My record is 8 taxis.
Awesome creative concept! Fairly certain there isn't another one in the 7k submissions. Great progression curve with more traffic as the game goes on. The was one small bug or feature I don't understand but sometimes taxis would disappear, unsure if that was because there is a time limit or if the drop-off location spawned on the same location as the taxis were.
Very cool game idea through, I could see this as a simple indie game if you plan to expand this past the game jam. The only change I would do is to make it where the drop and pick up buttons are the same.