diff --git a/obj/roadsign.cc b/obj/roadsign.cc
index 857c2276e..331a41631 100644
--- a/obj/roadsign.cc
+++ b/obj/roadsign.cc
@@ -627,9 +627,10 @@ sync_result roadsign_t::sync_step(uint32 /*delta_t*/)
 	}
 	else {
 		// change every ~32s
-		uint32 ticks = ((welt->get_ticks()>>10)+ticks_offset) % (ticks_ns+ticks_ow);
+		// Must not overflow if ticks_ns+ticks_ow=256
+		uint32 ticks = ((welt->get_ticks()>>10)+ticks_offset) % ((uint32)ticks_ns+(uint32)ticks_ow);
 
-		uint8 new_state = (ticks >= ticks_ns) ^ (welt->get_settings().get_rotation() & 1);
+		uint8 new_state = (ticks >= ticks_ns);
 		if(state!=new_state) {
 			state = new_state;
 			dir = (new_state==0) ? ribi_t::northsouth : ribi_t::eastwest;
@@ -646,6 +647,11 @@ void roadsign_t::rotate90()
 	obj_t::rotate90();
 	if(automatic  &&  !desc->is_private_way()) {
 		state = (state+1)&1;
+		if (ticks_offset >= ticks_ns) {
+			ticks_offset -= ticks_ns;
+		} else {
+			ticks_offset += ticks_ow;
+		}
 		uint8 temp = ticks_ns;
 		ticks_ns = ticks_ow;
 		ticks_ow = temp;
diff --git a/obj/roadsign.h b/obj/roadsign.h
index c00d11d15..55d788e92 100644
--- a/obj/roadsign.h
+++ b/obj/roadsign.h
@@ -131,9 +131,21 @@ public:
 
 	// change the phases of the traffic lights
 	uint8 get_ticks_ns() const { return ticks_ns; }
-	void set_ticks_ns(uint8 ns) { ticks_ns = ns; }
+	void set_ticks_ns(uint8 ns) {
+		ticks_ns = ns;
+		// To prevent overflow in ticks_offset when rotating
+		if (ticks_ow > 256-ticks_ns) {
+			ticks_ow = 256-ticks_ns;
+		}
+	}
 	uint8 get_ticks_ow() const { return ticks_ow; }
-	void set_ticks_ow(uint8 ow) { ticks_ow = ow; }
+	void set_ticks_ow(uint8 ow) {
+		ticks_ow = ow;
+		// To prevent overflow in ticks_offset when rotating
+		if (ticks_ns > 256-ticks_ow) {
+			ticks_ns = 256-ticks_ow;
+		}
+	}
 	uint8 get_ticks_offset() const { return ticks_offset; }
 	void set_ticks_offset(uint8 offset) { ticks_offset = offset; }