Hi, I switched on the mkgmap logging and I noticed, compiling "the most simple failing map" I attched to a mail yesterday, that when the routing is faulty (routing nodes collapsing) the TableA used by the NOD builder has 5 nodes and 5 arcs. This should means that the central node (the collapsed) has a routing Arc going to itself. This may cause the problem. In the file \parabola\imgfmt\app\net\NOD1Part.java there is the function that populates the TableA. The original function is: /** * Add a node to this part. * * The node is used to populate the tables. If an * arc points outside the bbox, we know it's not * an internal arc. It might still turn into an * external arc at a deeper level of recursion. */ public void addNode(RouteNode node) { assert bbox == null || bbox.contains(node.getCoord()) : "trying to add out-of-bounds node: " + node; bboxActual.extend(node.getCoord()); nodes.add(node); for (RouteArc arc : node.arcsIteration()) { tabA.addArc(arc); RouteNode dest = arc.getDest(); if (bbox != null && !bbox.contains(dest.getCoord())) { arc.setInternal(false); tabB.addNode(dest); } } nodesSize += node.boundSize(); } The instruction adding the arcs to the table A is tabA.addArc(arc). We should try to change the function avoiding to add an arc to Table A if the arc from a node points to itself. I propose to change the code in a way similar to the following: .... nodes.add(node); for (RouteArc arc : node.arcsIteration()) { RouteNode dest = arc.getDest(); if (dest!=node) tabA.addArc(arc); if (bbox != null && !bbox.contains(dest.getCoord())) { ..... I don't know if this works, (for example I don't if the comparison dest!=node can be done like that) but it should easy to try. Ciao.