[traffic] Dyamically determine radius in which to search for junctions

Signed-off-by: mvglasow <michael -at- vonglasow.com>

libs/traffxml/traff_decoder.hpp

@@ -540,6 +540,16 @@ private:
    */
   std::map<m2::PointD, double> m_endJunctions;
 
+  /**
+   * @brief Radius around reference points in which to search for junctions.
+   *
+   * Determined dynamically, based on distance between reference points.
+   * Maximum distance is never more than half the distance between endpoints.
+   * It should be between `kJunctionRadiusMin` and `kJunctionRadiusMax`, and as close as possible to
+   * 1/3 the distance.
+   */
+  double m_junctionRadius;
+
   /**
    * @brief The road ref of `m_message`, parsed with `ParseRef()`
    */