Index: rail.h
===================================================================
--- rail.h	(revision 3369)
+++ rail.h	(working copy)
@@ -528,6 +528,27 @@
 }
 
 /**
+ * Sets the state of the signal along the given trackdir.
+ *
+ * Along meaning if you are currently driving on the given trackdir, this is
+ * the signal that is facing us (for which we stop when it's red).
+ */
+static inline void SetSignalState(TileIndex tile, Trackdir trackdir, SignalState state)
+{
+	assert(IsValidTrackdir(trackdir));
+	assert(HasSignalOnTrack(tile, TrackdirToTrack(trackdir)));
+	
+	switch(state) {
+		case SIGNAL_STATE_RED:
+			_m[tile].m2 &= ~SignalAlongTrackdir(trackdir);
+			break;
+		case SIGNAL_STATE_GREEN:
+			_m[tile].m2 |= SignalAlongTrackdir(trackdir);
+			break;
+	}
+}
+
+/**
  * Gets the type of signal on a given track on a given rail tile with signals.
  *
  * Note that currently, the track argument is not used, since
Index: rail_cmd.c
===================================================================
--- rail_cmd.c	(revision 3369)
+++ rail_cmd.c	(working copy)
@@ -1802,37 +1802,32 @@
 	// then mark the signals in the segment accordingly
 	for (i = 0; i != ssd->cur; i++) {
 		TileIndex tile = ssd->tile[i];
-		byte bit = SignalAgainstTrackdir(ssd->bit[i]);
-		uint16 m2 = _m[tile].m2;
+		Trackdir signal = ReverseTrackdir(ssd->bit[i]);
+		SignalState state = GetSignalState(tile, signal);
+		SignalState newstate = ssd->stop ? SIGNAL_STATE_RED : SIGNAL_STATE_GREEN;
 
 		// presignals don't turn green if there is at least one presignal exit and none are free
-		if (_m[tile].m4 & 1) {
+		if (GetSignalType(tile, TrackdirToTrack(signal)) == SIGTYPE_ENTRY ||
+			GetSignalType(tile, TrackdirToTrack(signal)) == SIGTYPE_COMBO) {
 			int ex = ssd->presignal_exits, exfree = ssd->presignal_exits_free;
 
 			// subtract for dual combo signals so they don't count themselves
-			if (_m[tile].m4&2 && HasSignalOnTrackdir(tile, ssd->bit[i])) {
+			if (GetSignalType(tile, TrackdirToTrack(signal)) == SIGTYPE_COMBO && HasSignalOnTrackdir(tile, ssd->bit[i])) {
 				ex--;
 				if (GetSignalState(tile, ssd->bit[i]) != SIGNAL_STATE_RED) exfree--;
 			}
 
 			// if we have exits and none are free, make red.
-			if (ex && !exfree) goto make_red;
+			if (ex && !exfree) newstate = SIGNAL_STATE_RED;
 		}
 
 		// check if the signal is unaffected.
-		if (ssd->stop) {
-make_red:
-			// turn red
-			if ( (bit&m2) == 0 )
-				continue;
-		} else {
-			// turn green
-			if ( (bit&m2) != 0 )
-				continue;
-		}
+		if(newstate == state)
+			continue;
 
 		/* Update signals on the other side of this exit-combo signal; it changed. */
-		if (_m[tile].m4 & 2 ) {
+		if (GetSignalType(tile, TrackdirToTrack(signal)) == SIGTYPE_EXIT ||
+			GetSignalType(tile, TrackdirToTrack(signal)) == SIGTYPE_COMBO) {
 			if (ssd->cur_stack != NUM_SSD_STACK) {
 				ssd->next_tile[ssd->cur_stack] = tile;
 				ssd->next_dir[ssd->cur_stack] = _dir_from_track[ssd->bit[i]];
@@ -1842,8 +1837,7 @@
 			}
 		}
 
-		// it changed, so toggle it
-		_m[tile].m2 = m2 ^ bit;
+		SetSignalState(tile, signal, newstate);
 		MarkTileDirtyByTile(tile);
 	}
 }