First they're going to tear down the dilapidated Hudson River piers and the even more dilapidated West Side Highway, all the way from the Battery at the tip of Manhattan Island north to the Lincoln Tunnel at 42nd Street.

Then they're to fill in the river, cut a six-lane roadbed through the fill, cover the cut and put up some buildings on the 150 acres of land they've created. (Ninety-five acres of parkland have also been included.)

That, in brief, is Westway, the most complicated (and arguably most expensive) highway project ever contemplated. The total length is only 4.2 miles; depending on whose estimates you use the cost will run between $1.4 billion and $2.3 billion.

Ninety percent of the cost will come from the federal highway trust fund and Westway, Interstate 478, is by no means the only costly urban freeway on the list of uncompleted interstates (see chart).

Westway has been the focus of a long battle between the Transportation Department's Federal Highway Administration, which wants to build it, and the Environmental Protection Agency, which has worried aloud about Westway's potential for making New York City's bad air even worse.

New York's contractors and unions love it because it means jobs, and they extracted a campaign promise from Ronald Reagan that he would build it. Developers love it because it will provide more real estate in lower Manhattan.

The unhappiness comes from New York subway riders and environmentalists. The dollars for Westway could legally be transferred to the New York subway system, which desperately needs money for renovation. Despite its dreadful condition, New York subways carry almost one-third of the nation's public transit riders.