Inaccurate instruction to "turn onto" a road when a user is already on the road. about graphhopper

[karussell]

Something is off in your description. Your screenshots show foot routes and your /api queries have profile=car.

As you are using 9.0-SNAPSHOT can you try this on GraphHopper Maps (and provide a link) and see if the same problems occur there?

[jjeffchoi]

Here is the link to GraphHopper Maps. There is an instruction to "Turn right onto Mavis road" even though you're already on Mavis road. It looks like it's because of what's seemingly a kink in the road on the map, but in reality it's just a straight road.

Here is another instance where the instruction says to "Turn right onto Dundas Street West" even though you're already on the said road and it's a straight road.

[karussell]

Hm, it looks like these cases happen also relative frequently in the US and other OSM routing engines can handle them without creating a separate turn instruction (at least in your highlighted case). So we should find a way to fix this.

[otbutz]

Shouldn't this snippet cover the case?

graphhopper/core/src/main/java/com/graphhopper/routing/InstructionsFromEdges.java

Lines 363 to 372 in e765323

	// Very certain, this is a turn
	if (Math.abs(sign) > 1) {
	// Don't show an instruction if the user is following a street, even though the street is
	// bending. We should only do this, if following the street is the obvious choice.
	if (InstructionsHelper.isNameSimilar(name, prevName) && outgoingEdges.outgoingEdgesAreSlowerByFactor(2)) {
	return Instruction.IGNORE;
	}
	return sign;
	}

Edit:

outgoingEdges.outgoingEdgesAreSlowerByFactor(2)

is most likely the culprit here

[otbutz]

Are there valid cases where InstructionsHelper.isNameSimilar(name, prevName) is not enough?

[jjeffchoi]

Thank you for looking into this. Here is maybe a better example.

GraphHopper lists 3 unnecessary instructions:

1. Continue onto Bayview Avenue
2. Turn right onto Bayview Avenue
3. Turn slight right onto Bayview Avenue
4. Turn slight right onto Bayview Avenue
5. Arrive at destination

whereas Valhalla lists only two, which seems more intuitive for turn-by-turn:

1. Drive north on Bayview Avenue
2. Your destination is on the left

[karussell]

Thanks a lot for these examples. All those have the "split way" tagging in common associated with a lane count change (often doubling), which makes a good heuristic when to ignore these instructions. If you have time can you review my changes for your example area e.g. locally? (you'll need to add the lanes encoded value in the config graph.encoded_values: lanes)

At least all your linked examples should be fixed with this.

[jjeffchoi]

Works great! Thank you very much.