code: public static void setPreferredRoadInternDrawing(Boolean draw) {
  		final Preferences prefs = Preferences.userNodeForPackage(RoadNetworkLayerConstants.class);
  		if (prefs != null) {
  			if (draw == null) {
  				prefs.remove("ROAD_INTERN_DRAWING"); //$NON-NLS-1$
  			} else {
  				prefs.putBoolean("ROAD_INTERN_DRAWING", draw); //$NON-NLS-1$
  			}
  			try {
  				prefs.flush();
  			} catch (BackingStoreException exception) {
  				//
  			}
  		}
  	}
docs: Set if the internal data structure used to store the road network
  may be drawn on the displayers.
  
  @param draw is <code>true</code> if the internal data structures may be
  drawn on the displayers, <code>false</code> if the internal data structures
  may not be drawn on the displayers, <code>null</code> to restore
  the default value given by {@link #DEFAULT_ROAD_INTERN_DRAWING}.