title: Variability and seasonality of active transportation in USA: evidence from the 2001 NHTS.
abstract: BACKGROUND
  Active transportation including walking and bicycling is an important source of physical activity. Promoting active transportation is a challenge for the fields of public health and transportation. Descriptive data on the predictors of active transportation, including seasonal patterns in active transportation in the US as a whole, is needed to inform interventions and policies.
  
  
  METHODS
  This study analyzed monthly variation in active transportation for the US using National Household Travel Survey 2001 data. For each age group of children, adolescents, adults and elderly, logistic regression models were used to identify predictors of the odds of active transportation including gender, race/ethnicity, household income level, geographical region, urbanization level, and month.
  
  
  RESULTS
  The probability of engaging in active transportation was generally higher for children and adolescents than for adults and the elderly. Active transportation was greater in the lower income groups (except in the elderly), was lower in the South than in other regions of the US, and was greater in areas with higher urbanization. The percentage of people using active transportation exhibited clear seasonal patterns: high during summer months and low during winter months. Children and adolescents were more sensitive to seasonality than other age groups. Women, non-Caucasians, persons with lower household income, who resided in the Midwest or Northeast, and who lived in more urbanized areas had greater seasonal variation.
  
  
  CONCLUSIONS
  These descriptive results suggest that interventions and policies that target the promotion of active transportation need to consider socio-demographic factors and seasonality.
authors.affiliation: Department of Epidemiology, Center for Social Epidemiology and Population Health, University of Michigan, Ann Arbor, Michigan, USA. yongyang@umich.edu
authors.forename: Yong
authors.initials: Y
authors.lastname: Yang
authors.forename: Ana V
authors.initials: AV
authors.lastname: Diez Roux
authors.forename: C Raymond
authors.initials: CR
authors.lastname: Bingham
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D001642:Bicycling / Q000706:statistics & numerical data*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006293:Health Promotion; D006801:Humans; D007182:Income; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011634:Public Health; D044469:Racial Groups; D012621:Seasons; D012737:Sex Factors; D014186:Transportation / Q000706:statistics & numerical data*; D014195:Travel; D014481:United States; D014505:Urban Population; D016138:Walking / Q000706:statistics & numerical data*; D055815:Young Adult