Having pulled the emergency brake just in time, Sound Transit now faces a more challenging task. The regional transit agency must readjust its plans rapidly while remaining focused on the goal.

The mandate from the public is to create a regional light rail system which includes a serious start toward the north end. The Sound Transit governing board must make fulfilling the voters’ rail expectations the primary objective.

To be a real part of solving the region’s traffic problems, any light rail system must extend to the Northgate area of Seattle. Stopping at the University District, as has often been discussed, would do little more than create a super-expensive shuttle service between downtown Seattle and the university.

As the board recognized last week, the costs for the agency’s planned route between downtown and the university had grown way over budget. Continuing with the current plan would have broken trust with the public’s expectation of a plan that adheres at least reasonably well to promised costs. The added expenses would also have seriously jeopardized Sound Transit’s possibilities of finding the money to extend the line northward from the university.

The board brought the plan to a halt after hearing the latest price estimates from a contractor. The costs for designing and building a 4.5 mile tunnel under Capitol Hill and Portage Bay to the University of Washington were placed at $728 million. That’s a whopping 45 percent higher than the $500 million Sound Transit had budgeted for the project.

The board is right to stop and reassess its options as quickly as possible. The members have asked for staff reports next month on how the costs have grown and alternatives to the tunnel plan.

The largest complicating factor for the board is a pending federal grant of $500 million. Depending on how many changes are made to the light rail plan, Sound Transit risks losing the federal money either entirely or for several years. The board, though, is working with the congressional delegation and federal transportation officials to see how much leeway may be available. Federal officials ought to be willing to do whatever is possible to avoid punishing the region for trying to stick to a budget.

As Sound Transit looks ahead, it must focus on delivering the promise of light rail. The board’s review offers hope that more cost-effective options can be found for the route to the university. It’s clear that Seattle city representatives on the board may continue to argue for expensive measures to keep neighborhoods along the light-rail route happy. The entire board must keep in mind that the rail system is intended to be a regional service, not a pricey neighborhood amenity.

While watching costs, board members must also keep an eye on the clock — and the future. It’s OK for them to pause briefly to adjust their rail plans. But they cannot allow a review to turn into endless delay. The region needs a modern rail system as part of its solution to the growing transportation difficulties facing the entire metropolitan area. When Sound Transit finishes regrouping, it must be ready to make a real step northward.