Implications of attending the closest school on adolescents’ physical activity and car travel in Dunedin, New Zealand

Background: Home-to-school distances and the need for students to be driven to/from school may limit adolescents' physical activity levels. School choice and school zoning policies can influence rates of active transport to/from school, and traffic volumes during school commuting times. This study aimed to quantify the effects of adolescents' enrolment in the closest school or not, on private vehicle use and adolescents’ physical activity levels in Dunedin city, New Zealand. Methods: New Zealand Travel Survey data (2003–2013; 2493 Dunedin respondents) were analysed to examine school-travel related private motorised trips. Dunedin-specific data from adolescents (from six Dunedin non-integrated public schools without school zoning) were analysed including self-reported survey data on school travel modes (797 adolescents), distance to the current and closest schools (797 adolescents) and accelerometer-measured moderate-to-vigorous intensity physical activity (MVPA) (121 adolescents). Results: During the school commute time (8–9 am and 3–4 pm), an estimated 11.5% of car trips (95% CI 7.8%–16.8%) and 12.5% of car distance driven (95% CI 8.8%–17.7%) were related to secondary-school travel with approximately half of these involving trip-chaining. Compared to adolescents living beyond cycling distance (>4 km) from their current school, adolescents living within walkable distance (≤2.25 km) and cyclable distance (>2.25-≤4 km) accumulated an additional 12.1 min (95% CI 7.0 to 17.2) and 6.1 min (95%CI 1.0 to 11.2) of daily MVPA during the school commute time, respectively. If adolescents currently enrolled at a distant school were to attend the closest school, they could accrue an additional 3.4 min MVPA during the 2-h school commute time period and school travel-related private car trips would be reduced by 7%. Conclusions: In Dunedin, New Zealand, modest reductions in private vehicle traffic, particularly around schools, and increases in adolescents’ MVPA during the school commute period would be expected if all adolescents attended the closest school.