User:ManuelB701/Sandbox/Deprecate busway=*
A draft to deprecate busway=*
Proposal
This proposal aims to deprecate the key busway (and its subkeys busway:left resp. busway:right) because
- of the ambiguity with lanes=*
- doesn't tell data consumers the position of the bus lanes
- specifically for busway=opposite_lane, the same reasons as with cycleway=opposite i.e. combining two functions into one key
Naturally in the world OSM, this doesn't stop anyone from using busway=* (see Any tags you like) but it helps others to consider that better (and more widespread) alternatives exist.
Rationality
busway=* was first used in the early days of OSM to indicate whether a road has lanes dedicated to buses or not. Over the last decade, more and more specific tags (most notably, *:lanes=*) were developed which (partially) overlap with this key but without its major downsides.
The result is that busway=* is rarely used on its own or combined with other tagging which overlap in use with it. Here is a list of its issues:
- Ambiguity with lanes=*:
- lanes=* counts the total lanes for dual tracked vehicles of a road. This excludes bicycle lanes (bicycles are single tracked) but doesn't necessary exclude bus lanes. This becomes a problem on how data consumers count the total lanes of a street: Should you count busway=lane towards lanes=* or not? Example: Is a road with lanes=2 + busway=lane a three lane road with one lane reserved for buses or a two lane road with only lane for buses? The documentation for bus lanes does count busway=lane for lanes=* but some roads are tagged without including the busway=* lane to lanes=*.
- Lack of position information with busway=*:
- busway=lane (even with directional tags) only tells data consumers that a road has bus lanes but not where exactly. This makes it problematic to see whether a bus lane is located in the middle or at the edge of a carriageway (this is different from the related cycleway=* where bicycle lanes are always assumed to be near the edge, turn lanes aside). In the more extreme case, [bus lane is bi-directional] and busway=* is entirely insufficient of this purpose. One solution is to split the road into multiple ways but this goes against the OSM philosophy on mapping highways (see dual carriageway for a related case).
- Redundancy with other tags:
- Related to the above, busway=* got the alternatives lanes:bus=* and bus:lanes=* (resp. lanes:psv=* and psv:lanes=* but the article treats them as synonymous) for quite a while. In fact, most use of busway=* is already combined with bus:lanes=* which further suggests that one tagging style can be represented with the other.
- For busway=opposite_lane: All the issues of cycleway=opposite also apply for this value:
- See Proposal:Deprecate cycleway=opposite family for more details but in short, busway=opposite_lane was used at a time when oneway exceptions such as oneway:bus=* and oneway:psv=* weren't in use. However, because it combines two features into one tag (that being the existence of infrastructure and oneway regulations), being fairly inflexible (both in access aside from bicycles as well as inflexibility — not all oneway exceptions for buses take shape of a lane but busway=opposite was never widespread and possibly is never taken into account by data consumers) as well as (nowadays) better methods of excluding oneway restrictions on a per-vehicle-mode basis, this tag has nowadays little purpose even without deprecating busway=*.
All in all, considering these issues, there are few advantages of using busway=* over lanes:bus=* or bus:lanes=*. In fact, bus:lanes=* alone surpasses the use of busway=*, busway=left and busway=right together.
Tagging and Examples
Many of the examples are based of Bus lanes#Examples:
TODO: Add them.
Features/Pages affected
- Flag busway=* and all of its subtags as deprecated and recommend to not use anymore
- Rework all the other pages on which bus lane tagging is documented to only refer to the newer tagging variants without promoting busway=*.