Cooling with green © Jonathan Perrin

Tree-lined avenues

  • Water: 2
  • Heat: 2
  • Biodiversity: 2
  • Air quality: 2
  • Energy: 1
  • Multifunctional space usage: 1
  • Costs: 2
  • Maintenance/management: 1


The use of tree-lined avenues requires some extra attention. Tree-lined avenues in which the tree crowns merge above the road inhibit the mixture of polluted air with the cleaner air above the city. This causes a negative effect on air quality at street level. An often-used rule of thumb is that tree crowns should not merge overhead when fully grown and that they should not have an overhang covering more than one-third of the street. Trees are generally placed 15 metres apart and preferably not directly lining the road, so that they won’t cover the road as much.