Handle motorway forks with links as normal motorway intersections

CHANGELOG.md

@@ -6,6 +6,7 @@
       - 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)
+      - CHANGED #4893: Handle motorway forks with links as normal motorway intersections[#4893](https://github.com/Project-OSRM/osrm-backend/issues/4893)
     - 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

@@ -323,3 +323,25 @@ Feature: Motorway Guidance
             | a,c       | ,,    | depart,fork slight left,arrive                   |
             | a,e       | ,,,   | depart,fork slight right,fork slight left,arrive  |
             | a,f       | ,,,   | depart,fork slight right,fork slight right,arrive |
+
+
+    # https://www.openstreetmap.org/#map=19/53.46186/-2.24509
+    Scenario: Highway Fork with a Link
+        Given the node map
+            """
+                 /-----------d
+            a-b-c------------e
+                 \-----------f
+            """
+
+        And the ways
+            | nodes | highway       |
+            | abce  | motorway      |
+            | cf    | motorway      |
+            | cd    | motorway_link |
+
+       When I route I should get
+            | waypoints | route      | turns                              |
+            | a,d       | abce,cd,cd | depart,off ramp slight left,arrive |
+            | a,e       | abce,abce  | depart,arrive                      |
+            | a,f       | abce,cf,cf | depart,turn slight right,arrive |

src/guidance/motorway_handler.cpp

@@ -118,16 +118,6 @@ Intersection MotorwayHandler::fromMotorway(const EdgeID via_eid, Intersection in
         node_data_container.GetAnnotation(node_based_graph.GetEdgeData(via_eid).annotation_data);
     BOOST_ASSERT(isMotorwayClass(via_eid, node_based_graph));
 
-    const auto countExitingMotorways = [this](const Intersection &intersection) {
-        unsigned count = 0;
-        for (const auto &road : intersection)
-        {
-            if (road.entry_allowed && isMotorwayClass(road.eid, node_based_graph))
-                ++count;
-        }
-        return count;
-    };
-
     // find the angle that continues on our current highway
     const auto getContinueAngle = [this, in_data](const Intersection &intersection) {
         for (const auto &road : intersection)
@@ -219,7 +209,13 @@ Intersection MotorwayHandler::fromMotorway(const EdgeID via_eid, Intersection in
     }
     else
     {
-        const unsigned exiting_motorways = countExitingMotorways(intersection);
+        const auto valid_exits = std::count_if(intersection.begin(),
+                                               intersection.end(),
+                                               [](const auto &road) { return road.entry_allowed; });
+        const auto exiting_motorways =
+            std::count_if(intersection.begin(), intersection.end(), [this](const auto &road) {
+                return road.entry_allowed && isMotorwayClass(road.eid, node_based_graph);
+            });
 
         if (exiting_motorways == 0)
         {
@@ -233,7 +229,7 @@ Intersection MotorwayHandler::fromMotorway(const EdgeID via_eid, Intersection in
                 }
             }
         }
-        else if (exiting_motorways == 1)
+        else if (exiting_motorways == 1 || exiting_motorways != valid_exits)
         {
             // normal motorway passing some ramps or mering onto another motorway
             if (intersection.size() == 2)