Ridership declines spurred the MBTA on Monday to scale back service.

A T blog post Monday night proved put some numbers behind the trend: daily trips steadily declined every day last week as COVID-19 cases increased and as Massachusetts progressed into a state of emergency and more widespread business closures.

On Tuesday, March 10, total daily ridership on the subway and Silver Line was 12 percent lower than the weekly average during the week of Feb. 24. By Wednesday, that dropped to 20 percent lower; by Thursday, 32 percent lower; and by Friday, the MBTA's rapid transit ridership was 48 percent below the average the last week of February.

"Usually Fridays are of course lighter ridership, but not nearly this much," the T wrote, noting trends differed by line.

Bus ridership saw more variation by day, but was still about 32 percent lower on Friday than it was the comparison week.

MBTA officials did not have detailed ridership data for the commuter rail to offer, but parking at stations — sometimes used as a proxy — had dropped 69 percent by Friday.

Starting Tuesday, the T will run Saturday schedules on rapid transit and most bus routes, less commuter rail service than standard weekdays, and no ferries.