FLEXIBILITY IN DESIGN - Title Page - MIT

de Neufville + Scholtes D R A F T September 30, 2009Box 1.4_____________________________________________________________________________Flexible design: Tagus River BridgeThe Ponte de 25 Abril, the first bridge over the Tagus River at Lisbon, offers a good example offlexibility in design. The Salazar dictatorship inaugurated it in 1966 with a single deck forautomobile traffic, but with the strength to add on a second deck at some future time. Moreover,they also built a railroad station under the toll plaza, to minimize disruption in case Portugal everdecided to build rail connections.A generation later, Portugal was a democratic member of the European Union, whichallocated funds to develop commuter rail services throughout the region, and in 1999 the bridgereceived a second deck that carried these lines. 5When first built, designers recognized that the ultimate capacity of the bridge could belarger. Instead of trying to anticipate specific future requirements, they built for immediate use,with the flexibility to develop in many ways. In any case, if the original designers had tried todefine future requirements, they could hardly have imagined the overthrow of the dictatorship andthe creation of the European Union.The flexible design of the bridge saved money by not building too early or building morehighway capacity that might have been inappropriate. It also enabled Portugal to take advantageof the support of the European Union to create rail traffic across the river._____________________________________________________________________________Box 1.5_____________________________________________________________________________Flexibility leads to major gains: satellite fleetA detailed analysis of alternative ways to deploy geostationary satellites over different regionsshowed that a flexible system design, that enabled the system operators to reposition thesatellites as demand for broadcast services changed, greatly outperformed the system“optimized” for the specified “most likely” pattern of demand. 6As Table 1.2 shows, the flexible design increases the overall expected value. Instead oflaunching the final fleet right away, it initially launches a smaller fleet – this simultaneouslyreduces the amount initial capital expenditure, thus the amount at risk and possible losses. Theflexible design then deploys the second module sized and located according to actual need,thereby obtaining a maximum value if the demand exceeds original anticipations.[Table 1.2 here]_____________________________________________________________________________Part 1: Chapters 1 to 3 Page 14 of 69