Food Access

Dimension of time in food access

My study centers on dimension of time in shaping food access in urban contexts. Most food outlets have a limited time of operation over a day and some also have different daily operating hours over a week. The different store hours shaped by store policies create an hourly and daily variation of availability to buying food. I identify this inequality of temporal access in cities through cutting-edge geovisualization techniques (Chen and Clark, 2013). The space-time food access is related to socioeconomic status (SES) such as education attainment and poverty rate. A surprising finding is that low-SES neighborhoods are not at a disadvantage of spatial access, but their limited temporal access is a more pressing concern (Chen and Clark, 2015).


 Geovisualization of urban space-time food access

Social media in food exposure study

Food activities analyses on the individual level posed a daunting challenge for social scientists because of the tedious nature of data collection. I take an innovative approach to soliciting food-related activities from social media, or specifically Twitter.  After correlating with food environment such as grocery stores and fast food restaurants, I identify the relationship between food environment and individual food choices: exposure to a healthful food environment increases healthful choices; an obesogenic food environment such as prevalence of fast food restaurants, on the other hand, may not necessarily increase the likelihood of eating fast food (Chen and Yang, 2014).


Distribution of food tweets in Columbus, OH

Emergency Planning

Temporal hierachy of shelters

Relief resources are unevenly distributed over space. One overlooked facet in emergency shelter planning is that people’s needs for these resources vary over time. For example, it has been observed that camping equipment was mostly needed three days after the occurrence of this earthquake; however, ten days after the quake, more complex household necessities, such as shower facilities and kitchens, came to the forefront. I propose a three-level hierarchical location model for optimizing the placement of earthquake shelters by taking into account this temporal variance. The result has been eventually implemented in a real-world earthquake evacuation planning zone in Beijing, China (Chen et al, 2012).


Earthquake shelter planning in a suburban region of Beijing, China

Time Geography


Individuals combine many trips into a single trip chain to make more efficient use of their time. For example, on the way home from work, a person may shop for groceries at a local store and then visit a nearby post office. This effect called trip-chaining of multiple different activities received scant attentions in Time Geography. I then propose four formal mathematical models to  conceptualize the problem (Chen and Kwan, 2012).


 Four models of trip-chaining in Time Geography