Obsolescence & Service Life

H. Scott Matthews

January 27, 2003

Recap of Last LectureBuilt infrastructure deficiencies lead to

‘needs’Needs studies should estimate NEEDS

not WANTSCosts of infrastructure need to be

managed and planned over life cycle Infrastructure generally built to last

longer than it would actually be useful

ObsolescenceCondition of being antiquated, old-

fashioned, or out-of-dateNo longer meets current needs or

expectation levels Aging, technology, standard change 2-yr old computers good example

Inability to meet changing performance requirements

Obsolescence & Service Life “Always remember that someone,

somewhere is making a product that will make your product obsolete” -Georges Doriot

“Planned obsolescence” by Vince Packard’s The Waste Makers Practice of deliberately designing products

to last for a shorter period of time Systemically doing this leads to inferior

products

What Causes It?Technological changeRegulatory change

SDWA forced upgradesEconomic / social changesValue / behavior changes

EconomicsPerformance = P(S,D,t)S = Supply of infras. Services = S(X)

X = set of functional characteristics Planners want adequate X, S over time ‘Satisficing’ (Simon 57)

D = demand for these services

“Failure”Failure as not meeting expectationsHappens when P(t) < PF

Need to maintain performance level

Expectations increase over time

PPF

TD

Service vs. Physical LivesPhysical Lives: time it takes for

infrastructure to wear out/fail Predicting this may be irrelevant

Service life: time actually used In general these 2 are different

Power plants become obsolete because of technology/policy changes

In some cases, tax code drives expectations

Connections “Design service life” only meaningful if

defined in terms of obsolescence Assumptions about lifetime will likely

change over time Infrastructure seldom abandoned before

replacement in place Expectations will increase

Need to consider expectations and deterioration functions

Rates of Change Information economy is making older

transport modes obsolete E.g., ground -> air shipping

How long should infrastructure last? Physical or service? “How long do you want to use it?” Where will it go when we’re done? What could we do with Roman roads now?

Strategies to MitigatePlan and design for flexibilityBuild to assure optimum performance

level is achievedMonitor change to defer obsolescenceRefurbish and retrofit early