New designs for MBTA stations on the Mattapan trolley line are expected in the first half of next year, officials from the public transit agency said at a virtual public meeting on Tuesday.

The design process is underway for the stations along the high-speed trolley line that runs through Dorchester, Milton and Mattapan, with detailed concepts expected at the next public meeting planned in April 2023. There will be multiple options focused on what the stations will look like.

Since the last meeting earlier this year, the MBTA’s project team working on the modernization of the trolley line have reviewed existing conditions of the corridor, surveyed local wetlands and deployed ground-penetrating radar to see what’s under the tracks, as well as an assessment of the bridges and the line’s resiliency to flooding. All those will help with station concepts, MBTA officials said.

The MBTA still hasn’t yet determined what will happen to the current trolley cars when they’re retired. The modernization of the Mattapan line has been running on two tracks: The refurbishment of the current trolley cars, which have been in service for decades, and the overhaul of the stations as the MBTA will transition to using older Green Line trolleys on the line.

Phil Santos, who works for HNTB, the designated contractor on the modernization project, told attendees of Tuesday’s public meeting that while the design process is in the “early phase,” riders will see improved lighting, security cameras, wind screens and an emergency call box.

He raised the prospect of having a center island at the Milton stop, which straddles Dorchester’s Lower Mills neighborhood and the town of Milton. The stop currently has separate inbound and outbound station platforms.

If the T goes the center-island route, the existing platforms would need to be demolished and the tracks would need to be shifted, creating service disruptions.

Several of the meeting’s attendees focused on a pressing matter: The decrepit state of the Milton station’s stairs. The Adams Street stairs have been closed for years, prompting frustrated Milton town officials to recently sue the MBTA.

AJ Tanner, the MBTA’s project manager, said the agency is unable to repair the stairs. If they were to undertake repairs, they would need to install an elevator to comply with federal regulations, leading them to hold off until the modernization effort reaches Milton Station. They are, however, seeking a demolition contractor for the stairs this coming winter, Tanner said.

Sen. Walter Timilty of Milton called that “unacceptable” and noted that the overall modernization program is already behind schedule. The stairs are a “blight,” he added.

“This project needs to get moving and these stations need to be restored and repaired,” he said during the public meeting.

“I know it was delayed but we are moving it forward as quickly as we can,” Tanner said in response.

The MBTA is refurbishing the current trolleys, which are more than 75 years old, in order to get at least another decade of service out of them, before the transition to the Green Line trolleys.

The next refurbished trolley is expected to hit the tracks again in the next 30 days, and another one should be back by summer 2023, according to T officials.