With its court battles behind it, Oahu’s elevated rail project is poised to become a concrete-and-steel reality and city officials have launched an effort to show the public the construction that’s already happening.

On Thursday they offered a first glimpse of 50-ton concrete segments that will eventually form the guideway for the elevated rail line, during a media tour of the project’s casting yard in Kalaeloa.

The segments are like massive concrete snowflakes: At first glance they appear identical, but rail construction managers say each is unique and cast so that crews know exactly where they’ll fit along the winding, 20-mile rail route across Oahu’s southern shore.

The 130 or so segments completed so far line the 34-acre casting yard, awaiting transport sometime in the next couple of weeks to the West Oahu fields where columns are already in place.

In the next year and a half, some 5,200 segments will be cast to form the first 10-mile leg of the rail line to Aloha Stadium, project officials say.

Eventually the project will require twice that amount to form the entire route, which ends at Ala Moana Center. Each one typically measures 30 feet wide and 11 feet tall, and they’re designed to last 100 years.

"Never before in the history of Hawaii are we doing this kind of construction," Honolulu Mayor Kirk Caldwell said at the press tour, flanked by officials with construction contractor Kiewit Infrastructure West and the Honolulu Authority for Rapid Transportation, which oversees the project.

Lasers erected on pillars several dozen yards across from the site’s 13 casting beds provide precise targeting so that the crews can orient the segments so they’re cast in the exact manner needed.

As rail construction crews pour up to 12 new segments a day, officials continue to prepare for a complicated maneuver in June. It involves a towering engineering structure called a "balanced cantilever," which will extend the rail project’s guideway over the freeway Diamond Head of where the H-1 and H-2 freeways merge.

"It’s probably going to be one of the more visible aspects of our construction," HART Executive Director Dan Grabauskas said earlier this year. It will also require lane closures on the H-1 and H-2, and HART officials say they intend to give sufficient public notice as that work approaches.

Half of the rail transit system is slated to open in 2017, and the full system is planned to begin operating in 2019.