摘要：Objectives. To assess changes in walking and cycling in the United States between 2001 and 2009. Methods. The 2001 and 2009 National Household Travel Surveys were used to compute the frequency, duration, and distance of walking and cycling per capita. The population-weighted person and trip files were merged to calculate the prevalence of any walking and cycling and of walking and cycling at least 30 minutes per day. Results. The average American made 17 more walk trips in 2009 than in 2001, covering 9 more miles per year, compared with only 2 more bike trips, and 5 more miles cycling. At the population level, the prevalence of “any walking” remained unchanged (about 18%), whereas walking at least 30 minutes per day increased from 7.2% to 8.0%. The prevalence of “any cycling” and cycling 30 minutes per day remained unchanged (1.7% and 0.9%, respectively). Active travel declined for women, children, and seniors, but increased among men, the middle aged, employed, well-educated, and persons without a car. Conclusions. Walking increased slightly, whereas cycling levels stagnated, and the overall prevalence of active travel remained low. Improved infrastructure for walking and cycling must be combined with programs to encourage active travel among more groups, especially children, seniors, and women. Walking and cycling are healthy and sustainable means of transport. These forms of active travel contribute to daily physical activity, aerobic fitness, and cardiovascular health while helping to protect against obesity, diabetes, and various other diseases. 1 – 9 The mounting evidence on the health benefits of walking and cycling has led to public health advocacy for more walking and cycling to improve individual health and to reduce air pollution, carbon emissions, congestion, noise, traffic dangers, and other harmful impacts of car use. 10 – 15 Thus, it is important to monitor rates of walking and cycling over time and to assess differences among population subgroups. Rates of active travel to work declined sharply in the United States over the past few decades. The US Census Bureau reported a declining proportion of workers walking to work (as their main mode of transport) from 10.3% in 1960 to 2.9% in 2009. 16 , 17 Bicycling to work has only been reported since 1980, but it increased from 0.4% in 1980 to 0.6% in 2009. The share of workers taking public transport fell from 12.6% in 1960 to 4.7% in 2000, but then rose to 5.0% by 2009. Most public transport trips involve walking to get to and from public transport stops, but the Census only reports the main mode. Thus, the sharp decline in public transport mode share since 1960 also suggests a decline in walk trips combined with public transport until 2000 and then a slight increase between 2000 and 2009 (see Supplemental Table A, available as a supplement to the online version of this article at http://www.ajph.org ). Unlike the Census, the Nationwide Personal Transportation Survey (NPTS) and the National Household Travel Survey (NHTS) report on travel for all trip purposes, thus providing a more comprehensive view of travel behavior. The NPTS documented a decline in the walk share of trips from 9.3% in 1977 to 5.4% in 1995, but a slight increase in the share of bike trips, from 0.7% in 1977 to 0.9% in 1995. 16 , 18 The NHTS—successor to the NPTS—reported a higher walk share of trips in 2001 (8.6%) and a constant bike share (0.9%). However, changes in survey design limit the comparability of the 1995 NPTS and the 2001 NHTS. 16 , 19 Thus, it is unclear whether the walk share of trips increased between 1995 and 2001, or if it is a statistical artifact resulting from the improved methods for capturing previously unreported walk trips. After 3 decades of declining rates of active travel in the United States, the question is whether there has been a turnaround, and if rates of walking and cycling are now rising. The recently released 2009 NHTS provides a unique opportunity to answer that question, because it employed the same methodology as the 2001 NHTS. Moreover, the NHTS provides household travel information both for the previous day and the previous week. Finally, the NHTS specifically identifies walk and bike trips taken to and from public transport, which were an important component of active travel. 20 , 21 This article uses the 2 most recent NHTS surveys to measure changes in active travel in the United States from 2001 to 2009. The NHTS data on walking and cycling are analyzed from both the trip-based perspective of travel behavior and the public health perspective of population physical activity rates, adapting the methodology recently developed to analyze transport surveys in Australia. 22
