Groups pushing to get an anti-rail ordinance on the November ballot said they'll give up their opposition if voters approve plans to build a commuter rail system on O'ahu.

Stop Rail Now and Honolulu traffic.com also said they'll go to court this week to try to force a November vote on their proposed ordinance, which states: "Honolulu mass transit shall not include trains or rail."

Project opponents say the train will cost too much, create too much noise and won't address ever-increasing traffic problems. Mayor Mufi Hannemann, construction trade unions and other proponents say the train will curb urban sprawl and provide commuters a speedier alternative to vehicles and TheBus.

Dennis Callan, co-chairman of Stop Rail Now, and Cliff Slater, chairman of the anti-rail Web site Honolulutraffic.com, yesterday said they'd stop opposing the project if voters reject the anti-rail ordinance.

If that happens, "personally, I'm done," Callan said.

"Yeah, we're done," Slater said.

Both still hope they'll prevail in derailing the project in favor of alternatives such as elevated high-occupancy toll lanes.

"Once rail is gone, then we can look at real alternatives," Callan said.

However, getting that ordinance on the general election ballot is a challenge. That's because anti-rail groups and the city clerk are at odds over several key issues, including the number of signatures required to place the issue before voters and when such a vote could occur.

Last week, City Clerk Denise C. De Costa said the ordinance could not be placed on the November ballot. However, a special election on the issue is still possible sometime next year, according to a letter from De Costa to Stop Rail Now released last week.

Ultimately, the issue is likely to end up in court. Callan and Slater said they plan to seek a judicial opinion on whether their anti-rail ordinance can be voted on in November.

"We are very confident that we're going to win this one," Slater said.

Hannemann wants to begin construction next year on the 20-mile elevated commuter rail line from east Kapolei to Ala Moana and complete the project by 2018.

Stop Rail Now had threatened to sue the city, alleging that its pro-rail ad campaign is misleading and inaccurate. The group decided not to follow through with the lawsuit after the city stopped running the ads, Callan said.

City spokesman Bill Brennan was unavailable to comment on the city's advertising practices.

The city spent $1.4 million in taxpayer money on public relations and outreach efforts related to the rail project from August 2005 through February 2008. Millions more are likely to be spent promoting and informing the public about the project.