diff --git a/include/MapAPI/reference_line.h b/include/MapAPI/reference_line.h
index 99328b86ad690b8f8b1bd0399a0d284646d9f059..84530144015967dc4bf11ccd2c261bf813c5ab8c 100644
--- a/include/MapAPI/reference_line.h
+++ b/include/MapAPI/reference_line.h
@@ -27,8 +27,15 @@ struct ReferenceLinePoint
 
 struct ReferenceLine
 {
+  enum class Type : std::uint8_t
+  {
+    TYPE_POLYLINE = 0,
+    TYPE_POLYLINE_WITH_T_AXIS = 1
+  };
+
   Identifier id{UndefinedId};
-  std::vector<ReferenceLinePoint> poly_line;
+  std::vector<ReferenceLinePoint> poly_line{};
+  Type type{Type::TYPE_POLYLINE};
 };
 }  // namespace map_api