Index: src/script/api/script_rail.cpp
===================================================================
--- src/script/api/script_rail.cpp	(Revision 27604)
+++ src/script/api/script_rail.cpp	(Arbeitskopie)
@@ -458,6 +458,7 @@
 		p1 |= (signal_cycles << 15);
 	}
 	p1 |= ((signal >= SIGNALTYPE_TWOWAY ? signal ^ SIGNALTYPE_TWOWAY : signal) << 5);
+	SetBit(p1, 4); // Semaphore
 
 	return ScriptObject::DoCommand(tile, p1, 0, CMD_BUILD_SIGNALS);
 }