Reverting deletions

I’ve only recently become somewhat active, so I don’t know what the efficient way to deal with this is, and the wiki and forums seem a bit vague.

Someone deleted a few blocks of roads north of Harvard Square in Cambridge, MA, including a chunk of the metro system. How do I roll back the changes for a given area?

JOSM has a ‘reverter plugin’ that is an advanced use; especially if any edits have happened in the area, or if the entire changeset will not be reverted. Please provide a link to one of the deleted areas so that the change can be located.

The streets grid was restored by somebody about a day ago, so those are back. However, the subway line is still missing through 4 stations, as can be seen at http://www.openstreetmap.org/#map=17/42.36246/-71.09017&layers=T, where the line ends halfway up Main St.

Since part of the changes have been restored, the easiest way may be to manually recreate the remaining portions. Hopefully, the person who originally deleted it all has been contacted so that they realize they were editing a live database and they won’t do this again.