OGF:Making realistic metro/subway systems
This is a guide on making rapid transit networks, or metros or subways, in your city.
If you design a metro or subway system, please take care ...
- to smooth your curves. No train can run though rectangled curves.
- to draw both tracks of a line (with 5 to 6 m or 15 feet gap between). This is also for motorways. Shift+P to create parallel lines.
- to draw platforms with realistic length. Only 4 cars need 60 metres (200 ft) and 9 cars need 150 metres (490 ft).
- to draw metro or subway lines only there where there is very dense traffic in your town (sufficient demand, in other words).
- 1 Short history
- 2 Why build a metro-system?
- 3 Network designs
- 4 Lines and branches
- 5 Stations
- 6 Entrances, Steps and Tunnel for passengers
- 7 Technical details
- 8 Depots
- 9 So, what now?
- 10 Line-Relation
Before 1900, there were some steam-powered lines on elevated structures (viaducts) in major cities such as New York and local railways for urban transport. The first line using electric-traction with locomotives was the City & South London Railway in London in 1890. A multiple-unit system of electric railway operation was devised by Frank J. Sprague and then implemented in Chicago in 1892. Its success spurred the construction of other subway systems, such as Liverpool (1893), Budapest (1896), Boston (1897), Paris (1900), Berlin (1902), New York (1904), Philadelphia (1907), Hamburg (1912) and Buenos Aires (1913).
The word "Metro" (from the "Metropolitan" railway in London or from the "Chemin de Fer metropolitain" in Paris) is a widely-used name of a rapid transit system, with trains running typically in a tunnel with electric power. Other names used are "subway", "subte" from subterraneo in Buenos Aires, "underground" (in London) or "Untergrundbahn" (U-Bahn for short) for German towns.
In the early years, it was more affordable to build tracks on elevated iron viaducts as in american towns or Paris, Berlin or Hamburg. Such iron viaducts today retained its charm, though thought to be ugly and the trains produce noise pollution overground. Hence, most lines since the 1920s are built underground, though can be more expensive and not all nations may have such technology (such as Indonesia or Malaysia) to build tunnels underground.
Why build a metro-system?
In the real world, metro-systems exist in towns with sufficient demand (i.e. at least 1 million or more inhabitants) as constructing the tunnels and the infrastructure is expensive. The alignment of metro-line must be logical to alleviate heavy traffic in the densely urbanised areas and serve a notable number of passengers. For urban areas with lower demand (e.g. smaller towns), streetcars (trams), buses or light-rail may be a more appropriate and affordable solution instead of a mass rapid transit system.
Rapid transit topology is determined by a large number of factors, including geographical barriers (such as hard granite in the soil, rivers and soft soil which made be very dangerous to tunnel through), existing or expected travel patterns (more demand in the city centre compared to the outer sections), construction costs, politics, and historical constraints (landmarks like forts, old churches etc which must be preserved). Geographical barriers may cause chokepoints where transit lines must converge (for example, to cross a body of water), which are potential congestion sites but also offer an opportunity for transfers between lines. Ring lines provide good coverage, connect between the radial lines and serve tangential trips that would otherwise need to cross the typically congested core of the network. A study of the 15 world largest subway systems suggested a universal shape composed of a dense core with branches radiating from it.
In general, the outer suburbs of a city may have fewer passengers using the metro-line. It is possible to split a line to serve other outer areas of a town if necessary, or just have another different line. The branches may meet at an important location (e.g. before the centre of the city where it is denser), where branch services may terminate or continue down the line to the downtown. However, try to avoid unnecessary branches as they can cause switching and signalling problems. Systems such as New York or Stockholm use branches to serve a greater area in the outer suburbs.
More lines and stations may exist in the urban core. An efficient system also allows for better connectivity between lines, such as interchange stations, where two or more lines meet and where passengers can make a transfer between lines. The list below contains a few real-world examples with a corresponding Wikipedia article link, to compare with your town's population to match up the amount of lines needed.
|City||Geographical map of metro||Population of city||Daily Ridership||Length||Notes|
|Stockholm||1.6 million (urban)
2.4 million (metro)
|1.2 million||105.7 kilometres (66 mi)||Unusually longer and higher ridership compared to other cities with similar population|
|Milan||4,336,121 (metro)||1.393 million||96.8 kilometres (60 mi)|
|Singapore||5.639 million||3.4 million||203 kilometres (126 mi)|
|Washington||6.133 million||626,000||188 kilometres (117 mi)|
|Buenos Aires||15,594,428 (metro)||1.38 million||54.9 kilometres (34 mi)|
For a more detailed and comprehensive list, see this Wikipedia list.
Lines and branches
Forking of lines
On some metro lines, likely in the outskirts, a metro line may diverge into two branches for better coverage or just a spur to a depot. The station before the line branches off may have three or four tracks for optimal efficiency, though you don't necessarily need such an arrangement (some stations with two platforms may be sufficient if traffic isn't high.
Some arrangements can be made as follow:
- Three tracks. One platform (island platform) may accommodate the trains arriving at the station for efficiency. For the other direction, however, there is only one track, from which trains will run in either branch. This can be rather confusing for passengers if they do not look at the destination of the train. It is also possible to do the other way (i.e. having an island platform to serve two different destinations and having just one platform for the other side), though the other side may not be able to accommodate trains arriving at the station from the two branches. This is normally done in a stacked arrangement for the platforms (i.e. having the platforms on different levels).
- Four tracks. Similar to above, just that it combines both of the above ideas. The platforms can either the stacked or at the same level.
If the branch does not really have high passenger numbers, it may operate as a shuttle service to terminate at the station. Hence, it may use a middle track, from which passengers may transfer to either direction to continue the journey. The tracks drawn in blue may be used as sidings. This arrangement can also be used for a connection to a depot at "B".
There are several ways for interchanges.
Lines can cut across each other with two different stations with different platforms without any direct connection of the tracks. While this solution requires less space and more convenient (at least for mapping), it can be more troublesome for commuters who have to transfer between the lines.
If there are lines meeting each other in a parallel direction, the platforms can be parallel with the tracks crossing each other. It is best to have parallel platforms with different lines so that the passengers can change the lines at the same platform (see graphic # 5 with the blue and the black line), known as a cross-platform interchange. If there is limited space, both platforms can superimposed one another at different levels.
At this station in Hamburg, Germany, where two at-grade and elevated metro lines interchanges, the tracks at the station runs in the same direction at the same platform. A minimum of 150 metres (490 ft) of the track is needed before the bridge, where the one track of line A goes over the track of line B at the north of the station "Kellinghusenstraße". The situation is also similar underground for tunnels (though it requires an engineering feat in the real-world). For a track to go over or under another track (or any other obstacle), a distance of 85 to 100 m length is needed. It is not possible to have a branch-line with sharp curves; sufficient room is needed for the forking of the crossing lines.
If there is not the room enough for forking, the platforms for each direction can be at different levels, for example with one level for the downtown and another level to out of town. You can see an example in the OGF at, where the southern downtown platform is on a level higher than the northward platforms.
Sometimes two lines run parallel. Then between the first and the last stations can be forkings and both lines run over only two tracks at the parallel way. If this parallel way only is short (one or two stations), then both lines better run with 4 tracks. Here are three tunnels parallel with one, two and one track to avoid curves at the end of the stations and to avoid the statical problems at a broad tunnel.
At very long lines and dense traffic it is possible, to install express-lines. That means, that trains skip stations in the middle of the way to offer a faster service from the outer suburbs to downtown-city. Usual is, that at the "express"-stations all trains will stop and at the "local" stations only that trains, which serve this stations. Helpful is, that both sort of trains stop at the express-stations at the same platform for an easy interchange.
Cheapest soloution is, to have only the usual two tracks and only at the local stations special tracks for the stop at the platform. That means, that often the local train at the platform has to wait, til the express-train has passed the station. And sure - a lot of switches must work.
To offer an express-service at peak-hours 3 tracks can be used. At the morning the express-service run downtown and at the evening to outer laying suburbs. An example in the real world is the IRT-Flushing line (line # 7) in New York .
For a steady express-service you better lay four tracks. Usual is, to lay the express-tracks in the middle. The fast express-trains can run the straight way and waiting passangers at the local station then not are disturbed from these fast running train. Too here New York gives the example at the BMT-Brighton-line .
If your line do not go straigt, it is possible that your local trains serve some stations with a longer way and the express-tracks run a shorter way like lines "E" and "F" to Jackson Heights in Queens / New York. Here the express-trains take the hypothenuse of a triangle.
The distance between two stations of a line can be 500 to 800 m in the central area and probably much larger in the outskirts. Having more stations allows the line to serve as many passengers as possible, though less efficient as compared to having fewer stations, which allow a faster ride with fewer stops. Compromise and judgement are needed when determining the placement of stations.
There are two main types of platforms: Island platform (one platform in the middle serving the two tracks for both directions) or Side platform (two platforms serving each side). Some stations may have a combination of both, if several lines meet there. The locomotives on the metro-lines usually have doors at both sides, so that you can vary the types of platform alignments without problems, even on just one line.
Island platforms are more affordable and able to serve both directions or services more efficiently, with just a few escalators or stairs needed. However, such platforms may be overcrowded easily (and hence unable to expand). Also bear in mind the tracks have to make short curves to accommodate the platform in the middle. Also there can be the usable room on the platform very small at this places, where the stairs reach the platform, if this may be in the middle of the platform and not at the end.
First lines was build direct under the streets. This lines usually get side platforms, for one direction reachable from one side of the street with only short stairs. This soloution was cheap and give short ways to the platform. Modern lines lay deeper and modern side platforms need more stairs and escalators to access the platforms as a island platform, and more inconvenient for commuters if they were to come to the wrong platform. Nevertheless, the tracks can continue straight and the platforms can be expanded if necessary. Side platforms also are usually used for Infill stations or when there is limited space for the station. Some stations may not be straight but curved. This is not really recommended.
Stations may also have the Spanish solution with two railway platforms one on each side of the track and one island platform in the middle of both tracks. This platform arrangement allows the separation of passenger streams by using one side platform only for boarding and the island platform only for alighting. The concept of separate platforms for boarding and alighting has been proven effective at stations with high passenger numbers.
To tag a station for a metro-line, use "railway = station". In histor-style you can add an additional tag "service = metro" to get a different rendering than a normal railway-station, though it may not make a difference on the standard layer. If you give the station a name, you can add the line/service number/abbreviation in the name (e.g. "5 - Gomez") or just give the name.
To tag the platform, use "railway = platform" and additionally "area=yes" if it is an area. The length of the platforms should be able to accommodate the length of your trains. You can also tag the entrances "railway = subway_entrance" at the various sides of your station.
In OGF (and OSM) the platform most is mapped only as a way. In the topo-style this platforms will not be rendered, but in the standard-style and the histor-style you see this platforms. If you set no additional tag with "layer = x", in the standard-style the platform will be shown beneath the street, in the histor-style above the street. To render the platform-level correctly in all styles, you should add the layer-tag. With "layer = 1" the platform will be rendered above the street, with "layer = -1" beneath the street and with layer = -2" under the level of layer = -1. In short words: The platform should be tagged with the same layer as the track aside.
Metro lines can end with a loop (see Line 10 on the Paris Metro) which allows turnarounds and therefore not needing the driver to change sides at the terminus (though nowadays trains are fully automated and there are fewer such issues). Nevertheless, most lines end with a stop. Island platforms are recommended to accommodate terminating trains and allow passengers to chose which train departs earlier. Before the station, the tracks will have a diamond-crossing so that each train can switch tracks when arriving to or departing from the station.
The terminus may also extend to a depot or a maintenance yard or some sidings for waiting trains. If this sidings lay in the direction to "A" (see graphic) then it is usual to arrange this sidings at the track in direction "A", because here trains run with lesser speed and incoming trains will be not disturbed. Sure it is possible, to arrange such sidings in direction "B".
Some stations along the line may have additional platforms for terminating trains, possibly for shuttle services to accommodate heavier traffic for certain parts of the line, or trains requiring servicing to depots. Such stations before the end of the line can have three or four tracks. From point "C" in the diagram, the track can be connected to a depot or just a siding, where trains may be parked until they are needed to serve heavier traffic during peak periods. A middle track may be used for servicing and terminating trains so that other regular trains running from A to B or vice versa can run without any interruption. This middle track lays on the same island platform as the track to direction A, because the trains from the middle track also will move to A.
If the station is a temporary terminus (i.e. the line will be extended in the near future) and in a side-platform configuration, usually only one platform for a track is in operation. Ideally, it will be better to have an island platform with both sides operating to accommodate as many trains as possible.
Entrances, Steps and Tunnel for passengers
On town-maps metro- or subway-stations normally are only a point with a symbol. But the reality is, that a station can be long up to 150 m or more. For a map-user it is important, where the entrance is and how many entrances the station has. Older underground lines often lay direct under the street without any mezzanine. In this case an entrance leads to the platform for only one direction (Hamburg, Station "Mönkebergstraße" or New York, local stations at the 7th Avenue line).
The first and most important step for a better mapping is, to define the entrances with the tag "railway = subway_entrance". Entrances at both ends of the station instead of only one entrance in the middle of the station allows a greater distance between two stations, because the way for the passengers then is shorter or sayed with other words - you reach a greater area of 400 m around a station if you set entrances at both ends. To build a station is more expensive as to build only the tunnel. So you theoretical can set all 950 m a station instead of all 800 m , if your platforms are 150 m long.
A second step - and important at greater stations with several platforms - is to show the connecting ways with "highway = footway". "tunnel=yes" and "layer=X". X is the level beneath the earth. If your footway has level -1, your metro should have a level - 2. Third level of good mapping is to show the steps between entrance, footway-tunnel and platform.
The 'Track Gauge' refers to the distance between the two rails. The most common gauge is 1435 mm, or the 'standard gauge'. This is based on the 4' and 8 1/2" (English imperial) gauge of Stephenson and offers a good balance between the amount of space the rails will take up the curve radius possible, and the size of the trains.
There are also other instances where rail gauges may be wider or narrower, called 'broad gauge' and 'narrow-gauge' respectively. Gauges can range from 600mm to 3 meters. Narrow gauge offers the advantage of allowing tighter curves and cheaper construction, but the trains cannot go as fast or allow heavy goods. Broader gauges allow more space on the trains but use more room and there cannot be tight curves.
Most metro-systems worldwide use the Standard Gauge. However, there are numerous exceptions to this rule. In Russia and other former Soviet nations, the Russian Gauge of 1520 mm (1524 mm in Finland) is used, whereas in Japan some metros are constructed to 1067 mm (3'6" or Cape gauge). Likewise, the Glasgow Subway uses the 1219 mm (4') gauge, Brazil, Ireland, and parts of Australia use 1600 mm (5'3" or Irish) gauge, whilst Portugal and Spain utilise a gauge of 1,668 mm (5'5 21⁄32"). Finally, the BART in San Francisco and metros of the Indian subcontinent run on 1676 mm (5'6" or Indian) gauge.
There are tags for gauges for the tracks, but will not make any difference on the renderer. If you use gauges, remember that trains can't usually use more than one gauge. So there is no need to map a connecting track between different gauges unless you deal with three-rail-tracks or a gauge converter.
Electric trains have two possible sources of power: Overhead lines and third rail (or third and fourth rail). Overhead lines can be used for the fastest trains, up to 400kph. They are safer and allow higher speeds, but are more expensive and need a higher tunnel. Third rail systems are typically used for speeds up to 100mph/160kmh and are cheaper to build and maintain. However they are more dangerous in the event of people being on the tracks, and can be put out of use by icing and snow. Trains have a collector mounted next to the wheels of one car which draws power from the lines.
Some metro-systems run with overhead-wire, but most of them have the third rail, because then the tunnel can be constructed lower (and in most cases cheaper). With third rails often is used DC with roundabout 750 Volt.
Nowadays it is possible to have multiple sources of energy for a train. But ususally different power supply prevents trains from one system to use the other one. A metro net will therefore have no connecting tracks to the mainline rail in revenue service.
Diameter of curves
At the end of the first metro-lines in Paris were loops with a radius of 30 m - but later this was changed to 70 m. For metro-lines curves with radius down to 70 m / 220 feet are usual and possible (see this adventural part of a metro-line on a viaduct from 1912 in Hamburg / Germany[ ]. Use such small radius as 70 m only in the case, that there is no more place in the heart of your city. Here at this 70m radius in Hamburg the tracks always are made wet with water automatically, to avoid "queeky" loudness of the wheels in such a sharp curve. Maybe some radius in the real world is lesser as 70 m - but your metro / subway shall connect parts of your town in a fast manner - and trains can run faster if the curves have a great radius. Therefore again: Smooth your curves.
Number of tracks
Many of us draw motorways with two parallel blue lines, one for each direction, with a small space between. Since the beginning, railway lines with two tracks are only 24 to 28 feet broad (roundabout 8 to 9m) for two tracks (of 1.435mm spur). Calculate the gap between parallel tracks with roundabout 5m / 15 feet. Only if your metro-line has a broader gauge as in Spain or Russia, you can calculate a little bit more for two tracks.
It is better to draw both tracks of a metro-line. These lines look on the map significant broader as a single drawn metro-line and so a your metro-line looks more realistic at the map. You can see this in Khaiwoon,Stanton,Porto Colon or in Latina (Cidudad) as examples. It looks really better and this is the standard in real OpenStreetMap in the most great cities (see e.g. Paris / France).
You can give the single track a name, to hold the overlook at complicated knots of your metro-net (p.e. "Line 5 north" or "depot B"). The ID-editor will show you this name at the edition process and at several zoom-levels you can see it on the map.
Bridge and level-crossing
If one line crosses the other outside of a tunnel, then set a bridge. Snip the way at both side of the bridge and set there to the subway-tag the tags (bridge = yes) and (level = 1). The level must be 1 higher as the line, over which the bridge goes. Take care, that the metro-line have a soft ascent. From the fork of tracks to the bridge you need nearly 170m if one track holds his level or 85m, if one track goes half down and the other half up.
If one track crosses an other in tunnels, then no bridge is drawn. Tag the tunnel with different layers (may be one tunnel has "layer = -1" and the other has "layer = -2"). One track may only be a short piece with an other layer - just to dive under the other track.
In modern times level-crossings at metro-lines are avoided. Some have survived at the "loop" in Chicago or at Aldgate station in London, but the state of the art are different levels at crossings. Only at rails to depots can be crossings at same level.
Do not forget the place for the service for your metro-cars. For the depots of metro-lines you need place - as here []. Minimum lenght of the depot-halls should be the lenght of your trains - or the doubled length, if two trains are stored at one track. In this example there are 12 tracks in the halls, at left side at station "Saarlandstraße" too and this town (Hamburg / Germany) has a third depot of the same importance and some little placings for store the trains - and that only for a net of 4 lines. So plan in a generous manner and give your metro-net a good service. Normally this depots are at the outside end of the lines (at morning for the workers in the city, at evening back from work or pleasure).
At the station of "Barmbek" you see the reality in towns: from north to the south one track for goods-transportation by railway, two tracks of commuter-railway and four tracks of metro-lines (two for each direction at same platform). The platform itself is 150 m long, not too much for a modern metro-service (only in the beginning of the building of metros til 1920 platforms are only roundabout 60 or 80 meters).
How many depots you need? A rough calculation can be: The km of your net * 2 (both directions) / 32 or 40 (netto-speed of your line in km/h) are the trains, you need for a service every hour. If you have shorter distances between the stops or serveral curves with reduce speed, take 32 to 35 km/h. If there are longer distances between the stops and a straight line, 40 km/h is more realistic. In Hamburg / Germany the line U1 needs 30 minutes for 21 km with longer distance between the stops (means 42 km/h), but the line U3 15 minutes for 9 km at shorter distance between the stops (means 36 km/h).
With this calculation you need 1 train for a line of 20 km for a service every hour by a speed of 40 km/h (theoterically!). For a net of 100 km then are 5 trains necessary, if all hour shall come a train to the platform. Sure - that is only theoretical, because nobody build a metro / subway for this bad service only each hour.
So what we have (if your trains have a speed of 40 km/h) for a net (only one direction) of
|service||20 km||50 km||100 km||200 km||500 km||remarks|
|one hour||1 train||2.5 trains||5 trains||10 trains||25 trains||theoretical|
|every 10 minutes||6 trains||15 trains||30 trains||60 trains||150 trains|
|every 5 minutes||12 trains||30 trains||60 trains||120 trains||300 trains|
|every 3 minutes||20 train||50 trains||100 trains||200 trains||500 trains||p.e. in the peak-hours|
Roughly said - if you will serve your net all 3 minutes, you need one train for each km of your net (means one direction, do not double the lenght). If your average speed is lesser than 40 km/h, you need some more trains.
Trains does not mean wagons. Trains can vary in reality from 60 to 150 m of length with different structure of wagons or units.
Do not forget short service tracks from one line to the other (also in tunnel), that all trains can reach the depot too from this lines, who do not have a depot at the line itself. This service-connections can be made with one track only for both directions, because normally at the morning the trains go out of the depot and at the evening they run inside her nightly home.
So, what now?
As you now know the numerous features of a subway network, you might wonder which of these features to adopt, to make them fit to your city and look interesting. Of course you could just combine all the features without a coherent idea behind it. However, as with the motorways, just purposelessly spreading them through empty countries and having miles of tunnels through bays for no reason, there are also some quality aspects here to make your metro system anyone will see as realistic and may motivate them to follow your good example.
Coherence - one style or many?
When you look at Paris, you will see there are about 14 metro lines with mostly the same style. Apart from some running on rubber tires, the style is very coherent: Mostly underground, few branches, mostly within city limits, about the same length and frequency. A similar case is Moscow. These networks were generally planned and built by only one authority, over decades with continous funding. Also, they were NOT built by or based on mainline alignments. The German U-Bahn or Tunnelbanas in Northern Europe fit as well. Depending on the timeline, some sections may be overground even in the inner city. Nevertheless, there are subtle differences between the lines, which usually date from different decades or even centuries. They are usually updated to modern standards, but unlikely to exactly match those of the other lines so they are not in every case interoperable (such as smallter tunnels, shorter platforms etc). The lack of interoperability allows for a higher capacity for the cost of a reduced flexibility.
Then there is London, where the lines date back to former mainline alignments and are probably still shared with the mainline. The German S-Bahn, and French RER fall under this category as well. These lines have numerous branches, which are sometimes considered separate services. These branches share tracks, merge and separate again. Usually the big railways dominates the rail transportation industry in the area, like DB or SNCF. You won't find those lines on viaducts along boulevards, as the big railways would have needed to agree with the city autorities on such an alignment. These lines go quite far into the suburbs and may have travel times well beyond an hour to the very end.
NYC is a special case. Given the branches it looks like the London group, but staying within city limits and not using mainline tracks makes it similar to those the Paris group. One thing you may notice, there are two divisions, (numbered and lettered services) which never share tracks. This is caused by originally having three authorities involved. For the same reason you should not mix S-Bahn and U-Bahn as they are not interoperable.
Another case is - amongst others - Los Angeles, with a different approach for nearly every line. That may be the result of a lack of funding or a long term plan. New lines are built whenever political and financial support is available with the least possible effort to avoid the project to be scrapped altogether.
Then there are the prémetros. A hybrid between tram and metro. Also suffering from a lack funding, albeit with a long term plan in mind. You will often find ruins from prepared but never used infrastructure or weird connections between the two parts which were meant to be temporary but remain in place for decades.
This leads to "ghost stations" and "ghost tunnels". Times goes, things changed. Stations are closed, which lay too close together or a station get a new and better place and the old remain "as ghost". A piece of a subway-line first was planed to lead to point "A", but later the line will run to point "B" and - may be - the last piece of the old way was set out of use. There are many examples in the real world for this so called "ghost stations" and "ghost tunnels" formerly at systems, build in the first decades of the 20th century (check out this and this for examples). It is realistic in OGF to not delete a piece of metro / subway, which is used no more for your mapping, but let it as ghost section (O.k. - this means not, to behold beginner mistakes on your map). "Ghost Stations" may also be sections in your map for planed, but never constructed lines at the crossing with an existing line (for the future constructred with the existing line).
This is an imaginary world, so you may deviate from the main ideas or combine some of them. But it will be more realistic if you choose a subset of those and stick to it. Drawing a straight line through nothing is quick and easy. But drawing a line through a well mapped area, requiring you to stick to your rules (or rethink them) is much more pleasing and more interesting to look at.
So, like for designing a conlang: Pick your features/style. Consider if they are historically plausible. And stick to them. If that was too quick and boring or did not turn out well, rethink and start again.
If everything turned out nice and interesting, don't forget to draw a nice network diagram and wite a wiki page to explain your choices. (It is not overwikifying if you use the wiki to explain your mapping.)
To show your metro-line in the OGF-wiki, you can set the line into a relation. All tracks of one line are gathered in one relation. But not the tracks of other lines. Each line has its individual relation. Tracks, where two or more lines run are used in each relations respectively. Therefore it is necessary to cut the tracks at the fork. That means, you create a new relation with (type = route), (route = subway) and (name = line-number or town-name and line-number) and (ref = shortcut of town and line-number).
If you set at the OGF-wiki a link like "opengeofiction.net/relation/number of the relation" then your line you can be shown in the OGF-wiki as an orange line at the map. As example this is realisized at the metro of Khaiwoon or Porto Colon - please see 
Questions or comments? Things you would add or subtract? Feel free to share your thoughts on the Discussion page.