Tom Anderson wrote:
On Tue, 24 May 2005, Clive D. W. Feather wrote:

In article , Tom
Anderson writes

The discussion says that something called a '4-track relay terminal
with a 2-track relay' used to exist at Park Row on the New York
subway. No idea what that is, but the poster seemed to be impressed.


####D####
/--------------\
|------* ####A#### \
\-----------\ /--*----
X
/-----------/ \--*----
|------* ####D#### /
\--------------/
####A####


I've just realised how to build a terminal with arbitarily high
capacity, provided you don't mind making your passengers choose between
an equally arbitrary number of platforms:

+-[--------+-]-\
### / [ ### / ] \-----
-----+ [ -----+ ] /----
\ [ \ ] /
+-[--------+-]-/
n

Where the bit in square brackets with an n at the bottom is a repeated
unit (think polymers!). Trains come in from the east (and why do trains
always come in from the east in these things?), run along the road at
the southern edge of the structure, then pick a bay to stop in, run in
on the diagonal approach road, get in, stop, exchange passengers, then
pull out on the diagonal departure road, joining the main road at the
northern edge and heading back out east. The point is, there are no
conflicting movements, and no contention for anything except the running
roads, so the terminal doesn't restrict capacity below that which the
line supports (provided you can do the diverges and converges
perfectly). Note that when n = 0, this is a normal single-track
reversing terminal, and when n = 1, it's rather like a Sao Paulo
terminal (but with more irritating platform layout).

I think you have to be rather clever about the order in which bays are
used to preserve even intervals between trains, though.

If you replace the reversing bays with through lines, you get a
multi-track loop:

/-[--+-]-\
/ [ / ] \
|# [ |# ] \-----
|# [ |# ] /----
|# [ |# ] /
\ [ \ ] /
\-[--+-]-/
n

Which is wider, shorter, doesn't reverse the trains and is amenable to
the use of island platforms.

Probably not the most sensible use of railway space, either way!

I take it you've never played Transport Tycoon. You've just described a
Ro-Ro station.

http://www.transporttycoon.co.uk/rail2


--
Dave Arquati
Imperial College, SW7
www.alwaystouchout.com - Transport projects in London

Tom Anderson and Clive Feather wrote:
The discussion says that something called a '4-track relay terminal
with a 2-track relay' used to exist at Park Row on the New York subway.
No idea what that is, but the poster seemed to be impressed.

I asked a knowledgeable friend.

Firstly, it wasn't on the Subway but on the erstwhile Brooklyn Bridge
Railway, at the Manhattan end. Turning it into UK terms, the layout
would be:

####D####
/--------------\
|------* ####A#### \
\-----------\ /--*----
X
/-----------/ \--*----
|------* ####D#### /
\--------------/
####A####

The platforms marked D were for departing passengers and A for arriving
ones.

Wow. I can't even begin to figure out what the capacity of that would be!

Do trains drive on the left in the US, then?

No: remember Clive "turned it into UK terms".

I was Cc'd on that email thread, and it turns out that the above
description may not be exactly right. My interpretation of the
somewhat contradictory information is that the layout actually
worked *this* way:

/--------------\
|------* ######### \
\ /--------------o---------
X
/ \--------------o---------
|------* ######### /
\--------------/

This gives separate arrival and departure platforms, and also makes
it impossible for two trains with passengers aboard to collide
head-on on the diamond.

As a further safety aid, the tracks at the right were actually
gauntleted (interlaced), with two pairs of rails that diverged
(if my interpretation is right) at the positions o. That is, in
terms of individual rails, the layout at each o was:

-------------------------------------------------
/---------------------------------
/
-------------+-----------------------------------
/ /-----------------------------
/ /
/ /

And if a particular train started from the south face of the departure
platform, then it would use the south face of the departure platform
all day, and also the south face of the arrival platform, staying
always on the south rail of each pair. One more source of danger
elimnated.


The X is a simple diamond crossing without slips.

Is the entirety of railway terminology invented purely to wind me up?
I'm guessing a diamond crossing is just where two pairs of rails cross...

Uh-huh.

what's a slip?

A slip is where one of those is combined with points so the train can
change from one line to another *or* go straight across. It's expensive
to build and maintain, and therefore normally used only where there
are space constraints. The usual kind is a double slip, with two pairs
of curved rails and four sets of points:

http://www.iwsteamrailway.co.uk/pages/Civ_engineering/photos/Track%20Pack%20Apr%2004/TP%20Apr%2004%205.jpg

A single slip has only one pair of curved rails, allowing 3 rather than
4 moves in each direction. Near major terminal stations, a series of
slips is often used to form a layout allowing a train to cross (in one
direction, say to the left) from any one to any other of a set of tracks.
This example http://wvs.topleftpixel.com/photos/union_rail_tracks.jpg
is the western approach to Union Station here in Toronto; note the
single slip near the white post as well as the double slips.
--
Mark Brader "Inventions reached their limit long ago,
Toronto and I see no hope for further development."
-- Julius Frontinus, 1st century A.D.

My text in this article is in the public domain.

lonelytraveller wrote:

Blackfriars - The Waterloo & City line passes directly beneath here, a
connection to it would alleviate travel from Bank to Blackfriars (thus
rendered 1 stop rather than 4) and from Blackfriars to Waterloo
(currently 4 stops including interchange), assuming the frequency of
the line was changed to something more similar to the other tube lines,
so that it could cope with the number of passengers. A connection here
would be amazingly significant to journey times from this area, and
routes from more north that involve using thameslink, as well as
connecting the area up much better.

Waterloo to Blackfriars was my school commute, at least until a change in
timetable gave me more time to enjoy a walk through the city. I would
certainly have found this useful, but it would have added time to the W&C
line and I honestly doubt there would be would be tolerable usage. There's
already links from Thameslink to Waterloo at both London Bridge and Elephant
& Castle, whilst City Thameslink provides better access for the City.

Alternately, I am also surprised that
they never considered a station at Holborn Viaduct on the original
central line, which would also have provided such a connection, since
this is quite a busy area, and the gap between St Pauls and Chancery
Lane is quite large.

Didn't the original St. Paul's (in its Post Office days) lift shafts come up
much closer to Holborn Viaduct? Would this have been a viable additional
station or would it have just overlapped?

Tom Anderson wrote:

Or something, so you can do it all at Aldgate. This, however, would be
awful for anyone who just wanted to head east - you'd have to choose
between two platforms and hope you picked the one with the first train,
whereas at present, you just have one. I'm not really sure who it would
make life easier for; the stations on either side provide easier changes
from the District and H&C to the Circle.

Maybe, but the service on the H&C is frankly poor. Many times when I've had
to travel Euston Square to Stepney Green I've found it impossible to catch a
through service and instead wind up having to change two or three times
using the Circle/Met (sometimes both if one stops at Moorgate), H&C and
District. An integrated Aldgate station would usually allow me a single
interchange rather than perpetually catching trains for two stops at a time
on a through route.

What i'd do, if we were going to dig up bits of the City, is rearrange
Tower Hill - possibly with an extra bit of track from Minories junction -
so that Metropolitan trains could terminate there instead of Aldgate. Oh,
and link the station up with Fenchurch Street and Tower Gateway properly
while i'm down there.

Are the through platforms at Aldgate long enough to support Met trains?
Otherwise I'm inclined to agree with this.

In article , Tom
Anderson writes
I asked a knowledgeable friend.

Firstly, it wasn't on the Subway but on the erstwhile Brooklyn Bridge
Railway, at the Manhattan end. Turning it into UK terms, the layout
would be:

Or, rather, wouldn't be. Further checks showed he'd misunderstood
things, and it was actually:

/----------\
|-------* ######## ==========================
\ /--------/
X
/ \--------\
|-------* ######## ==========================
\----------/

where the equals signs show interlaced ("gantletted") tracks over the
bridge. The necks were used for loco shunting, not the trains
themselves.

The idea was that the passengers travelled over *zero* sets of points.

Do trains drive on the left in the US, then?

No, I deliberately put it in UK layout.

I'm guessing a diamond crossing is just where two pairs of rails cross;

Correct.

Is that right? If so, what's a slip?

A connection from top-left to top-right (or bottom-left to bottom-right)
of a diamond, with one rail of the connection going within the diamond.
A double-slip involves both.

--
Clive D.W. Feather | Home:
Tel: +44 20 8495 6138 (work) | Web: http://www.davros.org
Fax: +44 870 051 9937 | Work:
Please reply to the Reply-To address, which is:

On Tue, 24 May 2005, Dave Arquati wrote:

Tom Anderson wrote:
On Tue, 24 May 2005, Clive D. W. Feather wrote:

Probably not the most sensible use of railway space, either way!

I take it you've never played Transport Tycoon.

Could never get it recognise my sound card .

You've just described a Ro-Ro station.

http://www.transporttycoon.co.uk/rail2

Curses!

I love the idea of using TT as a sort of eye-candified SIMSIG or
something. It does buses too, so one could try using it to model bits of
London. I understand Ken is a SimCity fan (or at least was during the
interregnum), so he might be open to using it as a strategic planning
tool.

You might consider doing your master's project on a TT model of London.
You'd be unlikely to graduate, but you'd probably make Slashdot.

tom

--
The revolution will not be televised. The revolution will be live.

Firstly, thanks to you both for the explanations.

On Wed, 25 May 2005, Mark Brader wrote:

Tom Anderson and Clive Feather wrote:

The discussion says that something called a '4-track relay terminal
with a 2-track relay' used to exist at Park Row on the New York subway.
No idea what that is, but the poster seemed to be impressed.

I asked a knowledgeable friend.

Firstly, it wasn't on the Subway but on the erstwhile Brooklyn Bridge
Railway, at the Manhattan end. Turning it into UK terms, the layout
would be:

####D####
/--------------\
|------* ####A#### \
\-----------\ /--*----
X
/-----------/ \--*----
|------* ####D#### /
\--------------/
####A####

The platforms marked D were for departing passengers and A for arriving
ones.

Wow. I can't even begin to figure out what the capacity of that would be!

Do trains drive on the left in the US, then?

No: remember Clive "turned it into UK terms".

Doh. Sorry Clive!

I was Cc'd on that email thread, and it turns out that the above
description may not be exactly right. My interpretation of the
somewhat contradictory information is that the layout actually
worked *this* way:

/--------------\
|------* ######### \
\ /--------------o---------
X
/ \--------------o---------
|------* ######### /
\--------------/

This gives separate arrival and departure platforms, and also makes
it impossible for two trains with passengers aboard to collide
head-on on the diamond.

That seems like a much better arrangement.

As a further safety aid, the tracks at the right were actually
gauntleted (interlaced), with two pairs of rails that diverged
(if my interpretation is right) at the positions o. That is, in
terms of individual rails, the layout at each o was:

-------------------------------------------------
/---------------------------------
/
-------------+-----------------------------------
/ /-----------------------------
/ /
/ /

And if a particular train started from the south face of the departure
platform, then it would use the south face of the departure platform all
day, and also the south face of the arrival platform, staying always on
the south rail of each pair.

So each track was in fact four rails, of which only two were in use at
once? There are two logical tracks sharing the same space?

One more source of danger elimnated.

How so?

The X is a simple diamond crossing without slips.

Is the entirety of railway terminology invented purely to wind me up?
I'm guessing a diamond crossing is just where two pairs of rails cross...

Uh-huh.

what's a slip?

A slip is where one of those is combined with points so the train can
change from one line to another *or* go straight across. It's expensive
to build and maintain, and therefore normally used only where there
are space constraints.

You mean not enough to build a proper curve? Proper curves being cheaper?

The usual kind is a double slip, with two pairs of curved rails and four
sets of points:

http://www.iwsteamrailway.co.uk/pages/Civ_engineering/photos/Track%20Pack%20Apr%2004/TP%20Apr%2004%205.jpg

A single slip has only one pair of curved rails, allowing 3 rather than
4 moves in each direction. Near major terminal stations, a series of
slips is often used to form a layout allowing a train to cross (in one
direction, say to the left) from any one to any other of a set of
tracks. This example
http://wvs.topleftpixel.com/photos/union_rail_tracks.jpg is the
western approach to Union Station here in Toronto; note the single slip
near the white post as well as the double slips.

Got it.

Is there some sort of encyclopedia of railway engineering that i could get
hold of which would save you from these questions?

tom

--
The revolution will not be televised. The revolution will be live.

On Wed, 25 May 2005, Tim Roll-Pickering wrote:

Tom Anderson wrote:

Or something, so you can do it all at Aldgate. This, however, would be
awful for anyone who just wanted to head east - you'd have to choose
between two platforms and hope you picked the one with the first train,
whereas at present, you just have one. I'm not really sure who it would
make life easier for; the stations on either side provide easier
changes from the District and H&C to the Circle.

Maybe, but the service on the H&C is frankly poor. Many times when I've
had to travel Euston Square to Stepney Green I've found it impossible to
catch a through service and instead wind up having to change two or
three times using the Circle/Met (sometimes both if one stops at
Moorgate), H&C and District.

That's true - a friend of mine used to live in Stepney Green, and visiting
her after work, which in my case is near Euston Square, was no fun. Having
the off-peak H&C end at Whitechapel doesn't help with this, either.

This is not a reason to further impede interchange, though, it's a reason
to improve the service - ramping up the H&C frequency, or swapping the
eastern ends of the H&C and Metropolitan lines, would be a start. The
tangele of flat junctions round there doesn't help, of course; maybe we
should grade them all while we've got the spades out .

An integrated Aldgate station would usually allow me a single
interchange rather than perpetually catching trains for two stops at a
time on a through route.

The only thing it would allow that you can't do now is to change from Met
to District; you can do Circle - H&C at Liverpool Street (or you could
have waited for an H&C at Euston Square), Circle - District at Tower
Hill, and H&C - District (to get past Whitechapel off-peak) at Aldgate
East. My suggestion for Tower Hill would enable the Met - District
change, and brutal suppression of Moorgate short-stoppers and extension of
the H&C beyond Whitechapel off-peak, should patch the other issues.

That said, if the integration can be done without destroying the single
eastbound platform, say by building a better foot tunnel, that's fine by
me. Perhaps what we need is three platforms, one on the outbound line just
beyond each of the three corners of the triangle (so there's only one
platform per destination), connected by huge foot tunnels. Or not.

What i'd do, if we were going to dig up bits of the City, is rearrange
Tower Hill - possibly with an extra bit of track from Minories junction
- so that Metropolitan trains could terminate there instead of Aldgate.
Oh, and link the station up with Fenchurch Street and Tower Gateway
properly while i'm down there.

Are the through platforms at Aldgate long enough to support Met trains?
Otherwise I'm inclined to agree with this.

I haven't been there in ages, but from my memory of looking at a track
map, i think the platforms are islands, with the through faces a few feet
away from the terminal ones, and presumably the same length, BICBW.

tom

--
The revolution will not be televised. The revolution will be live.

Mark Brader:
As a further safety aid, the tracks at the right were actually
gauntleted (interlaced), with two pairs of rails that diverged
(if my interpretation is right) at the positions o. That is, in
terms of individual rails, the layout at each o was:

-------------------------------------------------
/---------------------------------
/
-------------+-----------------------------------
/ /-----------------------------
/ /
/ /

And if a particular train started from the south face of the departure
platform, then it would use the south face of the departure platform all
day, and also the south face of the arrival platform, staying always on
the south rail of each pair.

Tom Anderson:
So each track was in fact four rails, of which only two were in use at
once? There are two logical tracks sharing the same space?

Uh-huh. This is more commonly done in locations where clearance
considerations force what would otherwise be a short section of
single track on a double-track line. Here's an old image from
Colwyn Bay in Wales: http://dewi.ca/trains/lcber/b039.jpg. Another
use is to allow wide trains to pass a platform on a track designed
for narrow trains on what would otherwise be a single track, like this
one: http://image03.webshots.com/3/0/83/44/21408344mgAUFPpzaa_ph.jpg
near Chicago.

The corresponding rails can also be set much closer, as on this narrow
Amsterdam street. You might think this was a single track at first glance:

http://www.railfaneurope.net/pix/nl/trams/Amsterdam/Combino/line_1/amsterdam_2001.jpg


One more source of danger elimnated.

How so?

No possibility of the points being set wrong, routing the train into the
wrong arrival platform, which most likely would already be occupied.
(Similarly, in situations like the Welsh and Dutch examples, no possibility
of the car going onto the wrong track and colliding head-on with another.)
No possibility of points changing under the train, either.

Is there some sort of encyclopedia of railway engineering that i could get
hold of which would save you from these questions?

Hey, what fun would that be? :-)
--
Mark Brader, Toronto | "Any story that needs a critic to explain it,
| needs rewriting." -- Larry Niven

My text in this article is in the public domain.

In article , Tim Roll-Pickering
writes
Maybe, but the service on the H&C is frankly poor. Many times when I've had
to travel Euston Square to Stepney Green I've found it impossible to catch a
through service and instead wind up having to change two or three times
using the Circle/Met (sometimes both if one stops at Moorgate), H&C and
District. An integrated Aldgate station would usually allow me a single
interchange rather than perpetually catching trains for two stops at a time
on a through route.

Absent the *extremely* rare reversal at King's Cross or Farringdon,
*ALL* eastbound H&C trains call at both Euston Square and Aldgate East
and are not overtaken by Circle or Met. trains en route. So you can
*never* save time by doing what you say you do; you simply wait at a
different place.

Yes, an Aldgate interchange would allow you to take a Circle/Met. to
Aldgate and then walk through long enough passages to miss the following
H&C train, but I'm not sure that there's a great public benefit there.

Are the through platforms at Aldgate long enough to support Met trains?

No.

--
Clive D.W. Feather | Home:
Tel: +44 20 8495 6138 (work) | Web: http://www.davros.org
Fax: +44 870 051 9937 | Work:
Please reply to the Reply-To address, which is: