NEW YORK CITY — Commuters who use Metro-North’s Harlem line now have a new way to buy tickets. The Metropolitan Transportation Authority’s new ticketing app, MTA eTix, became available for commuters on Monday and allows people to purchase tickets using their smartphone.

The app is already in use for commuters who use the Hudson Line. It will be available for Metro-North’s New Haven Line during the week of Aug. 22.

“We are rolling out this customer convenience across both railroads in an expedited manner,” said MTA Chairman and CEO Thomas F. Prendergast. “This app will help save railroad customers time by making it easier to purchase a train ticket. Anyone who wants to see the future of train ticketing should download this app to experience how easy and convenient it makes the transactions.”

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The app, which is available for iOS and Android devices, allows people to buy a ticket by selecting their site of origin and final destination, and then selecting the type of ticket—one-way, 10-trip, weekly or monthly. The ticket is then saved in an electronic “ticket wallet” feature in the app.  Prior to boarding the train, commuters must then pull up the ticket from the ticket wallet and activate it by tapping on the “activate ticket” button. Then, when a conductor comes through the train asking for tickets, conductors will visually validate the ticket by looking at the screen. Officials say as the rollout proceeds, conductors will use a handheld device to scan the mobile tickets.

Metro-North’s Harlem Line customers are also able to check schedules and see train service status using the app.

The developer for the app is Masabi, Ltd., which has also created electronic mobile ticketing programs for the MBTA Commuter Rail in Boston, NICE bus on Long Island and Metrolink in Los Angeles.