Proposed features/PTv2 Improvements wrt Rapid Transit
|PTv2 Improvements wrt Rapid Transit|
|Status:||Proposed (under way)|
This proposal aims to clarify tagging of metro stations and lines, in the light of the modern Public Transport schema, and to make the data usable to data consumers. It lists only proposed changes to the existing wiki pages.
Having all metro systems tagged in a uniform and complete way would allow for making metro schemes and for proper routing. More than 70 metro networks all over the world have been already mapped as this document proposes.
All things written here apply to subway, light_rail and monorail routes and stations. Some parts of the proposal may apply to other modes of transportation (e.g. trains), but the purpose is to tidy up rapid transit systems.
Subway Entrances and Exits
No subway entrance should be outside a stop area.
- Reason: in most cases it is unclear where the entrance leads. Spatial relationships do not work in this case. Some entrances lead to more than one station.
- Reason: these elevators are entrances, and we need a way of differentiating between these and elevators between levels. The proposal page for elevators allows mapping these as ways: in case of subway entrances they should be remapped as nodes, or there should be a subway_entrance node on the contour.
To tell exits from entrances, either:
- Use entry_only and exit_only roles in stop_area relations.
- Add entrance=entrance if you cannot exit a station at the subway_entrance, or entrance=exit if you cannot enter there.
- Reason: currently we have no way of tagging "one way" subway_entrances, except for connecting oneway footways. But using these footways in determining the mode of an entrance is too hard (you have to implement a full-fledged pedestrian router), and not all subway stations have footways mapped.
Stop Positions and Platforms
- Reason: to link stops and platforms to a station object. There is no other way: these objects can be far from platforms, and there can be many stations nearby.
Restricting Stop Areas
For a subway station, a stop area relation should have only objects that are directly related to the station. Rule of thumb is, only objects with these tags (roles are optional, except for oneway subway entrances):
- railway=station — one and only one, with optional role 'station'.
- railway=platform with role 'platform'.
- public_transport=stop_position with role 'stop'.
- railway=subway_entrance with optional role 'entrance', or mandatory 'entry_only' or 'exit_only'.
You should not add any tracks, footways, taxi stands, or bus stops.
- Reason: let's use stop_area for public transport, and e.g. "site" relations for marking all the contents of a station. Tracks and footways get in the way of constructing a station model in applications, and make editing a station much harder. Imagine what happens if such station gets edited via iD editor later. The less objects in a stop_area, the better.
- Reason: these points of interest are rare and play an important role in station navigation. Of course it would be better without these in a stop_area relation for PT routers, but such objects do not make using the relation harder.
Stop Area Groups
Stations, stops or platforms that are far enough from each other (e.g. more than a walking minute away), or belong to different modes of transportation (e.g. a bus station and a subway stop), should belong to separate stop_area relations.
- Reason: otherwise they comprise a single station, and a data consumer will be suprised when "get off one train and enter another" suddenly includes a ten-minute walk, or a paid network change.
- Reason: with the above, there is no other way of tagging an interchange. Some people suggested using nested stop_area relations, but why complicate things, when we have a well-used and proposed in 2009 stop_area_group type.
For example, similarly named stops or stations close to each other, subway stations that are connected with underground tunnels, bus stops near exits from a subway station, subway and train stations on different levels.
For detailed recommendations for mapping stop area groups, see Proposed features/Metro Mapping#Interchange.
Railway Tracks Direction
- Reason: "oneway" tag marks a legal restriction, and trains do not have these. An engineer won't be fined if he drives a train in an opposing direction. There are very few railway tracks that even have signs forbidding the reverse movement.
Optional Route Members
Tracks are optional for a route relation.
- Reason: on the ground, splitting roads and tracing a route is hard. Underground, tracing tracks is virtually impossible. One should not be penalized for wishing to add a route with a requirement to draw proper tracks. By experience, many currently mapped subway networks do not have tracks in them.
Platforms are also optional, but only if they are not mapped, or there is a single "island" platform for a stop_area relation. When there are two or more platforms (e.g. side platforms for each direction), adding a platform for each stop to a route relation is mandatory.
- Reason: because mapping an underground platform is also hard (you don't expect a mapper to visit and measure every station in a city), and in case of a single platform, it is easily deducible from a stop_area relation it should be in.
Mandatory Route Tags
These tags are mandatory for a route and route_master relations:
- ref=* with a line number or short reference.
- Reason: it is mandatory in GTFS and using a route is hard without a reference id. Also these group routes in absence of a route_master.
- colour=* with an official line colour, either a hexadecimal value (#ffeedd) or a CSS3 colour name (red). Get it from an official metro map. Optional in case there is no official metro map.
- Reason: it is very easy to acquire (just one google search away) and is highly useful in visualizing a route map.
- Reason: switching between networks almost always imposes an extra fee, so the networks should be separate. In case there are no official network names, take one from wikipedia or from common knowledge.
When a line has an evident casing on the official map, especially when the line colour is white, put the main colour (of the casing) in colour=*, and the inner colour — in colour:infill=*. This way you won't have a dozen white lines in software that doesn't support infill. For example, colour=cyan + colour:infill=white for London DLR routes.
- Reason: casing won't work, because with that most lines become "white", which is bad for consumers that do not understand casings. Other options sounded worse.
Introducing an optional route relation tag, proposed in 2014 and now used in some big cities:
- interval=* with a service interval in minutes.
- Reason: while exact schedules are changing rapidly, intervals mostly stay the same over years. This value is highly useful to plot a better public transport route, to not prefer a train route with 1 hour intervals to a longer subway route, but with a 5 minute intervals.
Please comment on the discussion page.
The previous version of the proposal was extensively discussed and may provide some answers.