摘要：Objectives. We assessed changes in transit-associated walking in the United States from 2001 to 2009 and documented their importance to public health. Methods. We examined transit walk times using the National Household Travel Survey, a telephone survey administered by the US Department of Transportation to examine travel behavior in the United States. Results. People are more likely to transit walk if they are from lower income households, are non-White, and live in large urban areas with access to rail systems. Transit walkers in large urban areas with a rail system were 72% more likely to transit walk 30 minutes or more per day than were those without a rail system. From 2001 to 2009, the estimated number of transit walkers rose from 7.5 million to 9.6 million (a 28% increase); those whose transit-associated walking time was 30 minutes or more increased from approximately 2.6 million to 3.4 million (a 31% increase). Conclusions. Transit walking contributes to meeting physical activity recommendations. Study results may contribute to transportation-related health impact assessment studies evaluating the impact of proposed transit systems on physical activity, potentially influencing transportation planning decisions. The health benefits of physical activity have been well documented; 1–4 still, only 64.5% of Americans are physically active, and 25.4% do not participate in leisure time physical activity at all. 5 Inadequate physical activity contributes to numerous health problems, causing an estimated 200 000 annual deaths in the United States and significantly increasing medical costs. 6 In contrast, average annual medical expenditures are 32% lower among physically able adults who get regular exercise than the expenditures of those who lead a sedentary lifestyle. 7 The US Department of Health and Human Services created guidelines to describe the amount and type of physical activity most likely to provide health benefits. The 2008 Physical Activity Guidelines for Americans recommended that adults get at least 150 minutes of aerobic physical activity per week. 8 The guidelines also recommended that physical activity be moderate in intensity, such as brisk walking, and last at least 10 consecutive minutes. Morabia and Costanza 9 demonstrated the health value of brisk walking for as little as 15 minutes per day or slow walking 30 minutes per day in preventing weight gain on the basis of caloric expenditures. Because most public transit trips begin or end with walking, 10–13 public transit use can be an important opportunity to add physical activity into one’s day. Additional research has shown that walking to or from public transit, “transit walking,” may help people meet physical activity recommendations. 10,14–17 The community environment can affect whether and how community members engage in physical activity. 18 The way communities are built has an impact on the viability of public transit and the safety of its users and influences whether healthy choices, such as walking, are easy or difficult. 17,19,20 Socioeconomic factors, such as household income levels 21 and employment status, 22 also strongly influence the viability of public transit for community members. Whatever the forces driving people to use public transit, a growing body of evidence has suggested that its use benefits community public health and directly benefits the personal health of transit users. Previous research has found links between the use of public transit and physical activity, 10 lower body mass index (defined as weight in kilograms divided by the square of height in meters), 1,23,24 and travel safety. 25 The Centers for Disease Control and Prevention and the National Center for Environmental Health have formally recognized the health impact of transportation systems. Consequently, they developed transportation recommendations that promote travel choices to improve health, such as those that include opportunities for physical activity. 26 Current demographic and economic trends (i.e., aging population, rising fuel prices, increasing health and environmental concerns, rising medical care costs) are increasing the value of public transportation–related health benefits 27 ; however, little is known about how these current trends influence physical activity. Examining the influence of current demographic and economic trends on transportation patterns is vital for informing community design and transportation decisions. The purposes of this study were to estimate the daily level of physical activity attained by Americans solely through transit walking, to describe the demographic and socioeconomic characteristics of transit walkers, to determine transit-walker and environmental factors that influence transit walking, to help predict those who will achieve 30 minutes or more of physical activity solely by walking to or from public transit, and to assess changes in transit walking over time.
