The source I found agree with 1-4% for bus routes within Manhattan, but it also said:
> Commutes on Hudson River and East River crossings for several express bus routes linking the boroughs with Manhattan have, on some lines, shaved more than 15 minutes off commuting times.
> Commutes on Hudson River and East River crossings for several express bus routes linking the boroughs with Manhattan have, on some lines, shaved more than 15 minutes off commuting times.
That’s a rather dramatic improvement.