Idea: how to avoid residential roads

[Manfred Frommel]

Motivation:
The "avoid main roads" feature does a good job in finding small roads, but sometimes prefers residential roads, which no human would choose.
There is no easy way to avoid "residential" without sacrificing the routes via the "unclassified" roads.

Problem:
The issue with OSM and small roads is, that many "unclassified" roads are interrupted with "residential" in villages.
(see german discussion)
IMHO the "unclassified" roads should be continued inside villages as it is done with the other roads (primary, secondary, tertiary)

Idea for a possible solution:
It might be possible to fill the gaps during the preprocessing stage of GraphHopper.
See what "Netzwolf" has done here
On his map you can see where the "unclassified"(blue) ends in a "residential"(red) 

You could try to continue those "unclassified" roads in the preprocessing stage of GraphHopper
Whenever an "unclassified" ends in a "residential", replace the "residential" with "unclassified", until you hit the next "unclassified" or higher road.

Definitely not an easy task and with many pitfalls.

Greetings
Manfred

[Robin]

Hi Manfred,

thanks for taking the time :).

> IMHO the "unclassified" roads should be continued inside villages as it is done with the other roads (primary, secondary, tertiary)

I agree.

> Whenever an "unclassified" ends in a "residential", replace the "residential" with "unclassified", until you hit the next "unclassified" or higher road.

What happens at an intersection :)?

This could lead to unexpected behavior, I thought about something like this as well. This might work for 50% of the cases, but fail for the other 50%. Just think about what happens if there is more than one potential residential street that should be converted to unclassified. How would you determine the path through a village if there is more than one residential road etc. Changing all residentials to unclassified is not the solution as well. There are too many variables. In the long-term, it would be great if we could fix these things in OSM.

If you look at the visualization of Netwolf, (s)he "only" visualizes the first difference, propagating further through the street network is not a trivial task.

In conclusion, I don't think that this would work, WDYT?

Best,

Robin