The planning firm selected to figure out O'ahu's best mass transit alternatives has been put on a spectacularly tight schedule.

It must look at all the alternatives and come up with a package of the best by next fall, a very short time frame for this kind of work.

Given the tight schedule and looking at how similar studies have unfolded in the past, it would be easy for Parsons Brinckerhoff Quade & Douglas to zero in on some form of rail transit in line with what the city may already have in mind.

So it is encouraging to hear company officials say they will look seriously at all alternatives, from the "no-build" option to various technologies and theories about keeping Honolulu's residents moving.

This is important because the credibility of the project and its funding will depend deeply on how well it has been analyzed. In the past, technical planning appeared to support existing political decision-making.

That must not happen here.

If the public concludes, even unfairly, that this is the case the project won't get the crucial support it needs to succeed.

Parsons Brinckerhoff is in a good position so far. It has consulted with the city on previous transit projects and it has a mountain of previous studies and analyses to start with.

The final plan should include innovative traffic management ideas, alternatives ranging from ferries to high-tech car pooling and some form of high-occupancy transit service.

The key for O'ahu commuters and taxpayers is to understand that all the key decisions have yet to be made. Now is the time to make your voice heard if you want the island's transportation future to reflect your ideas.

The city has not yet set up a clear channel for public input, but it soon will. Work is under way on a Web site, newsletter and public information hot line.

In fact, the consulting contract signed by Parsons Brinckerhoff requires just that. That part of the contract — creating avenues for public input — is key to gaining substantial public buy-in for this important effort.