Improving Trip Generation Methods for Livable Communities

Kelly Clifton, Portland State University


  • Nico Larco, University of Oregon


Recent efforts to improve trip generation data available for transportation impact analysis of new development include the collection of multimodal
trip generation data, development of models that account for the built environment, and new recommendations for practice. Building on a long line
of research on transportation and built environment, many studies have identified important features of the surrounding built environment that most
impact trip rates and mode shares, building on a long line of research on transportation and the built environment. Despite these improvements in
data and methods, less attention is placed on identifying the conditions of the site itself and the immediate surrounding environment that influence
trip generation and mode choice. To fill this gap, this study builds upon previous work (Contextual Influences on Trip Generation (Project Number:
OTREC 2011-407), 2012), re-examines the information collected in that study, and includes new site-level observations. The objective of this study
is to examine establishment multimodal trip generation more closely from a finer-grained scale and identify site-level attributes of the built
environment that help explain multimodal trip generation. From this, we have the additional objective of developing a framework for trip generation
analysis that takes findings from this study into consideration. We placed emphasis on those sites in our previous study with a discord between the
expected travel patterns, based upon the larger urban context and built environment of the site, and the observed. The research approach will make
use of mixed methods. In addition to using archived data from the previous study, site visits provided direct observation of the overall performance
of the site, including travel patterns on and around the site as well as specific site configuration, urban design details and traffic operations. The
analysis of this combination of data provided a more complete picture of site-level trip generation and our findings highlight the influence of: people
living nearby and using the site; the nature of the land use on the site; the development along arterial roadways; site permeability and access; and
the local culture around walking and cycling. Finally, this report ends by reflecting on the numerous concerns identified from practice, the research
findings from various recent studies, and the need for a sustainable process for evaluating the transportation impacts of new land development. We
present a potential framework to advance the methods for how site plans fit into neighborhood and regional planning, using locally defined standards
and goals. Here, we de-emphasize the site and its immediate environs as the primary (and only) scale of analysis and lessen the reliance on the
problematic methodologies for estimating site-level travel demand. Rather, we argue that transportation impact analysis would benefit by first taking
a district, neighborhood or area-wide approach with attention to the urban context—the built and social environment—where a site is located. At
this larger scale, there is a better ability to understand the various elements that work together to shape travel demand and allows for a better
assessment of how a specific site proposal will integrate into this larger context. This effort involves several faculty from across the country, including Kelly Clifton (PSU Engineering) and Nico Larco (UO Architecture) from our consortium and Susan Handy (UC Davis Environmental Studies) and Robert Schneider (UW Milwaukee Planning) as consultants/advisors.

Project Details

Project Type:
Project Status:
End Date:
June 30,2016
UTC Grant Cycle:
Natl Round 1
UTC Funding: