Commuter rail customers on all North Station lines will be able to purchase and display tickets on their smartphones starting Monday, with South Station lines and ferries expected to follow after Thanksgiving.

The launch follows a successful test among some South Shore customers and comes half a year after the T signed an agreement with a British mobile-ticketing developer to make it the first major US commuter rail to offer passengers an alternative to paper.

Widespread use would save the Massachusetts Bay Transportation Authority from handling much of the $20 million in cash now changing hands in annual on-board transactions, which slow conductors trying to reach everyone on crowded trains. It would also cut down on the punch-ticket debris littering cars at the end of each day.

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But the state’s top transportation official said the biggest benefit will be for the three-quarters of customers who carry smartphones, and who no longer need to wait in lines at ticket windows or vending machines, or scrounge for cash on board. “The goal was to give people as much time back as possible,” said Richard A. Davey, state transportation secretary. “Here, literally, the ticket machine is in your pocket.”

Such applications are widespread in Europe, and Masabi, the company that developed the MBTA’s mobile ticket, has already created apps for half of Britain’s rail lines.

The T is ahead of New York’s Metro-North Railroad, which announced a pilot with Masabi in July. Dallas’s DART and TriMet in Portland, Ore., followed suit, signing recent agreements with developers to create mobile ticketing for their commuter rail as well as light rail and bus.

Starting Monday, customers who download the MBTA mTicket app from the Apple and Android stores — a BlackBerry version is coming — can purchase one-way, round-trip, or 10-ride tickets using credit or debit cards. Monthly passes will likely be added this winter.

Selecting actual station names for origin and destination means customers avoid the travel-zone jargon required with the T’s less-than-intuitive automated vending machines.

Those who store credit card and travel information for reuse can purchase tickets in five seconds, said Joshua K. Robin, the T’s director of innovation.

The mTicket is similar to Starbucks or LevelUp apps many customers already use to buy coffee or pay at small businesses, down to the unique scannable codes generated. But conductors will not carry expensive scanners or read those codes. Instead, they will verify passes by glancing at digital watermarks and animated colors that change daily.

Those are displayed on one-time-use images customers generate by hitting an “activate” button when the conductor approaches.

Cara Willis, one of about 100 riders who helped the T test the app on the Old Colony and Greenbush lines this fall, said heads turned every time she flashed her iPhone for a conductor.

“People around me would notice and ask about it, and they would all get excited,” said Willis, a 27-year-old who commutes a few days a week between East Weymouth and a nonprofit near South Station and previously used 10-ride punch tickets.

“It’s been so nice and relaxing to just always have my phone to buy my passes and not need to worry about whether I have the paper pass or worry about buying it at South Station before I get on the commuter rail to go home,” Willis said. “I’m notorious for being one of those folks running through South Station to make it to my train on time.”

Only one in five commuter rail stations offers a vending machine or a ticket-selling retailer, such as a coffee shop.

Until now, customers needed to buy tickets in advance at select stations or pay cash on board, with a $3 surcharge imposed for buying on the train when boarding at a station with a ticket seller.

In an increasingly cashless society, new customers are often surprised they cannot pay with cards, but they all have phones, and even those with tickets sometime misplace them, conductor Cory Moniz said.

“A lot of times you go up to people and they go through their purse and they’re looking for this and that, but they know where their phone is,” said Moniz, who at 28 is approaching his fifth anniversary as a conductor.

Researchers affiliated with Harvard and MIT found recently that 76 percent of Newburyport and Worcester line riders carry smartphones — 10 percentage points higher than in a survey a year earlier — and half of all riders had used their phones to make purchases.

Moniz said a question from one customer about the coming app last week was enough to set the car abuzz as he worked a train on the South Acton line crowded with Brandeis University students.

And conductors are as enthusiastic as passengers, because it will allow them to spend more time opening and closing doors, making announcements, and answering questions.

The MBTA spent years and invested more than $150 million to create and deploy the CharlieCard payment system for subway, trolley, and bus. Though officials promised to extend it to commuter rail, they abandoned it over the estimated $70 million cost of outfitting all stations with vending machines and giving conductors hand-held readers.

This app cost the T nothing up front — save for an in-house marketing campaign and staff time — while Masabi will retain 2.8 percent of sales, the same percentage that brick-and-mortar partners receive for selling tickets and passes, Robin said.

As with the introduction of next-train countdown signs at subway stations and the release of data for software developers to create real-time apps for customers, the T is rolling out mobile ticketing in phases, to manage expectations and quality control, Robin said.

For Willis, the South Station commuter who participated in the two-month pilot, the only downside was that it ended. “I’m going to miss it until it starts up again,” she said.