Using GIS to measure walkability : A Case study in New York City

Sammanfattning: Obesity has become a global epidemic due to changes in society and in behavioral patterns of communities over the last decades. The decline in physical activity is one of the major contributors to the global obesity epidemic. Thus programs, plans and policies that promote walking could be a possible solution against obesity and its comorbidities. That is because walking is the simplest and most common form of physical activity among adults, regardless of age, sex, ethnic group, education or income level. The characteristics of the built environment might be significant factors that affect people’s decision to walk. Thus, measurable characteristics can assist in determining the extent to which the built environment affects the people. These characteristics can also provide indirect evidence of the state of population health for the area under study. Towards the analysis and assessment of potential associations between a number of measures of the built environment and walking, Geographic Information Systems have an increasing acceptance. Composite measures, also known as Walkability Indices, are a promising method to measure the degree to which an area provides opportunities to walk to various destinations. The main objective of this research is to develop a method to model walkability drawing partially from previously developed Walkability Indices and walkability measures, and suggest eventually an improved Walkability Index composed of 6 parameters. These are: i) Residential Density, ii) Diversity – Entropy Index, iii) Connectivity, iv) Proximity, v) Environmental Friendliness, vi) Commercial Density – FAR. The chosen spatial unit of analysis is the Census Tract level. The method of buffering that defines spatial units around geocoded locations at a given distance is also employed in an attempt to suggest an improvement of previously used methods. The study area is New York City (NYC). The results imply that Manhattan is the most walkable Borough, while Staten Island is the least walkable Borough. It is also suggested that NYC has a centripetal structure, meaning that the historical center and the entire island of Manhattan is more developed, and more walkable, followed by the adjacent areas of the neighboring Boroughs of Bronx, Brooklyn and Queens. The farthest areas of NYC’s periphery are consistently found to have the lowest walkability. Additionally, neighborhoods that are extremely homogeneous in terms of land-use and do not include considerable number of commercial parcels score very low. Hence, Census Tracts that are mainly characterized by primarily industrial land-use or contain large transportation infrastructures (e.g. ports, airports, large train stations) or even large metropolitan parks display limited walkability. The results and findings coincide to a satisfactory extent with the results of previous studies. However, the comparison is simple and barely based on easily observed patterns. As a result, the validity of the new Walkability Index might need further assessment due to limitations and lack of data. All types of limitations have been identified including limitations in data and in methodology. Suggestions for further research include possible additional parameters that can be employed in our Walkability Indices (e.g. crime rate, and separate parameter for parks and green areas) and further research whether the components of a Walkability Index should be weighted or not. In general, Walkability Indices are promising GIS applications that still need further research and development.