Chūō-Sōbu Line local service, Mitaka to Chiba

[Sacto1985]

YouTube user Super Masaki posted this zenmen tenbou video of the Chūō-Sōbu Line local service from Mitaka Station (the east end of Chūō-Sōbu Line service) to Chiba Station:

 

 

I believe this is taken from a 209 or E231 Series EMU. It will be interesting to see if JR East will replace these EMU's with the new E235 Series EMU on this line before 2020.

[kvp]

This line is one of the most interesting JR lines around Tokyo with great scenery.

[Guest keio6000]

I can't figure out who exactly (other than the elderly who want to sit) takes this line from mitaka to shinjuku (other than those alighting at higashi nakao and okubo).  the chuo line rapid service (orange) trains are almost always faster and/or more frequent and you can always switch back to the sobu line if there's somewehre in particular you want to go.   think of the interaction of the chuo and sobu lines at ochanomizu and you get my drift.

 

maybe i just havent thought it through, but i used to take the parallel chuo line often and it occurred to me that it would make somewhat more sense to run the up chuo and sobu lines on the same platform with one effectively acting as the local service of the other - kind of how the keihin tokoku and yamanote interact north of shinagawa.  as far as i can tell, my plan would require some moderate rework of the tracks around nakano (a single "up and over" to switch two tracks, i think) but the customer benefits would be enormous.  there would be no effect to chuo line express services nor, i think, to mita line stuff.  what's more, the necessary work would all be in the vicinity of the yard at nakano, so alternate/temporary tracks might not be a problem spacewise.

[railsquid]

I can't figure out who exactly (other than the elderly who want to sit) takes this line from mitaka to shinjuku (other than those alighting at higashi nakao and okubo).  the chuo line rapid service (orange) trains are almost always faster and/or more frequent and you can always switch back to the sobu line if there's somewehre in particular you want to go.   think of the interaction of the chuo and sobu lines at ochanomizu and you get my drift.

 

Easier interchange with the Tozai line (through-running) and with the Yamanote Line at Shinjuku/Yoyogi are a couple of good reasons.

 

maybe i just havent thought it through, but i used to take the parallel chuo line often and it occurred to me that it would make somewhat more sense to run the up chuo and sobu lines on the same platform with one effectively acting as the local service of the other - kind of how the keihin tokoku and yamanote interact north of shinagawa.  as far as i can tell, my plan would require some moderate rework of the tracks around nakano (a single "up and over" to switch two tracks, i think) but the customer benefits would be enormous.  there would be no effect to chuo line express services nor, i think, to mita line stuff.  what's more, the necessary work would all be in the vicinity of the yard at nakano, so alternate/temporary tracks might not be a problem spacewise.

 

 

Don't forget you'd need to work in the Tozai line there too... which is what I find annoying at Nakano - the Sobu/Tozai platforms are all over the place.

 

And bear in mind Mitaka is the terminus for the Sobu line, with a yard immediately behind it which probably doesn't have much wiggle room if the trains have to cross a Chuo line track. I suppose you could do the swapover before Mitaka, but good luck finding the space.

[Guest keio6000]

Easier interchange with the Tozai line (through-running) and with the Yamanote Line at Shinjuku/Yoyogi are a couple of good reasons.

 

 

Don't forget you'd need to work in the Tozai line there too... which is what I find annoying at Nakano - the Sobu/Tozai platforms are all over the place.

 

And bear in mind Mitaka is the terminus for the Sobu line, with a yard immediately behind it which probably doesn't have much wiggle room if the trains have to cross a Chuo line track. I suppose you could do the swapover before Mitaka, but good luck finding the space.

 

Ok, I've spent well too much time today thinking about this.  These are my conclusions.

 

1.  the benefits of a realignment are huge.  right now, you have the sobu line (you know what i mean) acting as a de facto local service for the chuo line between mitaka and nakano or mitaka and ochanomizu, depending on how you see things.  however, for the part in discussion here, mitaka to nakano, it does so very badly - that is - without the benefit of easy interchange between the lines and without the benefit of a passenger being able to stand on a platform and choose the next available train.  furthermore, the lack of effective local service limits the amount of faster services that the orange trains can do to some extent.

 

2.  furthermore, the alignment as i propose it will not cause a loss to the 'benefits' of easier interchange at shinjuku to the yamanote.  in fact, quite the opposite, it will improve this by allowing inbound passengers the opportunity to go chuo->sobu->yamanote by just walking accross the platform at nakano or koenji.

 

3.  mitaka is mostly a non-issue.  most sobu/tozai trains would reverse there anyway.   yes, empty sobu/tozai trains needing to enter/leave the depot would need to cross a single active chuo line track.  but since they begin their service at mitaka and are empty at that time anyway, this should not be, i think, a significant issue. 

 

4.  tozai services likewise can be unaffected.  some thought beyond what i have done here might be necessary to figure out how to make best use of the 4 island platforms at nakano, but this is almost an 'overabundance of options' problem and not a constraint.

 

5.  the only fundamental problem is this: how to get the westbound chuo line track from shinjuku into the southernmost boarding platform (platform 1) at nakano and the secondary problem of how to do this without disrupting the sobu yard at nakano.  i think this is not easy, but it is solvable with minimum impact on the neighborhood.

 

the image below is not to scale. it represents what needs to be done just east of nakano to make this plan work. 

 

 

 

basically, one big s to get the chuo line track to the other side of the sobu tracks - either the chuo line track can be elevated or both the sobu line ones can (the latter requires a double track bridge, but with the beneftit that faster chuo main line services don't have to slow down as much and that the ride will be smoother for most people).  variants are also possible that put the westbound sobu track at the very bottom, which improves yard access but makes connections with the tozai line trickier - well, it does if we're under the assumption of the yellow-vs-orange platform assignments to be fixed.  if we remove this assumption and make it more flexible (using dynamic signs, but remember, the passengers would still be on the same island platform) then this becomes less of an issue.

 

it is also possible to make yard access simpler by elevating or partially elevating platform 1-2 at nakano.

 

railfans have always gone out of their way to make sure people call it the "chuo-sobu line" or the "chuo line rapid service" or whatever, even though in practice the orange and yellow trains have operated as living parallel but unconnected lives.  this plan addresses that.  it also maintains the ability for tozai trains to contnue to mitaka, though i have always thought of this somewhat as a gimmick.  critically, the scheme i propose decreases the number of empty seats on underutilized sobu services while also allowing passengers to choose the next best train more easily and with greater frequency.

[bikkuri bahn]

You have to think, is the expense of improvements really necessary?  A common characteristic of western Tokyo commuter services (taking from the Seibu Ikebukuro Line case), is a heavy peak inflow of commuters from the outer suburbs, with relatively little demand for local services (and transfers to/from such) in the inner portions close to the Yamanote loop.  How are the needs of local commuters in the sections concerned served by the existing arrangement, and by other services, such as the Seibu Shinjuku Line, Tokyo Metro or buses?  Flying junctions/crossovers are extremely expensive and disruptive to construct, and flat junctions/crossovers are a non-starter.

[Sacto1985]

I really have to ask this question: is the Chūō-Sōbu Line service a legacy of the time when this was the main commuter rail service from central Tokyo to the outlying city of Chiba?

[railsquid]

The  Chūō and Sōbu lines, serving western Tokyo and eastern Tokyo/Chiba respectively were expanded from 2 to 4 tracks in the 1960s to provide additional capacity; the  Chūō-Sōbu line became the local all-stations stopping service on both lines, which are connected by the two-track line between Ryogoku and Ochanomizu via Akihabara.

[railsquid]

3.  mitaka is mostly a non-issue.  most sobu/tozai trains would reverse there anyway.   yes, empty sobu/tozai trains needing to enter/leave the depot would need to cross a single active chuo line track.  but since they begin their service at mitaka and are empty at that time anyway, this should not be, i think, a significant issue.

 

Mitaka has three platforms, two of which are used by the Chuo line services, which means if the Chuo-Sobu line services ended up as the central platform, they'd need to cross two very active Chuo line tracks, which I somehow don't see happening. Not on the Chuo line, especially not around peak hours which is when trains will be entering/leaving the depot. Squeezing in a workable flying junction to avoid the problem looks geometrically tricky. Not saying it can't be done (I never cease to be amazed by the construction tricks performed in restricted spaces here) but I'm not sure if the costs of the whole operation would be viable for the additional benefit.

[Mudkip Orange]

If you were going to switch the Chuo and Chuo-Sobu operation from UK-style slow/fast lines to US-style center express tracks, I don't see why you should limit that to Mitaka. The tracks are *already* set up that way at Ochanomizu.

 

So what you do is slowly infill "ghost" side platforms on the far side of the express tracks - that is, on the south side east of Shinjuku, and the north side west of there. Then once you've got all the infrastructure in place, you tear out the flyover between Ochanomizu and Suidobashi over a long weekend, and at the same time open all the side platforms you've constructed over 5-10 years. You can even keep the yard throat as a flat junction provided you retrack it so that 2-3 trains can enter/exit the yard simultaneously. Tower A-2 @ Western Avenue in Chicago has run on this principle for 100 years.

[kvp]

Is there a platform/track layout image for all involved lines? I think the original problem might come from the way the lines join and split. Any change in the platform layouts could be done there, so they are properly joined and separated. This would get rid of any flyovers within the common parts. Also i think the with the japanese train frequencies any flat junction would be a problem sooner or later. The chicago system has a very relaxed schedule, so flat junctions are a possibility. When two trains are running exactly parallel (and there are example of this on these two lines), you can't use a flat junction (not even for yard moves) without stopping one of the trains and slowing down the other because of turnouts and/or crossings.

Edited November 20, 2014 by kvp

[railsquid]

If you were going to switch the Chuo and Chuo-Sobu operation from UK-style slow/fast lines to US-style center express tracks, I don't see why you should limit that to Mitaka. The tracks are *already* set up that way at Ochanomizu.

 

So what you do is slowly infill "ghost" side platforms on the far side of the express tracks - that is, on the south side east of Shinjuku, and the north side west of there. Then once you've got all the infrastructure in place, you tear out the flyover between Ochanomizu and Suidobashi over a long weekend, and at the same time open all the side platforms you've constructed over 5-10 years. You can even keep the yard throat as a flat junction provided you retrack it so that 2-3 trains can enter/exit the yard simultaneously. Tower A-2 @ Western Avenue in Chicago has run on this principle for 100 years.

 

The unique thing about the lines between Nakano and Mitaka is that there are parallel platforms on both lines; between Ochanomizu and Shinjuku the Chuo line only stops at Yotsuya. While it would be nice to have same-direction platform transfer there, otherwise switching tracks seems a pretty pointless (hah) operation. Also you'd need to have another flyover arrangement before Shinjuku, where the Chuo-sobu has cross-platform interchange with the Yamanote line and the Chuo line itself has 3 platforms.

[miyakoji]

Very interesting thread!  It makes me want to observe operations around Mitaka for a day... or 5 :).   I can dream...

[railsquid]

I live about 10 minutes away by bike :). Not that I go there very often. There's a footbridge to the west of the station which gives an excellent view of the station and the yard.

[Mudkip Orange]

Also you'd need to have another flyover arrangement before Shinjuku, where the Chuo-sobu has cross-platform interchange with the Yamanote line and the Chuo line itself has 3 platforms.

 

I don't know that I'd build that flyover. In a low-cost option you just retain the WB/Clockwise transfer at platforms 15/16 while shifting EB Chuo-Sobu to platforms 7 and 8.

 

But if one *was* to to get flyover-happy, I'd move the southbound/anticlockwise Yamanote track all the way out to platform 8 with a cross-platform transfer to the EB Chuo-Sobu line on platform 7. Then you have 1-2 Rapid tracks inside of that and the Ltd Express/Liner services in the center.