Aspecial-purpose district would most likely be created when a city is starting to lose population. village needs to build a new elementary school. public transit system is being planned for a metropolitan area. police car must be purchased to patrol a city neighborhood.

A special-purpose district would most likely be created when a public transit system is being planned for a metropolitan area.
In case that such a venture is being planned and about to be implemented, a special-purpose district has to be created in order to make the entire venture much easier. This will help the metropolitan area continue to exist normally.