|Feature : Sidewalks|
|Sidewalks (also footways, footpaths or pavements) are provided beside the carriageway of a highway for use by pedestrians and sometimes also cyclists.|
The sidewalk (or pavement) is that part of a highway set aside for the use of pedestrians and sometimes also cyclists, separated from the carriageway (or roadway). A sidewalk may be separated from the carriageway by only a kerb (or curb), by a road verge or alternatively may be at some distance from the road (but still associated with it). It also may be separated from the road by some form of barrier, for example bushes or a line of trees. A road may have a sidewalk on only one side of the carriageway, or both side or have no sidewalks.
Caution over use of terms:
The legal UK term for a pavement or a sidewalk is footway. However, the term footway is used within OSM for any path, be it beside a carriageway or otherwise. The term pavement which is often used in the UK as an alternative to footway is used in the USA for the surface of the carriageway (which incidentally is known as a roadway in the USA!)
So because footway and pavement, the British English alternatives, are open to confusion, the North American English sidewalk is used in this case even though British English is the preferred language for OSM tagging and wiki.
How to map
The inclusion of sidewalk information makes it easier to provide effective pedestrian routing, and in particular good narrative descriptions of pedestrian routes along motorised roads.
Sidewalk as refinement to a highway
The simplest method is to tag the associated highway with sidewalk=both/left/right/no (
none is also used synonymously to
no) as appropriate for those sections of sidewalk that are parallel with the carriageway and to use highway=footway where the path diverges from the carriageway.
Attributes of sidewalks are commonly added as further tags on the highway, for example:
- sidewalk:left:width = 3 m
- sidewalk:left:kerb = raised
- sidewalk:both:surface = paving_stones
This mapping method is not providing information about geometry of sidewalk itself (including lack of information how far from highway=* line representing center of road sidewalk is located). On the other hand it makes possible to easily check whatever given road has sidewalks.
Note that it is extremely hard to correctly render place where a pedestrian route diverges from highway where it was mapped using sidewalk tag.
If sidewalk tags on the highway are used instead, free crossing across road at any location may be very easily implemented in routing programs. This function is desirable by many people, and is significantly more complicated to achieve for places where sidewalks are tagged as separate ways. Conversely, it is recommended to represent the sidewalk as a separate way, if the sidewalk is not just attached with a kerb but separated by a road verge or other barriers, to prevent routers from assuming free crossing.
Access information for pedestrians
The above tagging provides information about the physical infrastructure rather than legal access details which can be included using foot=yes/no. The assumption is that all roads are legally accessible to pedestrians except for highway=motorway where it is assumed that pedestrians are not allowed unless otherwise stated.
Sidewalk as separate way
A different approach is to map each sidewalk as separate ways using highway=footway. Use footway=crossing for places where the footway crosses a street. Use footway=sidewalk where the footway runs more or less along the street. The tag is is a hint for renderers that may be used for special handling of sidewalks.
The method produces a visible result in existing routing engines and renderers, as they will usually treat it the same manner as footways that are not associated with a road, unlike footway=sidewalk tag that is rarely displayed on maps. It has number of consequences, some desirable, some undesirable, depending on many factors. Footways represented as separate objects for some are desirable as map is more detailed and readable at high zoom. On the other hand on lower zoom this approach tends to produce a more cluttered map and occasionally other undesirable effects.
It is sometimes recommended that sidewalks should have name tag with name of the associated road. This depends on the choices of each local community. The name tag is used tens of thousands of times, but these are nonetheless just 4% of all footway=sidewalk ways. The main disadvantage of not having the name is that pedestrian routers would need to associate the footway way with the highway to produce narrative directions (e.g. "Follow the sidewalk along Main Street").
Crossing only on explicitly marked crossings may be sometimes desirable, examples including wheelchair users, countries where pedestrians may not cross roads at any location legally, people who anyway prefer cross roads at explicit crossings. But sometimes people would prefer to allow crossing smaller roads at any point along the road. If you wanted to build a (non barrier-free) router that enforces that then you would need more sophisticated processing.
In some regions one of these tagging schemes is clearly more popular than other. In such case it is strongly preferable to continue mapping using established method. For example in Warszawa, Poland large part of sidewalks are mapped using separate way scheme, without copying road names. Changing this would require massive amount of work and would be unlikely to be considered as a good idea by local mappers.
A view of sidewalks in Washington, DC from ITO Map showing roads with sidewalks in dark green, those without sidewalks in dark red and other paths in light green. A mapCSS stylesheet is available for josm.
- Bicycle: similar concepts for cycleways
- "Improving sidewalks globally in OpenStreetMap", MapBox Blog posting by Tim Channell, 27 October 2015