(svn r20156) -Fix [FS#3937]: [YAPP] Converting a one-way block to a path signal with trains on both sides could lead to a train crash.

src/pbs.cpp

@@ -314,6 +314,10 @@ Train *GetTrainForReservation(TileIndex tile, Track track)
 	 * have a train on it. We need FollowReservation to ignore one-way signals
 	 * here, as one of the two search directions will be the "wrong" way. */
 	for (int i = 0; i < 2; ++i, trackdir = ReverseTrackdir(trackdir)) {
+		/* If the tile has a one-way block signal in the current trackdir, skip the
+		 * search in this direction as the reservation can't come from this side.*/
+		if (HasOnewaySignalBlockingTrackdir(tile, ReverseTrackdir(trackdir)) && !HasPbsSignalOnTrackdir(tile, trackdir)) continue;
+
 		FindTrainOnTrackInfo ftoti;
 		ftoti.res = FollowReservation(GetTileOwner(tile), rts, tile, trackdir, true);