Measuring the Success of Transit-Oriented Development Retail Market Dynamics and Other Key Determinants

Transit-oriented development (TOD) has become the dominant urban growth planning paradigm in the United States. Yet scant evidence has been proffered to indicate that it will produce significant environmental and social benefits commensurate with the costs of the major transportation system improvements that it requires. Sixteen distinct planning issues will determine whether TOD significantly changes travel behavior in a metropolitan region. While some analysis exists, understanding of these issues needs improvement. In particular, more research is needed on non-work travel, retail market dynamics, and the likely constraints this $2.3 trillion area of business and human behavior imposes on TOD. Introduction Over the past two decades numerous metropolitan areas in the United States have embraced the concept of transit-oriented development (TOD) in an attempt to control and manage the negative environmental and social impacts of dispersed growth patterns (Porter 1997). TOD, it is suggested, will increase pedestrian and transit trip taking while reducing the number and length of auto trips, and it will contribute to the livability that some feel is lacking in modern suburban development (Calthorpe 1993). In essence, TOD means the creation of denser, mixed use activity nodes connected by high quality public transportation. Proponents believe that a combination of design features will induce travel mode shifts that result in reduced area-wide traffic congestion and improved air quality. These features include improved street connectivity, public amenities, and a concentration of residences and jobs in proximity to transit stations and commercial businesses. As an additional benefit, the enhanced pedestrian environment will increase "casual encounters" among neighbors that can contribute to a sense of community. These efforts typically begin implementation with major new "mass" transit investments, often light-rail systems, that are designed to link central city cores, suburban downtowns, and other major activity centers. TOD is possible without new transit, but most metro areas choose to make the transit investment. Bernick and Measuring the Success of Transit-Oriented Development http://www.globaltelematics.com/apa99.htm 1 of 15 7/6/2009 10:52 AM Cervero (1996) suggest that what is needed for TOD to succeed is a "transit metropolis," meaning a sufficient number of TODs having balanced or special uses that are connected and allow for efficient rail travel with bi-directional travel flows. Construction of the new transit system usually precedes the land use restructuring required to effectively support the investment, i.e., the concentrations of population, employment, public amenities, and commercial activities that will attract transit riders in sufficient numbers to satisfy the transit system’s fare box recovery requirements. Commercial activities, in particular, often become a consideration after the transit system alignment is finalized and station areas are identified. A useful review of previous studies in the urban planning and transportation literature of the transportation impacts of neo-traditional development and TOD is provided by Berman (1996). This paper summarizes several more recent empirical and modeling studies of TOD, and it indicates how TOD success should be measured. Specifically, it outlines the key factors that need to be understood and weighed before significant new transit investments are made. Our aim is to enhance the regional planning process in a way that leads to cost-effective investments of scarce public dollars. Local Benefits vs. Regional Benefits It is important to distinguish between regional and local benefits produced by TOD, and the magnitude of benefits at both scales of measurement. Intuition suggests that station-area development involving mixed use and higher employment and residential densities will induce more pedestrian and transit trips. Several studies lend credence to this belief. However, since the ideal TOD is still a planner’s vision, researchers have resorted to comparing older neighborhoods that approximate TOD with conventional suburban neighborhoods that do not. These studies suggest that the increase in non-auto trips, although small, is measurable (Bernick and Cervero 1996). Yet local area benefits may not translate to regional benefits, especially when weighed against the costs of the transit investments needed to link individual TOD centers. Consequently, the central question for planners and decision makers is the magnitude of TOD’s regional impact, namely reduced congestion and improved air quality that are the principle concerns of the traveling public. Nelson and Niles (1999), after reviewing the empirical studies to date, suggest that they provide insufficient evidence that TOD on a regional scale, even when supported by large transit investments, is likely to produce significant regional benefits. It is important, therefore, to understand the factors that determine the regional and local success of TOD. This paper reviews the key factors and suggests where further work is needed that will expand our understanding of the strength of each and hence of TOD’s potential. We focus particularly on the obstacles posed to TOD by the dynamic nature of the commercial marketplace, an important area of inquiry that has been largely overlooked in previous studies. Our purpose is not to be exhaustive, but to provide a overview which might stimulate more in-depth work. Key Factors Determining TOD Success A number of variables will determine the success of TOD at both the station-area and corridor or regional scale (Table 1). As indicated previously, we define success as the extent of the mode shift -from autos to pedestrian and transit modes -that is attributable to TOD. In economic terms, success is the benefits of this shift net the costs of building and operating new transit facilities. As thusly defined, success is measurable, and may be predictable. Other measures of success, such as sense of community and livability, although appropriate and important, do not easily lend themselves to either empirical measurement nor estimation through the use of models (Project for Public Spaces 1997). Some factors play a major role in determining local, station-area success, while others have a significant Measuring the Success of Transit-Oriented Development http://www.globaltelematics.com/apa99.htm 2 of 15 7/6/2009 10:52 AM impact at both the local and the larger, corridor/regional scale. In other words, success may be achieved at one or several TODs if a few positive factors are present, but success will probably not be achieved at a regional scale unless a greater number of factors contribute in a positive fashion. We are not suggesting either the relative magnitude nor the sign of the impact of these factors, only that each may be significant in determining the success of TOD. Together, these factors in Table 1 represent independent (exogenous) variables in equations that might be written to predict either the probability of success or its magnitude at both scales of interest. Several studies have attempted to dissaggregate the effect of some of these variables, while others have measured their combined effects. In the following, we cite the most recent research into these factors, and we suggest gaps in our understanding that need to be addressed. TABLE 1. Factors determining the success of TOD Factor Station-area success Regional success Number of TODs (& station areas) X