Index: /src/org/openstreetmap/josm/actions/SplitWayAction.java
===================================================================
--- /src/org/openstreetmap/josm/actions/SplitWayAction.java	(revision 186)
+++ /src/org/openstreetmap/josm/actions/SplitWayAction.java	(revision 186)
@@ -0,0 +1,174 @@
+package org.openstreetmap.josm.actions;
+
+import static org.openstreetmap.josm.tools.I18n.tr;
+
+import java.awt.event.ActionEvent;
+import java.awt.event.KeyEvent;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.HashSet;
+
+import javax.swing.JOptionPane;
+
+import org.openstreetmap.josm.Main;
+import org.openstreetmap.josm.command.AddCommand;
+import org.openstreetmap.josm.command.ChangeCommand;
+import org.openstreetmap.josm.command.Command;
+import org.openstreetmap.josm.command.SequenceCommand;
+import org.openstreetmap.josm.data.SelectionChangedListener;
+import org.openstreetmap.josm.data.osm.Node;
+import org.openstreetmap.josm.data.osm.OsmPrimitive;
+import org.openstreetmap.josm.data.osm.Segment;
+import org.openstreetmap.josm.data.osm.Way;
+import org.openstreetmap.josm.data.osm.visitor.NameVisitor;
+
+/**
+ *
+ * @author framm
+ */
+public class SplitWayAction extends JosmAction implements SelectionChangedListener {
+
+	private Way way;
+	private Node node;
+
+	/**
+	 * Create a new SplitWayAction.
+	 */
+	public SplitWayAction() {
+		super(tr("Split Way"), "splitway", tr("Split a way at the selected node."), KeyEvent.VK_P, KeyEvent.CTRL_MASK | KeyEvent.SHIFT_MASK, true);
+		Main.ds.addSelectionChangedListener(this);
+	}
+
+	/**
+	 * Called when the action is executed
+	 */
+	public void actionPerformed(ActionEvent e) {
+		if (!checkSelection(Main.ds.getSelected())) {
+			JOptionPane.showMessageDialog(Main.parent, tr("Select exactly one way to split and one node to split the way at."));
+			return;
+		}
+
+		if (way == null) {
+			for (Way w : Main.ds.ways) {
+				for (Segment s : w.segments) {
+					if (s.from == node || s.to == node) {
+						if (way != null) {
+							JOptionPane.showMessageDialog(Main.parent, tr("The selected node belongs to more than one way. Please select both, the node and the way to split."));
+							return;
+						}
+						way = w;
+						break;
+					}
+				}
+			}
+		}
+		if (way == null) {
+			JOptionPane.showMessageDialog(Main.parent, tr("The seleced node is not part of any way."));
+			return;
+		}
+		
+		boolean node_found = false;
+		for (Segment s : way.segments) {
+			if (s.incomplete) {
+				JOptionPane.showMessageDialog(Main.parent, tr("Warning: This way is incomplete. Try to download it before splitting."));
+				return;
+			}
+			if (!node_found && (s.from.equals(node) || s.to.equals(node))) {
+				node_found = true;
+			}
+		}
+
+		if (!node_found) {
+			JOptionPane.showMessageDialog(Main.parent, tr("The seleced node is not part of the selected way."));
+			return;
+		}
+
+		splitWay();
+	}
+
+	/** 
+	 * Checks if the selection consists of eactly one way and one node.
+	 * Does not check whether the node is part of the way.
+	 */
+	private boolean checkSelection(Collection<? extends OsmPrimitive> selection) {
+		if (selection.isEmpty() || selection.size() > 2)
+			return false;
+		way = null;
+		node = null;
+		for (OsmPrimitive p : selection) {
+			if ((p instanceof Way) && (way == null)) {
+				way = (Way)p;
+			} else if ((p instanceof Node) && (node == null)) {
+				node = (Node)p;
+			} else {
+				return false;
+			}
+		}
+		return node != null;
+	}
+
+	/**
+	 * Split a way into two parts.
+	 */
+	private void splitWay() {
+
+		HashSet<Node> nodesInFirstHalf = new HashSet<Node>();
+
+		for (Segment s : way.segments) {
+			if (s.from.equals(node)) {
+				nodesInFirstHalf.add(s.to);
+				break;
+			} else if (s.to.equals(node)) {
+				nodesInFirstHalf.add(s.from);
+				break;
+			}
+		}
+
+		boolean loop = true;
+		while (loop) {
+			loop = false;
+			for (Segment s : way.segments) {
+				if (nodesInFirstHalf.contains(s.from) && (!s.to.equals(node))
+				        && !nodesInFirstHalf.contains(s.to)) {
+					nodesInFirstHalf.add(s.to);
+					loop = true;
+				} else if (nodesInFirstHalf.contains(s.to)
+				        && (!s.from.equals(node))
+				        && !nodesInFirstHalf.contains(s.from)) {
+					nodesInFirstHalf.add(s.from);
+					loop = true;
+				}
+			}
+		}
+
+		Way wayToAdd = new Way(way);
+		wayToAdd.id = 0;
+		Way changedWay = new Way(way);
+
+		for (Segment s : way.segments) {
+			if (nodesInFirstHalf.contains(s.from) || nodesInFirstHalf.contains(s.to)) {
+				changedWay.segments.remove(s);
+			} else {
+				wayToAdd.segments.remove(s);
+			}
+		}
+		
+		if (wayToAdd.segments.isEmpty() || changedWay.segments.isEmpty()) {
+			JOptionPane.showMessageDialog(Main.parent, tr("The selected node is not in the middle of the way."));
+			return;
+		}
+
+		NameVisitor v = new NameVisitor();
+		v.visit(way);
+		Main.main.editLayer().add(new SequenceCommand(tr("Split way {0}",v.name),
+			Arrays.asList(new Command[]{new ChangeCommand(way, changedWay), new AddCommand(wayToAdd)})));
+		Main.ds.clearSelection();
+		way = null;
+		node = null;
+		return;
+	}
+
+	public void selectionChanged(Collection<? extends OsmPrimitive> newSelection) {
+		setEnabled(checkSelection(newSelection));
+	}
+}
Index: /src/org/openstreetmap/josm/gui/MainMenu.java
===================================================================
--- /src/org/openstreetmap/josm/gui/MainMenu.java	(revision 185)
+++ /src/org/openstreetmap/josm/gui/MainMenu.java	(revision 186)
@@ -25,4 +25,5 @@
 import org.openstreetmap.josm.actions.SaveAsAction;
 import org.openstreetmap.josm.actions.SelectAllAction;
+import org.openstreetmap.josm.actions.SplitWayAction;
 import org.openstreetmap.josm.actions.UndoAction;
 import org.openstreetmap.josm.actions.UnselectAllAction;
@@ -47,4 +48,5 @@
 	public final DownloadAction download = new DownloadAction();
 	public final Action reverseSegment = new ReverseSegmentAction();
+	public final Action splitWay = new SplitWayAction();
 	public final Action alignInCircle = new AlignInCircleAction();
 	public final Action alignInLine = new AlignInLineAction();
@@ -87,4 +89,5 @@
 		editMenu.addSeparator();
 		editMenu.add(reverseSegment);
+		editMenu.add(splitWay);
 		editMenu.add(alignInCircle);
 		editMenu.add(alignInLine);
Index: /src/org/openstreetmap/josm/gui/layer/OsmDataLayer.java
===================================================================
--- /src/org/openstreetmap/josm/gui/layer/OsmDataLayer.java	(revision 185)
+++ /src/org/openstreetmap/josm/gui/layer/OsmDataLayer.java	(revision 186)
@@ -201,6 +201,5 @@
 		c.undoCommand();
 		redoCommands.push(c);
-		//TODO: Replace with listener scheme
-		setModified(uploadedModified);
+		setModified(uploadedModified || !commands.isEmpty());
 		Main.ds.clearSelection();
 		fireCommandsChanged();
Index: /src/org/openstreetmap/josm/gui/preferences/PreferenceDialog.java
===================================================================
--- /src/org/openstreetmap/josm/gui/preferences/PreferenceDialog.java	(revision 185)
+++ /src/org/openstreetmap/josm/gui/preferences/PreferenceDialog.java	(revision 186)
@@ -76,5 +76,5 @@
 			setting.ok();
 		if (requiresRestart)
-			JOptionPane.showMessageDialog(PreferenceDialog.this,tr("You have to restart JOSM for some settings to take effect."));
+			JOptionPane.showMessageDialog(Main.parent,tr("You have to restart JOSM for some settings to take effect."));
 		Main.parent.repaint();
 	}