City staff must trim trees year-round due to public safety, accessibility and safety requirements. For example, we must keep trees pruned at a height that allows the safe passage of large vehicles (such as fire trucks, school buses and trash trucks) the visibility of street and crossing signs, and sidewalk access. City crews must also schedule tree trimming around other important work that they do, which includes maintaining more than 270 miles of roadways and 450 miles of sidewalks.