Traditionally, overlays have allow individual neighborhoods to limit or encourage specific kinds of commercial development and create a desired aesthetic. They dictate how tall structures can be and how they should look, and guide the interaction between public and private spaces. In many cases, they also include lengthy and specific lists of prohibited business uses.
In the proposed city zoning code, the Northwest overlays are absorbed into a new category called Neighborhood Commercial Area, or NCA, "intended to preserve the integrity of the neighborhood commercial areas and to promote and help guide appropriate commercial development." In general, the NCAs deal more broadly with the form and design of the built environment, rather than enumerating specific uses. In many– but not all– cases, those individual prohibited uses will be left to the control of the new commercial zoning that will replace current designations.