Dissertation
Click here to view my dissertation
Doing exercise is good for our health. Walking and bicycling on the street helps you to do more exercise and can make you happy. For the past two decades, public health sectors and transportation sectors have worked together to improve the built environment design, because they believe that good designs can make people more willing to walk or bike outside.
But what if the environment surrounding you is poor, such as poor air quality, bad traffic, and too cold or too hot? Considering these environmental conditions, how would you feel about walking on the street? Would you still prefer to walk or bike outside?
My dissertation explores how the U.S. public perceives the environment surrounding them, and investigates whether our current investments in the built environment are effective. The figures below show my dissertation structure, which includes three studies.
Dissertation Structure
Click here to see my dissertation proposal.
Links to the Three Studies
Study 1: Infrastructure Effectiveness
Have you ever noticed these situations: when a new bicycle lane is built, a street is redesigned, or a waterfront commercial area is developed with great visions, nobody actually uses them? Even if some people might use them, did the new constructions change people's behavior at all? Or think about it this way: when a new option, say, a new bicycle route, is created, will you really get a bike and travel on that new lane?
As the first step, I conducted a systematic literature review to figure out when environmental designs "failed." I want to contribute to the current scholarship by finding out why some built environment interventions cannot change people's behavior. So far, a lot of researchers have meta-analyzed the positive outcomes of the built environment interventions (e.g., Kärmeniemi et al., MacMillan et al., Smith et al., Stappers et al., Tcymbal et al., Travert et al., Ding et al.), but my approach is different from previous ones. I looked at the negative outcomes and analyzed why they were negative. My literature analysis directs people to think more about the attitudes, values, and behaviors of people instead of the built environment.
I found that small-scale improvements tend to be more effective than large-scale infrastructure development because small-scale projects tend to be more engaging with the local community. By actively participating in such projects, community members tend to develop a better sense of place and thus change their behaviors. I also highlighted why large-scale interventions are not effective in changing behavior from four perspectives: activity budget, time threshold, regional context, and behavioral mechanism.
Study 2: Health Benefits and Risks
This study investigates attitudes and behavioral preferences toward active transportation given health benefits and risks. In light of behavior theories, I generate two major hypotheses. First, people’s attitudes toward health are heterogeneous by travel experience, neighborhood environment, and sociodemographic characteristics. Second, people’s beliefs may not align with their behavioral preferences, known as “cognitive dissonance” in social psychology, implying a conflict between health attitude and active travel behavior—they may feel strongly about certain issues such as air pollution, lack of physical activity, or traffic safety, but these issues may not be their top concerns when making travel decisions.
I focus on the most sustainable and accessible mode of transportation—walking—as both a travel behavior and a health behavior. Two types of walking are considered: (1) Walking for transportation: utility walking for a transportation purpose, such as going to work, school, church, grocery store, restaurant, or visiting friends. In these cases, walking is a means of transportation. (2) Walking for leisure/exercise: walking around the neighborhood to relax, brisk walking, attending a walking group or walking event, walking dogs, etc., where the primary purpose of the trip is walking itself.
The study considers four health-related factors that encompass the benefits and risks of walking in the built environment: air quality, travel time, traffic safety, and personal heat exposure. I am interested in the public’s attitude toward these four health-related factors, as well as how they actually make walking decisions given the combinations of the four factors. I examine the perceptions of walking for transportation and walking for leisure scenarios, respectively. Even though transport walking and leisure walking are both walking, people may have different perceptions of them. For example, some may perceive 30 minutes of walking for transportation to be longer than 30 minutes of walking for leisure, such that they may be willing to spend more time on leisure over transportation.
I use a discrete choice experiment (DCE) research design and collect data from a stated preference (SP) survey that examines walking preferences under different scenarios. The SP survey has three essential purposes. First, it identifies perceived barriers to walking, as well as the marginal willingness to walk with respect to air quality, travel time, traffic safety, and temperature. Second, it enables the calculation of the marginal rate of substitution among travel time and health benefits or risks. In particular, how much time would the respondents give up in exchange for avoiding a health risk (e.g., unsafe traffic conditions, air pollution, excessive heat)? Third, it enables the calculation of the relative importance, or rank order, of the four health-related attributes, implying the degree of risk aversion to each attribute. In addition, the survey questionnaire also includes attitude questions that directly ask about respondents’ attitudes toward the four health-related issues, respectively. This study further examines the alignment between the public’s attitudes (obtained by attitude questions) and behavioral preferences (obtained by stated preference survey and discrete choice modeling).
I use a time tracker to see where my time goes. I believe that having to work/study is the worst excuse for not doing exercise. I'm very interested in how people use their time for travel and how they find time to do physical activities. In my dissertation, I got a chance to investigate the relationship between transport infrastructure investment and time used for active transportation. To a large extent, my idea was inspired by the concept of "activity budget" I first read in a journal article.
In this study, I integrated four large public datasets and used causal inference in econometrics (difference-in-difference with continuous treatment, fixed effects regression model, and path/mediation analysis) to examine the pathways from active transportation policies and investments to behavior change.