diff --git a/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.cpp b/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.cpp
index e3f09290..e3a0d7da 100644
--- a/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.cpp
+++ b/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.cpp
@@ -97,29 +97,6 @@ void HGEdge::detach()
 	detach(vertex2->incident_edges);
 }
 
-// write line to tmg collapsed edge file
-void HGEdge::collapsed_tmg_line(std::ofstream& file, char* fstr, unsigned int threadnum, std::vector<HighwaySystem*> *systems)
-{	file << vertex1->c_vertex_num[threadnum] << ' ' << vertex2->c_vertex_num[threadnum] << ' ';
-	segment->write_label(file, systems);
-	for (HGVertex *intermediate : intermediate_points)
-	{	*fmt::format_to(fstr, " {:.15} {:.15}", intermediate->lat, intermediate->lng) = 0;
-		file << fstr;
-	}
-	file << '\n';
-}
-
-// write line to tmg traveled edge file
-void HGEdge::traveled_tmg_line(std::ofstream& file, char* fstr, unsigned int threadnum, std::vector<HighwaySystem*> *systems, bool trav, char* code)
-{	file << vertex1->t_vertex_num[threadnum] << ' ' << vertex2->t_vertex_num[threadnum] << ' ';
-	segment->write_label(file, systems);
-	file << ' ' << (trav ? segment->clinchedby_code(code, threadnum) : "0");
-	for (HGVertex *intermediate : intermediate_points)
-	{	*fmt::format_to(fstr, " {:.15} {:.15}", intermediate->lat, intermediate->lng) = 0;
-		file << fstr;
-	}
-	file << '\n';
-}
-
 /* line appropriate for a tmg collapsed edge file, with debug info
 std::string HGEdge::debug_tmg_line(std::vector<HighwaySystem*> *systems, unsigned int threadnum)
 {	std::string line = std::to_string(vertex1->c_vertex_num[threadnum]) + " [" + *vertex1->unique_name + "] " \
diff --git a/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.h b/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.h
index eae10da8..c1667b27 100644
--- a/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.h
+++ b/siteupdate/cplusplus/classes/GraphGeneration/HGEdge.h
@@ -31,8 +31,6 @@ class HGEdge
 	HGEdge(HGVertex *, unsigned char, HGEdge*, HGEdge*);
 
 	void detach();
-	void collapsed_tmg_line(std::ofstream&, char*, unsigned int, std::vector<HighwaySystem*>*);
-	void traveled_tmg_line (std::ofstream&, char*, unsigned int, std::vector<HighwaySystem*>*, bool, char*);
 	std::string debug_tmg_line(std::vector<HighwaySystem*> *, unsigned int);
 	std::string str();
 	std::string intermediate_point_string();
diff --git a/siteupdate/cplusplus/classes/GraphGeneration/HGVertex.cpp b/siteupdate/cplusplus/classes/GraphGeneration/HGVertex.cpp
index 80190149..88ca5e87 100644
--- a/siteupdate/cplusplus/classes/GraphGeneration/HGVertex.cpp
+++ b/siteupdate/cplusplus/classes/GraphGeneration/HGVertex.cpp
@@ -1,3 +1,4 @@
+#define FMT_HEADER_ONLY
 #include "HGVertex.h"
 #include "../Args/Args.h"
 #include "../Datacheck/Datacheck.h"
@@ -6,17 +7,15 @@
 #include "../Region/Region.h"
 #include "../Route/Route.h"
 #include "../Waypoint/Waypoint.h"
+#include <fmt/format.h>
 
 std::atomic_uint HGVertex::num_hidden(0);
+thread_local int* HGVertex::vnums;
 
 void HGVertex::setup(Waypoint *wpt, const std::string *n)
 {	lat = wpt->lat;
 	lng = wpt->lng;
 	wpt->vertex = this;
-	s_vertex_num = new int[Args::numthreads];
-	c_vertex_num = new int[Args::numthreads];
-	t_vertex_num = new int[Args::numthreads];
-		       // deleted by ~HGVertex
 	unique_name = n;
 	edge_count = 0;
 	visibility = 0;
@@ -38,13 +37,6 @@ void HGVertex::setup(Waypoint *wpt, const std::string *n)
 	else	num_hidden++;
 }
 
-HGVertex::~HGVertex()
-{	//std::cout << "deleting vertex at " << first_waypoint->str() << std::endl;
-	delete[] s_vertex_num;
-	delete[] c_vertex_num;
-	delete[] t_vertex_num;
-}
-
 HGEdge* HGVertex::front(unsigned char format)
 {	for (HGEdge* e : incident_edges)
 	  if (e->format & format)
@@ -66,3 +58,12 @@ HGEdge* HGVertex::back(unsigned char format)
 	// Nonetheless, let's stop the compiler from complaining.
 	throw this;
 }
+
+void HGVertex::format_coordstr()
+{	// sanity checks to avoid buffer overflows via >3 digits to L of decimal point
+	while (lat > 90)	lat -= 360;
+	while (lat < -90)	lat += 360;
+	while (lng >= 540)	lng -= 360;
+	while (lng <= -540)	lng += 360;
+	*fmt::format_to(coordstr, " {:.15} {:.15}", lat, lng) = 0;
+}
diff --git a/siteupdate/cplusplus/classes/GraphGeneration/HGVertex.h b/siteupdate/cplusplus/classes/GraphGeneration/HGVertex.h
index 61d61d5d..1cd1ffbf 100644
--- a/siteupdate/cplusplus/classes/GraphGeneration/HGVertex.h
+++ b/siteupdate/cplusplus/classes/GraphGeneration/HGVertex.h
@@ -14,17 +14,16 @@ class HGVertex
 	double lat, lng;
 	const std::string *unique_name;
 	std::vector<HGEdge*> incident_edges;
-	int *s_vertex_num;
-	int *c_vertex_num;
-	int *t_vertex_num;
 	uint16_t edge_count;
 	char visibility;
+	char coordstr[45]; // only need 43, but alignment requires extra anyway
 
 	static std::atomic_uint num_hidden;
+	static thread_local int* vnums;
 
 	void setup(Waypoint*, const std::string*);
-	~HGVertex();
 
 	HGEdge* front(unsigned char);
 	HGEdge* back (unsigned char);
+	void format_coordstr();
 };
diff --git a/siteupdate/cplusplus/classes/GraphGeneration/HighwayGraph.cpp b/siteupdate/cplusplus/classes/GraphGeneration/HighwayGraph.cpp
index 3d9d6b74..651a0679 100644
--- a/siteupdate/cplusplus/classes/GraphGeneration/HighwayGraph.cpp
+++ b/siteupdate/cplusplus/classes/GraphGeneration/HighwayGraph.cpp
@@ -14,8 +14,7 @@
 #include "../Waypoint/Waypoint.h"
 #include "../WaypointQuadtree/WaypointQuadtree.h"
 #include "../../templates/contains.cpp"
-#include <fmt/format.h>
-#include <fstream>
+#include <fmt/ostream.h>
 #include <thread>
 
 HighwayGraph::HighwayGraph(WaypointQuadtree &all_waypoints, ElapsedTime &et)
@@ -374,13 +373,13 @@ void HighwayGraph::write_master_graphs_tmg()
 	unsigned int sv = 0;
 	unsigned int cv = 0;
 	unsigned int tv = 0;
-	char fstr[57];
+	int* vnum = HGVertex::vnums;
 	for (HGVertex& v : vertices)
-	{	*fmt::format_to(fstr, " {:.15} {:.15}", v.lat, v.lng) = 0;
-		switch (v.visibility) // fall-thru is a Good Thing!
-		{ case 2:  collapfile << *(v.unique_name) << fstr << '\n'; v.c_vertex_num[0] = cv++;
-		  case 1:  travelfile << *(v.unique_name) << fstr << '\n'; v.t_vertex_num[0] = tv++;
-		  default: simplefile << *(v.unique_name) << fstr << '\n'; v.s_vertex_num[0] = sv++;
+	{	switch (v.visibility) // fall-thru is a Good Thing!
+		{ case 2:  collapfile << *(v.unique_name) << v.coordstr << '\n'; vnum[1] = cv++;
+		  case 1:  travelfile << *(v.unique_name) << v.coordstr << '\n'; vnum[2] = tv++;
+		  default: simplefile << *(v.unique_name) << v.coordstr << '\n'; vnum[0] = sv++;
+			   vnum += 3;
 		}
 	}
 
@@ -393,16 +392,28 @@ void HighwayGraph::write_master_graphs_tmg()
 	// write edges
 	//TODO: multiple functions performing the same instructions for multiple files?
 	for (HGEdge *e = edges.begin(), *end = edges.end(); e != end; ++e)
-	{ if (e->format & HGEdge::collapsed)
-		e->collapsed_tmg_line(collapfile, fstr, 0, 0);
+	{ int* v1num = HGVertex::vnums+(e->vertex1-vertices.data())*3;
+	  int* v2num = HGVertex::vnums+(e->vertex2-vertices.data())*3;
+
+	  if (e->format & HGEdge::collapsed)
+	  {	fmt::print(collapfile, "{} {} ", v1num[1], v2num[1]);
+		collapfile << e->segment_name;
+		for (HGVertex *intermediate : e->intermediate_points)
+			collapfile << intermediate->coordstr;
+		collapfile << '\n';
+	  }
 	  if (e->format & HGEdge::traveled)
 	  {	for (char*n=cbycode; n<cbycode+nibbles; ++n) *n = '0';
-		e->traveled_tmg_line(travelfile, fstr, 0, 0, TravelerList::allusers.size, cbycode);
+		fmt::print(travelfile, "{} {} ", v1num[2], v2num[2]);
+		travelfile << e->segment_name;
+		travelfile << ' ' << (TravelerList::allusers.size ? e->segment->clinchedby_code(cbycode, 0) : "0");
+		for (HGVertex *intermediate : e->intermediate_points)
+			travelfile << intermediate->coordstr;
+		travelfile << '\n';
 	  }
 	  if (e->format & HGEdge::simple)
-	  {	simplefile << e->vertex1->s_vertex_num[0] << ' '
-			   << e->vertex2->s_vertex_num[0] << ' ';
-		e->segment->write_label(simplefile, 0);
+	  {	fmt::print(simplefile, "{} {} ", v1num[0], v2num[0]);
+		simplefile << e->segment_name;
 		simplefile << '\n';
 	  }
 	}
@@ -466,16 +477,11 @@ void HighwayGraph::write_subgraphs_tmg
 	travelfile << tv_count << ' ' << te_count << ' ' << travnum << '\n';
 
 	// write vertices
-	unsigned int sv = 0;
-	unsigned int cv = 0;
-	unsigned int tv = 0;
-	char fstr[57];
 	for (HGVertex *v : mv)
-	{	*fmt::format_to(fstr, " {:.15} {:.15}", v->lat, v->lng) = 0;
-		switch(v->visibility) // fall-thru is a Good Thing!
-		{ case 2:  collapfile << *(v->unique_name) << fstr << '\n'; v->c_vertex_num[threadnum] = cv++;
-		  case 1:  travelfile << *(v->unique_name) << fstr << '\n'; v->t_vertex_num[threadnum] = tv++;
-		  default: simplefile << *(v->unique_name) << fstr << '\n'; v->s_vertex_num[threadnum] = sv++;
+	{	switch(v->visibility) // fall-thru is a Good Thing!
+		{ case 2:  collapfile << *(v->unique_name) << v->coordstr << '\n';
+		  case 1:  travelfile << *(v->unique_name) << v->coordstr << '\n';
+		  default: simplefile << *(v->unique_name) << v->coordstr << '\n';
 		}
 	}
 
@@ -487,17 +493,35 @@ void HighwayGraph::write_subgraphs_tmg
 
 	// write edges
 	for (HGEdge *e : me) //TODO: multiple functions performing the same instructions for multiple files?
-	{ if (e->format & HGEdge::simple)
-	  {	simplefile << e->vertex1->s_vertex_num[threadnum] << ' '
-			   << e->vertex2->s_vertex_num[threadnum] << ' ';
-		e->segment->write_label(simplefile, g->systems);
+	{ int* v1num = HGVertex::vnums+(e->vertex1-vertices.data())*3;
+	  int* v2num = HGVertex::vnums+(e->vertex2-vertices.data())*3;
+
+	  if (e->format & HGEdge::simple)
+	  {	fmt::print(simplefile, "{} {} ", v1num[0], v2num[0]);
+		if (g->systems)
+			e->segment->write_label(simplefile, g->systems);
+		else	simplefile << e->segment_name;
 		simplefile << '\n';
 	  }
 	  if (e->format & HGEdge::collapsed)
-		e->collapsed_tmg_line(collapfile, fstr, threadnum, g->systems);
+	  {	fmt::print(collapfile, "{} {} ", v1num[1], v2num[1]);
+		if (g->systems)
+			e->segment->write_label(collapfile, g->systems);
+		else	collapfile << e->segment_name;
+		for (HGVertex *intermediate : e->intermediate_points)
+			collapfile << intermediate->coordstr;
+		collapfile << '\n';
+	  }
 	  if (e->format & HGEdge::traveled)
 	  {	for (char*n=cbycode; n<cbycode+nibbles; ++n) *n = '0';
-		e->traveled_tmg_line (travelfile, fstr, threadnum, g->systems, travnum, cbycode);
+		fmt::print(travelfile, "{} {} ", v1num[2], v2num[2]);
+		if (g->systems)
+			e->segment->write_label(travelfile, g->systems);
+		else	travelfile << e->segment_name;
+		travelfile << ' ' << (travnum ? e->segment->clinchedby_code(cbycode, threadnum) : "0");
+		for (HGVertex *intermediate : e->intermediate_points)
+			travelfile << intermediate->coordstr;
+		travelfile << '\n';
 	  }
 	}
 	delete[] cbycode;
diff --git a/siteupdate/cplusplus/classes/GraphGeneration/get_subgraph_data.cpp b/siteupdate/cplusplus/classes/GraphGeneration/get_subgraph_data.cpp
index 6e153f2e..285d9fab 100644
--- a/siteupdate/cplusplus/classes/GraphGeneration/get_subgraph_data.cpp
+++ b/siteupdate/cplusplus/classes/GraphGeneration/get_subgraph_data.cpp
@@ -49,12 +49,13 @@ else {	// We know there's a PlaceRadius, as no GraphListEntry
 	me.shrink_to_fit();
      }
 
-// count vertices
+// count vertices & initialize vertex numbers
 for (HGVertex* v : mv)
-{	switch (v->visibility) // fall-thru is a Good Thing!
-	{	case 2:	 cv_count++;
-		case 1:	 tv_count++;
-		default: sv_count++;
+{	int* vnum = HGVertex::vnums+(v-vertices.data())*3;
+	switch (v->visibility) // fall-thru is a Good Thing!
+	{	case 2:	 vnum[1] = cv_count++;
+		case 1:	 vnum[2] = tv_count++;
+		default: vnum[0] = sv_count++;
 	}
 }
 
diff --git a/siteupdate/cplusplus/classes/HighwaySegment/HighwaySegment.cpp b/siteupdate/cplusplus/classes/HighwaySegment/HighwaySegment.cpp
index 8e9e9f90..deb4f39b 100644
--- a/siteupdate/cplusplus/classes/HighwaySegment/HighwaySegment.cpp
+++ b/siteupdate/cplusplus/classes/HighwaySegment/HighwaySegment.cpp
@@ -97,12 +97,13 @@ const char* HighwaySegment::clinchedby_code(char* code, unsigned int threadnum)
 	return code;
 }
 
-// compute an edge label, optionally restricted by systems
+// write an edge label, restricted by systems
 void HighwaySegment::write_label(std::ofstream& file, std::vector<HighwaySystem*> *systems)
 {	if (concurrent)
 	     {	bool write_comma = 0;
 		for (HighwaySegment* cs : *concurrent)
-		  if ( !cs->route->system->devel() && (!systems || contains(*systems, cs->route->system)) )
+		  // This function is only called when systems is nonzero. Safe to dereference.
+		  if ( !cs->route->system->devel() && contains(*systems, cs->route->system) )
 		  {	if  (write_comma) file << ',';
 			else write_comma = 1;
 			file << cs->route->route;
diff --git a/siteupdate/cplusplus/tasks/graph_generation.cpp b/siteupdate/cplusplus/tasks/graph_generation.cpp
index fcee32fd..4e75ba39 100644
--- a/siteupdate/cplusplus/tasks/graph_generation.cpp
+++ b/siteupdate/cplusplus/tasks/graph_generation.cpp
@@ -12,6 +12,14 @@ graph_data.waypoint_naming_log.clear();
 {	// Let's keep these braces here, for easily commenting out subgraph generation when developing waypoint simplification routines
 	GraphListEntry::num = 3;
 
+	cout << et.et() << "Formatting vertex coordinate strings." << endl;
+      #ifdef threading_enabled
+	THREADLOOP thr[t] = thread(VtxFmtThread, t, &graph_data.vertices);
+	THREADLOOP thr[t].join();
+      #else
+	for (HGVertex& v : graph_data.vertices) v.format_coordstr();
+      #endif
+
 	cout << et.et() << "Writing master TM graph files." << endl;
 	// print summary info
 	std::cout << "   Simple graph has " << graph_data.vertices.size() << " vertices, " << graph_data.se << " edges." << std::endl;
@@ -26,10 +34,12 @@ graph_data.waypoint_naming_log.clear();
 	  thr[t] = thread(SubgraphThread, t, &list_mtx, &term_mtx, &graph_data, &all_waypoints, &et);
 	THREADLOOP thr[t].join();
       #else
+	HGVertex::vnums = new int[graph_data.vertices.size()*3];
 	for (	graph_data.write_master_graphs_tmg();
 		GraphListEntry::num < GraphListEntry::entries.size();
 		GraphListEntry::num += 3
 	    )	graph_data.write_subgraphs_tmg(GraphListEntry::num, 0, &all_waypoints, &et, &term_mtx);
+	delete[] HGVertex::vnums;
       #endif
 	cout << '!' << endl;
 } //*/
diff --git a/siteupdate/cplusplus/threads/MasterTmgThread.cpp b/siteupdate/cplusplus/threads/MasterTmgThread.cpp
index 23b1f898..ececcc86 100644
--- a/siteupdate/cplusplus/threads/MasterTmgThread.cpp
+++ b/siteupdate/cplusplus/threads/MasterTmgThread.cpp
@@ -1,4 +1,6 @@
 void MasterTmgThread(HighwayGraph* graph_data, std::mutex* l, std::mutex* t, WaypointQuadtree *qt, ElapsedTime *et)
-{	graph_data->write_master_graphs_tmg();
+{	HGVertex::vnums = new int[graph_data->vertices.size()*3];
+	graph_data->write_master_graphs_tmg();
+	delete[] HGVertex::vnums;
 	SubgraphThread(0, l, t, graph_data, qt, et);
 }
diff --git a/siteupdate/cplusplus/threads/SubgraphThread.cpp b/siteupdate/cplusplus/threads/SubgraphThread.cpp
index 84bf5e4f..26f7690e 100644
--- a/siteupdate/cplusplus/threads/SubgraphThread.cpp
+++ b/siteupdate/cplusplus/threads/SubgraphThread.cpp
@@ -3,6 +3,7 @@ void SubgraphThread
 	HighwayGraph* graph_data, WaypointQuadtree* qt, ElapsedTime* et
 )
 {	//std::cout << "Starting SubgraphThread " << id << std::endl;
+	HGVertex::vnums = new int[graph_data->vertices.size()*3];
 	while (GraphListEntry::num < GraphListEntry::entries.size())
 	{	l->lock();
 		if (GraphListEntry::num >= GraphListEntry::entries.size())
@@ -16,4 +17,5 @@ void SubgraphThread
 		l->unlock();
 		graph_data->write_subgraphs_tmg(i, id, qt, et, t);
 	}
+	delete[] HGVertex::vnums;
 }
diff --git a/siteupdate/cplusplus/threads/VtxFmtThread.cpp b/siteupdate/cplusplus/threads/VtxFmtThread.cpp
new file mode 100644
index 00000000..ec4ada06
--- /dev/null
+++ b/siteupdate/cplusplus/threads/VtxFmtThread.cpp
@@ -0,0 +1,4 @@
+void VtxFmtThread(unsigned int id, std::vector<HGVertex>* vertices)
+{	for (auto v = vertices->begin()+id, end = vertices->end(); v < end; v += Args::numthreads)
+		v->format_coordstr();
+}
diff --git a/siteupdate/cplusplus/threads/threads.cpp b/siteupdate/cplusplus/threads/threads.cpp
index 302c9822..ea0a3a36 100644
--- a/siteupdate/cplusplus/threads/threads.cpp
+++ b/siteupdate/cplusplus/threads/threads.cpp
@@ -1,5 +1,6 @@
 #include "threads.h"
 #include "../classes/GraphGeneration/GraphListEntry.h"
+#include "../classes/GraphGeneration/HGVertex.h"
 #include "../classes/GraphGeneration/HighwayGraph.h"
 #include "../classes/HighwaySegment/HighwaySegment.h"
 #include "../classes/HighwaySystem/HighwaySystem.h"
@@ -22,3 +23,4 @@
 #include "StatsCsvThread.cpp"
 #include "SubgraphThread.cpp"
 #include "UserLogThread.cpp"
+#include "VtxFmtThread.cpp"
diff --git a/siteupdate/cplusplus/threads/threads.h b/siteupdate/cplusplus/threads/threads.h
index 367aac85..aa24ee9f 100644
--- a/siteupdate/cplusplus/threads/threads.h
+++ b/siteupdate/cplusplus/threads/threads.h
@@ -1,5 +1,6 @@
 class ElapsedTime;
 class ErrorList;
+class HGVertex;
 class HighwayGraph;
 class WaypointQuadtree;
 #include <mutex>
@@ -16,3 +17,4 @@ void RteIntThread    (unsigned int, std::mutex*, ErrorList*);
 void StatsCsvThread  (unsigned int, std::mutex*);
 void SubgraphThread  (unsigned int, std::mutex*, std::mutex*, HighwayGraph*, WaypointQuadtree*, ElapsedTime*);
 void UserLogThread   (unsigned int, std::mutex*, const double, const double);
+void VtxFmtThread    (unsigned int, std::vector<HGVertex>*);