A new Interstate 985 interchange between Flowery Branch and Oakwood is behind schedule because of uncertainty over federal highway funding — a debate that’s expected to drag on this week in Congress. “With only short-term extensions of transportation authorization, it is hard to plan projects of this magnitude,” said Sam Baker, senior transportation planner for the Gainesville-Hall Metropolitan Planning Organization, the area’s main road planning agency. “We’ll just have to wait and see how the transportation legislation at the federal level pans out for this project to move forward,” he said.