Index: plugins/rt_topo/laa3_solve.c
===================================================================
--- plugins/rt_topo/laa3_solve.c	(revision 1466)
+++ plugins/rt_topo/laa3_solve.c	(revision 1467)
@@ -29,6 +29,11 @@
 /* LAA step III: find the optimal resolution of crossings by activating
    vias and detorus */
 
+/* bloat up via bboxes so via-via placement leaves enough room for a trace; also
+   make sure vias are not placed closer than this initially */
+#define VIA_SPACING_BLOAT ((rt_topo_cfg.wire_thick + rt_topo_cfg.wire_clr) * rt_topo_cfg.via_via_space)
+
+
 static double laa_cost_2net_update(rt_topo_laa_2net_t *tn)
 {
 	double cost = 0;
@@ -93,6 +98,33 @@
 	printf("initial board cost: %f\n", cost);
 }
 
+/* Return 1 if layer assignment along a tn has 2 vias too close */
+static int laa3_vias_too_close(rt_topo_laa_2net_t *tn, double min_dist2)
+{
+	double lastx, lasty;
+	long bi;
+
+	/* printf("VIAS-too-close: %f;%f to %f;%f:\n", tn->br.array[0].x, tn->br.array[0].y,  tn->br.array[tn->br.used-1].x, tn->br.array[tn->br.used-1].y); */
+
+	lastx = tn->br.array[0].x;
+	lasty = tn->br.array[0].y;
+	for(bi = 1; bi < tn->br.used; bi++) {
+		if (tn->asg[bi] != tn->asg[bi-1]) {
+			double dx = tn->br.array[bi].x - lastx;
+			double dy = tn->br.array[bi].y - lasty;
+			double dist2 = dx*dx + dy*dy;
+
+			/* printf(" dist2=%f (< %f) at %f;%f\n", dist2, min_dist2, tn->br.array[bi].x, tn->br.array[bi].y); */
+			if (dist2 < min_dist2)
+				return 1;
+			lastx = tn->br.array[bi].x;
+			lasty = tn->br.array[bi].y;
+		}
+	}
+
+	return 0;
+}
+
 static double laa3_solve_best(laa3_t *laa3)
 {
 	htsp_entry_t *e;
@@ -100,7 +132,10 @@
 	double best_gain = 0, gain, best_detcost, detcost, best_vialayercost, vialayercost;
 	rt_topo_laa_2net_t *tn, *best_tn = NULL;
 	int lid, ci, best_ci = -1, best_lid = -1, orig_lid;
+	double min_dist2 = VIA_SPACING_BLOAT + rt_topo_cfg.via_dia + rt_topo_cfg.via_clr;
 
+	min_dist2 = min_dist2 * min_dist2;
+
 	/* take each crossing... */
 	for(e = htsp_first(&ctx->board->nets); e != NULL; e = htsp_next(&ctx->board->nets, e)) {
 		rtrnd_net_t *net = e->value;
@@ -121,6 +156,7 @@
 						detcost = laa_cost_2net_calc_cross(laa3, tn, ci, 0);
 						vialayercost = laa_cost_2net_calc_via_layer(laa3, tn, 0);
 						gain = (cr->detcost + tn->cost_vialayer) - (detcost + vialayercost);
+						if (laa3_vias_too_close(tn, min_dist2)) gain = 0;
 						if (gain > best_gain) {
 							best_gain = gain;
 							best_tn = tn;
@@ -270,10 +306,8 @@
 {
 	rtrnd_t *ctx = laa3->ctx;
 	long n;
-	double bloat;
+	double bloat = VIA_SPACING_BLOAT;
 
- /* bloat up via bboxes so via-via placement leaves enough room for a trace */
-	bloat = (rt_topo_cfg.wire_thick + rt_topo_cfg.wire_clr) * rt_topo_cfg.via_via_space;
 
 	rtrnd_rtree_init(rtv);
 	for(n = 0; n < vias->used; n++) {