The MBTA’s plan to institute cashless fare payments is good news for the harried commuter tired of waiting for the person in front to search for change to get on board.

But what about riders — mainly low-income and the elderly — who don’t have credit cards or aren’t comfortable with smartphones? There is growing concern that the new system could be inaccessible for them.

The changes are part of a newly adopted $723 million contract to implement a fare- collection system that transit officials laud as a critical move to modernize the Massachusetts Bay Transportation Authority.