WHITE PLAINS, N.Y. (AP) – Officials are expected to announce Friday that the aging, overcrowded Tappan Zee Bridge will be replaced rather than repaired.

The state Department of Transportation, which has led a nine-year, $54 million study of options for the suburban bridge, called a news conference in Tarrytown, near the span’s eastern end, for a “major announcement.”

DOT spokesman Charles Carrier would not confirm the choice Thursday, and details about construction and funding were not made public.

In the current rocky economic climate, public funds may be scarce.

But in recent years, officials have suggested that it would cost no more to replace the Hudson River bridge than to refurbish it and keep it safe for the 140,000 vehicles that cross it every day. The 53-year-old bridge is now under constant repair; in July, a crater 31/2 feet wide opened in the roadbed, providing a clear view of the Hudson below.

Besides choosing a new bridge, the DOT, the state Thruway Authority and the Metro-North Railroad are likely to announce what form of mass transit – enhanced bus service, light rail or railroad – a new Tappan Zee would accommodate. Planners have stressed mass transit as a key to the future of the bridge and Interstate 287, which it carries between Rockland and Westchester counties north of New York City.

The most expensive option that was under consideration included a long east-west commuter rail line from Suffern to Port Chester, linking existing Metro-North lines. That would involve tunneling at both ends of the bridge and beneath White Plains and cost up to $14.5 billion in 2004 dollars, planners said last year. Enhanced bus service, with dedicated lanes on the bridge and along the corridor, would be billions of dollars cheaper.

Project leader Michael Anderson said at the 2007 briefing that some private land, including some homes, may have to be taken for the project, although extensive efforts would be taken to minimize that.

Consultant Mark Roche said a new bridge would be built in two stages, one for eastbound and one for westbound traffic, each about as wide as the current bridge and possibly with two levels. When one section is completed, all the traffic from the current bridge would be routed onto that section temporarily while the old bridge is demolished and the second stage is built.

When the Tappan Zee opened on Dec. 15, 1955, it provided the missing link in the state Thruway and helped transform the northern suburbs, particularly those on the west side of the river in previously isolated Rockland County.