What kind of built environment favours walking? A systematic review of the walkability indices

Neighbourhood walkability provides important insights if an environment encourages (or discourages) walking. One of the most commonly used approaches to measure neighbourhood walkability is the walkability index. Walkability index is constructed as a composite measure of variables that are considered to influence walking. Typically, these include the characteristics of the built environment, the quality of the walking environment (safety and security) and pedestrian characteristics. However, there is a continued lack of a systematic understanding on the association between built environment variables with walking, which has important implications to effective planning and policymaking. By systematically reviewing publications between year 2000 and 2016, this paper examines the various factors of the built environment associated with walking in developing the walkability index, their combination, and the methods adopted to construct as well as evaluate the index. Results show that the association of walkability index to walking without prior validation of each variables of the built environment may not be able to inform or formulate appropriate strategy to improve walkability nor inform policy makers to formulate the right strategy.Nevertheless, objectively measured composite index of walkability have the potential to be an important planning tool to support policy recommendations. This research recommends that more research is needed to improve measures of the built environment so that the effectiveness of walkability index as a planning and policy tool is enhanced.