diff --git a/docs/TODO_ux.md b/docs/TODO_ux.md
index 4cf68533fb..dbdb7cc041 100644
--- a/docs/TODO_ux.md
+++ b/docs/TODO_ux.md
@@ -4,6 +4,7 @@
 
 - cache draw stuff
 - lazy SimStats
+	- dont consider it when comparing or serializing
 
 ## Quick n easy
 
diff --git a/editor/src/objects.rs b/editor/src/objects.rs
index 12c0415987..ef3f71455a 100644
--- a/editor/src/objects.rs
+++ b/editor/src/objects.rs
@@ -93,7 +93,7 @@ impl ID {
             ID::Parcel(id) => map.maybe_get_p(id).map(|p| Pt2D::center(&p.points)),
             ID::BusStop(id) => map.maybe_get_bs(id).map(|bs| bs.sidewalk_pos.pt(map)),
             ID::Area(id) => map.maybe_get_a(id).map(|a| Pt2D::center(&a.points)),
-            ID::Trip(id) => sim.get_stats().canonical_pt_per_trip.get(&id).cloned(),
+            ID::Trip(id) => sim.get_canonical_pt_per_trip(id, map),
         }
     }
 }
diff --git a/editor/src/plugins/sim/diff_trip.rs b/editor/src/plugins/sim/diff_trip.rs
index 12e4aed5f7..5b8f69aa2c 100644
--- a/editor/src/plugins/sim/diff_trip.rs
+++ b/editor/src/plugins/sim/diff_trip.rs
@@ -79,10 +79,10 @@ fn diff_trip(trip: TripID, ctx: &mut PluginCtx) -> DiffTripState {
         .map(|(s, _)| (&s.sim, &s.map))
         .unwrap();
 
-    let pt1 = primary_sim.get_stats().canonical_pt_per_trip.get(&trip);
-    let pt2 = secondary_sim.get_stats().canonical_pt_per_trip.get(&trip);
+    let pt1 = primary_sim.get_canonical_pt_per_trip(trip, primary_map);
+    let pt2 = secondary_sim.get_canonical_pt_per_trip(trip, secondary_map);
     let line = if pt1.is_some() && pt2.is_some() {
-        Line::maybe_new(*pt1.unwrap(), *pt2.unwrap())
+        Line::maybe_new(pt1.unwrap(), pt2.unwrap())
     } else {
         None
     };
diff --git a/editor/src/plugins/view/follow.rs b/editor/src/plugins/view/follow.rs
index 7647f4a012..79d78bfe8a 100644
--- a/editor/src/plugins/view/follow.rs
+++ b/editor/src/plugins/view/follow.rs
@@ -28,8 +28,12 @@ impl Plugin for FollowState {
         }
 
         if let Some(trip) = self.trip {
-            if let Some(pt) = ctx.primary.sim.get_stats().canonical_pt_per_trip.get(&trip) {
-                ctx.canvas.center_on_map_pt(*pt);
+            if let Some(pt) = ctx
+                .primary
+                .sim
+                .get_canonical_pt_per_trip(trip, &ctx.primary.map)
+            {
+                ctx.canvas.center_on_map_pt(pt);
             } else {
                 // TODO ideally they wouldnt vanish for so long according to
                 // get_canonical_point_for_trip
diff --git a/sim/src/sim.rs b/sim/src/sim.rs
index 6770dedd22..6bf5b96c7c 100644
--- a/sim/src/sim.rs
+++ b/sim/src/sim.rs
@@ -12,7 +12,7 @@ use crate::{AgentID, CarID, Event, ParkedCar, PedestrianID, SimStats, Tick, Trip
 use abstutil;
 use abstutil::Error;
 use derivative::Derivative;
-use geom::Distance;
+use geom::{Distance, Pt2D};
 use map_model::{BuildingID, IntersectionID, LaneID, LaneType, Map, Path, Trace, Turn};
 use rand::{FromEntropy, SeedableRng};
 use rand_xorshift::XorShiftRng;
@@ -397,23 +397,33 @@ impl Sim {
         &self.stats
     }
 
+    pub fn get_canonical_pt_per_trip(&self, trip: TripID, map: &Map) -> Option<Pt2D> {
+        self.trips_state
+            .trip_to_agent(trip)
+            .and_then(|id| self.canonical_pt_for_agent(id, map))
+    }
+
     fn collect_stats(&mut self, map: &Map) {
         self.stats = SimStats::new(self.time);
         for trip in self.trips_state.get_active_trips().into_iter() {
-            let pt = match self.trips_state.trip_to_agent(trip) {
-                Some(AgentID::Car(id)) => self
-                    .driving_state
-                    .get_draw_car(id, self.time, map)
-                    .map(|c| c.body.last_pt()),
-                Some(AgentID::Pedestrian(id)) => self
-                    .walking_state
-                    .get_draw_ped(id, map, self.time)
-                    .map(|p| p.pos),
-                None => None,
-            };
-            if let Some(pt) = pt {
-                self.stats.canonical_pt_per_trip.insert(trip, pt);
+            if let Some(agent) = self.trips_state.trip_to_agent(trip) {
+                if let Some(pt) = self.canonical_pt_for_agent(agent, map) {
+                    self.stats.canonical_pt_per_trip.insert(trip, pt);
+                }
             }
         }
     }
+
+    fn canonical_pt_for_agent(&self, id: AgentID, map: &Map) -> Option<Pt2D> {
+        match id {
+            AgentID::Car(id) => self
+                .driving_state
+                .get_draw_car(id, self.time, map)
+                .map(|c| c.body.last_pt()),
+            AgentID::Pedestrian(id) => self
+                .walking_state
+                .get_draw_ped(id, map, self.time)
+                .map(|p| p.pos),
+        }
+    }
 }