Conclusions
Only a small fraction of respondents walk, but trips longer than 0.25 miles are common. There is substantial variability in the distance and duration of walking trips by purpose and population subgroups. These differences have implications for developing strategies to increase physical activity through walking.
istance decay functions have been used in geography to mathematically describe how a given phenomenon varies as a function of distance.27, 28 Specifically, the longer the distance to the destination, the less likely people are to travel to it by walking. Distance decay functions have been used to describe the distribution of walking as a function of distance for walking generally,29 for different walking purposes,20, 21 for transit walking,30, 31 and for multimodal trips.32
It is generally well accepted that the exponential function is more appropriate for analyzing processes involving relatively short distances.29, 33–35 Since walking involves relatively short distances, the negative exponential form was used in this study as it yielded a better fit than other forms such as power and Gaussian, as reflected in the R2. The distance decay function is specified as:
Overall, 16.4% of respondents reported at least one valid walking trip per day, and 3.7% of respondents had three or more valid walking trips per day. Among those who took at least one walking trip per day, the mean number of walking trips was 2.25 and the mean cumulative distance walked was 1.64 miles. Table 1 shows the distribution of walking trips by distance and duration using the 2009 NHTS.