Simulating crowding of urban green areas to manage access during lockdowns

•The trade-off between green areas access and crowding is made explicit.•Different policy scenarios have different impact on green areas access and crowding.•Limiting maximum travel distance has small effects on the number of crowded parks.•Hotspots where green areas are too far or at higher risk of crowding are identified.•Off-the-shelf measures (e.g., opening schoolyards) work and can be adopted rapidly.