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Demographic and economic trends-and new community concerns-are changing the way that practitioners define transportation problems and evaluate potential solutions. A new paradigm expands the range of modes, objectives, impacts, and options considered in transport planning. This article discusses this paradigm shift and its implications for our profession.
Introduction
Aparadigm refers to the basic assumptions used to define a problem and to evaluate solutions. A discipline's paradigm sometimes shirts, forcing practitioners to reexamine their basic assumptions and analysis methods. The Copernican revolution, which recognized that the earth revolves around the sun, and the theory of evolution, which explained biological change through natural selection, are well-known paradigm shifts.
Transportation planning is undergoing its own paradigm shift, and it is changing the way we define transportation problems and how we evaluate transportation system performance, the range of planning objectives and impacts considered when evaluating these options, and the types of solutions considered for solving transport problems.
The old paradigm evaluated transport system performance primarily on the speed, convenience, and affordability of motor vehicle travel - and so favored automobile-oriented improvements. The new paradigm is more comprehensive and multimodal. It considers a broader range of modes, objectives, impacts, and improvement options.
As a transportation professional, you are probably already involved in these changes. You may apply more comprehensive and multimodal analysis and implement more demand management solutions than was previously common.2'3 These changes have been previously discussed in ITE Journal. However, most previous discussions considered these changes individually. This article investigates their roots - the paradigm shift that is changing the way we think about transportation problems and solutions - and discusses why these changes are occurring, how they affect our work, how they fit together, and how they can help us better serve transport system users.
Why a New Paradigm
This is a timely issue. Motor vehicle travel grew steadily during the twentieth century, so it made sense to invest significant resources in building roadway systems. For example, in the 1 960s, if a two-lane road started to experience congestion, it seemed rational to expand it to four or even six lanes. Maximizing capacity was considered "conservative" because it was cheaper to build extra capacity now than to add it later. There was little risk of overbuilding,...