20% of people employed in NYC don’t live there. So that explains ~940,000 people who are probably driving.
13,000 vehicles in NYC are taxis. 77,000 active ride share drivers. These are used by the 176,000 daily tourists.
That brings the total number of cars in NYC largely serving people who don’t actually live there to 1.1m most days.
There are 2.1 million registered cars in NYC. That means 1:3 cars currently in the city represent people who don’t live there. That is roughly 1/3 of all cars in NYC. Likely closer to 50% or more of the actual traffic since the average NYC resident does not drive their car every day.