Don't use obvious directions at ramp bifurcations, #4895

CHANGELOG.md

@@ -5,6 +5,7 @@
       - CHANGED #4830: Announce reference change if names are empty
       - CHANGED #4835: MAXIMAL_ALLOWED_SEPARATION_WIDTH increased to 12 meters
       - CHANGED #4842: Lower priority links from a motorway now are used as motorway links [#4842](https://github.com/Project-OSRM/osrm-backend/pull/4842)
+      - CHANGED #4895: Use ramp bifurcations as fork intersections [#4895](https://github.com/Project-OSRM/osrm-backend/issues/4895)
     - Profile:
       - FIXED: `highway=service` will now be used for restricted access, `access=private` is still disabled for snapping.
       - ADDED #4775: Exposes more information to the turn function, now being able to set turn weights with highway and access information of the turn as well as other roads at the intersection [#4775](https://github.com/Project-OSRM/osrm-backend/issues/4775)

features/guidance/motorway.feature

@@ -315,6 +315,6 @@ Feature: Motorway Guidance
             | bd    | motorway_link |      | Ravenholm   |
 
        When I route I should get
-            | waypoints | route | turns                          |
-            | a,c       | ,,    | depart,turn slight left,arrive |
-            | a,d       | ,     | depart,arrive                  |
+            | waypoints | route | turns                           |
+            | a,c       | ,,    | depart,fork slight left,arrive  |
+            | a,d       | ,,    | depart,fork slight right,arrive |

src/guidance/turn_handler.cpp

@@ -249,8 +249,13 @@ Intersection TurnHandler::handleThreeWayTurn(const EdgeID via_edge, Intersection
                OOOOOOO
      */
 
+    const auto all_ramps =
+        std::all_of(intersection.begin(), intersection.end(), [this](const auto &road) {
+            return node_based_graph.GetEdgeData(road.eid).flags.road_classification.IsRampClass();
+        });
+
     auto fork = findFork(via_edge, intersection);
-    if (fork && obvious_index == 0)
+    if (fork && (all_ramps || obvious_index == 0))
     {
         assignFork(via_edge, fork->getLeft(), fork->getRight());
     }