One proposed definition for walkability is: "The extent to which the built environment is friendly to the presence of people living, shopping, visiting, enjoying or spending time in an area".[3] Factors affecting walkability include, but are not limited to: street connectivity; land use mix; residential density (residential units per area of residential use); frequency and variety of buildings, entrances and other sensations along street frontages, "transparency" which includes amount of glass in windows and doors, as well as orientation and proximity of homes and buildings to watch over the street; plenty of places to go to near the majority of homes; placemaking, street designs that work for people, not just cars and retail floor area ratio.[4] Major infrastructural factors include access to mass transit, presence and quality of footpaths, buffers to moving traffic (planter strips, on-street parking or bike lanes) and pedestrian crossings, aesthetics, nearby local destinations, air quality, shade or sun in appropriate seasons, street furniture, traffic volume and speed.[1][5] and wind conditions.
Walkability indices have been found to correlate with both Body Mass Index (BMI) and physical activity of local populations.[4][10] Due to discrepancies between residents' health in inner city neighborhoods and suburban neighborhoods with similar walkability measures, it has been suggested that further research is needed to find additional built environment factors to be included in walkability indices.[11]
Increased walkability has proven to have many other individual and community health benefits, such as opportunities for increased social interaction, an increase in the average number of friends and associates where people live, reduced crime (with more people walking and watching over neighborhoods, open space and main streets), increased sense of pride, and increased volunteerism. One of most important benefits of walkability is the decrease of the automobile footprint in the community. Carbon emissions can be reduced if more people choose to walk rather than drive.
Walkability has also been found to have many economic benefits, including accessibility, cost savings both to individuals and to the public, increased efficiency of land use, increased livability, economic benefits from improved public health, and economic development, among others.[12] The benefits of walkability are best guaranteed if the entire system of public corridors is walkable - not limited to certain specialized routes. The World Cancer Research Fund and American Institute for Cancer Research released a report that new developments should be designed to encourage walking, on the grounds that walking contributes to a reduction of cancer.[13]