You have to study a map carefully before deciding which route makes the most sense. That is essentially what is happening with discussions of an elevated roadway — one of the alternatives under consideration to improve our mass-transportation capacity.

It's critical that the community examine this idea carefully, along with all the options covered by the study being prepared by Parsons Brinckerhoff Quade & Douglas under a $9.7 million city contract.

At first glance, the idea of creating a decked roadway following the Kamehameha Highway alignment would seem the cheaper, quicker answer to transit woes. The lanes could handle inbound traffic in the morning rush and reverse to the outbound direction in the afternoon.

The convenience of hopping in the car certainly would attract drivers to the expressway, even if a toll is charged per use. By comparison, predictions of commuter participation in a fixed-rail system have always been punctuated with a bold question mark.

However, the advantage of a speedier drive into town could be offset by the bottleneck elevated lanes would create, dumping more cars into the congestion of downtown Ho-nolulu. A rational cost analysis would have to include the expense of a roadway redevelopment on the town side of the route and on the 'Ewa end.

A fixed-rail system presents its own set of challenges to city planners, but ultimately it would seem to offer a solution with a longer shelf life. Even if Honolulu is relatively small compared with cities that support fixed rail, the population will continue to grow to the point where rail will be necessary but eventually no longer affordable.

Once the studies are done, O'ahu's leaders must move ahead decisively with the transit alternatives that offer the most promise. We've already waited too long for traffic solutions. The City Council must feel satisfied that all options have been given serious consideration. Now's the time to look at them, from every angle.