--- a/src/tunnelbridge_cmd.cpp	Thu Apr 19 14:43:25 2007 +0000
+++ b/src/tunnelbridge_cmd.cpp	Thu Apr 19 14:48:10 2007 +0000
@@ -696,6 +696,16 @@
 	return CMD_ERROR;
 }
 
+/**
+ * Switches the rail type for a tunnel or a bridgehead. As the railtype
+ * on the bridge are determined by the one of the bridgehead, this
+ * functions converts the railtype on the entire bridge.
+ * @param tile        The tile on which the railtype is to be convert.
+ * @param totype      The railtype we want to convert to
+ * @param exec        Switches between test and execute mode
+ * @return            The cost and state of the operation
+ * @retval CMD_ERROR  An error occured during the operation.
+ */
 int32 DoConvertTunnelBridgeRail(TileIndex tile, RailType totype, bool exec)
 {
 	TileIndex endtile;