diff --git a/book/src/dev/api.md b/book/src/dev/api.md
index 4e00e158fa..139d3cc1dc 100644
--- a/book/src/dev/api.md
+++ b/book/src/dev/api.md
@@ -70,6 +70,8 @@ are missing, etc. A summary of the commands available so far:
     [PermanentMapEdits](https://dabreegster.github.io/abstreet/rustdoc/map_model/struct.PermanentMapEdits.html)
     in JSON format. This is the same as the files in `data/player/edits/`. The
     edits will remain as you call `/sim/reset`, but get reset with `/sim/load`.
+  - **GET /map/get-edit-road-command?id=123**: Returns an object that can be
+    modified and then added to map edits.
 
 ## Working with the map model
 
diff --git a/headless/examples/abst_helpers.py b/headless/examples/abst_helpers.py
index 47c22a8ca0..1fd6316f7b 100644
--- a/headless/examples/abst_helpers.py
+++ b/headless/examples/abst_helpers.py
@@ -3,11 +3,13 @@ import statistics
 
 
 # Returns Results
-def run_sim(args, modifiers=[]):
+def run_sim(args, modifiers=[], edits=None):
     requests.post(args.api + '/sim/load', json={
         'load': 'data/system/scenarios/{}/weekday.bin'.format(args.map_name),
         'modifiers': modifiers,
     })
+    if edits:
+        requests.post(args.api + '/map/set-edits', json=edits)
     requests.get(args.api + '/sim/goto-time',
                  params={'t': '{}:00:00'.format(args.hours)})
     raw_trips = requests.get(
@@ -49,6 +51,13 @@ class Results:
                     slower.append(after_dt - before_dt)
 
         print('{:,} trips faster, average {:.1f}s savings'.format(
-            len(faster), statistics.mean(faster)))
+            len(faster), avg(faster)))
         print('{:,} trips slower, average {:.1f}s loss'.format(
-            len(slower), statistics.mean(slower)))
+            len(slower), avg(slower)))
+
+
+def avg(data):
+    if data:
+        return statistics.mean(data)
+    else:
+        return 0.0
diff --git a/headless/examples/cap_experiment.py b/headless/examples/cap_experiment.py
index 82a69c9a43..2ff6d51cab 100755
--- a/headless/examples/cap_experiment.py
+++ b/headless/examples/cap_experiment.py
@@ -21,13 +21,32 @@ def main():
     parser.add_argument('--api', default='http://localhost:1234')
     parser.add_argument('--map_name', default='montlake')
     parser.add_argument('--hours', type=int, default=24)
+    parser.add_argument('--cap_pct', type=int, default=80)
     args = parser.parse_args()
     print('Simulating {} hours of data/system/scenarios/{}/weekday.bin'.format(args.hours, args.map_name))
     print('')
 
     baseline = abst_helpers.run_sim(args)
+    busiest_road, thruput = find_busiest_road(args)
 
-    # Find the road with the most car traffic in any one hour period
+    # Cap that road
+    edits = requests.get(args.api + '/map/get-edits').json()
+    cmd = requests.get(args.api + '/map/get-edit-road-command',
+                       params={'id': busiest_road}).json()
+    cmd['ChangeRoad']['new']['access_restrictions']['cap_vehicles_per_hour'] = int(
+        (args.cap_pct / 100.0) * thruput)
+    edits['commands'].append(cmd)
+
+    # See what happened
+    print('Rerunning with {}% cap on that road'.format(args.cap_pct))
+    print('')
+    experiment = abst_helpers.run_sim(args, edits=edits)
+    busiest_road, thruput = find_busiest_road(args)
+    baseline.compare(experiment)
+
+
+# Find the road with the most car traffic in any one hour period
+def find_busiest_road(args):
     thruput = requests.get(
         args.api + '/data/get-road-thruput').json()['counts']
     max_key = None
@@ -39,6 +58,7 @@ def main():
                 max_value = count
     print('Busiest road is #{}, with {} cars crossing during hour {}'.format(
         max_key[0], max_value, max_key[1]))
+    return (max_key[0], max_value)
 
 
 if __name__ == '__main__':
diff --git a/headless/src/main.rs b/headless/src/main.rs
index 44fef7cfb2..2f7966f25b 100644
--- a/headless/src/main.rs
+++ b/headless/src/main.rs
@@ -274,6 +274,12 @@ fn handle_command(
             apply_edits(map);
             Ok(format!("loaded edits"))
         }
+        "/map/get-edit-road-command" => {
+            let r = RoadID(params["id"].parse::<usize>()?);
+            Ok(abstutil::to_json(
+                &map.edit_road_cmd(r, |_| {}).to_perma(map),
+            ))
+        }
         _ => Err("Unknown command".into()),
     }
 }
diff --git a/map_model/src/edits/perma.rs b/map_model/src/edits/perma.rs
index 72e6c7f065..d01aabecd8 100644
--- a/map_model/src/edits/perma.rs
+++ b/map_model/src/edits/perma.rs
@@ -22,7 +22,7 @@ pub struct PermanentMapEdits {
 }
 
 #[derive(Serialize, Deserialize, Clone)]
-pub(crate) enum PermanentEditIntersection {
+pub enum PermanentEditIntersection {
     StopSign {
         #[serde(
             serialize_with = "serialize_btreemap",
@@ -35,7 +35,7 @@ pub(crate) enum PermanentEditIntersection {
 }
 
 #[derive(Serialize, Deserialize, Clone)]
-pub(crate) enum PermanentEditCmd {
+pub enum PermanentEditCmd {
     ChangeRoad {
         r: OriginalRoad,
         new: EditRoad,
@@ -54,7 +54,7 @@ pub(crate) enum PermanentEditCmd {
 }
 
 impl EditCmd {
-    pub(crate) fn to_perma(&self, map: &Map) -> PermanentEditCmd {
+    pub fn to_perma(&self, map: &Map) -> PermanentEditCmd {
         match self {
             EditCmd::ChangeRoad { r, new, old } => PermanentEditCmd::ChangeRoad {
                 r: map.get_r(*r).orig_id,