diff --git src/simutrans/obj/roadsign.cc src/simutrans/obj/roadsign.cc
index d091b81fe..ac058615e 100644
--- src/simutrans/obj/roadsign.cc
+++ src/simutrans/obj/roadsign.cc
@@ -174,7 +174,7 @@ DBG_MESSAGE("roadsign_t::set_dir()","ribi %i",dir);
 void roadsign_t::set_two_ways(bool yesno)
 {
 	 ticks_ns = yesno ? 1 : 0;
-	 if(desc->is_signal_type()) {
+	 if(desc->is_signal_type() && !preview) {
 		 // Mask needs a change
 		 weg_t *weg = welt->lookup(get_pos())->get_weg(desc->get_wtyp()!=tram_wt ? desc->get_wtyp() : track_wt);
 		 if (weg) {