diff --git a/pavement_parking/src/boundaries.rs b/pavement_parking/src/boundaries.rs
index 6b1a39c..b242a90 100644
--- a/pavement_parking/src/boundaries.rs
+++ b/pavement_parking/src/boundaries.rs
@@ -8,7 +8,7 @@ use geo::{Contains, MultiPolygon, Polygon};
 use geojson::{Feature, FeatureCollection, FeatureWriter, Value};
 use rstar::{primitives::GeomWithData, RTree, RTreeObject};
 
-use crate::{Rating, Road, Scenario};
+use crate::{Intervention, Rating, Road, Scenario};
 
 /// Aggregate counts per LAD and CA boundaries
 pub struct Boundaries {
@@ -21,6 +21,9 @@ struct Boundary {
     // Given a scenario and rating, count the roads and sum the length
     counts: EnumMap<Scenario, EnumMap<Rating, usize>>,
     total_length: EnumMap<Scenario, EnumMap<Rating, f64>>,
+
+    intervention_counts: EnumMap<Intervention, usize>,
+    intervention_total_length: EnumMap<Intervention, f64>,
 }
 
 impl Boundaries {
@@ -47,6 +50,8 @@ impl Boundaries {
                     any_matches: false,
                     counts: EnumMap::default(),
                     total_length: EnumMap::default(),
+                    intervention_counts: EnumMap::default(),
+                    intervention_total_length: EnumMap::default(),
                 },
             );
         }
@@ -73,6 +78,8 @@ impl Boundaries {
                 for (scenario, lengths) in &mut info.total_length {
                     lengths[road.ratings[scenario]] += road.length;
                 }
+                info.intervention_counts[road.intervention] += 1;
+                info.intervention_total_length[road.intervention] += road.length;
             }
         }
     }
@@ -104,6 +111,15 @@ impl Boundaries {
                     );
                 }
             }
+            for (intervention, count) in &info.intervention_counts {
+                f.set_property(format!("intervention_counts_{:?}", intervention), *count);
+            }
+            for (intervention, length) in &info.intervention_total_length {
+                f.set_property(
+                    format!("intervention_lengths_{:?}", intervention),
+                    length.round() as usize,
+                );
+            }
 
             summaries_writer.write_feature(&f)?;
         }
diff --git a/pavement_parking/src/main.rs b/pavement_parking/src/main.rs
index 0457990..fe77811 100644
--- a/pavement_parking/src/main.rs
+++ b/pavement_parking/src/main.rs
@@ -10,7 +10,7 @@ use indicatif::{ProgressBar, ProgressStyle};
 
 use crate::boundaries::Boundaries;
 use crate::census_areas::CensusAreas;
-use crate::ratings::{Rating, Scenario};
+use crate::ratings::{Intervention, Rating, Scenario};
 use crate::roads::{Class, Road};
 
 mod boundaries;
@@ -101,7 +101,7 @@ fn tippecanoe(input: &str, output: &str) -> Result<()> {
         .arg("-Z10")
         .arg("-z11")
         .arg("--drop-densest-as-needed");
-    println!("Running: {cmd:?}");
+    println!("\nRunning: {cmd:?}");
     if !cmd.status()?.success() {
         bail!("tippecanoe failed");
     }
diff --git a/pavement_parking/src/ratings.rs b/pavement_parking/src/ratings.rs
index 0ad6bec..05403e4 100644
--- a/pavement_parking/src/ratings.rs
+++ b/pavement_parking/src/ratings.rs
@@ -1,4 +1,4 @@
-use enum_map::Enum;
+use enum_map::{Enum, EnumMap};
 
 use crate::Class;
 
@@ -64,3 +64,37 @@ impl Rating {
         }
     }
 }
+
+/// Isomorphic to `Option<Scenario>`, but seems more clear to represent this way.
+#[derive(Clone, Copy, Debug, PartialEq, Enum)]
+pub enum Intervention {
+    /// No change needed (Scenario::U)
+    None,
+    Y,
+    X,
+    Z,
+    /// No scenario yields green
+    Impossible,
+}
+
+impl Intervention {
+    // TODO The ordering here may need to vary locally, especially depending on the total
+    // supply/demand of parking.
+    pub fn calculate(ratings: &EnumMap<Scenario, Rating>, already_one_way: bool) -> Self {
+        for (scenario, intervention) in [
+            (Scenario::U, Intervention::None),
+            (Scenario::Y, Intervention::Y),
+            (Scenario::X, Intervention::X),
+            (Scenario::Z, Intervention::Z),
+        ] {
+            if already_one_way && scenario == Scenario::X {
+                continue;
+            }
+
+            if ratings[scenario] == Rating::Green {
+                return intervention;
+            }
+        }
+        Intervention::Impossible
+    }
+}
diff --git a/pavement_parking/src/roads.rs b/pavement_parking/src/roads.rs
index 8b82c60..b241856 100644
--- a/pavement_parking/src/roads.rs
+++ b/pavement_parking/src/roads.rs
@@ -3,7 +3,7 @@ use enum_map::EnumMap;
 use geo::{Coord, HaversineLength, LineString, MapCoordsInPlace};
 use geojson::{Feature, Value};
 
-use crate::{Rating, Scenario};
+use crate::{Intervention, Rating, Scenario};
 
 // All distance units are in meters
 pub struct Road {
@@ -21,6 +21,7 @@ pub struct Road {
     pub pavement_average_width: f64,
 
     pub ratings: EnumMap<Scenario, Rating>,
+    pub intervention: Intervention,
 }
 
 #[derive(Clone, Copy, Debug)]
@@ -90,6 +91,7 @@ impl Road {
         // TODO Only consider road width as input, or do we want to continue to also try with
         // pavement width?
         let ratings = EnumMap::from_fn(|scenario| Rating::new(scenario, class, road_average_width));
+        let intervention = Intervention::calculate(&ratings, direction == "one-way");
 
         Ok(Some(Self {
             geom,
@@ -104,6 +106,7 @@ impl Road {
             pavement_average_width,
 
             ratings,
+            intervention,
         }))
     }
 
@@ -122,6 +125,7 @@ impl Road {
         for (scenario, rating) in self.ratings {
             f.set_property(format!("rating_{:?}", scenario), rating.to_str());
         }
+        f.set_property("intervention", format!("{:?}", self.intervention));
 
         f.set_property("parkable_length", trim_meters(parkable_length));
         // TODO Just debug right now, not used in the UI
diff --git a/pavement_parking/web/src/PavementLayers.svelte b/pavement_parking/web/src/PavementLayers.svelte
index 30e6f27..462457e 100644
--- a/pavement_parking/web/src/PavementLayers.svelte
+++ b/pavement_parking/web/src/PavementLayers.svelte
@@ -6,7 +6,13 @@
     VectorTileSource,
     hoverStateFilter,
   } from "svelte-maplibre";
-  import { colors, scenarios, type Mode, type Filters } from "./types";
+  import {
+    colors,
+    scenarios,
+    interventions,
+    type Mode,
+    type Filters,
+  } from "./types";
   import type { ExpressionSpecification } from "maplibre-gl";
 
   export let show: Mode;
@@ -73,6 +79,9 @@
             ]}
           </p>
         {/each}
+        <p>
+          Intervention required: {interventions[data.properties.intervention]}
+        </p>
       {/if}
     </Popup>
   </LineLayer>
diff --git a/pavement_parking/web/src/SummaryLayers.svelte b/pavement_parking/web/src/SummaryLayers.svelte
index c018b0b..94438bb 100644
--- a/pavement_parking/web/src/SummaryLayers.svelte
+++ b/pavement_parking/web/src/SummaryLayers.svelte
@@ -6,7 +6,13 @@
     hoverStateFilter,
     FillLayer,
   } from "svelte-maplibre";
-  import { colors, scenarios, ratings, type Mode } from "./types";
+  import {
+    colors,
+    scenarios,
+    ratings,
+    interventions,
+    type Mode,
+  } from "./types";
 
   export let show: Mode;
   export let url: string;
@@ -30,6 +36,7 @@
     <Popup openOn="hover" let:data>
       {#if data?.properties}
         <h1>{data.properties.name}</h1>
+
         <table>
           <tr>
             <th>Scenario</th>
@@ -53,6 +60,29 @@
             </tr>
           {/each}
         </table>
+
+        <table>
+          <tr>
+            <th>Intervention</th>
+            <th>Number of roads</th>
+            <th>Total km</th>
+          </tr>
+          {#each Object.entries(interventions) as [intervention, label]}
+            <tr>
+              <th>{label}</th>
+              <td>
+                {data.properties[
+                  `intervention_counts_${intervention}`
+                ].toLocaleString()}
+              </td>
+              <td>
+                {(
+                  data.properties[`intervention_lengths_${intervention}`] / 1000
+                ).toFixed(2)}
+              </td>
+            </tr>
+          {/each}
+        </table>
       {/if}
     </Popup>
   </FillLayer>
diff --git a/pavement_parking/web/src/types.ts b/pavement_parking/web/src/types.ts
index a6a609f..50aa0d5 100644
--- a/pavement_parking/web/src/types.ts
+++ b/pavement_parking/web/src/types.ts
@@ -52,3 +52,11 @@ export const scenarios = [
   ["Y", "One-way, parking both sides"],
   ["Z", "One-way, parking one side only"],
 ];
+
+export const interventions = {
+  None: "U: No change needed",
+  Y: "Y: One-way, parking both sides",
+  X: "X: Parking one side only",
+  Z: "Z: One-way, parking one side only",
+  Impossible: "Impossible: No scenario makes the road green",
+};