We went to Southampton to get away from the convention. Now I have a photo album of its Main Street. It's a good town center and commercial street.
Many retail consultants will tell you that commercial streets shouldn't have trees, because they make it hard for drivers and people across the street to see the names of the stores. I think they really mean drivers. For people not in their cars, the trees are a very big part of what makes Southampton's Main Street, and many of the best American streets, such pleasant places to be.
The trees create a well-proportioned, sun-dappled but shaded place on a hot summer's day. Their sturdy trunks keep the cars at bay. They add a complement of softness, nature and beauty to a good-but-not-great, man-made place.
For the driver, they narrow and soften what would otherwise be a too-wide street with too many cars. This is one of the reasons why people come here instead of to the many and more convenient nearby shopping centers. (For more, see The Seven Roles of the Urban Street Tree.)