diff --git a/vehicle.h b/vehicle.h
--- a/vehicle.h
+++ b/vehicle.h
@@ -85,7 +85,7 @@ struct WorldSprite {
 
 struct Vehicle {
 	byte type;				// type, ie roadven,train,ship,aircraft,special
-	byte subtype;			// subtype
+	byte subtype;			// subtype (for trains, 0 == loco, 4 wagon ??)
 
 	uint16 index;			// NOSAVE: Index in vehicle array
 	uint16 next_in_chain_old; // Next vehicle index for chained vehicles