Data and Methodological Issues in Assessing Multimodal Transportation Impacts for Urban Development

Kristina Currans, Portland State University

Summary:

In 1976, the Institute of Transportation Engineers (ITE) compiled their first Handbook of guidelines and methods for evaluating development-level transportation impacts, specifically vehicular impacts (Institute of Transportation Engineers 1976). Decades later, these methods— essentially the same as when they were originally conceived—are used ubiquitously across the US and Canada. Only recently, with the guidelines in its third edition of the ITE’s Trip Generation Handbook (Institute of Transportation Engineers 2014) new data and approaches been adopted—despite substantial evidence that questions the accuracy of older data (Clifton, Currans, and Muhs 2012; Shafizadeh et al. 2012; Weinberger et al. 2015), automobile bias (Clifton et al. 2012; Millard-Ball 2015; Manville 2017), and lack of sensitivity to urban contexts (Currans and Clifton 2015; Ewing et al. 2011; Schneider, Shafizadeh, and Handy 2015; Weinberger et al. 2015). 

This dissertation contributes to this literature by focusing on the data, methods, and assumptions so commonly included in development- or sitelevel evaluation of transportation impacts. These methods are omnipresent in development-level review—used in transportation impact analyses or studies (TIAs/TISs) of vehicular or mode-based impacts, vehicle miles traveled (VMT) and estimates of emissions, scaling or scoping development size, and evaluating transportation system development, impact or utility fees or charges. However, few have evaluated the underlying characteristics of these foundational data—with few exceptions (Shoup 2003)—this manuscript takes aim at understanding inherent issues in the collection and application of ITE’s data and methods in various urban contexts. 

This manuscript includes a compiled dissertation, four papers written consecutively. The first, evaluates state-of-the-art methods in Chapter 2— identifying gaps in the literature. Two such gaps are explored in Chapter 3 and Chapter 4. In Chapter 3, a larger implicit assumption present in ITE’s methods—that the existing land-use taxonomy is an optimal and accurate way to describe land use and segment data. Results indicate a simplified taxonomy would provide substantial reductions in cost corresponding with a minor loss in the model’s explanation of variance. Following, Chapter 4 explores a common assumption that requires ITE’s vehicle trips be converted into person trips and applied across contexts. The results point to the need to consider demographics in site-level transportation impact analysis, particularly to estimate overall demand (person trips, transaction activity) at retail and service development. 

In Chapter 5, the findings from this research and previous studies are extrapolated to evaluate and quantify the potential bias when temporal, special, and social contexts are ignored. The results indicate the compounding overestimation of automobile demand may inflate estimation by more than 100% in contexts where ITE should be applicable (suburban areas with moderate incomes). In the conclusions (Chapter 6), the implications of this work are explored, followed by recommendations for practice and a discussion of the limitations of this research and future work.

Impacts:

Both parts of my dissertation will influence the way that trip generation data are treated. In the first part (transaction counts), this analysis will provide support for how transportation activity is treated in practice. The second part (variation in trip rates across land use categories), will provide statistical support for defining land use categories. The concluding chapter will provide an overview of compounding propagation of issues identified, outlining guidance for agencies in how to identify and treat said issues where possible.

Project Details

Project Type:
Dissertation
Project Status:
Completed
End Date:
June 30,2017
UTC Grant Cycle:
Natl Dissertation Fellowships Spr. '16
UTC Funding:
$15,000

Other Products

  • Data and Methodological Issues in Trip Generation Estimation for Impact Analyses of Urban Land Development (PRESENTATION)
  • Currans, Kristina M. (2017). Issues in Trip Generation Methods for Transportation Impact Estimation of Land Use Development: A Review and Discussion of the State-of-the-Art Approaches. Forthcoming in Journal of Planning Literature. Accessible at http://journals.sagepub.com/doi/full/10.1177/0885412217706505. (PUBLICATION)
  • Issues in Trip Generation Methods for Transportation Impact Estimation of Land Use Development: A Review and Discussion of the State-of-the-Art Approaches (PRESENTATION)
  • Contextual Effects On Overall Activity at Food Retail Establishments in Portland, Oregon: A Count-Based Multilevel Model of Repeated Transaction Count Measures to Improve Transportation Impact Analyses (PRESENTATION)
  • Institute of Transportation Engineer’s Expert Panel on Urban Trip Generation. Urban and Person Trip Generation. White Paper published by Institute of Transportation Engineers, (forthcoming, 2016). (PUBLICATION)
  • Data and Methodological Issues in Assessing Multimodal Transportation Impacts for Urban Development: A Review of the State-of-the-art and State-of-the-practice (PRESENTATION)
  • Bochner, Brian S.; Currans, Kristina M.; Dock, Stephanie P.; Clifton, Kelly J.; Gibson, Patrick A.; Hardy, Daniel K.; Hooper, Kevin, G.; Kim, Lee-Jung; McCourt, Ransford, S.; Samdahl, Donald R.; Sokolow, Gary, H.; Tierney, Lisa F. Advances in Urban Trip Generation Estimation. Institute of Transportation Engineer’s Journal, (2016). (PUBLICATION)
  • Improving Multimodal Transportation Impact Methods for Livable Communitie (PRESENTATION)
  • Transforming Transportation Impact Analysis: A New Vision for Coordinating Transportation and Land Use (PRESENTATION)