All study materials were sent by mail, with an option to complete surveys

online or return by mail (Sallis et al., 2009). A total of 2199 participants completed an initial survey, and n = 1745 (79%) of these returned a second survey six months later. Because the bicycling-related items were in the second survey, the GSK1120212 sample for present analyses was 1745. About half of the sample were men (51.7%), and the mean age was 46 years (SD = 10.6). The majority of participants identified themselves as Caucasian (75.1%, White non-Hispanic), with other groups including African Americans (12.1%), Asian Americans (5.6%), and Hispanic/Mexican/Latin American (3.3%). BMI ranged from 15.0 to 62.6 (M = 26.7, SD = 5.5). The sample was well educated with only 8% having a high school education or less, 24.7% with some college, 34.6% with a college degree, and 32.7% with a graduate degree. Access to a bicycle in the home, yard, or apartment complex was assessed by one item in a yes/no format HIF-1 pathway (Sallis et al., 1997). Bicycling frequency questions were based on a previous study and excluded stationary biking (Frank et al., 2001). Biking frequency was assessed

through the question, “How often do you bicycle, either in your neighborhood or starting from your neighborhood?” (Frank et al., 2001). Five response options ranged from “never” to “every day”. An additional question was developed by NQLS researchers: “How often would you bike if you thought it was safe from cars?” Response options were the same as for current bicycling frequency. Projected changes in bicycling frequency if participants thought riding was safe from cars were computed by “frequency if safer” minus “current frequency”. The GIS-based

block group walkability procedures for neighborhood selection (described above) were modified to construct GIS walkability measures for each participant using a 1000-meter street network buffer around the residence (Frank et al., 2010 and Saelens et al., 2012). The four components, along with the walkability index, were analyzed, all at the individual level. The Neighborhood Environment Walkability Scale (NEWS) assessed perceived environmental the variables thought to be related to physical activity (Saelens et al., 2003). Test–retest reliability and validity of NEWS have been supported (Brownson et al., 2004, De Bourdeaudhuij et al., 2003 and Saelens et al., 2003). Eight established subscales were analyzed: residential density, land use mix-diversity, land use mix-access, connectivity, pedestrian/bicycling facilities, aesthetics, safety from traffic, and safety from crime. All subscales were coded so higher scores were expected to be related to more physical activity. Four items within the NEWS with particular relevance to bicycling were selected for exploratory analyses based on previous findings (Moritz, 1998, Vernez-Moudon et al., 2005 and Wardman et al.