diff --git a/editor/src/main.rs b/editor/src/main.rs
index 102662d6e1..996f3c6e42 100644
--- a/editor/src/main.rs
+++ b/editor/src/main.rs
@@ -61,12 +61,22 @@ struct Flags {
     /// Scenario name for savestating
     #[structopt(long = "scenario_name", default_value = "editor")]
     scenario_name: String,
+
+    /// Name of map edits
+    #[structopt(long = "edits_name", default_value = "no_edits")]
+    edits_name: String,
 }
 
 fn main() {
     let flags = Flags::from_args();
     ezgui::run(
-        ui::UIWrapper::new(flags.load, flags.scenario_name, flags.rng_seed, flags.kml),
+        ui::UIWrapper::new(
+            flags.load,
+            flags.scenario_name,
+            flags.edits_name,
+            flags.rng_seed,
+            flags.kml,
+        ),
         "A/B Street",
         1024,
         768,
diff --git a/editor/src/ui.rs b/editor/src/ui.rs
index e4d36ac242..b7c8458d9b 100644
--- a/editor/src/ui.rs
+++ b/editor/src/ui.rs
@@ -68,6 +68,7 @@ impl UIWrapper {
     pub fn new(
         load: String,
         scenario_name: String,
+        edits_name: String,
         rng_seed: Option<u8>,
         kml: Option<String>,
     ) -> UIWrapper {
@@ -78,6 +79,7 @@ impl UIWrapper {
         let (map, control_map, sim) = sim::load(
             load,
             scenario_name,
+            edits_name,
             rng_seed,
             Some(sim::Tick::from_seconds(30)),
         );
@@ -384,10 +386,11 @@ impl UI {
             // TODO maybe make state line up with the map, so loading from a new map doesn't break
             abstutil::write_json("editor_state", &state).expect("Saving editor_state failed");
             abstutil::write_json("color_scheme", &self.cs).expect("Saving color_scheme failed");
+            // TODO do this from a plugin!
             abstutil::write_json(
-                "map_edits.json",
+                &format!("../data/edits/{}/ui.json", self.map.get_name()),
                 &MapEdits {
-                    edits_name: "nameless".to_string(),
+                    edits_name: "ui".to_string(),
                     map_name: self.map.get_name().to_string(),
                     road_edits: self.road_editor.get_edits().clone(),
                     stop_signs: self.control_map.get_stop_signs_savestate(),
diff --git a/headless/src/main.rs b/headless/src/main.rs
index 5da3c2b24d..77a604066d 100644
--- a/headless/src/main.rs
+++ b/headless/src/main.rs
@@ -36,6 +36,10 @@ struct Flags {
     /// Scenario name for savestating
     #[structopt(long = "scenario_name", default_value = "headless")]
     scenario_name: String,
+
+    /// Name of map edits
+    #[structopt(long = "edits_name", default_value = "no_edits")]
+    edits_name: String,
 }
 
 fn main() {
@@ -47,6 +51,7 @@ fn main() {
     let (map, control_map, mut sim) = sim::load(
         flags.load.clone(),
         flags.scenario_name,
+        flags.edits_name,
         flags.rng_seed,
         Some(sim::Tick::from_seconds(30)),
     );
diff --git a/sim/src/edits.rs b/sim/src/edits.rs
index dccb822bc2..b36719c315 100644
--- a/sim/src/edits.rs
+++ b/sim/src/edits.rs
@@ -15,7 +15,7 @@ pub struct MapEdits {
 impl MapEdits {
     pub fn new() -> MapEdits {
         MapEdits {
-            edits_name: "unnamed".to_string(),
+            edits_name: "no_edits".to_string(),
             map_name: "TODO".to_string(), // TODO er
             road_edits: RoadEdits::new(),
             stop_signs: BTreeMap::new(),
diff --git a/sim/src/helpers.rs b/sim/src/helpers.rs
index 2f1ed12964..c0a7718d90 100644
--- a/sim/src/helpers.rs
+++ b/sim/src/helpers.rs
@@ -11,18 +11,20 @@ use {CarID, Event, MapEdits, PedestrianID, RouteID, Scenario, Sim, Tick};
 pub fn load(
     input: String,
     scenario_name: String,
+    edits_name: String,
     rng_seed: Option<u8>,
     savestate_every: Option<Tick>,
 ) -> (Map, ControlMap, Sim) {
-    // TODO read a specific one
-    let edits: MapEdits = abstutil::read_json("map_edits.json").unwrap_or(MapEdits::new());
-
     if input.contains("data/save/") {
         info!("Resuming from {}", input);
         flame::start("read sim savestate");
         let sim: Sim = abstutil::read_json(&input).expect("loading sim state failed");
         flame::end("read sim savestate");
         // TODO assuming the relative path :(
+        let edits: MapEdits = abstutil::read_json(&format!(
+            "../data/edits/{}/{}.json",
+            sim.map_name, edits_name
+        )).unwrap_or(MapEdits::new());
         let map_path = format!("../data/maps/{}.abst", sim.map_name);
         let map = Map::new(&map_path, edits.road_edits.clone())
             .expect(&format!("Couldn't load map from {}", map_path));
@@ -31,6 +33,10 @@ pub fn load(
     } else if input.contains("data/scenarios/") {
         info!("Seeding the simulation from scenario {}", input);
         let scenario: Scenario = abstutil::read_json(&input).expect("loading scenario failed");
+        let edits: MapEdits = abstutil::read_json(&format!(
+            "../data/edits/{}/{}.json",
+            scenario.map_name, edits_name
+        )).unwrap_or(MapEdits::new());
         let map_path = format!("../data/maps/{}.abst", scenario.map_name);
         let map = Map::new(&map_path, edits.road_edits.clone())
             .expect(&format!("Couldn't load map from {}", map_path));
@@ -44,7 +50,15 @@ pub fn load(
         scenario.instantiate(&mut sim, &map);
         (map, control_map, sim)
     } else {
+        // TODO relative dir is brittle; match more cautiously
+        let map_name = input
+            .trim_left_matches("../data/maps/")
+            .trim_right_matches(".abst")
+            .to_string();
         info!("Loading map {}", input);
+        let edits: MapEdits =
+            abstutil::read_json(&format!("../data/edits/{}/{}.json", map_name, edits_name))
+                .unwrap_or(MapEdits::new());
         let map = Map::new(&input, edits.road_edits.clone()).expect("Couldn't load map");
         let control_map = ControlMap::new(&map, &edits.stop_signs, &edits.traffic_signals);
         flame::start("create sim");
diff --git a/sim/tests/completion.rs b/sim/tests/completion.rs
index 70aec26851..e245793378 100644
--- a/sim/tests/completion.rs
+++ b/sim/tests/completion.rs
@@ -8,6 +8,7 @@ fn aorta_model_completes() {
     let (map, control_map, mut sim) = sim::load(
         "../data/maps/small.abst".to_string(),
         "aorta_model_completes".to_string(),
+        "no_edits".to_string(),
         Some(42),
         Some(sim::Tick::from_seconds(30)),
     );
diff --git a/sim/tests/determinism.rs b/sim/tests/determinism.rs
index 8c7e29aa1b..fc0a1eb768 100644
--- a/sim/tests/determinism.rs
+++ b/sim/tests/determinism.rs
@@ -8,6 +8,7 @@ fn serialization() {
     let (map, _, mut sim) = sim::load(
         "../data/maps/small.abst".to_string(),
         "serialization".to_string(),
+        "no_edits".to_string(),
         Some(42),
         None,
     );
@@ -25,6 +26,7 @@ fn from_scratch() {
     let (map, control_map, mut sim1) = sim::load(
         "../data/maps/small.abst".to_string(),
         "from_scratch_1".to_string(),
+        "no_edits".to_string(),
         Some(42),
         None,
     );
@@ -52,6 +54,7 @@ fn with_savestating() {
     let (map, control_map, mut sim1) = sim::load(
         "../data/maps/small.abst".to_string(),
         "with_savestating_1".to_string(),
+        "no_edits".to_string(),
         Some(42),
         None,
     );
diff --git a/sim/tests/transit.rs b/sim/tests/transit.rs
index 4306e6b228..5a6212319f 100644
--- a/sim/tests/transit.rs
+++ b/sim/tests/transit.rs
@@ -8,6 +8,7 @@ fn bus_reaches_stops() {
     let (map, control_map, mut sim) = sim::load(
         "../data/maps/small.abst".to_string(),
         "bus_reaches_stops".to_string(),
+        "no_edits".to_string(),
         Some(42),
         Some(sim::Tick::from_seconds(30)),
     );
@@ -36,6 +37,7 @@ fn ped_uses_bus() {
     let (map, control_map, mut sim) = sim::load(
         "../data/maps/small.abst".to_string(),
         "bus_reaches_stops".to_string(),
+        "no_edits".to_string(),
         Some(42),
         Some(sim::Tick::from_seconds(30)),
     );