A reduced T schedule takes effect today. Here’s what that means.

A commuter took the Orange line, Monday, at the State Street stop as the T adopted its Saturday schedule on the Blue, Orange, and Red lines on weekdays.David L. Ryan/Globe Staff

Starting Monday, the MBTA is running fewer trains on the Blue, Orange, and Red lines on weekdays because it doesn’t have enough dispatchers to safely staff subway operations. The move comes in response to orders from federal authorities investigating T operations in the wake of a series of recent accidents, including the death of one rider.

The service changes essentially mean the T is adopting its Saturday schedule, and its longer wait times between arriving trains, for the entire work week. There will be no changes to Green Line service, the MBTA said, and weekend service on the Blue, Orange, and Red lines will remain the same. The Commuter Rail is not affected by the changes.

“With a limited number of dispatchers, these new timetables allow the MBTA to schedule dispatchers in compliance with Federal Transit Administration directives, and continue delivering service in a safe and reliable manner,” the T said in a recent statement.

Last week, the FTA issued a grim assessment of safety at the T, citing staffing shortages and describing subway dispatchers working 20-hour shifts in the operations control center. As of April 29, four of 18 heavy rail dispatcher positions and two of 11 supervisor jobs were vacant, the FTA found.

On Friday, transit advocates and business leaders said they’ve warned the MBTA for years it had to do a better job prioritizing safety and investing in its workforce, or face service reductions that will disproportionately hit low-income residents.

Longer wait times between trains, they said, will be felt most deeply among T riders who can’t work from home and lack other transportation options. Fewer trains, they said, will also delay the MBTA’s efforts to restore ridership to pre-pandemic levels.

The FTA ordered the MBTA to submit a detailed staffing plan for subway dispatchers that ensures the workers get enough rest between shifts. The plan must be in effect for at least six weeks and the MBTA has to prove it is giving subway dispatchers appropriate time for rest, according to the directive.

The MBTA said the new weekday schedules on the three lines will remain in effect for the rest of the summer. The agency said it is exploring options for adding more staff to the operations control center, including a recruitment campaign, $10,000 hiring bonuses for heavy rail dispatchers, and the possibility of returning former dispatchers to work.

Under the new schedule, the longest waits will be on the southern end of the Red Line along the Ashmont and Braintree branches, when weekday trains will operate every 14 to 15 minutes, the T said. Red Line trains running between Alewife and JFK/UMass stations will run every seven to eight minutes.

The normal summer schedule for the Red Line is typically nine to 10 minutes between trains during rush-hour periods, 10 to 12 minutes during off-peak hours, and every five to six minutes on the section between Alewife and JFK/UMass stations, the T said.

On the Orange Line, weekday trains will operate every 10 minutes in the mornings, with 11 minutes between trains during the evening, and eight to nine minutes during mid-day periods. Those are as much as four minutes slower than normal scheduling, depending on the time of day.

On the Blue Line, weekday trains will operate every seven minutes until 9 a.m., and every eight to nine minutes for the rest of the day, about one to two minutes slower for most of the day.

Material from prior Globe stories was used in this report. This story will be updated as more information becomes available.