Perhaps cities waiting for light rail should lower their expectations again. Usually, environmental impact reports promise at least slight congestion relief. At this point, folks in Minneapolis would be thankful for a completely neutral effect: Officials poorly planned the traffic-signal system along the Hiawatha light-rail line, subjecting drivers on south Minneapolis streets to unnecessary waiting at train crossings, according to a review by federal highway experts. A Federal Highway Administration team that reviewed the planning and engineering of the signals said, “more time, effort and money should have been allocated to ensuring that they operate as efficiently as possible before committing to construction.” Some relief may be in sight for drivers waiting at train crossings, because officials plan to adjust the timing of safety gates. But Hiawatha Avenue traffic will never flow as smoothly as before trains started running, the experts concluded. Since the line opened in June, drivers have faced traffic tie-ups and excessive waiting on cross streets, where the light-rail trains always have the right of way. Hiawatha Avenue traffic also has slowed because traffic lights no longer can be coordinated to minimize stops.