For over a decade, Ellen Fishman has been waiting for business to improve at Amorina Cucina Rustica, the restaurant she owns with her husband on Vanderbilt Avenue in Brooklyn.

Her pizzeria sits in the shadow of the $4.9 billion megadevelopment once known as Atlantic Yards, which has promised to deliver thousands of new residents and visitors to the area since it was proposed in 2003. But so far, the biggest change Ms. Fishman and other Vanderbilt Avenue merchants have seen is rising rent.

The project has been troubled by delays, financial setbacks, lawsuits and political wrangling. And the opening of the Barclays Center, the centerpiece of the development, in 2012, did not deliver substantial new business to Vanderbilt, despite expectations that it would.

All the while, Prospect Heights merchants on Vanderbilt, on the southeastern edge of the development, have been waiting for thousands of new residents to settle at the 22-acre development, now called Pacific Park Brooklyn, and stream into their shops.