The first data for New York City’s new congestion pricing program shows that gridlock lessened in its initial week as fewer drivers traveled into the core of Manhattan, though traffic continued to be heavy in parts of the tolling zone.

In the first six days of the program, officials estimated, there were tens of thousands fewer vehicles entering the busiest parts of Manhattan below 60th Street, which includes some of the city’s most famous destinations like Times Square, the Empire State Building and the High Line.

Congestion pricing aims to lure people out of their cars and onto mass transit. Most passenger cars are now charged $9 a day to enter the tolling zone at peak hours, with additional fees for trucks and other vehicles as well as overnight discounts.

The program started on a Sunday, which typically has light traffic, but the real test came the next day as many workers returned after the holidays. The average weekday entries into the zone and the highways that surround it fell by 7.5 percent compared with an estimate of an average workday in January before the program, according to the Metropolitan Transportation Authority. On Sunday, entries fell by about 18.5 percent, when compared with the same base line.

“There’s so much evidence that people are experiencing a much less traffic-congested environment,” said Janno Lieber, the chairman and chief executive of the M.T.A., which is overseeing the program. “They’re seeing streets that are moving more efficiently, and they’re hearing less noise, and they’re feeling a less tense environment around tunnels and bridges.”