code: @Pure
  	public static String getPreferredAttributeValueForTrafficDirection(TrafficDirection direction, int index) {
  		final Preferences prefs = Preferences.userNodeForPackage(RoadNetworkConstants.class);
  		if (prefs != null) {
  			final StringBuilder b = new StringBuilder();
  			b.append("TRAFFIC_DIRECTION_VALUE_"); //$NON-NLS-1$
  			b.append(direction.name());
  			b.append("_"); //$NON-NLS-1$
  			b.append(index);
  			final String v = prefs.get(b.toString(), null);
  			if (v != null && !"".equals(v)) { //$NON-NLS-1$
  				return v;
  			}
  		}
  		try {
  			return getSystemDefault(direction, index);
  		} catch (AssertionError e) {
  			throw e;
  		} catch (Throwable exception) {
  			return null;
  		}
  	}
docs: Replies the preferred value of traffic direction
  used in the attributes for the traffic direction on the roads.
  
  @param direction a direction.
  @param index is the index of the supported string to reply
  @return the preferred name for the traffic direction on the roads,
  or <code>null</code> if there is no string value for the given index.