Cross-sectional and longitudinal analysis of the active commuting behaviors of U.S. Department of the Interior employees

Evidence supporting the promotion of physical activity as a means to reduce the risk of developing non-communicable diseases has become well accepted, and in turn, led to the development of a National Physical Activity Plan [1] and recommendations by the US Department of Health and Human Services [2]. The National Physical Activity Plan [1] recognized that physical activity is influenced by an array of factors that span personal, family, institutional, community, and policy levels. Furthermore, the plan recommended that different societal sectors, such as business and industry promote physical activity in their employees by providing opportunities and incentives for adopting and maintaining a physically active lifestyle.

However, a potential problem with these guidelines is the inability of many Americans to dedicate time in their day to meet them. One alternative to meet recommended levels of physical activity is to promote active transportation (AT; transportation mode that involves moving from place to place by any human-powered transportation mode) to work instead of driving. Individuals that choose AT modes (or a combination of modes) may be more physically active than individuals that choose non-active modes [3, 4]. Costa et al. [5] estimated that approximately half of the generally recommended amount of moderate-to-vigorous physical activity could obtained by AT to work. Active transportation to work has been associated with a reduced likelihood of obesity and cardiovascular disease risk, and higher fitness [6, 7].

Despite the promise of AT as a way for Americans to meet physical activity guidelines, overall participation in AT to work is rather low [2, 8, 9]. A variety of sociodemographic characteristics may be associated with the reasons for not choosing AT to work, such as age [9‐15], race/ethnicity [9, 12, 16], education [9, 17], income [9, 14, 15], and sex [9, 11, 12, 15‐19]. Also, living in metro (urban) or non-metro (rural) areas may impact the odds of commuting to work by walking, biking, or mixed modes [8, 9], possibly in part due to a lack of infrastructure that would support AT modes [8, 20].

An array of environmental correlates may also impact AT [14, 21, 22]. Macro-level examinations of AT behavior settings suggest that environmental attributes such as population density, accessibility of public transit, and other commuting infrastructure may determine travel behavior [8, 14, 23]. A study focused on commuting in the metro core and inner suburbs of the Washington, DC region found that population density and residence in the metro core area were both positively correlated with the likelihood of choosing AT to work [16]. Yet, questions remain about how this wide range of factors impact AT choice to work in large organizations, particularly those with employees working in a variety of metro and non-metro sites. Unfortunately, much of what is known about AT behavior comes from relatively small scale studies from a particular community [10, 20] or large regional/national studies [8, 14].

Factors specific to the location of home relative to work also appear to be significant predictors of choosing AT to work. For example, Cerin et al. [24] reported that distance between work and home was the most important factor for choosing to walk to work. Similarly, Yang et al. [25] found that both walking distance from a transit stop, and distance between home and work were significant predictors of AT. Overall, AT may be appropriate for distances of up to 5 km [20] and that people who live closer to work are more likely to be active commuters [9, 10, 19, 22]. However, it should be noted that variables such as self-reported AT distance may be subject to recall bias [26].

Another aspect of understanding the nature of commuting behavior in organizations is how trends may change over time. Reports from the US Census Bureau [27] indicate that the rates of AT to work are low for biking (0.5–0.6%) and walking (2.0–6.0%), and have changed little over time. The National Household Travel Survey [28] indicated that commuting to work with private vehicles has only ranged from a low of 91.4% to a high of 92.8%, and walking has only ranged from 3.0 to 4.0%. Although changes in AT behavior may be modest, factors that are associated with adopting AT are no children in the household, access to public transportation, convenient access to bicycle routes, and distance living from work [22, 29]. However, changes in the rates of AT of a large organization over time have not been reported despite recommendations that surveillance systems should be in place for workplaces [1].

An additional benefit associated with increasing physical activity by AT is the possibility of reduced health care expenditures [30‐33] due to a reduction in the risk of non-communicable diseases such as coronary heart disease, stroke, type 2 diabetes, breast cancer, obesity, hypertension, and colon cancer [12, 34, 35]. The health care expenditures associated with physical inactivity not only impacts individuals, but federal and third party resources (such as health insurance) [34]. The health benefits to individuals also extends to employers, including reduced cost of health care and improved worker performance [1]. Overall, a majority of worksite physical activity interventions result in positive impacts for employees, such as providing organizational and environmental supports for AT [36].

Therefore, the goal of the present investigation was to examine the correlates of AT to work in a large organization within a cross-sectional analysis from a single year of data (2010) and report on changes in the rates of AT by conducting a repeated cross-sectional analysis over time (2010, 2012–2016).

The results of this study suggest a significant association between a range of factors related to the daily commute and AT mode choice to work. Distance between home and work, distance between home and nearest public transition station, workplace location (metro vs. non-metro), sex, and age were related to choosing AT modes. For example, commute distance to work was a significant negative determinant of being an active commuter, which is consistent with previous research [10, 22, 24]. These findings are supported by Panter and colleagues [17] who reported that if residents lived close enough to their workplace, they were more likely to commute by walking or biking. The number of respondents that chose AT modes was reasonably stable over time, although there was a tendency for the choice of mixed-modes to increase. Non-metro respondents were more likely to walk to work, but less likely to bike or choose mixed-modes. Finally, commuting distances tended to decrease over time, were higher in non-metro dwellers, and were lower for AT modes.

The results of this investigation confirm that there are differences between the AT choices of metro and non-metro respondents, whereby employees that worked in metro areas were more likely to bike and take mixed modes to work [8]. However, non-metro respondents were more likely to walk to work, which is inconsistent with Quinn et al. [9], who reported that metro dwellers were more likely to both walk and bike to work. A work-related AT study in the Washington DC region suggested that bikeway infrastructure was significantly related to higher rates of bicycling [16]. At the same time, safe route environments and presence of green space are perceived as important environmental determinants of bicycle commuting [44]. Therefore, a potential exists to develop infrastructure to encourage non-metro commuters to choose bicycling to work, although physical activity choices may also play a role. For example, other research has demonstrated that non-metro residents may engage in less moderate-to-vigorous physical activity than their metro counterparts [45], suggesting that there are other differences between metro and non-metro residents that may impact choosing AT to work. Therefore, further research is warranted to explore environmental and social barriers of AT among non-metro residents.

Understanding demographic influences such as sex and age on AT is critical for developing tailored strategies that encourage AT to work. Consistent with prior investigations [15, 46, 47], our study found that men were more likely to choose AT modes than women, and the oldest respondents were less likely to bike to work than the youngest age group. The likelihood of walking to work was higher in men (OR = 1.559, p < 0.0001), but the difference between men and women was particularly strong for bike commuting (OR = 3.968, p < 0.0001). Overall, previous research has indicated that bicycle commuting is more popular among men [9, 19, 46, 48, 49], and walking more popular among women [17, 48, 49]. Another explanation for fewer female active commuters is that women may bear the responsibility for day-to-day household tasks, such as child care and housework [48]. The influence of age has also been reported by Quinn et al. [9], whereby they found that walking and bicycling to work decreased with increasing age. Based on the current analysis, we speculate that the age effect on bicycling may be related to safety concerns among older individuals [13]. Future studies should direct attention to the study of demographic differences for AT to understand the challenges for specific subgroups, especially women and older adults.

One of the unique aspects of this study was the longitudinal analysis, perhaps the most comprehensive of its kind. Similar to the present results, Panter et al. [29] reported small changes in walking (+ 3 min/wk) or bicycling (− 5.3 min/wk) commuting over the course of a year. In a follow-up study over the course of seven years, Yang et al. [22] reported that 76% of commuters chose non-active modes and tended to not change their mode, while 8% switched to an active mode. Based on a report from the US Census Bureau [27], the percentage of workers that bicycled to work has only varied between 0.5% in 1980 to 0.6% in the 2008–2012 American Community Survey. In the same report, the percentage of walkers was 5.6% in 1980, which declined to 2.9% in 2000 and remained similar (2.8%) to the 2008–2012 American Community Survey. The National Household Travel Survey [28] indicates that driving a private vehicle to and from work ranged from a high of 92.8% in 1995 to 91.4% in 2009, while walking reached a high of 4.0% in 1990 to 3.0% in 2009 (low of 2.3% in 1995). Therefore, it appears as though AT behaviors have remained relatively constant over time.

Social and cultural supports provided by employers, although not tested in our model, may pose a substantial influence on choice of AT to the workplace. Both governmental agencies and employers could foster an AT culture by increasing awareness of the benefits of AT and offering incentives to promote AT behaviors [25]. For example, employees could be incentivized by programs that provide tax breaks, health insurance premium reductions, public transportation discount/refunds, and other financial incentives [16]. A large organization having multiple worksites in metro and non-metro areas could provide extra support for those who work in non-AT-friendly areas. There is evidence of benefits for an organization to incentivize AT, particularly in health-related factors such as obesity, hypertension, diabetes, and physical fitness [6, 12, 35]. Flint et al. [7] reported that commuting by AT is associated with lower body mass index (BMI) in both men and women. A change from non-active to active modes of commuting is associated with a decrease in BMI [50, 51], as is the maintenance of bicycling commuting over time [52]. However, not all longitudinal analyses support the impact of AT on BMI [52]. Overall, it appears as though increases in physical activity associated with AT use may result in improved health outcomes, potentially resulting in cost savings associated with reduced health care expenditures for workers and their employers [33].

Furthermore, joint efforts between public health and urban planning agencies could advocate for additional environmental supports, such as improved walking and biking infrastructure, and expanded public transit systems. A range of correlates are associated with AT, but environmental constraints appear to be particularly important [21]. Supportive transportation environments may increase the chances of employees taking up walking or bicycling to work [29]. Another option is to provide educational materials, which has been shown to increase walking to work, but not bicycling [53].

The main strength of this study is the inclusion of a nationwide sample of respondents from a large federal agency in the US over the course of six years. Furthermore, this study examines differences in AT mode choice to work from respondents with a wide array of personal characteristics and location of where they live and work. Despite these strengths, a number of limitations of this study should be noted. The self-reported measures of AT may be subject to recall bias, therefore measures such as work distance and commute time may be over- or underestimated [26]. The commuting categories chosen for this study could be considered arbitrary. Moreover, important confounders such as AT for non-work purposes, daily physical activity level, home location, and general health status were not controlled for this analysis. Due to the repeated cross-sectional analysis design, individual respondents could not be tracked over the course of the study. Finally, the respondents from our study only included employees from one organization, thus limiting the generalizability of our findings to other organizations.

The current study represents the largest of its kind to investigate the characteristics of employees that choose active transportation to work, then subsequently track trends over the course of six years. A range of environmental variables related to the location of home and work, and a number of demographic factors were associated with AT to work for US Department of the Interior employees. However, it is worth noting that approximately 88% of DOI employees reported taking non-active modes to and from work, which is similar to the findings from the American Community Survey [27], the National Household Travel Survey [28], and others [20, 25], but higher than similar investigations [7, 12, 22, 35]. Overall, the percentage of respondents that took active modes was low when compared to other investigations [9, 14, 21, 25], and relatively stable over time.