The $2 SL bus from Logan Airport to South Station Red Line subway and Amtrak train terminal is the absolute fastest route to escape Boston Logan International Airport Island on the cheap.
A dedicated no traffic tunnel for the SL was made so it can speed thru the thing with stops at tourist attractions, federal courts and business centers.
Center city travelers have the $5 airport to Back Bay bus for their use. It’s trip begins at the back of the expensive Prudential Center taxi line and ends at Logan and visa versa. This route is also good for people heading anywhere along Massachusetts Avenue because the corridor and bridge to Cambridge is less than five minutes walking distance from the Back Bay stop.
Buses won’t be used by everyone because most people prefer cars, but that’s changing.