diff --git a/Convert_Matlab/overlap_v6.py b/Convert_Matlab/overlap_v6.py
index 69c0961a6d356eca89cbad22e246605644b5047a..a5f82966088c68569af346aaa6a253203afaed81 100755
--- a/Convert_Matlab/overlap_v6.py
+++ b/Convert_Matlab/overlap_v6.py
@@ -55,9 +55,7 @@ if __name__ == "__main__":
     e_overestim = id_child.shape[0]
     print("e_overestim =", e_overestim)
     d_init = to_days_1950(date_num[0])
-
-    with open("node_id_param.json", "w") as f:
-        json.dump({"e_overestim": e_overestim, "d_init": d_init}, f)
+    with open("e_overestim.txt", "w") as f: f.write(str(e_overestim) + "\n")
 
     with open("edgelist.csv", "w", newline = '') as edgelist:
         writer = csv.writer(edgelist, delimiter = ' ', lineterminator = "\n")
diff --git a/Inst_eddies/Analysis/eddy_dump.py b/Inst_eddies/Analysis/eddy_dump.py
index a9be69ed4929035bb585e2b91e13468e5ba7e576..3e32309f0e2caab94edb93c621a4a17b1933fda9 100755
--- a/Inst_eddies/Analysis/eddy_dump.py
+++ b/Inst_eddies/Analysis/eddy_dump.py
@@ -27,9 +27,9 @@ if args.ishape:
     ishape = args.ishape
 else:
     if args.node:
-        with open("node_id_param.json") as f: node_id_param = json.load(f)
-        date, eddy_index = report_graph\
-            .node_to_date_eddy(args.node, node_id_param["e_overestim"])
+        with open("e_overestim.txt") as f: e_overestim = int(f.read())
+        date, eddy_index = report_graph.node_to_date_eddy(args.node,
+                                                          e_overestim)
     else:
         reply = input("date, eddy_index = ? ").split(",")
         date = int(reply[0])
diff --git a/Overlap/Tests/test_overlap.f90 b/Overlap/Tests/test_overlap.f90
index f5c8f8e4672badd3fa546a0a530ccff5014f859d..c95e675bce4b3b71a55c3b7b774cca47f9abfb25 100644
--- a/Overlap/Tests/test_overlap.f90
+++ b/Overlap/Tests/test_overlap.f90
@@ -70,9 +70,8 @@ program test_overlap
        < hshp%d0 + n_dates, "test_overlap k_test_1, k_test_2")
   e_overestim = maxval([hshp%ishape_last(hshp%d0) + 1, &
        ediff1d(hshp%ishape_last)])
-  open(unit, file = "node_id_param.json", status = "replace", &
-       action = "write")
-  write(unit, fmt = *) '{"e_overestim": ', e_overestim, '}'
+  open(unit, file = "e_overestim.txt", status = "replace", action = "write")
+  write(unit, fmt = *) e_overestim
   close(unit)
   call read_snapshot(flow(1), [hshp], nlon, nlat, k_test_1, corner, step, copy)
   call read_snapshot(flow(max_delta + 1), [hshp], nlon, nlat, k_test_2, &
diff --git a/Overlap/eddy_graph.f90 b/Overlap/eddy_graph.f90
index 35f6ba1725c116ab3b72c11b59ab39d8da1db85a..6b999e1f17a8f8e0d9a2c4d0e8dfaf9c32f769bd 100644
--- a/Overlap/eddy_graph.f90
+++ b/Overlap/eddy_graph.f90
@@ -112,9 +112,8 @@ program eddy_graph
           "eddy_graph: n_proc should be <= n_dates / (max_delta + 1)")
      e_overestim = maxval([(hshpc(i)%ishape_last(hshpc(i)%d0) + 1, &
           ediff1d(hshpc(i)%ishape_last), i = 1, n_shpc)])
-     open(unit, file = "node_id_param.json", status = "replace", &
-          action = "write")
-     write(unit, fmt = *) '{"e_overestim": ', e_overestim, '}'
+     open(unit, file = "e_overestim.txt", status = "replace", action = "write")
+     write(unit, fmt = *) e_overestim
      close(unit)
      corner = corner_deg * deg_to_rad
      step = step_deg * deg_to_rad
diff --git a/Overlap/eddy_graph.sh.in b/Overlap/eddy_graph.sh.in
index e5c28f7419d41a7220d617f5c291185b88ad97dd..40c5bf6379b5147d8a47a4b0aa9e4b514d6e35be 100644
--- a/Overlap/eddy_graph.sh.in
+++ b/Overlap/eddy_graph.sh.in
@@ -34,4 +34,4 @@ sort --key=1,1 --key=2,2 --numeric-sort --output=edgelist.csv \
 rm edgelist_unsorted.csv
 
 echo "Created files \"edgelist.csv\", \"isolated_nodes.txt\" and " \
-     "\"node_id_param.json\"."
+     "\"e_overestim.txt\"."
diff --git a/Overlap/report_graph.py b/Overlap/report_graph.py
index 76b3504eaa5769550b77c629fdd5d55168a7112b..1990f49fbf3d08d4444f110b3b2a209786888070 100755
--- a/Overlap/report_graph.py
+++ b/Overlap/report_graph.py
@@ -32,9 +32,8 @@ def read_eddy_graph(edgelist, shpc_dir = None):
         G = nx.read_edgelist(edgelist, create_using = nx.DiGraph,
                              nodetype = int)
         dir_edgelist = path.dirname(edgelist)
-        node_id_param_file = path.join(dir_edgelist, "node_id_param.json")
-        with open(node_id_param_file) as f: node_id_param = json.load(f)
-        G.graph["e_overestim"] = node_id_param["e_overestim"]
+        e_overestim_file = path.join(dir_edgelist, "e_overestim.txt")
+        with open(e_overestim_file) as f: G.graph["e_overestim"] = int(f.read())
 
         if shpc_dir is not None:
             # Read and set attributes of eddies:
diff --git a/Trajectories/cost_function.py b/Trajectories/cost_function.py
index 7dc58f11392bdee7987684ed3c2121018225eada..83dc3fb56b9bafce4204e33e688357af1c997e00 100755
--- a/Trajectories/cost_function.py
+++ b/Trajectories/cost_function.py
@@ -5,7 +5,7 @@ computes the non-local cost functions applied to edges.
 
 Input:
 
-- "node_id_param.json", expected to be in the current directory
+- "e_overestim.txt", expected to be in the current directory
 
 - the graph of segments without cost functions, "segments.gt" or
   "segments.graphml", expected to be in the current directory
@@ -95,10 +95,7 @@ parser.add_argument("SHPC_dir", nargs='+')
 parser.add_argument("--graphml", action = "store_true",
                     help = "save to graphml format")
 args = parser.parse_args()
-
-# Grab e_overestim:
-with open("node_id_param.json") as f: node_id_param = json.load(f)
-e_overestim = node_id_param["e_overestim"]
+with open("e_overestim.txt") as f: e_overestim = int(f.read())
 
 # Set some values needed for the cost function:
 
diff --git a/Trajectories/tests.json b/Trajectories/tests.json
index 521960c3fbadd565dc5bdc78c750be27d78279dc..ece315aaf4bd8d6f1c1e162d0764a096289d1504 100644
--- a/Trajectories/tests.json
+++ b/Trajectories/tests.json
@@ -17,7 +17,7 @@
 	"env": {"PYTHONPATH": "$src_dir/Overlap:$src_dir/Common"},
 	"symlink":
 	[
-	    "$tests_old_dir/EGr2nd15md4/node_id_param.json",
+	    "$tests_old_dir/EGr2nd15md4/e_overestim.txt",
 	    "$tests_old_dir/Segments/segments.graphml"
 	],
 	"exclude_cmp": ["timings.txt"]
@@ -44,7 +44,7 @@
 	"env": {"PYTHONPATH": "$src_dir/Overlap:$src_dir/Common"},
 	"symlink":
 	[
-	    "$tests_old_dir/Greece_graph/node_id_param.json",
+	    "$tests_old_dir/Greece_graph/e_overestim.txt",
 	    "$tests_old_dir/Greece_segments/segments.graphml"
 	]
     },