diff -r e2e8432018f6 -r 716c6dd9322a src/newgrf_engine.cpp
--- a/src/newgrf_engine.cpp	Mon Jun 11 13:38:11 2007 +0000
+++ b/src/newgrf_engine.cpp	Mon Jun 11 14:00:16 2007 +0000
@@ -507,7 +507,7 @@
 	switch (variable) {
 		case 0x40: // Get length of consist
 		case 0x41: // Get length of same consecutive wagons
-			if (v->type != VEH_TRAIN) return 1;
+			if (!v->HasFront()) return 1;
 
 			{
 				const Vehicle* u;
@@ -830,7 +830,7 @@
 	res->ResolveReal   = &VehicleResolveReal;
 
 	res->u.vehicle.self   = v;
-	res->u.vehicle.parent = (v != NULL && v->type == VEH_TRAIN) ? GetFirstVehicleInChain(v) : v;
+	res->u.vehicle.parent = (v != NULL && v->HasFront()) ? GetFirstVehicleInChain(v) : v;
 
 	res->u.vehicle.self_type = engine_type;