A firm decision on whether Honolulu's planned multibillion-dollar mass transit system will feature elevated trains on steel rails or another type of vehicle on a raised platform is likely at least one year away.

But planners say the entire project could be significantly delayed — even jeopardized — if the City Council revives a possibility that had been ruled out: a system of bus-like vehicles that branch out onto city streets after descending from a main elevated guideway.

Councilwoman Ann Kobayashi and some others argued yesterday that such a system could be more efficient and flexible than the rail plan favored by Mayor Mufi Hannemann.

They are interested in a system built by Phileas Advanced Public Transport System of the Netherlands, which has invited council members to visit operations in European cities, and offered to pay for their trip.

Honolulu could seek federal money to build a system that uses the Dutch company's vehicles and includes city streets, but it would not meet specifications the council approved earlier in key planning documents, said Toru Hamayasu, the chief city transit planner.

Planning work completed over the past two years would essentially have to start over, Hamayasu said.

"You have selected a locally preferred alternative, and we need to proceed with it rather than go back," Hamayasu told the council's transportation committee.

Bus-like vehicles on rubber tires could still be considered under the approved guidelines if they can be configured to carry 300 passengers and travel at certain speeds between transit stations on an elevated guideway, he said.

There does not appear to be enough support on the council to junk two years of planning, but the pending decision on vehicle technology remains contentious.

Though Hannemann and others often refer to the planned system as "rail" transit, it officially remains a "fixed guideway" proposal and awaits a decision on the specific vehicle technology.

The choice probably won't be made until after a key environmental analysis is completed about one year from now, council transportation chairman Nestor Garcia said in an interview.

Garcia said he generally agrees with Hannemann's preference for rail, but remains open to other ideas to ensure the project is viable.

Along with rubber-tire vehicles, trains that float on a magnetic field could also be considered under the current guidelines, Hamayasu said.

But it remains unclear how a decision will be made — and who will make it.

The council earlier passed a measure that allows it to make the choice, but Garcia said that may not conform with procurement regulations, and that he is reviewing the issue closely.

Hannemann has said he believes his administration should decide on the vehicle technology, and is firmly convinced it should be rail.

Hamayasu said the city needs an official decision before a final environmental impact statement — due in 2009 — can be completed. Hannemann has said he hopes to break ground on the system that year.

The system is to run between East Kapolei and Ala Moana Center at first, with later branches to Manoa, Waikiki and West Kapolei.

The city plans to finance much of the project through a general excise tax surcharge that took effect in January on O'ahu and is expected to generate $3 billion over 15 years. A partial count in April found that more than $14 million had been collected by then.

Congress is considering granting the city up to $20 million this year to help pay for preliminary engineering of the project. The money would be lost if the city abandons the planning that has been done so far, to consider other options, Hamayasu said.

The city plans to seek a major grant from the Federal Transit Administration to help pay for construction costs.

Reach Johnny Brannon at jbrannon@honoluluadvertiser.com.