diff --git a/osi_roadmarking.proto b/osi_roadmarking.proto
index 29d27d6ef..6fe6e4cad 100644
--- a/osi_roadmarking.proto
+++ b/osi_roadmarking.proto
@@ -96,6 +96,18 @@ message RoadMarking
     //
     optional ColorDescription color_description = 5;
 
+    // Opaque reference of an associated 3D model of the road marking.
+    //
+    // \note It is implementation-specific how model_references are resolved to
+    // 3d models.
+    //
+    // \note Road markings' base objects are positioned differently from other
+    // OSI objects: their local z-axis corresponds to how the marking is placed
+    // on the xy-plane of the lane, rather than pointing upwards as it does for
+    // other objects.
+    //
+    optional string model_reference = 6;
+
     //
     // \brief \c Classification data for a road surface marking.
     //