It's December and your Beijingologist's back in Subway Mode. Line 4 has been bringing the masses from the northwest to the South Railway Station for a fair bit now. At present, it's a boring line, interchange-wise: there are only four such interchanges.

By 2015, we're looking a few more: National Library (Line 9), Ping'anli (Line 6), Caishikou (Line 7), Beijing South Railway Station (Line 14) and Jiaomen West (Line 10). We did mention Xiyuan and Yuanmingyuan Park as potential candidates for Line 15, but Tsinghua University doesn't like the idea of frequent subterranean earthquakes... and some are saying that if Line 15 (which goes from Shunyi via the Olympic Green) does continue further west, that we might end it at the East Gate of Peking University.

But here's the scary bit: that's not all. Yep, from unreleased and still shakey-ish info, here's what we foresee (with, of course, a WARNING that ALL THIS DATA BELOW IS NEITHER OFFICIAL NOR FINAL):

• National Library and Beijing Zoo interchange with the planned Line 12: Nobody's heard of Line 12 yet, and for a good reason: it's not in the 2015 plans. (It has not been made public, either... all of this is subject to change with the least bit of notice!) We don't know what'll happen to the brilliant wall art at these two stations; we especially don't like the idea that the Beijing Zoo station's animal wall art will see two holes...

• Xinjiekou interchange with the planned Line 16: This is a good likelihood. Line 16 will head up to near this great big suburban community known as Huilongguan, and will become another north-south line in the Jing.

• Ping'anli interchange with Line 6 and the planned Line 16: This is pretty much "for real". From plans your Beijingologist has been able to snatch from "relevant sources", a three-line interchange is surely in the works for Ping'anli. The Line 16 bit will be right by Zhaodengyu Road (a crossing further west from the present-day Ping'anli station).

• Xisi interchange with the planned Line 3: Ever been to Dongsi Shitiao and noticed this staircase that leads to a floor beneath? That's Line 3 for ya... it'll be a crosstown line, going west-to-east. Line 3 is now more and more likely and can soon be pretty much considered to be part of life.

• Lingjing Hutong interchange with the planned Line 12 (again): That Lingjing Hutong interchange is a funny one, as the station did not really appear to be an interchange at first sight... but have you ever noticed how north of the crossing the thing was built? That bit to the south might very well be a Line 12 station...

• Xidan interchange with the planned Line 12 (again): Line 4 and Line 12, two folks in love it must seem... We're not sure if Xidan can handle a three-line interchange (thus finally creating Beijing's People's Square), but oh well: the plans have it that it'll do a three-liner at Xidan.

• Taoranting interchange with the planned Line 11: Please get ready for your arrival for what must be about the 14th stop in a string of 15 Line 4 interchanges. Yep, Taoranting might quite likely be a host of Beijing's "U"-shaped Subway Line, the planned Line 11.

• Xingong interchange with the planned Line 8: This is pretty much official "as the press had told you this", but this will involve a huge curve out west from Line 8, which in Phase III will head straight via the north-south axis to the soon-to-be-retired Nanyuan Airport.

The guys at the MTR, obviously, are smart people, investing in such an interchange-heavy line...