Which of public transit or driving is faster depends on the city, i.e. it depends on how congested the streets available for private cars are, in comparison with what is available for public transit.

I live in a city with subway and going by subway to any place that is not too close (so that the time to walk to a subway station is not a too large fraction of the total time) is much faster than driving a car, with the possible exception of late in the night, when the streets might be empty. In most cities with subways where I have been, this was also true, because they also had congested street traffic.

I have also been in several cities where the buses had their own street lanes, which were forbidden for private cars. In such cities, I have also seen frequently cases when going by bus was faster than driving.