When I took the subway from Boston, there were two advantages.
The first is that you can pay by credit card.
In the United States, it is easy to use a credit card rather than cash.
When you use cash, many coins appear unexpectedly, and coins sometimes become an illness complex.
It is often convenient to settle the card.
The second is that you can use the One Day Pass.
There are places with and without One Day Pass when you visit major cities around the world.
Sometimes there are places that sell only one day passes to travelers.
But you can easily buy One Day passes in Boston.
If you travel to major areas of Boston, one day is enough.