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.
shows the distribution of walking trips by purpose and groups. The probabilities of walking varied by purpose. Among people with at least one trip to work, 6.5% had at least one walking trip. The percentage of people with at least one walking trip (among those with at least one trip in the category) was much higher for recreation (40%) and pet-related activities (72%). The percentage of respondents who walked at least once a day varied by sociodemographic characteristics with the largest variation observed by place of residence (as high as 21% among urban residents and as low as 11.6% among town and country residents). There was also substantial regional variability (22% in the Northeast to 12.5% in the South). The number of total walking trips among those who walked at least once a day ranged from 2.0 to 2.4.