Maryland has petitioned the U.S. Court of Appeals to force a ruling in a long-running environmental lawsuit that has stalled the start of construction on the Purple Line light-rail project for nearly nine months. The petition, filed in the Court’s District of Columbia Circuit on May 12, asks that U.S. District Judge Richard J. Leon be required to rule on the lawsuit, which claims approvals for the $5.6-billion project were based on flawed ridership projections. Last August, the judge revoked the Purple Line’s environmental approval, saying that state and federal transportation officials had not fully considered potential effects of safety issues and declining ridership on the separately operated Washington, D.C., Metro system. Approximately 27% of Purple Line riders are expected to come via transfers with Metro, which will connect with five of the 21 stations planned for the 16-mile Purple Line. A court-ordered Federal Transit Administration analysis completed in December deemed Metro’s issues insufficient to warrant updating the environmental study. Since then, Maryland’s petition claims, Purple Line costs have increased by as much as $13 million a month, and that any further delay in resolving the lawsuit threatens the project’s financial viability.