On some buses, the first signs of a new MBTA fare system

The MBTA has begun testing new fare equipment on a small number of buses, as it prepares to roll out the technology across the entire system in the coming years.Lane Turner/Globe Staff

A handful of buses in Boston’s southern neighborhoods are carrying the most visible signs yet of the sea change coming to the MBTA’s fare system in the next few years.

These are small fare readers installed on some buses for routes 28 and 39 that eventually will be able to scan not just CharlieCards, but credit cards or smartphone apps to accept payment for T rides. And the technology is coming to the entire transit system someday.

But not yet. For now, the readers on these buses are just for testing by MBTA employees to confirm they are properly installed and the technology is working. While the T will install the readers on more than 40 of its 60-foot buses in the coming weeks, according to spokesman Joe Pesaturo, it will still be a few years before all riders are actually using them to pay for their trips.

For passengers, however, the test readers are a visible harbinger of the change to come — especially because of where they are located. The readers aren’t placed just at the front of the buses, but also near the back doors, attached to poles as riders enter the vehicles.

This is in keeping with one of the major promises of the fare system replacement: after putting the small readers near the back of buses and trolleys, the T is planning to let riders enter through front and back doors, hopefully speeding up the boarding process.

That’s also the reason Governor Charlie Baker and the state Legislature recently moved to ban arrests for fare evasion, and authorized lowering the financial penalties for those caught skipping payments. Since riders won’t be paying right in front of drivers, the MBTA will in the future deploy fare inspectors to scan riders’ fare cards for proof that they paid, and issue fines if they didn’t.

The nearly $1 billion electronic fare project, led by California-based Cubic Corp., was originally proposed in 2016. It has already taken longer than expected: the MBTA doesn’t expect to allow all-door boarding until 2023, and the technology won’t be installed on the commuter rail until 2024.

In the meantime, the agency has promised to improve some existing fare equipment. Last year, the T added new fare readers on some subway gates, and installed technology along the Fairmount commuter rail line that allows those riders to pay for their trips with a CharlieCard and transfer to the bus and subway. That functionality will eventually come to the rest of the commuter rail, but not until the fare system has turned over.

The project’s long schedule and hefty price tag, as well as the plan to end cash payments onboard, has sparked concerns from some transit and social justice advocates, who have asked whether it is the most pressing upgrade facing a system with many needs.

It also comes as several elected officials and transit groups have increasingly advocated for free fares as a better approach to fare collection in the future, though there is little sign that the MBTA has any interest in that idea.