diff --git a/doc/wip/advtrains_tcb_dump.lua b/doc/wip/advtrains_tcb_dump.lua
new file mode 100644
index 0000000..fe21c12
--- /dev/null
+++ b/doc/wip/advtrains_tcb_dump.lua
@@ -0,0 +1,28 @@
+minetest.after(2, function()
+        local world_path = minetest.get_worldpath()
+        local file, err = io.open(world_path .. "advtrains_tcbs.json", "w")
+
+        local data = advtrains.interlocking.db.save()
+	local tmp = {}
+
+	for _, entry in pairs(data.tcbs) do
+		local tcb = entry[1]
+		-- print(dump(tcb))
+		if tcb.signal then
+			table.insert(tmp, {
+				signal = tcb.signal,
+				aspect = tcb.aspect,
+				signal_name = tcb.signal_name
+			})
+		end
+	end
+
+        local json, err = minetest.write_json(tmp, true)
+
+	if err then
+		error(err)
+	end
+
+        file:write(json)
+        file:close()
+end)
diff --git a/doc/wip/advtrains_tcbs.json b/doc/wip/advtrains_tcbs.json
new file mode 100644
index 0000000..42d6310
--- /dev/null
+++ b/doc/wip/advtrains_tcbs.json
@@ -0,0 +1,222 @@
+[
+   {
+      "signal" : {
+         "x" : -2103,
+         "y" : 22,
+         "z" : 790
+      },
+      "signal_name" : "Signal at (-2109,22,787)"
+   },
+   {
+      "aspect" : {
+         "dst" : {
+            "free" : true,
+            "speed" : -1
+         },
+         "info" : null,
+         "main" : {
+            "free" : true,
+            "speed" : -1
+         },
+         "shunt" : {
+            "free" : false
+         }
+      },
+      "signal" : {
+         "x" : -2125,
+         "y" : 28,
+         "z" : 562
+      },
+      "signal_name" : "Signal at (-2124,28,562)"
+   },
+   {
+      "signal" : {
+         "x" : 10003,
+         "y" : 9699,
+         "z" : 15558
+      },
+      "signal_name" : "Signal at (10003,9696,15559)"
+   },
+   {
+      "aspect" : {
+         "dst" : {
+            "free" : true,
+            "speed" : -1
+         },
+         "info" : null,
+         "main" : {
+            "free" : true,
+            "speed" : -1
+         },
+         "shunt" : {
+            "free" : false
+         }
+      },
+      "signal" : {
+         "x" : 10000,
+         "y" : 9699,
+         "z" : 15391
+      },
+      "signal_name" : "Signal at (10000,9696,15391)"
+   },
+   {
+      "signal" : {
+         "x" : -2087,
+         "y" : 21,
+         "z" : 775
+      },
+      "signal_name" : "Signal at (-2088,21,774)"
+   },
+   {
+      "signal" : {
+         "x" : -1323,
+         "y" : 42,
+         "z" : 393
+      },
+      "signal_name" : "Signal at (-1323,42,392)"
+   },
+   {
+      "aspect" : {
+         "dst" : {
+            "free" : true,
+            "speed" : -1
+         },
+         "info" : null,
+         "main" : {
+            "free" : true,
+            "speed" : -1
+         },
+         "shunt" : {
+            "free" : false
+         }
+      },
+      "signal" : {
+         "x" : 10003,
+         "y" : 9699,
+         "z" : 15027
+      },
+      "signal_name" : "Signal at (10003,9696,15027)"
+   },
+   {
+      "aspect" : {
+         "dst" : {
+            "free" : true,
+            "speed" : -1
+         },
+         "info" : null,
+         "main" : {
+            "free" : true,
+            "speed" : -1
+         },
+         "shunt" : {
+            "free" : false
+         }
+      },
+      "signal" : {
+         "x" : -1044,
+         "y" : 42,
+         "z" : 393
+      },
+      "signal_name" : "Signal at (-1045,42,392)"
+   },
+   {
+      "signal" : {
+         "x" : -1019,
+         "y" : 42,
+         "z" : 396
+      },
+      "signal_name" : "Signal at (-1021,42,395)"
+   },
+   {
+      "signal" : {
+         "x" : -2428,
+         "y" : 18,
+         "z" : 3954
+      },
+      "signal_name" : "Signal at (-2426,18,3953)"
+   },
+   {
+      "signal" : {
+         "x" : -1875,
+         "y" : 42,
+         "z" : 393
+      },
+      "signal_name" : "Signal at (-1875,42,392)"
+   },
+   {
+      "signal" : {
+         "x" : -1925,
+         "y" : 42,
+         "z" : 388
+      },
+      "signal_name" : "Signal at (-1924,42,390)"
+   },
+   {
+      "aspect" : {
+         "dst" : {
+            "free" : true,
+            "speed" : -1
+         },
+         "info" : null,
+         "main" : {
+            "free" : true,
+            "speed" : -1
+         },
+         "shunt" : {
+            "free" : false
+         }
+      },
+      "signal" : {
+         "x" : -1079,
+         "y" : 42,
+         "z" : 393
+      },
+      "signal_name" : "Signal at (-1080,42,392)"
+   },
+   {
+      "signal" : {
+         "x" : 10003,
+         "y" : 9699,
+         "z" : 15160
+      },
+      "signal_name" : "Signal at (10003,9696,15160)"
+   },
+   {
+      "signal" : {
+         "x" : -1292,
+         "y" : 42,
+         "z" : 393
+      },
+      "signal_name" : "Signal at (-1292,42,392)"
+   },
+   {
+      "aspect" : {
+         "dst" : {
+            "free" : true,
+            "speed" : -1
+         },
+         "info" : null,
+         "main" : {
+            "free" : true,
+            "speed" : -1
+         },
+         "shunt" : {
+            "free" : false
+         }
+      },
+      "signal" : {
+         "x" : -2125,
+         "y" : 28,
+         "z" : 595
+      },
+      "signal_name" : "Signal at (-2124,28,593)"
+   },
+   {
+      "signal" : {
+         "x" : 10003,
+         "y" : 9699,
+         "z" : 15249
+      },
+      "signal_name" : "Signal at (10003,9696,15249)"
+   }
+]