Once a community is established, the residents sometimes get a say in how it changes, but in piecemeal fashion: Should a shopping mall go here, a subdivision added there?

But now residents across many parts of O'ahu will have the rarest of opportunities: A chance to reshape large portions of their communities, from the ground up.

Transit-oriented development — known in urban-planning circles by the acronym TOD — offers a distinct upside to hosting a transit line through the community. In the process of bringing the rail through town, residents can participate in deciding what will be built around it.

So it's imperative that residents speak up about what they want in the "special district" that will emerge. These decisions will define a community's characteristics for generations to come.

Waipahu has already embarked on this process. It's the first community along Honolulu's planned transit corridor to hold community workshops and form a grassroots advisory committee to keep a finger on the pulse of the neighborhood.

Three community workshops have been held. The turnout was robust at first but then diminished; not everybody is inclined to go to town meetings. So the advisory panel is planning to meet July 16 with businesses that border the rail line and would be affected by redevelopment. That's the right move.

There is a good deal of anxiety among the businesses about how redevelopment will play out, and whether there will be enough incentives to make any investment pay off.

Other communities down the line are watching Waipahu and waiting for their own discussions to begin.

The City Council is still uncertain how much specific direction to put in the legislation enabling the planning process. The bill is still sitting in committee.

A generic blueprint might be easier, but it's best to let each community craft its own district plan, complete with the incentives designed to encourage the development that's right for that neighborhood.

The Waipahu plan is moving along — the goal is to submit the plan to the Planning Commission by the end of the year. The city should try to stick to that timetable so other communities can move ahead with their planning as soon as possible.

It's easy to postpone planning for rail redevelopment until it starts to look more like a reality. But here's a reality check: Just last week, hundreds of businesses hoping to take part in construction turned out for another city workshop.

It's closer than it looks.

Timeliness is of the essence, and the voice of Waipahu residents must be heard. The next large public workshop isn't set until October, but residents meanwhile can catch up on the process so far.

If Waipahu residents want to help direct the way their home will look in the coming decades, now's their chance.