The only thing I'd note is that whatever alt labels are done for I-290 should probably be done with MassDOT's proposal to merge it into I-395 should the dual mile markers cause confusion in mind.
I-290 will not have any AltLabels -- annoyingly, it will be broken for
literally everybody.
Every in-use waypoint label will have to move to a new mileage-based location, except for 7 & 8.
Exit 8 is only used in jweeks.list:
MA I-290 8 19. Rather than create bad stats & maps, removing the
8 AltLabel from the file will create
a lack of stats & maps -- and leave a note in jweeks.log that something needs attention.
Exit 7 is the same deal on a much larger scale: Everything it's paired with, in every .list line, is already broken. So I'll also remove the
7 AltLabel and nudge everybody to make the changes they'd need to make anyway.
Should the extension/redesignation happen, I-290 would become an
AltRouteName of I-395, the same way
NY I-895 in a list file redirects to
NY NY895, and I-290's data would get tacked onto the end of the I-395 file.
Old sequential numbers on I-290 that become new mileage-based numbers on I-395 are 7, 9, and 11.
9 & 11 are not in use on I-290, so they'll just be deleted; no AltLabels, no problem.
Any stray .list lines with
MA I-290 7 would end up pointing to the new Exit 7 on the extended I-395, though this is unavoidable with 7 needed at the new location.
EDIT: fittingly enough, the board is telling me this is post #290 for me!