From just west of Yawkey station all the way to Worcester, track #1 is on the north side of the line. In other words, looking or traveling from Boston out to Worcester, track #1 is on the right. Therefore, track #2 is the track closest to the parking lots in Wellesley Hills and West Natick. Through the stations in Newton, the platforms are only on the track #2 side. At Worcester station, the platform is on track #1 only.
In Back Bay station, tracks #1, #2, and #3 are on the Providence / Northeast Corridor line (sometimes just called the "corridor"). So that forces us to have different track names, otherwise we would all get on trains to Providence! From just outside South Station to just past Yawkey (including in Back Bay station), track #7 is closest to the Mass Pike, is the northernmost track, and is almost exclusively outbound. From just outside South Station to just past Yawkey (including in Back Bay station), track #5 is closest to the Orange Line, is the southernmost track, and is almost exclusively inbound.
In Allston, where there is only one track, it is just called the "main" or the "single track." This is the section of track that runs alongside the former Beacon Park freight yard between Exit 17 on the Mass Pike and Boston University. Although there are multiple parallel tracks, only the track closest to BU (the "single track") can be used for through train traffic. All of the other tracks are not signaled or controlled for traffic - they can only be used as part of the freight yard. So this "single track" doesn't have a track number, even though it could logically be considered track #2, since traveling straight from the single track in either direction puts you back on track #2 where the track becomes two parallel tracks.
But the Back Bay naming oddities and the Allston single track situation are not that important - the important thing to remember is that track #1 is on the north side of the line and track #2 is on the south side for the main part of the line west of Allston.
I wanted to post this info here since it will be important for a couple of future blog post topics:
1) The current construction won't solve all of our heat restriction problems; and
2) Why do inbound and outbound rush hour trains use the same track from Framingham to Boston? [This topic is why I never refer to any track as "inbound" or "outbound" - the MBTA uses those names, but that really bugs me, since the trains travel in both directions on either track depending on the time of the day. Oh well.]