Transferability & Forecasting of the Pedestrian Index Environment (PIE) for Modeling Applications

Kelly Clifton, Portland State University


There have been important advances in non-motorized planning tools in recent years, including the development of the MoPeD pedestrian demand model (Clifton et al., 2013, 2015). This tool and others are increasingly requested by governments and agencies seeking to increase walking activity and create more walkable places. To date, the MoPeD tool has been piloted with success in the Portland region using data unique to Metro, the metropolitan planning organization. However, there is increasing interest from planning agencies in adapting the pedestrian modeling tools and their inputs for use in their own jurisdictions. Unfortunately, other regions often do not have uniform access to the same kinds of pedestrian environment data as Metro, particularly at such a fine-grained scale. 

In this next phase of our pedestrian modeling work (see Clifton et al., 2013, 2015), this project focuses on making our measures, models, and methods more transferable to other locations. Specifically, we will re-evaluate, compare and test our pedestrian index of the environment (PIE) measure using data resources more commonly available to planning agencies across the country. Next, we test the results of PIE and its input data in models of pedestrian mode choice for stability of estimation results within a region (intraregional) and between regions (interregional). This research is the next logical step in the MoPeD’s enhancement and is critical to enabling its utility beyond the Portland region. 

In terms of index inputs, the results of this project show that population density and pedestrian connectivity had the most consistent and strong relationship to walk mode choice across all of our regions, which echoed the long literature on this topic. However, the other components of the built environment included in PIE had more variability in their ability to explain walk mode choice. Employment density and its subset urban living infrastructure (ULI), intended to capture retail and service access, had less explanatory power and stability in the cities tested. Based upon these findings, we provide several guidelines for the construct of walkability indices, including variables and spatial scales. 

Our findings raise questions about the relationship between walking and the built environment within a region and thus, the intraregional transferability of one walkability index is suspect. Estimation results suggest that there may be different responses to the built environment in lower-density vs. higher density regimes and that these relationships may be nonlinear. However, smaller sample sizes of travel survey data in high density areas in all of the US cities tested pose limitations to drawing more confident conclusions from these results. 

The interregional comparisons of PIE and walk mode share between Los Angeles and Portland showed promise for the use of the index in different regions. In these two regions, model results showed a similar walk mode share for the same values of PIE constructed at the block group level. This provides initial support that the PIEbg construct may be transferrable between metropolitan regions, in part, due to population density's prominent role in PIE.


Notably, this project advances the work completed in previous NITC-funded projects that developed a pedestrian planning method to better represent the pedestrian environment in travel demand modeling. It will leverage past research to further advance the state-of-the-art. Building off of the methods previously developed will improve the techniques for forecasting pedestrian demand and make them more widely applied by interested practitioners. 

This research will have broad impacts on the research and educational objectives of PSU, TREC, and NITC. Students will have an opportunity to engage in and conduct research while seeing how that research ultimately guides planning and policy-making. The collaboration between PSU and Tigard will strengthen relationships and contribute to supporting PSU’s motto of “Let knowledge serve the city.” This research will continue a long tradition of NITC and PSU as an acknowledged center for pedestrian behavior and modeling research. Furthermore, the work will advance the integration of land use, transportation, and active travel modes into the University curriculum and strengthen the “livable communities” focus area for which Portland, PSU, TREC, and NITC have built a national reputation. 

The project will also have long-lasting impacts to the broader community by advancing the state of the knowledge and practice in the area of pedestrian planning and modeling. Most significantly, easily-applied pedestrian modeling methods that utilize widely-available data is a missing resource that would be valuable to regions and planning agencies across the country. Tackling the tough issues of forecasting is another obstacle that needs to be overcome before we see widespread adoption of pedestrian modeling techniques. The research will also contribute to the understanding of pedestrian behavior, especially sensitivity to the built environment in urban and suburban locations. Furthermore, this project is groundbreaking and advances the state-of-the-art modeling methods by developing novel and useful ways to forecast the demand for walking. 

Project Details

Project Type:
Project Status:
End Date:
March 31,2018
UTC Grant Cycle:
Natl Round 3
UTC Funding:

Other Products

  • Singleton, P. A., Totten, J. C., Orrego-Onate, J. P., Schneider, R. J., & Clifton, K. J. (2018). Making Strides: State of the Practice of Pedestrian Forecasting in Regional Travel Models. Transportation Research Record, 2672(35), 58-68. doi:10.1177/0361198118773555 (PUBLICATION)
  • An exploration of the inter- and intra-regional relationships between the built environment and walking (PRESENTATION)
  • Density Differences: Exploring Built Environment Relationships with Walking Between and Within Metropolitan (PRESENTATION)
  • Transferring the pedestrian index of the environment: models and measures across and within regions (PRESENTATION)
  • Walk don't run (PRESENTATION)
  • Analyzing the relationship of walking and the built environment (PRESENTATION)
  • Assessing the transferability of the Pedestrian Index of the Environment (PIE) walkability measure for pedestrian modeling (PRESENTATION)