Civil Engineering Reference
In-Depth Information
SEVEN
IS IT WORTH IT?
Costs, Benefits, and Tough Decisions
Whether to build an item of infrastructure, or reconstruct it, or find ways
to avoid the need for it—these are tough decisions in part because they
are expensive. While humanity does have many vices, the lack of imagina-
tion about how to spend money is not one of them. Should the money go
for a four-lane downtown truss bridge with room for light-rail cars on the
assumption that public transit will increase, or a six-lane suburban cable-
stayed bridge where traffic has been growing and land is cheaper? Then
again, shouldn't it rather go for a new airport, waterfront park, or hospital
emergency rooms?
The bridge project will require years of engineering design, environ-
mental studies, and construction, and will have to be paid for before its
benefits are felt, so there are likely to be shorter-term needs on peoples'
minds. The money could, after all, be used to fix potholes, which may be
doing more to slow traffic than the lack of a bridge does, or could be just
the ticket for bridging not the local river but the year's budget gap. So, when
it comes to, say, a few tens of millions set aside for a new bridge, it's safe to
say that there will be contending ideas about what to do with the money.
Of several ways of trying to resolve the issue, the most widely respected
is cost-benefit analysis, which turns out to be a fairly intricate procedure.
It is not its logic that is difficult; the fundamental ideas are straightfor-
ward. Rather, the problem is that, to do the analysis, we have to make lots
of assumptions, sometimes guesses, and the data we gather may be wrong.
What's more, we may have to decide whether the bridge seems worthwhile
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