I need to draw tram tracks which are either street running, running on bus lanes or segregated way. Yet the way they’re drawn confuse me a bit, because in many cases tram tracks just look like they’re on segregated ways, while they’re street running :
Here for exemple in Dietikon Switzerland, it looks like Bremgarten-Dietikon-Bahn tracks are aside of the road while they’re not (StreetView), wouldn’t it be better to have two road lines each for one direction and have the tram line on top of the left one, this would be more precise.
Could we in case of street running instead of drawing one two-way road and draw tram tracks aside of it draw two lines for the road each within one direction and have the tram tracks “built” on top of each road-line ?
Here are two exemples of Charleroi (light rail) Here you can see that trams are street running because the tram tracks were drawn on top of the road, it is realistic and more precise. Here is another for one way-tram tracks while the other way is only used by cars.
“because in many cases tram tracks just look like they’re on segregated ways, while they’re street running” is the result from renderer. Most if not all renderers don’t vary line thickness according to road width either. “wouldn’t it be better to have two road lines each for one direction and have the tram line on top of the left one, this would be more precise.” is a no ---- each line represents a carriageway. If there’s no physical separation, it shouldn’t splitted. This how it is reperesented with lines. For your “Could we in case of street running instead of drawing one two-way road and draw tram tracks aside of it draw two lines for the road each within one direction and have the tram tracks “built” on top of each road-line ?” thought, you should be mapping areas. embedded_rails:lanes=* may be used on the road to indicate such.
The point you might want to explain a little more is what you mean with “I need to”?
Is your local government asking for something to show up on the map? Are you making statistics of any kind where you want to query the map to get this data? A navigation tool unable to deal with tram crossings?
Renderers aren’t the problem, mapping areas is not the solution here, this “carriageway rule” for which there is no explanation I found on the wiki is what confuse me,
railways used to follow this rule with one line and a tracks=2 tag, yet we no longer follow this rule and it’s more precise, then why not do the same for roads, it would only benefits from being more precise
this “carriageway rule” isn’t even actually always used (here for exemple where there is no physical barrier between the bus/tram lanes and the rest of the carriageway)
in the way we map tram lines we currently have 3 ways one of which if for the highway= and two for the tram, while using a two-way road with the tram tag along with the highway one would still be fine ; simplier and more precise ;
using embeed_rails:lanes= just makes things complicated while we just need a two way road with the railway tag on it
this way we don’t also need to duplicate crossing trafic lights tags
some might point out that using railway + highway tags contradicts the “One feature, one OSM element” policy, while this is true for trams on segregated ways, this isn’t for street running sections as rails are part of the road bed. The cycleway tag on the contrary which is a different feature of the main road used by motor vehicles is used along it.
There is no exchange of traffic possible between rail tracks, so they are more comparable to carriageways than lanes. The increase in precision by drawing each train track separately can therefore be compared to the increase in precision by drawing each carriageway separately for a road.
Lanes on roads are tagged with the lanes-tag and :lanes-suffix on the ways. The ways represent the carriageway.
I think wrong tagging should be corrected, instead of used as an example to implement wrong tagging in other places.
I’d consider drawing a non-existing median as less precise.
Drawing many roads as separate carriageways when there are no physical barriers is likely to break pedestrian routing entirely. The rule of OSM is that we map the centre lines of roads. We can map the edges too, but we need both & it’s inherently much harder to get the precision needed for roads as areas.
Additional point: doubling the number of ways for a road (or possibly quadrupling if sidewalks are included) greatly increases the amount of work required to maintain the data. As roads change quite frequently (and bus services using them even more) this pushes the burden back to editors, whereas for around 90-95% of existing use-cases the current approach is either entirely adequate, or additional features needed can be added programmatically when data is processed for a particular use.
Railways have a slightly different history. Apart from rendering the tracks, many of the actual use cases are interested in details of track layout. A large number of enthusiastic amateurs have been joined by professional railway folk in using OSM for a host of different applications. SNCF gave a talk at the last SotM about how they’ve been using it to help improve calculating train scheduling (not recorded, a shame as it was a good talk). Way back in 2011 someone gave a talk at SotM-EU in Vienna on some detailed considerations about processing OSM railway data.
I presume there is also interest from people who build model railways as having high quality detail can help if making a model of a particular piece of track.