diff --git a/brouter-map-creator/src/main/java/btools/mapcreator/WayIterator.java b/brouter-map-creator/src/main/java/btools/mapcreator/WayIterator.java
index 1ab7b33..7c79b8a 100644
--- a/brouter-map-creator/src/main/java/btools/mapcreator/WayIterator.java
+++ b/brouter-map-creator/src/main/java/btools/mapcreator/WayIterator.java
@@ -16,6 +16,7 @@ public class WayIterator extends MapCreatorBase
 {
   private WayListener listener;
   private boolean delete;
+  private boolean descendingSize;
 
   public WayIterator( WayListener wayListener, boolean deleteAfterReading )
   {
@@ -23,6 +24,12 @@ public class WayIterator extends MapCreatorBase
     delete = deleteAfterReading;
   }
 
+  public WayIterator( WayListener wayListener, boolean deleteAfterReading, boolean descendingSize )
+  {
+    this( wayListener, deleteAfterReading );    
+    this.descendingSize = descendingSize;
+  }
+
   public void processDir( File indir, String inSuffix ) throws Exception
   {
     if ( !indir.isDirectory() )
@@ -33,7 +40,7 @@ public class WayIterator extends MapCreatorBase
     File[] af = sortBySizeAsc( indir.listFiles() );
     for( int i=0; i<af.length; i++ )
     {
-      File wayfile = af[i];
+      File wayfile = descendingSize ? af[af.length -1 - i] : af[i];
       if ( wayfile.getName().endsWith( inSuffix ) )
       {
         processFile( wayfile );
diff --git a/brouter-map-creator/src/main/java/btools/mapcreator/WayLinker.java b/brouter-map-creator/src/main/java/btools/mapcreator/WayLinker.java
index 3d45117..cf398cb 100644
--- a/brouter-map-creator/src/main/java/btools/mapcreator/WayLinker.java
+++ b/brouter-map-creator/src/main/java/btools/mapcreator/WayLinker.java
@@ -32,9 +32,10 @@ import btools.util.LazyArrayOfLists;
  *
  * @author ab
  */
-public class WayLinker extends MapCreatorBase
+public class WayLinker extends MapCreatorBase implements Runnable
 {
   private File nodeTilesIn;
+  private File wayTilesIn;
   private File trafficTilesIn;
   private File dataTilesOut;
   private File borderFileIn;
@@ -66,6 +67,57 @@ public class WayLinker extends MapCreatorBase
 
   private boolean skipEncodingCheck;
 
+  private boolean isSlave;
+  private ThreadController tc;
+
+  public static final class ThreadController
+  {
+    long maxFileSize = 0L;
+    long currentSlaveSize;   
+    long currentMasterSize;
+    
+    synchronized boolean setCurrentMasterSize( long size )
+    {
+      try
+      {
+        if ( size <= currentSlaveSize )
+        {
+          maxFileSize = Long.MAX_VALUE;
+          return false;
+        }
+        currentMasterSize = size;
+        if ( maxFileSize == 0L )
+        {
+          maxFileSize = size;
+        }
+        return true;
+      }
+      finally
+      {
+        notify();
+      }
+    }
+
+    synchronized boolean setCurrentSlaveSize( long size ) throws Exception
+    {
+      if ( size >= currentMasterSize )
+      {
+        return false;
+      }
+      
+      while ( size + currentMasterSize + 50000000L > maxFileSize )
+      {
+        System.out.println( "****** slave thread waiting for permission to process file of size " + size 
+          + " currentMaster=" + currentMasterSize + " maxFileSize=" + maxFileSize );
+        wait( 10000 );
+      }
+      currentSlaveSize = size;
+      return true;
+    }
+  }
+  
+  
+
   private void reset()
   {
     minLon = -1;
@@ -83,14 +135,39 @@ public class WayLinker extends MapCreatorBase
           .println( "usage: java WayLinker <node-tiles-in> <way-tiles-in> <bordernodes> <restrictions> <lookup-file> <profile-file> <data-tiles-out> <data-tiles-suffix> " );
       return;
     }
+    
     new WayLinker().process( new File( args[0] ), new File( args[1] ), new File( args[2] ), new File( args[3] ), new File( args[4] ), new File( args[5] ), new File(
         args[6] ), args[7] );
   }
 
   public void process( File nodeTilesIn, File wayTilesIn, File borderFileIn, File restrictionsFileIn, File lookupFile, File profileFile, File dataTilesOut,
       String dataTilesSuffix ) throws Exception
+  {
+    WayLinker master = new WayLinker();
+    WayLinker slave = new WayLinker();
+    slave.isSlave = true;
+    master.isSlave = false;
+    
+    ThreadController tc = new ThreadController();
+    slave.tc = tc;
+    master.tc = tc;
+    
+    master._process( nodeTilesIn, wayTilesIn, borderFileIn, restrictionsFileIn, lookupFile,  profileFile, dataTilesOut, dataTilesSuffix );
+    slave._process( nodeTilesIn, wayTilesIn, borderFileIn, restrictionsFileIn, lookupFile,  profileFile, dataTilesOut, dataTilesSuffix );
+        
+    Thread m = new Thread( master );
+    Thread s = new Thread( slave );
+    m.start();
+    s.start();
+    m.join();
+    s.join();
+  }
+
+  private void _process( File nodeTilesIn, File wayTilesIn, File borderFileIn, File restrictionsFileIn, File lookupFile, File profileFile, File dataTilesOut,
+      String dataTilesSuffix ) throws Exception
   {
     this.nodeTilesIn = nodeTilesIn;
+    this.wayTilesIn = wayTilesIn;
     this.trafficTilesIn = new File( "traffic" );
     this.dataTilesOut = dataTilesOut;
     this.borderFileIn = borderFileIn;
@@ -114,13 +191,61 @@ public class WayLinker extends MapCreatorBase
 
     skipEncodingCheck = Boolean.getBoolean( "skipEncodingCheck" );
 
-    // then process all segments
-    new WayIterator( this, true ).processDir( wayTilesIn, ".wt5" );
+  }
+  
+  @Override
+  public void run()
+  {
+    try
+    {
+      // then process all segments
+      new WayIterator( this, true, !isSlave ).processDir( wayTilesIn, ".wt5" );
+    }
+    catch( Exception e )
+    {
+      System.out.println( "******* thread (slave=" + isSlave + ") got Exception: " + e );
+      throw new RuntimeException( e );
+    }
+    finally
+    {
+      if (!isSlave)
+      {
+        tc.setCurrentMasterSize( 0L );
+      }
+    }
   }
 
   @Override
   public boolean wayFileStart( File wayfile ) throws Exception
   {
+
+    // master/slave logic:
+    // total memory size should stay below a maximum
+    // and no file should be processed twice
+
+    long filesize = wayfile.length();    
+
+    System.out.println( "**** wayFileStart() for isSlave=" + isSlave + " size=" + filesize );
+
+    if ( isSlave )
+    {
+      if ( !tc.setCurrentSlaveSize( filesize ) )
+      {
+        return false;
+      }
+    }
+    else
+    {
+      if ( !tc.setCurrentMasterSize( filesize ) )
+      {
+        return false;
+      }
+    }
+  
+    
+  
+  
+  
     File trafficFile = fileFromTemplate( wayfile, trafficTilesIn, "trf" );
     if ( trafficTilesIn.isDirectory() && !trafficFile.exists() )
     {