Oahu residents voted to approve the City Charter amendment supporting the 20-mile elevated steel-rail transit system from Kapolei to Ala Moana, the single-largest public works project in state history.

Mayor Mufi Hannemann, the leading advocate for a steel-rail system, said it was a tough campaign, but asked opponents to find a way to support the project.

“;The feeling has been let the people decide and the people have spoken,”; he said.

The mayor said the economy and environment need the steel-wheel-on-steel-rail system. “;But most of all, our families need traffic relief,”; he said.

As about 200 supporters celebrated the victory at the pro-rail headquarters on Bethel Street, Justin Fanslau, campaign manager for Go Rail Go, credited the thousands of volunteers who gave their “;blood, sweat and tears.”;

The vote was a blow to Stop Rail Now, the group that opposed the project.

Cliff Slater, a leader of the group, which gathered at a computer store on South Street, said he was disappointed.

“;The group will reconvene and consider what's next,”; he said.

He said he doesn't know whether the federal government will consider the vote results enough of a mandate to provide the federal funding for the project.

“;It's hardly a consensus,”; he said of the 52.6 percent to 47.4 percent vote in favor of rail. “;It's pretty close.”;

Dennis Callan, another leader of the group, said he'll get involved in the environmental impact study for the project. He said there's still a lot of opportunity for public input.

The rail system's cost is estimated to be $3.9 million in 2008 dollars, but it is expected to be closer to $5 billion after adjusting for inflation during the life of the 20-mile project. City officials expect to cover the costs with $1.2 billion in federal funding and a 0.5 percent surcharge to the general excise tax that would bring in $4.1 billion through 2022.

Rail supporters contended the transit system would be the best way to ease traffic, which is expected to increase with new homes planned for Central Oahu and the Ewa Plain. Opponents argued the system is too costly to build and maintain, too ugly, too noisy and not the best alternative to relieve traffic congestion.

In addition to Hannemann, supporters include Hawaii's congressional delegation and the Hawaii Carpenters Union and other labor groups. Opponents include mayoral candidate Ann Kobayashi and Panos Prevedouros, an engineering professor who threw his support to Kobayashi.