They've been bustituting on the weekends north of Harvard to replace the concrete under the rails. Wonder if today is related to that.
https://www.mbta.com/projects/red-line-floating-slab-maintenance
Probably something to do with that. This is the actual message (still in effect, apparently):
"Due to a track condition discovered during an inspection and out of an abundance of caution, trains are operating at reduced speeds southbound between Harvard and Central. There are delays up to 15 minutes in both directions due to the restriction."
I'm guessing this will be an all day nuisance. Maybe even into tomorrow.