demote trunk from divided highways to normal roads, anounce ramps whe…

[MoKob]

…n entering a motorway directly

Issue

resolves #4274

Tasklist

• add regression / cucumber cases (see docs/testing.md)
• review
• adjust for comments

[TheMarex]

How does this affect scenarios that use a trunk_link like this example? Do we emit a on ramp in this case, or would this become a turn right?

[MoKob]

Sadly these would be labeled a simple turn. The problem is that we need a way to find out about these dual-carriage ways. We might be able to assign the motorway tag based on available references/country level.
While the linked example would surely be best described as a ramp, we have many other cases just like here osrm which surely aren't ramps :(

[TheMarex]

I think the OSM tagging in the highway 101 case is actually wrong. This segment is clearly part of the normal traffic flow of the highway. For example this segment also just connects two trunk roads but is also tagged trunk.

We should first get a good understanding of what the trade-off here is. We might be improving instructions inside some US cities but seems like we could vastly decrease our guidance quality in other areas. Maybe the answer here can be to insist on better tagging on OSM side.

[MoKob]

I think you are right and we should investigate further. It might be that we just need another level of country awareness, based on tagging schemes. I am tagging this as experimental and feature request for now.

[daniel-j-h]

Why 91?!