The southbound Barham Boulevard exit ramp is set to permanently close, probably in the coming year, as part of NBCUniversal’s $1.6-billion Evolution plan to expand its Universal Studios theme park.

The planned offramp closure has infuriated neighbors who say the area is already gridlocked and that closing the busy exit will only make it worse. A group of residents calling itself Keep the Barham Ramp Assn. filed suit in Los Angeles County Superior Court on New Year’s Eve.

The lawsuit, which seeks to halt the Barham closure until further study is done, names Universal City Studios and the California Department of Transportation, as well as the city and county of Los Angeles — both of which approved the plan.

As part of NBCUniversal’s expansion plan, a new southbound 101 Freeway onramp is to be built on Universal Studios Boulevard, allowing departing park guests to get directly onto the freeway, bypassing the neighborhood.

In an emailed statement, NBCUniversal said: “The new southbound 101 onramp was fully vetted in the public through a seven-year environmental review process. We are confident that the courts will stand by the city, county and Caltrans approvals.”

Caltrans determined last year that the…