reduce verbosity of use-lane in combination with lane-anticipation

include/engine/guidance/lane_processing.hpp

@@ -20,7 +20,7 @@ namespace guidance
 // as separate maneuvers.
 OSRM_ATTR_WARN_UNUSED
 std::vector<RouteStep> anticipateLaneChange(std::vector<RouteStep> steps,
-                                            const double min_duration_needed_for_lane_change = 15);
+                                            const double min_duration_needed_for_lane_change = 10);
 
 } // namespace guidance
 } // namespace engine

include/engine/guidance/post_processing.hpp

@@ -28,6 +28,7 @@ std::vector<RouteStep> collapseTurns(std::vector<RouteStep> steps);
 
 // A check whether two instructions can be treated as one. This is only the case for very short
 // maneuvers that can, in some form, be seen as one. Lookahead of one step.
+// This is only a pre-check and does not necessarily allow collapsing turns!!!
 bool collapsable(const RouteStep &step, const RouteStep &next);
 
 // trim initial/final segment of very short length.