The Port Authority board made a difficult, and correct, decision Thursday to move ahead with the North Shore Connector that will extend Allegheny County's light-rail system to the North Side.

The $435 million project, which will build twin tunnels under the Allegheny River, has become controversial because of rising construction bids and the transit system's dicey operating budget.

Skeptics should keep two things in mind. The federal government is still committed to pay for 80 percent of the project, a generous level of subsidy that Washington has discontinued for future projects. And light rail accounts for only 16 percent of the Port Authority's operating budget, a funding area that the governor and Legislature nonetheless have pledged to stabilize, if not enhance.

The benefits of the decade-old project remain. By extending light rail beyond the river, mass transit can spur the business development getting under way between the stadiums; reduce workday traffic Downtown by carrying commuters who will park on the North Side; serve travelers bound for neighborhood attractions like the community college, the Carnegie Science Center and the Andy Warhol Museum, not to mention the Pirates and Steelers; and also put the light-rail system in position to serve points north or west in the future.

It was unfortunate last fall that the Port Authority had to cancel the part of the project that would have extended light rail to the convention center. But the authority was concerned about rising costs and maintaining federal support -- both legitimate concerns.

We can only hope that the convention connector will return someday to the drawing board. Till then, however, we're glad Pittsburgh and the Port Authority will have their hands full with the dig under the Allegheny.