u_turn_costs on highways

[tudor]

I’m running my own instance of graphhopper. However, I need to work around some of the data being incorrect while the maps are updated. Specifically, the U-Turn is not allowed at a highway intersection.

My workaround involves enabling u_turn_costs, however it doesn’t seem to be having any effect. Despite adding various values to u_turn_costs, it still constructs and lists a U-Turn at that intersection.

My test route is this:

Driving Directions - GraphHopper Maps

The first turn on the highway is listed as a U-turn.

My profile looks like:

  profiles:
   - name: car
     turn_costs: 
         vehicle_types: [motorcar, motor_vehicle]
         u_turn_costs: 5000
     custom_model_files: [car.json]

Why is my u_turn_costs value not having an effect at this intersection?

[easbar]

These u_turn_costs are only applied to cases where a route turns from one edge onto the exact same edge in the other direction.

[tudor]

That’s interesting. Is Graphhopper able to enforce intersectlons like this from OSM data where vehicles can turn right but are not allowed to U-turn?

I’ve noticed odd placements of no-u-turn symbols in the map data. Is that why there is a no u-turn symbol is at the end of the link road?

[tudor]

Or should there have been a no u-turn symbol at the first turn?

[tudor]

It’s possible that the no-u-turn restriction isn’t in the data because it’s a regional rule. No U-turns are allowed at any intersection of this type in that region.

[easbar]

@tudor

That’s interesting. Is Graphhopper able to enforce intersectlons like this from OSM data where vehicles can turn right but are not allowed to U-turn?

Yes.

@tudor

I’ve noticed odd placements of no-u-turn symbols in the map data. Is that why there is a no u-turn symbol is at the end of the link road?

I’m not sure what you are referring to. Do you have a link to the intersection you are talking about and can you explain which no-u-turn symbols you mean?

@tudor

It’s possible that the no-u-turn restriction isn’t in the data because it’s a regional rule. No U-turns are allowed at any intersection of this type in that region.

That is an interesting case I don’t think we have considered so far. Do you have a source for this rule? At what type of intersections are u-turns generally forbidden? And maybe you have an example for an exception to this rule where a u-turn is allowed explicitly at such an intersection?