User:Andyp/BDRR - Revision history

Andyp: some progress

2009-02-23T04:33:22Z

some progress

Andyp: added some pics and expanded text

2009-01-31T08:51:01Z

added some pics and expanded text

Andyp: complete rewrite started

2009-01-23T02:21:55Z

complete rewrite started

Andyp: /* Flexibility */

2008-08-30T22:00:34Z

‎Flexibility

Andyp at 17:40, 2 August 2008

2008-08-02T17:40:09Z

Andyp at 17:38, 2 August 2008

2008-08-02T17:38:37Z

Andyp: New page: '''Bi-Directional Roll-On, Roll-Off Stations''' == Background on my thought process == I came up with this idea in a single player game where I was trying to connect a city lying betwee...

2008-08-02T17:35:22Z

New page: '''Bi-Directional Roll-On, Roll-Off Stations''' == Background on my thought process == I came up with this idea in a single player game where I was trying to connect a city lying betwee...

New page

'''Bi-Directional Roll-On, Roll-Off Stations'''

== Background on my thought process ==

I came up with this idea in a single player game where I was trying to connect a city lying between the ML and shore. My options were to make one direction of traffic from the ML loop around and and enter the station with the opposite ML traffic, or make a station allowing traffic to enter from either side. This first layout isn't worth describing in detail since it is prone to jamming once traffic starts entering from both directions simultaneously. Soon after I began using space efficient terminus stations for primary industries. Noting that stations with more platforms were very inefficient, I began using the [http://openttdcoop.ppcis.org/blog/2007/10/10/terminus-station-tutorial/ Osai style terminus].

== An Efficient Bi-Directional Ro-Ro ==
After building enough of these I realized that I could duplicate the track layout on both sides and end up with a station having entrances from both directions and that exiting traffic would not interfere with entering traffic on other platforms.
[[Image:osaistyleroro.png]]
This layout proved to work very well, as long as four platforms were enough.

== The Building Block of a Modular Station ==
I began liking the Osai style terminus stations ability to have trains enter and exit simultaneously. So I started to approach all terminus stations with this concept. For two platform stations, I merely built half the station, like so:
[[Image:halfosaiterminus.png]]
Eventually it hit me that I had a single entrance and exit for the two station layout (as opposed to one entrance, two exits for a four platform layout), and I could build larger stations based on these two platform building blocks, with track on both sides, and apply traditional entrances and exits to the whole thing.
This basic building block:
[[Image:buildingblock.png]]
Here is an example station built with this building block:
[[Image:station1.png]]
There is room for a train between signals at A, in case the corresponding platforms fill from the opposite side of the station. A train may have to wait, but it will not block other trains from accessing platforms futhur down. B is a [[Presignal_Bypass_Station|Presignal Bypass]] under the exit bridges. Moving the PSB outside the exit track works just as well, and takes up just as much space. The pictured station is 43 tiles wide, 39 if the PSB is omitted. It does take up quite a bit of room. All curves and signal gaps are optimized for TL 3. It can be made shorter by omitting the bridges over tunnels, and continuing the diagonal track over the tunnel to the other exit. This is at the theoretical expense of exiting trains stopping at waring for the exiting train from the neighbor platform to clear the track. However, this seems unlikely since two trains cannot enter two adjacent platforms from the same direction at the same time, and therefore cannot exit two adjacent platforms in the same direction at the same time. Curve and signal efficiency can also be sacrificed to save space.

== Staggered Platforms ==
Today I saw the [http://www.openttdcoop.org/blog/2007/10/10/terminus-station-tutorial/#comment-2849 comment made by TheTiger] on the Osai Terminus Tutorial blog post. I immediately thought it could apply to the ro-ro station above. It seems like it should work very well, with a space savings of three tiles at seemingly not degradation in performance. This is a quick build that is not signaled. I was also playing with a different entry (necessitating a different exit) at the north side. I have yet to try this layout in an actual game.

== Flexibility ==
In practice I have noticed these layouts are better left for stations that have trains entering from both directions of the ML, such as a secondary industry drop. At a station with all traffic serving the same route (secondary pickups), these stations would be used from a single direction only. These layouts can also be used as a two entrance station with all traffic running the same direction from the ML, but it takes up far more space than more conventional two entrance layouts. It also works well for stations serving two separate loops. It allows for the two loops to share platforms without needing to mix traffic, see coal transfer in

@@ Line 1: / Line 1: @@
 '''Bi-Directional Roll-On, Roll-Off Stations'''
--->currently revising this page completely, right now I would consider this at best a rough draft<--
+-->Still slowing adding pics and clarifying text, if anyone has suggestions to clarify anything here drop me a line on IRC, or leave a note on this articles discussion page<--
 == Why Bi-Directional Ro-Ro (BDRR) stations? ==
@@ Line 62: / Line 62: @@
 The two center platforms have four tiles of combined entry/exit track on each side, compared to one for each of the outside platforms.  The result of this is that trains leaving the center platforms have to travel three tiles farther before a new train can enter that platform.  When I use this layout as a terminus station (frequently), I stagger the platforms to take up the extra three tiles, per the comment by TheTiger in [http://www.openttdcoop.org/blog/2007/10/10/terminus-station-tutorial/#more-215 Osai's Terminus Station Tutorial].  But in a BDRR layout, staggering the platforms merely shifts all of the combined entry/exit track to one side of the station.
-(''add pic to illustrate'')I also tend to view each bridge over tunnel as unnecessary.  When the flow of trains through the entry is considered, trains enter one at a time, as they are delivered to the station by the sideline.  There are two distinct station functions, drop and pickup.  When this layout is used in a drop station, all trains will spend an equal amount of time in the platform to unload, assuming of course full trains, trains of varying cargo loads will follow the pickup model.  Two trains arrive at the station one after the other.  Each train enters without waiting and unloads.  So the first train enters the station such that by the time it has cleared the exit, the second train will just be finished unloading.  When both trains are clear of the station exit, they are spaced apart the same distance that they were before they entered the station, without interference from the lack of a waiting space on the exit.  When used as a pickup, again consider traffic flow.  In the even that two trains in adjacent platforms (sharing an exit track) finish loading at the same time (think of a farm), then both trains leave their platforms at the same time.  One train will cause the other to stop partway out of the platform.  However, the stopped train in the platform does not cause any problem with entering traffic as that traffic is still entering one at a time.  The exiting train that is moving, will clear the exit, and a train from the entry may now choose the associated platform.  While this new train is entering, the stopped exiting train may begin moving through the exit.  By the time another train is at the station entrance, the second platform is now clear.
+(''add pic to illustrate'')I also tend to view each bridge over tunnel as unnecessary.  When the flow of trains through the entry is considered, trains enter one at a time, as they are delivered to the station by the sideline.  There are two distinct station functions, drop and pickup.  When this layout is used in a drop station, all trains will spend an equal amount of time in the platform to unload, assuming of course full trains, trains of varying cargo loads will follow the pickup model.  Two trains arrive at the station one after the other.  Each train enters without waiting and unloads.  So the first train enters the station such that by the time it has cleared the exit, the second train will just be finished unloading.  When both trains are clear of the station exit, they are spaced apart the same distance that they were before they entered the station, without interference from the lack of a waiting space on the exit.  When used as a pickup, again consider traffic flow.  In the event that two trains in adjacent platforms (sharing an exit track) finish loading at the same time (think of a farm), then both trains leave their platforms at the same time.  One train will cause the other to stop partway out of the platform.  However, the stopped train in the platform does not cause any problem with entering traffic as that traffic is still entering one at a time.  The exiting train that is moving, will clear the exit, and a train from the entry may now choose the associated platform.  While this new train is entering, the stopped exiting train may begin moving through the exit.  By the time another train is at the station entrance, the second platform is now clear.
 I also tend to favor bridges over tunnels, as bridges can have built in elevation change, which in some cases can cause a bridged crossing to be a full two tiles shorter than a tunnel crossing.
@@ Line 69: / Line 69: @@
 == Gallery and explanation of some BDRR building blocks I have come up with ==
-platform building block:
+'''2 platform building block:'''
-(pic)
-(explanation and key points)
-platform building block:
+[[Image:andyp-2platformbdrr.png]]
-(pic)
-(explanation and key points)
+This is a very simple arrangement.  The platforms are staggered by two tiles (three for presignals with waiting space, as an extra tile in needed between the bridge and platform).  I used path signals for the example, but presignals could also be used as previously explained.  Using path signals the entry layout on either side will work, if using presignals the entry on the right side must be used (no room for an exit signal before the bridge on the left side).
 platform building block:

@@ Line 17: / Line 17: @@
 *train length
 *curve length
 When choosing the number of platforms, there must be enough to meet the demands of the trains using the station, but too many creates a very bloated station.  Under ideal circumstances I like to have five platforms per entrance, as five platforms are generally enough to meet the demands of a single entry delivering trains at full capacity into a station.  However as this is rarely the case, five platforms per entry is generally not needed.
-Train length is important in its own right, and not just a factor in curve length.  Since trains suffer a penalty when encountering three or more turns in one train length (''insert picture to illustrate''), attention must be paid to this.  With how tight I like to build, I use a section of track TL-1 in length to allow trains to straighten out before entering another curve.  Although this will not apply in every case, it may be possible to use shorter straight sections.
+Train length is important in its own right, and not just a factor in curve length.  Since trains suffer a penalty when encountering track with four or more sections of turns in one train length, attention must be paid to this.  With how tight I like to build, I use a section of track TL-1 in length to allow trains to straighten out before entering another curve (''elaborate'').  Although this will not apply in every case, it may be possible to use shorter straight sections.
 Curve length is obvious and commonly dealt with in #openttdcoop games.  As it applies to BDRR layouts, I find myself having to make modifications to accommodate train length more often than curve length.  Be sure to built a test track and test the curve length with the actual engine and wagon combination(s) being used, as curve length is often less than TL.
@@ Line 31: / Line 38: @@
 This is one instance where I feel path signals have a distinct advantage over pre-signals.  With pre-signals it is possible, and likely, that trains entering from both sides of the station will choose the same platform.  This means one of them will get to the station, and the other will be stuck in the pre-signals waiting for a green light.  It is possible that a train stuck in the pre-signals will block access to all platforms from it's side of the station.  To avoid this waiting spaces can be used, built so that trains are choosing waiting spaces, not platforms (put a regular block signal before the station).  This can add considerable length to the station.  Using path signals has the advantage that trains not only choose platforms, but reserve them as well.  Every train passing the path signal has a platform, a train from the other side cannot "steal" it.  One important design consideration with path signals is to keep the distance from signal to platform as short as possible.  This is because a platform is reserved for the entire time it takes for the train to travel from the path signal to the platform, then out of the platform again.  Trains should get in and out of shared track blocks as quickly as possible to make way for the next train.
 == Inherent choice vs load balanced ==
-I am using the term inherent choice to describe a station where each entry has a built in choice of every platform.  This can be a daunting task with BDRR stations as the stations become very large, very quickly.  Generally I have been using sets of smaller station building blocks, and using a load balancer to distribute trains among the station sets.  An example is in the current PSG #127 at the coal drop station. The ML in this game is LLL_RRR, so I built three sets of three platforms and used a 3to3 load balancer in front of each entry.  This worked well for a time, but 154 trains is proving more than 9 platforms can handle.  I am currently expanding this to three sets of 4 platforms and am able to reuse the majority of the existing entry and exit track.  I have tested this layout on this map (in single player) and expect it to handle somewhere between 175-200 trains just fine.  Expansion to 3 sets of 5 will require a major overhaul of the layout.
+I am using the term inherent choice to describe a station where each entry has a built in choice of every platform.  This can be a daunting task with BDRR stations as the stations become very large, very quickly.  Generally I have been using sets of smaller station building blocks, and using a load balancer to distribute trains among the station sets.  An example is in PSG #127 at the coal drop station. The ML in this game is LLL_RRR, so I built three sets of three platforms and used a 3to3 load balancer in front of each entry.  This worked well for a time, but 154 trains is proved more than 9 platforms can handle.  I worked out a four track layout that fit into the same amount of space (lengthwise) as the three platform layout (shown below).  This 12 platform station (3x4) was able to handle the load presented to it.
 == Relationship with terminus stations ==
-BDRR layouts and terminus stations are closely related.  If you take a terminus station and mirror it about the platforms, you have a BDRR.  However, it may not be the most efficient BDRR.   I consider the Osai style terminus station to be a very good terminus station, but an inefficient BDRR.  (pic)(explanation)
+BDRR layouts and terminus stations are closely related.  If you take a terminus station and mirror it about the platforms, you have a BDRR.  However, it may not be the most efficient BDRR.   I consider the Osai style terminus station to be a very good terminus station, but an inefficient BDRR.
 == Gallery and explanation of some BDRR building blocks I have come up with ==

← Older revision		Revision as of 22:00, 30 August 2008
Line 39:		Line 39:

	== Flexibility ==		== Flexibility ==
−	In practice I have noticed these layouts are better left for stations that have trains entering from both directions of the ML, such as a secondary industry drop. At a station with all traffic serving the same route (secondary pickups), these stations would be used from a single direction only. These layouts can also be used as a two entrance station with all traffic running the same direction from the ML, but it takes up far more space than more conventional two entrance layouts. It also works well for stations serving two separate loops. It allows for the two loops to share platforms without needing to mix traffic, see coal transfer in	+	In practice I have noticed these layouts are better left for stations that have trains entering from both directions of the ML, such as a secondary industry drop. At a station with all traffic serving the same route (secondary pickups), these stations would be used from a single direction only. These layouts can also be used as a two entrance station with all traffic running the same direction from the ML, but it takes up far more space than more conventional two entrance layouts. It also works well for stations serving two separate loops. It allows for the two loops to share platforms without needing to mix traffic, see coal transfer in [[PublicServer:Archive_-_Games_101_-_110#gameid_103\|PSG #103]] for a working example.

@@ Line 1: / Line 1: @@
 '''Bi-Directional Roll-On, Roll-Off Stations'''
-== Background on my thought process ==
+== Why Bi-Directional Ro-Ro (BDRR) stations? ==
-I came up with this idea in a single player game where I was trying to connect a city lying between the ML and shore.  My options were to make one direction of traffic from the ML loop around and and enter the station with the opposite ML traffic, or make a station allowing traffic to enter from either side.  This first layout isn't worth describing in detail since it is prone to jamming once traffic starts entering from both directions simultaneously.  Soon after I began using space efficient terminus stations for primary industries.  Noting that stations with more platforms were very inefficient, I began using the [http://openttdcoop.ppcis.org/blog/2007/10/10/terminus-station-tutorial/ Osai style terminus].
+A big advantage of BDRR stations over traditional ro-ro layouts is that looping traffic around to one side is not required.  When building a station relatively close to the ML all that needs be done is to get traffic from the far side of the ML across the near side.  There is no need for trains from one direction to make a 180° turn before entering, or after exiting the station.  Stations can be built so that the only complete reversal of the direction a train is traveling in occurs in the platforms, provided this ability is enabled in the difficulty settings, which for #ottdcoop games it is.  This allows for the stations to be built closer to the ML allowing for shorter traveling time from ML through the station and back to the ML.
-== An Efficient Bi-Directional Ro-Ro ==
+Throughout this page I am choosing to ignore layouts that allow entering and exiting traffic from different platforms to interfere with one another, so no evil-x's or mess-o-track PBS layouts.
-After building enough of these I realized that I could duplicate the track layout on both sides and end up with a station having entrances from both directions and that exiting traffic would not interfere with entering traffic on other platforms.
-[[Image:osaistyleroro.png]]
+== Considerations when building a BDRR ==
-This layout proved to work very well, as long as four platforms were enough.
+The three most important things to consider when building a BDRR are:
-== The Building Block of a Modular Station ==
+Train length is important in its own right, and not just a factor in curve length.  Since trains suffer a penalty when encountering three or more turns in one train length (''insert picture to illustrate''), attention must be paid to this.  With how tight I like to build, I use a section of track TL-1 in length to allow trains to straighten out before entering another curve.  Although this will not apply in every case, it may be possible to use shorter straight sections.
-I began liking the Osai style terminus stations ability to have trains enter and exit simultaneously.  So I started to approach all terminus stations with this concept.  For two platform stations, I merely built half the station, like so:
-[[Image:halfosaiterminus.png]]
+Curve length is obvious and commonly dealt with in #openttdcoop games.  As it applies to BDRR layouts, I find myself having to make modifications to accommodate train length more often than curve length.  Be sure to built a test track and test the curve length with the actual engine and wagon combination(s) being used, as curve length is often less than TL.
-Eventually it hit me that I had a single entrance and exit for the two station layout (as opposed to one entrance, two exits for a four platform layout), and I could build larger stations based on these two platform building blocks, with track on both sides, and apply traditional entrances and exits to the whole thing.
+When building a station to serve two different train lengths, build to the longest TL and the longest CL, they may not be for the same train.
-This basic building block:
-[[Image:buildingblock.png]]
+Ideally it is best to split entering and exiting trains as soon as close to the platform as possible.  The quicker this can be accomplished, the quicker the platform is ready for the next train.
-Here is an example station built with this building block:
+== Pre-Signals vs Path Signals ==
-[[Image:station1.png]]
+This is one instance where I feel path signals have a distinct advantage over pre-signals.  With pre-signals it is possible, and likely, that trains entering from both sides of the station will choose the same platform.  This means one of them will get to the station, and the other will be stuck in the pre-signals waiting for a green light.  It is possible that a train stuck in the pre-signals will block access to all platforms from it's side of the station.  To avoid this waiting spaces can be used, built so that trains are choosing waiting spaces, not platforms (put a regular block signal before the station).  This can add considerable length to the station.  Using path signals has the advantage that trains not only choose platforms, but reserve them as well.  Every train passing the path signal has a platform, a train from the other side cannot "steal" it.  One important design consideration with path signals is to keep the distance from signal to platform as short as possible.  This is because a platform is reserved for the entire time it takes for the train to travel from the path signal to the platform, then out of the platform again.  Trains should get in and out of shared track blocks as quickly as possible to make way for the next train.
-== Staggered Platforms ==
+== Relationship with terminus stations ==
-Today I saw the [http://www.openttdcoop.org/blog/2007/10/10/terminus-station-tutorial/#comment-2849 comment made by TheTiger] on the Osai Terminus Tutorial blog post.  I immediately thought it could apply to the ro-ro station above.  It seems like it should work very well, with a space savings of three tiles at seemingly not degradation in performance.  This is a quick build that is not signaled.  I was also playing with a different entry (necessitating a different exit) at the north side.  I have yet to try this layout in an actual game.
+BDRR layouts and terminus stations are closely related.  If you take a terminus station and mirror it about the platforms, you have a BDRR.  However, it may not be the most efficient BDRR.   I consider the Osai style terminus station to be a very good terminus station, but an inefficient BDRR.  (pic)(explanation)
-[[Image:staggered.png]]
+== Gallery and explanation of some BDRR building blocks I have come up with ==
-== Flexibility ==
+platform building block:
-In practice I have noticed these layouts are better left for stations that have trains entering from both directions of the ML, such as a secondary industry drop.  At a station with all traffic serving the same route (secondary pickups), these stations would be used from a single direction only.  These layouts can also be used as a two entrance station with all traffic running the same direction from the ML, but it takes up far more space than more conventional two entrance layouts.  It also works well for stations serving two separate loops.  It allows for the two loops to share platforms without needing to mix traffic, see coal transfer in [[PublicServer:Archive_-_Games_101_-_110#gameid_103|PSG #103]] for a working example.
+(pic)