With ridership creeping up to its highest levels since the pandemic began, the MBTA will boost frequency on its subway system and more than two dozen bus routes next month, officials announced on Monday.

A new summer schedule that takes effect on June 20 will run Red, Orange, and Blue Line trains at close to the same frequency they did in the winter before a package of unpopular service cuts hit, plus deploy more Green Line trolleys on the C, D, and E branches.

During peak travel time, riders should expect headways between trains of five minutes on the main center “trunk” of the Red Line, down from 5.5 minutes this spring; 10 minutes on the Red Line’s “branches” after it splits to toward either Ashmont or Quincy; seven minutes on the Orange Line, down from eight minutes; five minutes on the Blue Line, down from 5.5 minutes; and anywhere from 7.3 to 8.5 minutes on each of the four Green Line branches, according to an outline of the new schedule MBTA Deputy General Manager Jeff Gonneville presented Monday.

The T will also boost midday frequency on the Red and Orange Lines to a level even higher than before the cuts took effect, with headways of 6 minutes on the Red Line trunk and 7.5 minutes on the Orange Line. That change is driven by a Covid-era shift in which typical rush hours have been less crowded and other times of day have been busier.

Roughly 30 bus routes will also run with greater frequency starting June 20. As previously announced, that target date will also feature restoration of four other bus lines that had been eliminated in the spring service cuts: the Route 18 through Dorchester, the Route 52 from Dedham to Watertown, the Route 55 from the Fenway neighborhood to Copley Square, and the Route 68 from Harvard Square to Kendall Square.

The frequency changes are scheduled to arrive five days after Gov. Baker lifts the state of emergency on June 15.

MBTA officials in December narrowly approved a package of service cuts trimming frequency 20 percent on the Red, Orange, and Green Lines and non-essential bus routes and 5 percent on the Blue Line and essential bus routes, responding to a pandemic-fueled sharp decline in travel and fare revenue.

After facing significant criticism and receiving nearly $2 billion in federal emergency aid, T higher-ups pledged in March to reverse the cuts and restore pre-Covid levels across the system “as soon as possible.”

The increased bus frequency coming to about 30 routes means that the T will not have as much flexibility in its scheduling, Gonneville said. The agency, which has been scrambling to hire enough workers to run pre-pandemic levels of service, will need to reallocate drivers who in recent months have been available to supplement more crowded routes as needed.

Under the summer schedule, a separate set of nearly 30 bus routes that saw their service increase during the pandemic will still run at elevated frequencies. Gonneville cautioned that MBTA officials face potentially tricky decisions in the fall on whether to keep those at their current levels or boost service on other routes.

Ridership remains well below past norms, but it continues to trend upward.

MBTA General Manager Steve Poftak said on Monday that the T carried more riders during the week of May 10, the most recent span with data available, than it has in any week since Covid-19 hit.

Subways reached about 30 percent of pre-pandemic crowds, Poftak said, while buses hit roughly 50 percent of that baseline. The commuter rail system – now operating on a new schedule with trains at regular intervals rather than bunched around morning and evening peaks – was close to 20 percent.

“We have every reason to believe that trend continued last week and will continue this week,” Poftak said.

The forthcoming end to Covid restrictions in Massachusetts could accelerate the “rising action” Poftak described.

Poftak also announced on Monday that on May 29 the T will switch back to its pre-Covid comfort and crowding standards, turning away from a lower threshold for crowding designed to ensure social distancing.

That will bring an end to the public-facing live crowding information that riders can now access. MBTA staff will continue to track passenger volumes and use that information to plan service levels, Poftak said.