Red Line made it a week before a slow zone popped up again

A new slow zone emerged on the Red Line this weekend, just one week after MBTA officials had declared the line free of speed restrictions for the first time in two decades.

For safety reasons, train drivers are required to go no faster than 10 m.p.h. in a one-tenth mile stretch of the inbound Ashmont branch just north of Savin Hill, according to the T's speed restrictions page - which does not specify the cause of the new restriction.

In announcing the seeming end of Red Line speed restrictions last week, T officials had expressed hope they could clear what at the time seemed like the last of the entire system's slow zones, two of them on the Green Line downtown, in work scheduled for this month.

Percentage of track per line with slow zones over the past month:

Via Boston Area Public Transit Photos & Discussion.