New York’s congestion pricing plan raised $48.6 million in tolls during its first month, a strong start for the program that exceeded expectations and kept it on track to raise billions of dollars for the region’s decaying mass transit system.

The revenue figures, expected to be released publicly on Monday by the Metropolitan Transportation Authority, are the latest sign that the tolling plan is working, even as President Trump has moved to kill the program.

The M.T.A., which oversees the plan, expected to collect an average of $40 million a month in the program’s first phase.

The first month’s revenue will pay for $11 million of expenses related to setting up tolling cameras and other parts of the system, and environmental projects to address concerns about urban pollution that might arise because of changing traffic patterns. The remaining $37.5 million can be applied toward financing a slew of major transit repair projects, said Jai Patel, the M.T.A.’s co-chief financial officer.

“We feel really good about that,” Ms. Patel said, adding that revenue from the toll, which started on Jan. 5, was achieved in less than a full month.

Yet, the program faces an uncertain future. President Trump, who has argued that the toll plan would hurt local business, ordered the Department of Transportation last week to revoke its federal authorization. The M.T.A. immediately filed a lawsuit to stop the interference, and vowed to keep collecting tolls.