First Advisor

Kelly J. Clifton

Term of Graduation

Summer 2022

Date of Publication


Document Type


Degree Name

Doctor of Philosophy (Ph.D.) in Civil & Environmental Engineering


Civil and Environmental Engineering




Choice of transportation, Built environment, Walking, Urban transportation



Physical Description

1 online resource (xii, 187 pages)


This dissertation aims to formulate a mechanism for the relationship between the urban form and walking choice that can be consistent across contexts. The motivation is the lack of concordant results in the magnitude of the environmental influence on walking choice in urban areas found in the literature. The dissertation identifies a series of limitations in previous research that could cause mixed results in the magnitudes of the association. This research elaborates an approach to overcome these limitations by proposing a mechanism of the activity density over walking modal share by controlling for trip distance distribution. The aim is an approach that can achieve consistent results across applications and help define standard planning policy guidelines.

The work is structured as a three-paper dissertation.

In the first paper, this research examines how travel choices vary across different urban contexts, challenging the assumptions of spatial homogeneity in the relationship between travel modes and the built environment. The study, using data from Portland, OR, uses an innovative method to spatially segment behavioral models based on the urban environment attributes associated with a spatial grid (cells). Each cell will be related to a combination of different traveler classes. These classes are latent as it is not observable by the analyst. Using the Latent Class Discrete Choice method, the study inferred the class from the travel data. The method assigns a probability of having each class of travelers to each cell (making the final behavior a probability-weighted combination). This probability is based on local accessibility measures (such as the number of people reachable at a certain walking distance) and regional accessibility measures (such as employment reachable by transit or car). Each traveler class is represented with a multinomial choice model based on their socioeconomic attributes and the trip distance. The article's contribution shows that segmentation of the travel choice increases the model's goodness of fit and offers a more realistic representation of the traveler and a more precise relationship. Moreover, local and regional accessibility interaction appears relevant in travel choices and should be included in planning policy.

The second paper investigates why previous literature could have found variable magnitudes in the relationship between the built environment and walking. The contribution of the article identifies possible sources of inconsistencies in previous works. Specifically, not controlling for distance in the relationship specification and the modifiable areal unit problem (MAUP) can contribute to inconsistent results across research studies when used in disaggregate analysis with an individual's decision-making as the focus. The findings identify that distance is a significant explanatory variable for walking as a key variable for accessibility. The absence of distance in specifications that include built environment density measures can be problematic and cause biased estimates. Finally, the paper argues in favor of spatial aggregates instead of the individual. Individual walking is associated with short trips, and the aggregated proportion of short trips is associated with the built environment. Thus, a higher ratio of shorter trips indicates more walking. Therefore, the aggregated approach can better characterize the contextual environment influences and possibly be less susceptible to previous limitations.

The third paper builds upon the results and approach of the previous two by using an aggregate analysis and controlling for the distance of the trips. The article also proposes a structure to compare different international cases. A proxy measure of activity density is constructed using weighted trip ends from the travel survey data in the same method for study cases. The results show higher walking modal share for short trips in higher activity density areas. Additionally, higher activity density may be associated with a higher proportion of short trips over the total trip attracted in a particular zone under some circumstances.

The dissertation contributes a new scheme for examining the association between the urban environment and walking. The distance acts as the mechanism in which the built environment influences the walking choice. The distance becomes an artifact of the built environment. Additionally, it proposes reconsidering aggregate analysis, which has been set aside in the last 25 years in favor of disaggregate models. Finally, the findings reconfirm that activity density is associated with more walking and that activity density should be considered in the urban planning process. The innovation here is that the scheme shows potential transferability as there is some consistency across international contexts.

The limitations is the assumption that trip making is not spatially segregated, which is not necessarily the case, as urban areas tend to have spatial segregation based on function or socioeconomics. Additionally, the analysis limits the method to accessibility measures and/or densities and does not include other specific attributes that can be relevant to explain the walking choice, such as aesthetics or security.


© 2022 Jaime Pablo Orrego-Oñate

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