Measures
phrasing:“It, Wilson et al.
SECONDARY
SES was calculated as the Winkler Index, a composite score considering parental education, parental occupations, and equivalized household net equivalent income. Scores on the Winkler Index range from 3 to 21 [The distance between home and school was calculated as the network distance from the home to school address using the Dijkstra algorithm [Information about means of transport (car, public transportation, walking, and/or cycling/skateboard/scooter), travel duration (minutes on each means of transport), and perceived barriers to AST were assessed in a questionnaire completed by the parents and, beginning at age 9.5, additionally by the children and adolescents themselves. Answers regarding the means of transport for participants below age 13.5 were primarily parent reports and only complemented with self-reports when parent reports were missing. For adolescents older than 13.5 years of age, self-reports were preferred because greater independence was assumed (Additional Fig. Associations between active school transport, age, and type of school: In general, a higher proportion of primary school children engage in active school transport. For both primary and secondary school children, the proportion increases with increasing ageAdolescents were additionally asked in a single-choice question to state which of the four given options they would prefer for their school transportation if they had free choice.The primary means of transport was categorized as (1) cycling or (2) walking for children and adolescents who used cycling or walking as their only means of transport or who used a combination that included at least 15 min of cycling or walking. The third category public transport was assigned when participants took the bus, tramway, or train; the fourth category was being taken by car. Cycling and walking were considered active school transport (AST), whereas using public transport or being taken by car were considered motorized school transportation.The perceived barriers were also assessed through questionnaires using the following phrasing:“It is difficult for me / for my child to walk or to cycle to school independently (without the company of an adult) because…”. The participants could rate each potential barrier on a four-level Likert scale with the following options: “I disagree”, “I mildly disagree”, “I mildly agree”, and “I fully agree”. The first two answer options were aggregated into the category “non-significant barrier” and the last two answer options into the category “perceived as a potent barrier".A list of questions and answers regarding the perceived barriers can be found in Table The phrasing of the questions is based on a Canadian research paper by Wilson et al. [Furthermore, children and parents were asked to state whether or not bad weather conditions hinder them/their children from walking/cycling to school on a scale from 0–100 (with 0 = not at all and 100 = a lot). Ratings > 50 were interpreted as considering weather as a significant barrier to AST. For parents stating that they have no reservations about letting their children cycle or walk to school without an adult’s company, the perceived barriers were set to “no barrier”. The barrier “bullying” was removed from the analysis because of the low number of positive answers (n < 10). The number of perceived effective barriers was also considered as a covariate.