diff --git a/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.cpp b/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.cpp
index b6781c18..12d90774 100644
--- a/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.cpp
+++ b/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.cpp
@@ -201,21 +201,23 @@ HGEdge::~HGEdge()
 }
 
 // compute an edge label, optionally resticted by systems
-std::string HGEdge::label(std::list<HighwaySystem*> *systems)
-{	std::string the_label;
+void HGEdge::write_label(std::ofstream& file, std::list<HighwaySystem*> *systems)
+{	bool write_comma = 0;
 	for (std::pair<std::string, HighwaySystem*> &ns : route_names_and_systems)
 	{	// test whether system in systems
 		if (!systems || contains(*systems, ns.second))
-		  if (the_label.empty())
-			the_label = ns.first;
-		  else	the_label += "," + ns.first;
+		  if (!write_comma)
+		  {	file << ns.first;
+			write_comma = 1;
+		  }
+		  else	file << "," << ns.first;
 	}
-	return the_label;
 }
 
 // write line to tmg collapsed edge file
 void HGEdge::collapsed_tmg_line(std::ofstream& file, char* fstr, unsigned int threadnum, std::list<HighwaySystem*> *systems)
-{	file << vertex1->c_vertex_num[threadnum] << ' ' << vertex2->c_vertex_num[threadnum] << ' ' << label(systems);
+{	file << vertex1->c_vertex_num[threadnum] << ' ' << vertex2->c_vertex_num[threadnum] << ' ';
+	write_label(file, systems);
 	for (HGVertex *intermediate : intermediate_points)
 	{	sprintf(fstr, " %.15g %.15g", intermediate->lat, intermediate->lng);
 		file << fstr;
@@ -225,7 +227,8 @@ void HGEdge::collapsed_tmg_line(std::ofstream& file, char* fstr, unsigned int th
 
 // write line to tmg traveled edge file
 void HGEdge::traveled_tmg_line(std::ofstream& file, char* fstr, unsigned int threadnum, std::list<HighwaySystem*> *systems, std::list<TravelerList*> *traveler_lists)
-{	file << vertex1->t_vertex_num[threadnum] << ' ' << vertex2->t_vertex_num[threadnum] << ' ' << label(systems);
+{	file << vertex1->t_vertex_num[threadnum] << ' ' << vertex2->t_vertex_num[threadnum] << ' ';
+	write_label(file, systems);
 	file << ' ' << segment->clinchedby_code(traveler_lists, threadnum);
 	for (HGVertex *intermediate : intermediate_points)
 	{	sprintf(fstr, " %.15g %.15g", intermediate->lat, intermediate->lng);
@@ -234,7 +237,7 @@ void HGEdge::traveled_tmg_line(std::ofstream& file, char* fstr, unsigned int thr
 	file << '\n';
 }
 
-// line appropriate for a tmg collapsed edge file, with debug info
+/* line appropriate for a tmg collapsed edge file, with debug info
 std::string HGEdge::debug_tmg_line(std::list<HighwaySystem*> *systems, unsigned int threadnum)
 {	std::string line = std::to_string(vertex1->c_vertex_num[threadnum]) + " [" + *vertex1->unique_name + "] " \
 			 + std::to_string(vertex2->c_vertex_num[threadnum]) + " [" + *vertex2->unique_name + "] " + label(systems);
@@ -244,7 +247,7 @@ std::string HGEdge::debug_tmg_line(std::list<HighwaySystem*> *systems, unsigned
 		line += " [" + *intermediate->unique_name + fstr;
 	}
 	return line;
-}
+}*/
 
 // printable string for this edge
 std::string HGEdge::str()
diff --git a/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.h b/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.h
index 7c40cba8..b3bb4e7e 100644
--- a/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.h
+++ b/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.h
@@ -29,7 +29,7 @@ class HGEdge
 	~HGEdge();
 
 	void detach(unsigned char);
-	std::string label(std::list<HighwaySystem*> *);
+	void write_label(std::ofstream&, std::list<HighwaySystem*> *);
 	void collapsed_tmg_line(std::ofstream&, char*, unsigned int, std::list<HighwaySystem*>*);
 	void traveled_tmg_line (std::ofstream&, char*, unsigned int, std::list<HighwaySystem*>*, std::list<TravelerList*>*);
 	std::string debug_tmg_line(std::list<HighwaySystem*> *, unsigned int);
diff --git a/siteupdate/cplusplus/classes/GraphGeneration/HighwayGraph.cpp b/siteupdate/cplusplus/classes/GraphGeneration/HighwayGraph.cpp
index 2fdd3e05..5298ea43 100644
--- a/siteupdate/cplusplus/classes/GraphGeneration/HighwayGraph.cpp
+++ b/siteupdate/cplusplus/classes/GraphGeneration/HighwayGraph.cpp
@@ -309,7 +309,9 @@ void HighwayGraph::write_master_graphs_tmg(std::vector<GraphListEntry> &graph_ve
 	{	for (HGEdge *e : wv.second->incident_s_edges)
 		  if (!e->s_written)
 		  {	e->s_written = 1;
-			simplefile << e->vertex1->s_vertex_num[0] << ' ' << e->vertex2->s_vertex_num[0] << ' ' << e->label(0) << '\n';
+			simplefile << e->vertex1->s_vertex_num[0] << ' ' << e->vertex2->s_vertex_num[0] << ' ';
+			e->write_label(simplefile, 0);
+			simplefile << '\n';
 		  }
 		// write edges if vertex is visible...
 		if (wv.second->visibility >= 1)
@@ -408,9 +410,11 @@ void HighwayGraph::write_subgraphs_tmg
 	}
 	// write edges
 	for (HGEdge *e : mse)
-		simplefile << e->vertex1->s_vertex_num[threadnum] << ' '
-			   << e->vertex2->s_vertex_num[threadnum] << ' '
-			   << e->label(graph_vector[graphnum].systems) << '\n';
+	{	simplefile << e->vertex1->s_vertex_num[threadnum] << ' '
+			   << e->vertex2->s_vertex_num[threadnum] << ' ';
+		e->write_label(simplefile, graph_vector[graphnum].systems);
+		simplefile << '\n';
+	}
 	char fstr[57];
 	for (HGEdge *e : mce)
 		e->collapsed_tmg_line(collapfile, fstr, threadnum, graph_vector[graphnum].systems);