OKLAHOMA CITY — The most expensive highway construction project ever undertaken by the state could be delayed if a federal agency denies an application to relocate a railway line that lies directly in the project's path, officials said Wednesday. The federal Surface Transportation Board is considering a request by the Burlington Northern Santa Fe Railway Co. to relocate about a mile of rail line it owns in Oklahoma City that is in the path of the Interstate 40 Crosstown Expressway relocation project. Construction of the $500 million, 4.5-mile relocation project has already begun and completion is scheduled for 2012, said Gary Ridley, director of the Oklahoma Department of Transportation and Gov. Brad Henry's transportation secretary. But no construction work can begin on that one-mile stretch until the rail line issue is resolved, Ridley said. "It's in the hands of the STB," Ridley said. He said the agency has been seeking public comments about the plan and that it is not known when it will decide the issue. "It's been some time," Ridley said. Although the rail line issue has not yet delayed the project's completion date, the area will become part of the critical path of the Crosstown relocation project this year and a decision must be handed down within the next 30 to 60 days to avoid construction delays, Ridley said. "It's getting fairly close," the ODOT director said. "We're optimistic that the ruling will come down that will allow this to be done." But a critic of the Crosstown project said it should have never been launched until the state had control of all of the right of way it needed for the project. Tom Elmore of the North American Transportation Institute, which promotes transportation issues including rail, also said relocation of the BNSF rail line will disrupt a critical east-west rail path that connects southwest Oklahoma with eastern parts of the state. "Why would the highway department try to destroy the state's rail center?" Elmore said. "We're in the catbird seat for railway development. We're a shovel-ready project waiting for an opportunity. "Why is ODOT trying to rip the center out from our railway network? Why does the Department of Transportation want to cripple our rail capacity?" Elmore said. Although BNSF filed the relocation request and the state is not directly involved, the state will pay for relocating the line as part of the Crosstown project, Ridley said. The project requires grading, drainage and construction of a railroad bridge. Eventually the new Crosstown Expressway will go under that railroad bridge, according to transportation officials. The new stretch of roadway where the rail line is now located will be 8 to 10 feet deep. The project's total cost will rise to $600 million if a planned boulevard is built along parts of the existing roadway's path, Ridley said. The board, which is affiliated with the Department of Transportation, was created in 1995 and succeeded the Interstate Commerce Commission. It is an economic regulatory agency whose fundamental mission is to resolve railroad rate and service disputes and review proposed railroad mergers. The relocation request was filed after the board last June reversed an earlier decision that gave the railroad authority to abandon and discontinue use of the line to facilitate the highway relocation project. BNSF had claimed that the line should be abandoned because no local traffic had moved over the line for at least two years prior to the railroad's abandonment request in September 2005, according to the board's ruling. But the board said evidence presented by opponents of the move, including photographs allegedly showing a train being pulled by two BNSF locomotives, indicated that BNSF's assertion "was false or misleading," the board's decision states.