diff --git a/osi_object.proto b/osi_object.proto
index 26c2026d1..49a10961f 100644
--- a/osi_object.proto
+++ b/osi_object.proto
@@ -93,8 +93,8 @@ message Vehicle
     // through.
     optional double ground_clearance = 12;
 
-    // Median radius of the wheels.
-    //
+    // Median radius of the wheels measured from a center of the wheel
+    // including tire.
     // Unit: [m]
     //    
     optional double radius_wheel = 13;
@@ -119,31 +119,31 @@ message Vehicle
         
         // Vehicle is a small car.
         //
-        // Definition:
+        // Definition: Hatchback car with maximum length 4 m.
         //
         TYPE_SMALL_CAR = 2;
         
         // Vehicle is a medium car.
         //
-        // Definition:
+        // Definition: Hatchback or sedan with lenght between 4.5 and 5 m.
         //
         TYPE_MEDIUM_CAR = 3;
         
         // Vehicle is a compact car.
         //
-        // Definition:
+        // Definition: Hatchback car with length between 4 and 4.5 m.
         //
         TYPE_COMPACT_CAR = 4;
         
         // Vehicle is a luxury  car.
         //
-        // Definition:
+        // Definition: Sedan or coupe that is longer then 5 m.
         //
         TYPE_LUXURY_CAR = 5;
         
         // Vehicle is a delivery van.
         //
-        // Definition:
+        // Definition: A delivery van.
         //
         TYPE_DELIVERY_VAN = 6;