Impacts of a city-wide 30 km/h speed limit intervention on physical activity, child safety and social behaviours: a natural experimental study in Amsterdam, The Netherlands

Lowering speed limits to 30 km/h (20 mph) is an increasingly adopted policy with anticipated public health benefits, yet evidence on these impacts is limited. This natural experimental study evaluated the impacts of a city-wide 30 km/h speed limit policy in Amsterdam, The Netherlands, on physical activity, child safety, and social interactions. Four intervention streets (reduced from 50 km/h to 30 km/h) were compared with two matched control streets (remained 50 km/h) at baseline (October-November 2023) and one-year follow-up (October-November 2024). Systematic street observations assessed physical activity behaviours (walking, cycling, cargo bike, child seat use), child safety indicators (helmet use, children under adult supervision), and social interactions (alone/in group, conversing). Multilevel regression models estimated intervention effects by age group (children, teenagers, adults), adjusting for day, time, and precipitation. Compared to controls, intervention streets showed significant increases in children cycling, children in child seats, adults in groups, and adults conversing. Teenagers observed alone decreased, while children alone increased. No significant changes were found for walking, cargo bike use, helmet use, or supervision. This is one of the first natural experimental studies suggesting that 30 km/h speed limits may produce benefits beyond road safety, supporting children’s independent travel and promoting social interactions.