We examined associations between objective measures of the local road environment and physical activity (including active transport) among youth. There is little empirical evidence of the impact of the road environment on physical activity among children/adolescents in their neighborhoods. Most recent studies have examined perceptions rather than objective measures of the road environment. This was a cross-sectional study of children aged 8-9 years (n = 188) and adolescents aged 13-15 years (n = 346) who were participants in the 3-year follow-up of the Children Living in Active Neighborhoods (CLAN) longitudinal study in Melbourne, Australia. At baseline (2001), they were recruited from 19 state primary schools in areas of varying socioeconomic status across Melbourne. Habitual walking/cycling to local destinations was parent-reported for children and self-reported for adolescents, while moderate-to-vigorous physical activity (MVPA) outside school hours was recorded using accelerometers. Road environment features in each participant's neighborhood (area of radius 800 m around the home) were measured objectively using a geographical information system. Regression analyses found no associations between road environment variables and children's likelihood of making at least seven walking/cycling trips per week to neighborhood destinations. Adolescent girls residing in neighborhoods with two to three traffic/pedestrian lights were more likely to make seven or more walking/cycling trips per week as those whose neighborhoods had fewer traffic lights (OR: 2.7; 95% CI: 1.2-6.2). For adolescent boys, residing on a cul-de-sac, compared with a through road, was associated with increases in MVPA of 9 min after school, 5 min in the evenings, and 22 min on weekend days. Speed humps were positively associated with adolescent boys' MVPA during evenings. The road environment influences physical activity among youth in different ways, according to age group, sex and type of physical activity.