Routing to appropriate side of a building

Many buildings are in close proximity to roads on more than one side. How do most routing applications use the map data to determine which side of a building to route to?

I raised a similar question maybe two years ago. I think the answer was basically that they don’t, and they will use the nearest road that they consider eligible for routing (in my case, the correct route involved a private back alley, behind shops.

I was actually asking if you could hint the correct road, and the answer appeared to be no.

My case was Starting from Preston Road Station, most routers get it right, but with a U-turn that would probably not be approved by the police. That seems to be because they allow the back alley, and it is closest. OSRM gets it wrong, presumably because it doesn’t allow the back alley.

My original position is that the routers should not be using the back alley without an explicit hint, especially if approaching on foot, as it is, at the very least, a place with high levels of fly tipping, so is probably not the safest place to be, especially after dark. Generally, I don’t think people should be routed onto back alleys except as a last resort.

Regarding the U turn, there is no No-U-Turn sign, so the on the ground rule means I cannot tag a restriction to stop the routers doing this. It is up to them to realise that the structure is a short section of dual carriageway, not a long thin traffic circle.

This issue seems related to how to map address housenumber. I’ve seen many mappers setting housenumber on building polygon. Since in real world housenumber plate is placed where mailman can see it, mapping housenumber as a node in plate location can solve the issue in most cases.

In theory, a navigator can route to the route which is nearest to the entrance tag, if it exists. I don’t know what’s the situation in practice.

Another “hint” would be connecting a footway from the road to the entrance, when mapping at that level of detail.

In practice, Garmin maps genetared by mkgmap DO route to entrance. No “hint” needed, only mapping the real entrance.

Ok, I was thinking entrance nodes and I’ve created a few but they aren’t commonly used in the area I have been editing. They make sense for cases where the POI structure is a closed way outlining the building. Placing an entrance node such that the closest road is the appropriate access road clears the ambiguity on the map in most cases. I just wasn’t sure that in practice routers used the map information in this way.

For cases where the POI is a single node instead of a polygon, as in many situations where there are multiple POIs within a single building outline, does it still make sense to use an entrance node? It would be the simplest to forego the entrance node and place the POI itself at or near the entrance location. An example of an exception though would be an indoor shopping center with multiple POIs associated with a single entrance. In that case it doesn’t seem appropriate to pile all POI nodes on top of the entrance location. For these cases, is there a standard way to explicitly link a POI node to an entrance node? Or would the relationship typically be implied?

userJeff, you could perhaps follow the responses to a similar query on the help site: