diff --git a/game/src/debug/mod.rs b/game/src/debug/mod.rs
index edd76fec6d..984cabbfc7 100644
--- a/game/src/debug/mod.rs
+++ b/game/src/debug/mod.rs
@@ -29,7 +29,6 @@ pub use self::routes::PathCostDebugger;
 
 mod blocked_by;
 mod floodfill;
-mod ltn;
 mod objects;
 pub mod path_counter;
 mod polygons;
@@ -611,7 +610,6 @@ impl ContextualActions for Actions {
                 if cfg!(not(target_arch = "wasm32")) {
                     actions.push((Key::M, "merge short segment".to_string()));
                 }
-                actions.push((Key::L, "LTN mode".to_string()));
             }
             ID::Intersection(i) => {
                 actions.push((Key::H, "hide this".to_string()));
@@ -813,9 +811,6 @@ impl ContextualActions for Actions {
                 abstio::write_json("merge_osm_ways.json".to_string(), &ways);
                 Transition::Push(reimport_map(ctx, app, Some(orig_ways)))
             }
-            (ID::Lane(l), "LTN mode") => {
-                Transition::Push(ltn::Viewer::start_from_road(ctx, app, l.road))
-            }
             (ID::Area(a), "debug area geometry") => {
                 let pts = &app.primary.map.get_a(a).polygon.points();
                 let center = if pts[0] == *pts.last().unwrap() {
diff --git a/game/src/lib.rs b/game/src/lib.rs
index 25f8e4fc3c..1ec427d91d 100644
--- a/game/src/lib.rs
+++ b/game/src/lib.rs
@@ -29,6 +29,7 @@ mod devtools;
 mod edit;
 mod info;
 mod layer;
+mod ltn;
 mod pregame;
 mod sandbox;
 mod ungap;
@@ -49,6 +50,7 @@ struct Setup {
     load_kml: Option<String>,
     diff_map: Option<String>,
     ungap: bool,
+    ltn: bool,
 }
 
 fn run(mut settings: Settings) {
@@ -80,6 +82,7 @@ fn run(mut settings: Settings) {
         load_kml: args.optional("--kml"),
         diff_map: args.optional("--diff"),
         ungap: args.enabled("--ungap"),
+        ltn: args.enabled("--ltn"),
     };
 
     settings = settings.canvas_settings(setup.opts.canvas_settings.clone());
@@ -158,7 +161,8 @@ fn setup_app(ctx: &mut EventCtx, mut setup: Setup) -> (App, Vec<Box<dyn State<Ap
         && !setup.flags.sim_flags.load.contains("player/save")
         && !setup.flags.sim_flags.load.contains("/scenarios/")
         && setup.maybe_mode.is_none()
-        && !setup.ungap;
+        && !setup.ungap
+        && !setup.ltn;
 
     // Load the map used previously if we're starting on the title screen without any overrides.
     if title && setup.flags.sim_flags.load == MapName::seattle("montlake").path() {
@@ -184,7 +188,7 @@ fn setup_app(ctx: &mut EventCtx, mut setup: Setup) -> (App, Vec<Box<dyn State<Ap
     if title {
         setup.opts.color_scheme = map_gui::colors::ColorSchemeChoice::Pregame;
     }
-    if setup.ungap {
+    if setup.ungap || setup.ltn {
         setup.opts.color_scheme = map_gui::colors::ColorSchemeChoice::DayMode;
     }
     let cs = map_gui::colors::ColorScheme::new(ctx, setup.opts.color_scheme);
@@ -415,6 +419,8 @@ fn finish_app_setup(
     } else if setup.ungap {
         let layers = ungap::Layers::new(ctx, app);
         vec![ungap::ExploreMap::new_state(ctx, app, layers)]
+    } else if setup.ltn {
+        vec![ltn::Viewer::start_anywhere(ctx, app)]
     } else {
         // Not attempting to keep the primary and secondary simulations synchronized at the same
         // time yet. Just handle this one startup case, so we can switch maps without constantly
diff --git a/game/src/debug/ltn/algorithms.rs b/game/src/ltn/algorithms.rs
similarity index 98%
rename from game/src/debug/ltn/algorithms.rs
rename to game/src/ltn/algorithms.rs
index bb11c13175..3680badaf5 100644
--- a/game/src/debug/ltn/algorithms.rs
+++ b/game/src/ltn/algorithms.rs
@@ -4,7 +4,7 @@ use geom::Distance;
 use map_model::osm::RoadRank;
 use map_model::{IntersectionID, Map, PathConstraints, RoadID};
 
-use crate::debug::ltn::{Neighborhood, RatRun};
+use crate::ltn::{Neighborhood, RatRun};
 
 impl Neighborhood {
     // TODO Doesn't find the full perimeter. But do we really need that?
diff --git a/game/src/debug/ltn/mod.rs b/game/src/ltn/mod.rs
similarity index 80%
rename from game/src/debug/ltn/mod.rs
rename to game/src/ltn/mod.rs
index ad39230b09..4b818252ad 100644
--- a/game/src/debug/ltn/mod.rs
+++ b/game/src/ltn/mod.rs
@@ -1,11 +1,11 @@
 use std::collections::BTreeSet;
 
-use map_gui::tools::ColorDiscrete;
+use map_gui::tools::{nice_map_name, CityPicker, ColorDiscrete};
 use map_gui::ID;
 use map_model::{IntersectionID, Map, Road, RoadID};
 use widgetry::{
-    Color, Drawable, EventCtx, GeomBatch, GfxCtx, HorizontalAlignment, Key, Line, Outcome, Panel,
-    State, Text, TextExt, VerticalAlignment, Widget,
+    lctrl, Color, Drawable, EventCtx, GeomBatch, GfxCtx, HorizontalAlignment, Key, Line, Outcome,
+    Panel, State, Text, TextExt, VerticalAlignment, Widget,
 };
 
 use crate::app::{App, Transition};
@@ -37,14 +37,34 @@ struct RatRun {
 }
 
 impl Viewer {
-    pub fn start_from_road(ctx: &mut EventCtx, app: &App, start: RoadID) -> Box<dyn State<App>> {
+    pub fn start_anywhere(ctx: &mut EventCtx, app: &App) -> Box<dyn State<App>> {
+        // Find some residential road to start on
+        let r = app
+            .primary
+            .map
+            .all_roads()
+            .iter()
+            .find(|r| r.get_rank() == map_model::osm::RoadRank::Local)
+            .unwrap();
+        Viewer::start_from_road(ctx, app, r.id)
+    }
+
+    fn start_from_road(ctx: &mut EventCtx, app: &App, start: RoadID) -> Box<dyn State<App>> {
         let neighborhood = Neighborhood::from_road(&app.primary.map, start);
         let (draw_neighborhood, legend) = neighborhood.render(ctx, app);
         let rat_runs = neighborhood.find_rat_runs(&app.primary.map);
         let panel = Panel::new_builder(Widget::col(vec![
             Widget::row(vec![
                 Line("LTN tool").small_heading().into_widget(ctx),
-                ctx.style().btn_close_widget(ctx),
+                ctx.style()
+                    .btn_popup_icon_text(
+                        "system/assets/tools/map.svg",
+                        nice_map_name(app.primary.map.get_name()),
+                    )
+                    .hotkey(lctrl(Key::L))
+                    .build_widget(ctx, "change map")
+                    .centered_vert()
+                    .align_right(),
             ]),
             legend,
             "Click a road to re-center".text_widget(ctx),
@@ -134,8 +154,12 @@ impl State<App> for Viewer {
 
         if let Outcome::Clicked(x) = self.panel.event(ctx) {
             match x.as_ref() {
-                "close" => {
-                    return Transition::Pop;
+                "change map" => {
+                    return Transition::Push(CityPicker::new_state(
+                        ctx,
+                        app,
+                        Box::new(|ctx, app| Transition::Replace(Viewer::start_anywhere(ctx, app))),
+                    ));
                 }
                 "previous rat run" => {
                     self.current_idx -= 1;
@@ -164,7 +188,7 @@ impl Neighborhood {
         let interior = Color::BLUE;
         let perimeter = Color::hex("#40B5AD");
         let border = Color::CYAN;
-        let mut colorer = ColorDiscrete::new(
+        let mut colorer = ColorDiscrete::no_fading(
             app,
             vec![
                 ("interior", interior),
diff --git a/game/src/ungap/layers.rs b/game/src/ungap/layers.rs
index 489223a318..4edcb95cd8 100644
--- a/game/src/ungap/layers.rs
+++ b/game/src/ungap/layers.rs
@@ -165,6 +165,7 @@ impl Layers {
                             crate::layer::elevation::SteepStreets::make_colorer(ctx, app);
                         // The Colorer fades the map as the very first thing in the batch, but we
                         // don't want to do that twice.
+                        // TODO Can't use no_fading without complicating make_colorer...
                         colorer.unzoomed.shift();
                         self.steep_streets = Some(colorer.unzoomed.upload(ctx));
                     } else {
diff --git a/game/src/ungap/predict.rs b/game/src/ungap/predict.rs
index f2d5894786..c7a8be09b4 100644
--- a/game/src/ungap/predict.rs
+++ b/game/src/ungap/predict.rs
@@ -464,11 +464,8 @@ impl ModeShiftData {
         // And convert grams to tons
         self.results.annual_co2_emissions_tons = 404.0 * annual_mileage / 907185.0;
 
-        let mut colorer = ColorNetwork::new(app);
+        let mut colorer = ColorNetwork::no_fading(app);
         colorer.ranked_roads(count_per_road.clone(), &app.cs.good_to_bad_red);
-        // The Colorer fades the map as the very first thing in the batch, but we don't want to do
-        // that twice.
-        colorer.unzoomed.shift();
         let (draw_unzoomed, draw_zoomed) = colorer.build(ctx);
         self.gaps = NetworkGaps {
             draw_unzoomed,
diff --git a/map_gui/src/tools/colors.rs b/map_gui/src/tools/colors.rs
index 585893ff82..a65a4076dc 100644
--- a/map_gui/src/tools/colors.rs
+++ b/map_gui/src/tools/colors.rs
@@ -38,6 +38,15 @@ impl<'a> ColorDiscrete<'a> {
         }
     }
 
+    pub fn no_fading<I: Into<String>>(
+        app: &'a dyn AppLike,
+        categories: Vec<(I, Color)>,
+    ) -> ColorDiscrete<'a> {
+        let mut c = ColorDiscrete::new(app, categories);
+        c.unzoomed = GeomBatch::new();
+        c
+    }
+
     pub fn add_l<I: AsRef<str>>(&mut self, l: LaneID, category: I) {
         let color = self.colors[category.as_ref()];
         self.unzoomed
@@ -270,6 +279,14 @@ impl<'a> ColorNetwork<'a> {
         }
     }
 
+    pub fn no_fading(app: &'a dyn AppLike) -> ColorNetwork {
+        ColorNetwork {
+            map: app.map(),
+            unzoomed: GeomBatch::new(),
+            zoomed: GeomBatch::new(),
+        }
+    }
+
     pub fn add_l(&mut self, l: LaneID, color: Color) {
         self.unzoomed
             .push(color, self.map.get_parent(l).get_thick_polygon());