It was supposed to improve “quality of life” in the bustling neighborhood of shops and boutiques that line Steinway Street near the foot of the Triborough Bridge in Queens.

But for the residents and merchants in Astoria who were supposed to benefit, the $15.3 million Steinway Bridge replacement project has done just the opposite.

Two months ago, a 3-ton, 60-foot slab of concrete tumbled off the 67-year-old pedestrian-and-vehicle overpass onto the Grand Central Parkway below, severely injuring a driver. The aftermath drew scores of city officials, journalists, and gawkers.

Within days, though, the throngs disappeared, leaving behind a pair of shiny chain-link fences, stacks of concrete slabs, and orange cones that have completely blocked off traffic on the two sides of the parkway.

Now, that part of Steinway Street has become a desolate backwater, where bored shopkeepers sit on their stoops, waiting to snare the few pedestrians who happen to pass by.

“Where did everybody go?” asked a lifelong resident of the neighborhood, Chris Poulos, who has been cut off from his friends and his favorite coffee shop directly across the way, and rarely braves the five-block detour and maze of one-way streets he now must take to get there. “Are the construction workers coming back? You gotta go all the way down to get around now – it’s ridiculous.”

The owner of My Favorite Butcher Shop, John Koukoularis, said he’s had to furlough 16 of his 21 employees. Before the bridge collapse, he sold $145,000 of meat a week, he said, and the number has plummeted to $25,000.

“No customers, nothing. They closed the whole area down. It’s dead,” Mr. Koukoularis said, motioning angrily at an orange cone at the end of the road.

Two weeks ago, the city Department of Transportation announced plans to construct a temporary two-lane bridge at Steinway across the Grand Central. Construction, officials said, would begin “shortly.” The new structure will probably be up in a couple of months, a DOT spokesman, Tom Cocola, said yesterday. The temporary solution will affect northbound traffic only. Southbound cars will continue to detour around the block.

“We are aware the business community is enduring an inconvenience because of the accident,” Mr. Cocola said. “Obviously we’re sorry about that, but we’re hoping this will alleviate some of the traffic problems.” Another city official said yesterday that state law grants government immunity from lawsuits claiming lost business as a result of a capital-improvement project.

When told of the plans for a temporary bridge, people expressed surprise and said they had not seen any construction workers in weeks.

“They should finish it fast,” one merchant, Hasham Ahmed, said this week. “See how quiet it is on a Monday? It was not like this before.” Mr. Ahmed is the owner of the El Sawy Market, on the opposite side of the parkway from Mr. Koukoularis’s butcher shop.

He also noted that since the accident, the city took away the two parking meters in front of his market and re placed them with No Standing signs. “I see plenty of policemen ticketing my customers,” Mr. Ahmed said. “I don’t see any workmen.”

The DOT has hired an independent engineering firm, Weidlinger Associates, to investigate the July 23 collapse. The injured motorist, Dimitrios Godosis, 46, is confined to a wheelchair and never leaves the house except to go to physical therapy, says his attorney, Charles Gucciarto.

The lawyer said Mr. Godosis plans to sue the city for $21 million and plans to sue Cal-Tran Associates, the New Jersey-based contractor originally hired to repair the bridge.

“The city was not keeping its eye on the ball,” Mr. Gucciarto said. “This is a simple case of negligence.”

This is not the first time a Cal-Tran construction project for the city has affected local businesses. In 1996, a deli owner in the Bensonhurst section of Brooklyn, Salvatore Vicenzino, complained to reporters that a city road repair project, led by Cal-Tran and nine months behind schedule, prevented his customers from parking, partly blocked access to the store and was driving him out of business. After the media attention, Mayor Giuliani demanded Cal-Tran finish the project within two months, then issued a press release touting his role in saving Mr. Vicenzino’s business.