--- a/yapf/yapf_rail.cpp	Sun May 28 17:45:26 2006 +0000
+++ b/yapf/yapf_rail.cpp	Sun May 28 19:01:29 2006 +0000
@@ -260,6 +260,7 @@
 	return ret;
 }
 
+/** if any track changes, this counter is incremented - that will invalidate segment cost cache */
 int CSegmentCostCacheBase::s_rail_change_counter = 0;
 
 void YapfNotifyTrackLayoutChange(TileIndex tile, Track track) {CSegmentCostCacheBase::NotifyTrackLayoutChange(tile, track);}