diff --git a/game/src/edit/mod.rs b/game/src/edit/mod.rs
index be8169cc71..5ebd6eea9b 100644
--- a/game/src/edit/mod.rs
+++ b/game/src/edit/mod.rs
@@ -2,7 +2,7 @@ use std::collections::BTreeSet;
 
 use maplit::btreeset;
 
-use abstutil::Timer;
+use abstutil::{prettyprint_usize, Timer};
 use geom::Speed;
 use map_model::{EditCmd, IntersectionID, LaneID, LaneType, MapEdits};
 use widgetry::{
@@ -98,8 +98,25 @@ impl EditMode {
                 app.primary
                     .sim
                     .handle_live_edited_traffic_signals(&app.primary.map);
-                app.primary.sim.handle_live_edits(&app.primary.map);
-                Transition::Pop
+                let (trips, parked_cars) = app.primary.sim.handle_live_edits(&app.primary.map);
+                if trips == 0 && parked_cars == 0 {
+                    Transition::Pop
+                } else {
+                    Transition::Replace(PopupMsg::new(
+                        ctx,
+                        "Map changes complete",
+                        vec![
+                            format!(
+                                "Your edits interrupted {} trips and displaced {} parked cars",
+                                prettyprint_usize(trips),
+                                prettyprint_usize(parked_cars)
+                            ),
+                            "Simulation results won't be finalized unless you restart from \
+                             midnight with your changes"
+                                .to_string(),
+                        ],
+                    ))
+                }
             } else {
                 Transition::Multi(vec![
                     Transition::Pop,
diff --git a/sim/src/sim/mod.rs b/sim/src/sim/mod.rs
index 5fea73507a..011c7346e5 100644
--- a/sim/src/sim/mod.rs
+++ b/sim/src/sim/mod.rs
@@ -885,10 +885,13 @@ impl Sim {
             .handle_live_edited_traffic_signals(self.time, map, &mut self.scheduler)
     }
 
-    pub fn handle_live_edits(&mut self, map: &Map) {
+    /// Respond to arbitrary map edits without resetting the simulation. Returns the number of
+    /// (trips cancelled, parked cars displaced).
+    pub fn handle_live_edits(&mut self, map: &Map) -> (usize, usize) {
         self.edits_name = map.get_edits().edits_name.clone();
 
-        let affected = self.find_trips_affected_by_live_edits(map);
+        let (affected, num_parked_cars) = self.find_trips_affected_by_live_edits(map);
+        let num_trips_cancelled = affected.len();
 
         // V1: Just cancel every trip crossing an affected area.
         // (V2 is probably rerouting everyone, only cancelling when that fails)
@@ -932,9 +935,12 @@ impl Sim {
 
         self.driving.handle_live_edits(map);
         self.intersections.handle_live_edits(map);
+
+        (num_trips_cancelled, num_parked_cars)
     }
 
-    fn find_trips_affected_by_live_edits(&mut self, map: &Map) -> Vec<(AgentID, TripID)> {
+    /// Returns (trips affected, number of parked cars displaced)
+    fn find_trips_affected_by_live_edits(&mut self, map: &Map) -> (Vec<(AgentID, TripID)>, usize) {
         let mut affected: Vec<(AgentID, TripID)> = Vec::new();
 
         // TODO Handle changes to access restrictions
@@ -964,9 +970,10 @@ impl Sim {
             }
         }
 
-        {
+        let num_evicted = {
             let (evicted_cars, cars_parking_in_the_void) =
                 self.parking.handle_live_edits(map, &mut Timer::throwaway());
+            let num_evicted = evicted_cars.len();
             affected.extend(self.walking.find_trips_to_parking(evicted_cars));
             for car in cars_parking_in_the_void {
                 let a = AgentID::Car(car);
@@ -980,9 +987,10 @@ impl Sim {
                 all_spots.extend(avail);
                 affected.extend(self.driving.find_trips_to_edited_parking(all_spots));
             }
-        }
+            num_evicted
+        };
 
-        affected
+        (affected, num_evicted)
     }
 }