars, and these
added cars soon recongest the downtown streets that were briefly freed up.
With the additional cycle of congestion, more land has to be given over
for parking, more pollution enters local lungs, the country depends more
on fossil fuels, and more carbon flows into the atmosphere.
Roads with high-speed traffic also act as barriers to pedestrian move-
ment (though bridges are different in this respect since they eliminate a
barrier, namely that posed by the river, and increase pedestrian access as long
as there is a lane for crossing by foot). More car dependence even causes
more obesity because of lack of exercise. The critics hold that conventional
cost-benefit analyses systematically omit these social costs, so they tend to
overinvest
in new road infrastructure.
Then there are intangible effects, including intangible social benefits.
A beautiful bridge can become a city's symbol, an object of pride, for genera-
tions. It can enhance rather than detract from the neighborhoods at which
it lands. If its structure is dramatic, and if it effectively frames the urban
downtown or a nearby mountain, it thrills people traversing it. To those
walking nearby or seeing it from a distance, it becomes a reason to stop and
gaze. The bridge becomes part of the lived experience of the environment.
When well designed, the bridge intangibly improves lives, to an extent
that technical methods like cost-benefit analysis are not good at measuring.
