road distance: trigger at launch + foreground, fall back to saved location

Road-distance routing previously only fired once a fresh GPS fix arrived via
the location hook/onChange. A returning user on a cold launch waited for that
fix, and if onboarding/flag issues kept tracking from starting, distances
stayed straight-line. Now:
- refreshRoadDistancesIfNeeded() uses the last saved location when the live
  fix isn't set yet, so it can run immediately.
- It's called explicitly on launch (already-onboarded branch), on foreground
  activation, and on the existing location paths.

FuelBoard/ContentView.swift

@@ -50,6 +50,23 @@ struct ContentView: View {
             // fires on every fix incl. background significant-change
             // wake-ups, so the Lock Screen pill stays live while driving.
             updateLiveActivity()
+            refreshRoadDistancesIfNeeded()
+        }
+    }
+
+    /// Kicks off a (throttled) Apple-Maps road-distance recompute for the
+    /// stations around the current fix. The app owns routing — the widget and
+    /// Live Activity only read the cached result. Falls back to the last saved
+    /// location so it can run before the first fresh GPS fix arrives.
+    private func refreshRoadDistancesIfNeeded() {
+        let origin = location ?? FuelStore.loadLocation()
+        guard let origin else { return }
+        Task {
+            await RoadDistanceService.refreshIfNeeded(
+                stations: stations,
+                lat: origin.lat,
+                lng: origin.lng
+            )
         }
     }
 
@@ -317,6 +334,10 @@ struct ContentView: View {
                                fuel: alertsFuel, radiusKM: effectiveAlertsRadiusKM)
                 monitor.setEnabled(alertsEnabled)
                 updateLiveActivity()
+                // Compute road distances early (throttled; falls back to the
+                // last saved location) so distance surfaces are road-matched
+                // as soon as stations are available.
+                refreshRoadDistancesIfNeeded()
                 // Refresh only when the cache is stale (twice-a-day policy).
                 // Skipped under the force-* hooks so the banner stays up.
 #if DEBUG
@@ -362,6 +383,7 @@ struct ContentView: View {
                 monitor.update(stations: stations, favourites: refreshedFavourites,
                                fuel: alertsFuel, radiusKM: effectiveAlertsRadiusKM)
                 updateLiveActivity()
+                refreshRoadDistancesIfNeeded()
                 // No network fetch on foreground — pull-to-refresh is the override.
             } else {
                 locationManager.stopForegroundTracking()
@@ -377,6 +399,7 @@ struct ContentView: View {
                 monitor.update(stations: stations, favourites: refreshedFavourites,
                                fuel: alertsFuel, radiusKM: effectiveAlertsRadiusKM)
                 updateLiveActivity()
+                refreshRoadDistancesIfNeeded()
             }
         }
         )
@@ -949,7 +972,7 @@ struct StationRow: View {
                     .lineLimit(1)
                     .truncationMode(.tail)
                 if let location {
-                    Text(distanceUnit.format(station.distanceKM(to: location.lat, lng2: location.lng)))
+                    Text(distanceUnit.format(FuelStore.displayDistanceKM(station: station, userLat: location.lat, userLng: location.lng)))
                         .font(.caption2)
                         .foregroundStyle(.secondary)
                         .monospacedDigit()

FuelBoard/FuelBoardApp.swift

@@ -1,7 +1,22 @@
+import ActivityKit
 import SwiftUI
 
 @main
 struct FuelBoardApp: App {
+    init() {
+        #if DEBUG
+        // QA hook (Debug builds only): `-qaLiveActivity e10|e5|diesel` starts a
+        // Live Activity with a long station name so the Lock Screen / island
+        // layout can be rendered in the Simulator for visual QA.
+        let args = ProcessInfo.processInfo.arguments
+        if let idx = args.firstIndex(of: "-qaLiveActivity"),
+           args.indices.contains(idx + 1),
+           let fuel = FuelType(rawValue: args[idx + 1]) {
+            startQALiveActivity(fuel: fuel)
+        }
+        #endif
+    }
+
     var body: some Scene {
         WindowGroup {
             ContentView()
@@ -9,6 +24,34 @@ struct FuelBoardApp: App {
         }
     }
 
+    #if DEBUG
+    private func startQALiveActivity(fuel: FuelType) {
+        let state = FuelBoardLiveActivityAttributes.ContentState(
+            fuel: fuel,
+            stationID: "qa-phoenix",
+            stationName: "Phoenix Filling Stations",
+            brand: "Phoenix",
+            pricePence: 1499,
+            priceDisplayStyle: FuelStore.loadPriceDisplayStyle(),
+            distanceKM: 8.0,
+            lat: 51.5,
+            lng: -0.12,
+            updatedAt: Date()
+        )
+        let attrs = FuelBoardLiveActivityAttributes()
+        do {
+            let activity = try Activity.request(
+                attributes: attrs,
+                content: .init(state: state, staleDate: nil),
+                pushType: nil
+            )
+            print("QA-LIVE-ACTIVITY STARTED id=\(activity.id)")
+        } catch {
+            print("QA-LIVE-ACTIVITY FAILED: \(error)")
+        }
+    }
+    #endif
+
     /// Handles deep links that end up in the app. Widget taps arrive here in
     /// two cases:
     ///   - legacy/cached widget timelines using the `fuelboard://` relay, or

FuelBoard/LiveActivityManager.swift

@@ -57,7 +57,7 @@ enum LiveActivityManager {
             brand: best.brand,
             pricePence: price,
             priceDisplayStyle: priceDisplayStyle ?? FuelStore.loadPriceDisplayStyle(),
-            distanceKM: best.distanceKM(to: location.lat, lng2: location.lng),
+            distanceKM: FuelStore.displayDistanceKM(station: best, userLat: location.lat, userLng: location.lng),
             lat: best.lat,
             lng: best.lng,
             updatedAt: Date()

FuelBoard/RoadDistanceService.swift

@@ -0,0 +1,93 @@
+// RoadDistanceService.swift — computes Apple-Maps-matched ROAD distances for
+// nearby stations and caches them (keychain) so widgets + Live Activity can
+// show real driving distance instead of straight-line haversine.
+//
+// Runs only in the APP: MKDirections is network-bound and the widget extension
+// has a tiny execution budget + a ~40-70/day refresh budget, so routing belongs
+// here, not in the widget. The widget/Live Activity just read the cache.
+//
+// Throttling: recompute at most every `throttleMinutes`, or when the user has
+// moved `moveThresholdMeters` from where the cache was built. Bounded to the
+// `candidatesPerPass` nearest stations so a pass stays a handful of route calls.
+
+import Foundation
+import MapKit
+import WidgetKit
+
+enum RoadDistanceService {
+    /// Upper bound on stations routed per pass, so a pass stays a bounded set of
+    /// route calls. Raised from 12 so stations past the old nearest-12 cutoff
+    /// still get real road distances instead of a straight-line fallback.
+    static let candidatesPerPass = 40
+    /// Only route stations within this straight-line radius (km). Covers the
+    /// largest search radius the UI exposes (15 mi ≈ 24.1 km) plus margin, so
+    /// every station a widget/Live Activity/list can actually show gets routed.
+    static let maxRadiusKM: Double = 25
+    /// Don't route again more often than this (minutes).
+    static let throttleMinutes: Double = 10
+    /// Recompute when the user moves more than this (metres) from the last
+    /// source location.
+    static let moveThresholdMeters: Double = 400
+
+    /// Refreshes the cached road distances for the in-radius stations around
+    /// `lat`/`lng`. Throttled by time + distance; safe to call on every fix.
+    static func refreshIfNeeded(stations: [FuelStation], lat: Double, lng: Double) async {
+        guard !stations.isEmpty else { return }
+
+        // Throttle: keep cached values when fresh and the user hasn't moved far.
+        if let cache = FuelStore.loadRoadDistances() {
+            let elapsed = Date().timeIntervalSince1970 - cache.updatedAt
+            let movedMeters = haversineMeters(cache.sourceLat, cache.sourceLng, lat, lng)
+            if elapsed < throttleMinutes * 60 && movedMeters < moveThresholdMeters {
+                return
+            }
+        }
+
+        // Candidate stations: the nearest-by-straight-line subset that the UI
+        // could actually display, capped so a pass stays bounded.
+        let nearest = stations
+            .sorted { $0.distanceKM(to: lat, lng2: lng) < $1.distanceKM(to: lat, lng2: lng) }
+            .prefix(candidatesPerPass)
+            .filter { $0.distanceKM(to: lat, lng2: lng) <= maxRadiusKM }
+
+        let origin = CLLocationCoordinate2D(latitude: lat, longitude: lng)
+        var entries: [String: Double] = [:]
+        for station in nearest {
+            let dest = CLLocationCoordinate2D(latitude: station.lat, longitude: station.lng)
+            if let meters = await roadMeters(from: origin, to: dest) {
+                entries[station.id] = meters
+            }
+        }
+        guard !entries.isEmpty else { return }
+
+        FuelStore.saveRoadDistances(sourceLat: lat, sourceLng: lng, entries: entries)
+        // Wake the widgets so the new road distances surface immediately.
+        WidgetCenter.shared.reloadAllTimelines()
+    }
+
+    /// Driving distance (metres) between two coordinates via Apple Maps routing.
+    private static func roadMeters(from: CLLocationCoordinate2D, to: CLLocationCoordinate2D) async -> Double? {
+        let request = MKDirections.Request()
+        request.source = MKMapItem(placemark: MKPlacemark(coordinate: from))
+        request.destination = MKMapItem(placemark: MKPlacemark(coordinate: to))
+        request.transportType = .automobile
+        request.requestsAlternateRoutes = false
+        do {
+            let response = try await MKDirections(request: request).calculate()
+            return response.routes.first?.distance
+        } catch {
+            return nil
+        }
+    }
+
+    /// Straight-line haversine distance between two coordinates, in metres.
+    private static func haversineMeters(_ lat1: Double, _ lng1: Double, _ lat2: Double, _ lng2: Double) -> Double {
+        let r = 6371000.0
+        let dLat = (lat2 - lat1) * .pi / 180
+        let dLng = (lng2 - lng1) * .pi / 180
+        let a = sin(dLat / 2) * sin(dLat / 2) +
+                cos(lat1 * .pi / 180) * cos(lat2 * .pi / 180) *
+                sin(dLng / 2) * sin(dLng / 2)
+        return r * 2 * atan2(sqrt(a), sqrt(1 - a))
+    }
+}

FuelBoard/StationsView.swift

@@ -317,17 +317,6 @@ extension FuelType {
         case .diesel: return "Diesel"
         }
     }
-
-    /// Fuel colour wheel (user-chosen palette): green = unleaded (#30D158),
-    /// yellow = premium (#FFD60A), cyan = diesel (#64D2FF). Used for the
-    /// fuel-type tab icons and the title icon.
-    var tintColor: Color {
-        switch self {
-        case .e10: return Color(red: 48/255.0, green: 209/255.0, blue: 88/255.0)      // #30D158
-        case .e5: return Color(red: 255/255.0, green: 214/255.0, blue: 10/255.0)      // #FFD60A
-        case .diesel: return Color(red: 100/255.0, green: 210/255.0, blue: 255/255.0) // #64D2FF
-        }
-    }
 }
 
 /// Fuel-type selector styled like a segmented control, with a coloured pump

FuelBoardTests/Tests/FuelBoardSharedTests/FuelBoardTests.swift

@@ -620,3 +620,54 @@ final class OfflineDataLabelTests: XCTestCase {
         XCTAssertNil(FuelStore.offlineDataLabel(from: "not-a-date"))
     }
 }
+
+// MARK: - Road distance cache
+
+final class RoadDistanceCacheTests: XCTestCase {
+    override func setUp() {
+        super.setUp()
+        // Keychain persists across invocations, so a cache left by an earlier
+        // test or run would pollute these. Overwrite with an empty, far-away
+        // cache (source at (0,0)) so every test starts from a clean slate.
+        FuelStore.saveRoadDistances(sourceLat: 0, sourceLng: 0, entries: [:])
+    }
+
+    private func station(_ id: String, _ lat: Double, _ lng: Double) -> FuelStation {
+        FuelStation(id: id, name: id, brand: "X", address: "", postcode: "",
+                    lat: lat, lng: lng, prices: [:], priceUpdated: nil)
+    }
+
+    func testDisplayDistanceFallsBackToStraightLineWhenNoCache() {
+        // London user, station ~ London -> no cache -> straight-line haversine.
+        let s = station("a", 51.5074, -0.1278)
+        let km = FuelStore.displayDistanceKM(station: s, userLat: 51.6, userLng: -0.1)
+        XCTAssertEqual(km, s.distanceKM(to: 51.6, lng2: -0.1), accuracy: 0.0001)
+    }
+
+    func testRoadDistanceUsedWhenCachedNear() {
+        let s = station("a", 51.5074, -0.1278)
+        // Cache a road distance of 3.2 km for this station from the user's fix.
+        FuelStore.saveRoadDistances(sourceLat: 51.6, sourceLng: -0.1, entries: ["a": 3200])
+        let km = FuelStore.displayDistanceKM(station: s, userLat: 51.6, userLng: -0.1)
+        XCTAssertEqual(km, 3.2, accuracy: 0.0001)
+    }
+
+    func testRoadDistanceNilWhenOriginFar() {
+        let s = station("a", 51.5074, -0.1278)
+        // Cache built in London, but the user is now ~200 km away -> stale.
+        FuelStore.saveRoadDistances(sourceLat: 51.5074, sourceLng: -0.1278, entries: ["a": 3200])
+        let meters = FuelStore.roadDistanceMeters(for: "a", userLat: 53.4808, userLng: -2.2426)
+        XCTAssertNil(meters)
+        // And display falls back to straight-line.
+        let km = FuelStore.displayDistanceKM(station: s, userLat: 53.4808, userLng: -2.2426)
+        XCTAssertEqual(km, s.distanceKM(to: 53.4808, lng2: -2.2426), accuracy: 0.0001)
+    }
+
+    func testRoadDistanceUsedForOtherStationNotFound() {
+        FuelStore.saveRoadDistances(sourceLat: 51.6, sourceLng: -0.1, entries: ["a": 3200])
+        // A station that isn't in the cache falls back to straight-line.
+        let s = station("z", 51.51, -0.13)
+        let km = FuelStore.displayDistanceKM(station: s, userLat: 51.6, userLng: -0.1)
+        XCTAssertEqual(km, s.distanceKM(to: 51.6, lng2: -0.1), accuracy: 0.0001)
+    }
+}

FuelBoardWidgets/FuelBoardLiveActivityView.swift

@@ -41,7 +41,7 @@ struct FuelBoardLiveActivity: Widget {
                 }
             } compactLeading: {
                 Image(systemName: "fuelpump.fill")
-                    .foregroundStyle(.green)
+                    .foregroundStyle(context.state.fuel.tintColor)
             } compactTrailing: {
                 FuelBoardLiveActivityPriceView(context: context)
             } minimal: {
@@ -49,12 +49,15 @@ struct FuelBoardLiveActivity: Widget {
                     .font(.caption2.bold().monospacedDigit())
             }
         }
-        // NOTE: deliberately NO `.supplementalActivityFamilies([.small])`.
+        .supplementalActivityFamilies([.small])
-        // That modifier makes iOS eligible to render this activity in the
+        // Why `.small` is kept: it lets the SHARED body render a compact form
-        // narrow `.small` form on the iPhone/iPad Lock Screen, which is what
+        // in genuinely small slots (CarPlay small / Apple Watch smart stack)
-        // produced the squeezed, small-text card. Dropping it keeps the
+        // instead of falling back to the Dynamic Island compact closure —
-        // full-width Lock Screen card on iPhone/iPad; CarPlay still shows a
+        // which could NOT show the station distance the user wants on CarPlay.
-        // small form via the Dynamic Island compact closures below.
+        // The full-width iPhone/iPad card is protected by the `richMinWidth`
+        // gate on `richBody` + its flexible, truncating middle column, so
+        // iPhone/iPad still get the full card; only truly small space picks
+        // the compact strip below.
     }
 }
 
@@ -62,29 +65,59 @@ struct FuelBoardLiveActivity: Widget {
 private struct FuelBoardLiveActivityView: View {
     let context: ActivityViewContext<FuelBoardLiveActivityAttributes>
 
+    /// Below this ACTUAL proposed width we show the compact strip (CarPlay
+    /// small / Watch smart stack); at/above it we show the full card. The
+    /// decision is made from the real width the system hands the body, read
+    /// via a background GeometryReader — NOT ViewThatFits ideal-width
+    /// measurement (that's broken for truncating text: a long station name
+    /// inflated the "ideal" width past the iPhone Lock Screen and collapsed
+    /// the full card).
+    private let compactWidthThreshold: CGFloat = 280
+
+    /// Measured slot width (drives the rich-vs-compact branch). Measured in a
+    /// background GeometryReader so it does NOT act as the layout container:
+    /// a GeometryReader root pins content top-left, and forcing a
+    /// maxHeight:.infinity frame on it over-claims the whole proposed height,
+    /// centring the content below true vertical centre (bigger gap above) on
+    /// the Lock Screen. Measuring behind the scenes keeps the content
+    /// intrinsic-sized so the system vertically centres it itself.
+    @State private var slotWidth: CGFloat = 400
+
     var body: some View {
         Link(destination: context.state.mapsURL) {
-            // Always the full three-column card. The station caption is
+            Group {
-            // line-limited + scale-down + tail-truncated, so a LONG station
+                // Branch on the ACTUAL proposed width. iPhone/iPad offer the
-            // name truncates in place instead of inflating this view's ideal
+                // full Lock Screen width (>= threshold) → rich card, no matter
-            // width and tricking ViewThatFits into falling back to the compact
+                // how long the station name is. Truly small slots (CarPlay /
-            // strip (that is exactly what made 5-mi / long-named activities
+                // Watch) offer much less → compact strip.
-            // render small while 10-15-mi / short names stayed full).
+                if slotWidth >= compactWidthThreshold {
-            //
+                    richBody
-            // No ViewThatFits / compactBody: with `.supplementalActivityFamilies`
+                } else {
-            // removed, this body is only ever handed Lock-Screen width, so the
+                    compactBody
-            // compact fallback was both dead weight and the cause of the bug.
+                }
-            richBody
+            }
+            // Fill the card width so the background measure reads the real
+            // slot, not the intrinsic content width.
+            .frame(maxWidth: .infinity)
+            // Side-channel width measurement — never the layout container.
+            .background(
+                GeometryReader { geo in
+                    Color.clear
+                        .onAppear { slotWidth = geo.size.width }
+                        .onChange(of: geo.size.width) { _, w in slotWidth = w }
+                }
+            )
         }
     }
 
     /// Full three-column design (unchanged): brand glyph · fuel+station · price.
     private var richBody: some View {
         HStack(spacing: 12) {
-            // LEFT — station brand glyph
+            // LEFT — station brand glyph: the fuel-tinted pump on its own. No
-            Image(systemName: "fuelpump.circle.fill")
+            // background circle behind it (user request).
-                .font(.system(size: 32))
+            Image(systemName: "fuelpump.fill")
-                .foregroundStyle(.green, .white)
+                .font(.system(size: 28, weight: .semibold))
+                .foregroundStyle(context.state.fuel.tintColor)
                 .frame(width: 40, height: 40)
 
             // MIDDLE — fuel + station
@@ -113,7 +146,31 @@ private struct FuelBoardLiveActivityView: View {
         .padding()
     }
 
-    // NOTE: `compactBody` was removed — always render `richBody` (see body).
+    /// Minimal strip for small space (CarPlay small / Watch smart stack):
+    /// fuel type + bold price on one line, station · distance below.
+    /// Deliberately no app name and no "Tap for directions" — CarPlay is
+    /// display-only, and the user's asks here are just fuel + price + distance.
+    private var compactBody: some View {
+        VStack(alignment: .leading, spacing: 3) {
+            HStack(spacing: 5) {
+                Text(context.state.fuel.displayName)
+                    .font(.caption.bold())
+                    .lineLimit(1)
+                Spacer(minLength: 4)
+                FuelStore.priceTextAttributed(context.state.pricePence,
+                                               style: context.state.priceDisplayStyle,
+                                               size: 15, weight: .bold)
+                    .lineLimit(1)
+            }
+            Text("\(context.state.stationName) · \(context.state.distanceText)")
+                .font(.system(size: 9))
+                .foregroundStyle(.secondary)
+                .lineLimit(1)
+                .minimumScaleFactor(0.7)
+                .truncationMode(.tail)
+        }
+        .padding(8)
+    }
 }
 
 /// Dynamic Island expanded regions + compact trailing — price only.

Shared/FuelPriceWidgetViews.swift

@@ -89,7 +89,7 @@ struct FuelPriceWidgetContent: View {
                 FuelStore.priceTextAttributed(price, size: 26, weight: .bold, color: .green)
             }
             if let location = entry.location {
-                Text(entry.unit.format(station.distanceKM(to: location.lat, lng2: location.lng)) + " away")
+                Text(entry.unit.format(FuelStore.displayDistanceKM(station: station, userLat: location.lat, userLng: location.lng)) + " away")
                     .font(.caption2)
                     .foregroundStyle(.secondary)
             } else {
@@ -148,7 +148,7 @@ struct FuelPriceWidgetContent: View {
                 .font(.caption.weight(.semibold))
                 .lineLimit(1)
             if let location = entry.location {
-                Text(entry.unit.format(station.distanceKM(to: location.lat, lng2: location.lng)))
+                Text(entry.unit.format(FuelStore.displayDistanceKM(station: station, userLat: location.lat, userLng: location.lng)))
                     .font(.caption2)
                     .foregroundStyle(.secondary)
             }

Shared/FuelStore.swift

@@ -8,6 +8,7 @@
 //   keychain → app-group defaults → fallback.
 
 import Foundation
+import SwiftUI
 import Security
 #if canImport(AppIntents)
 import AppIntents
@@ -99,6 +100,20 @@ enum FuelType: String, Codable, CaseIterable, Identifiable {
     }
 }
 
+/// Fuel colour wheel (user-chosen palette): green = unleaded (#30D158),
+/// yellow = premium (#FFD60A), cyan = diesel (#64D2FF). Lives here in Shared
+/// so the app, widget, and Live Activity all tint the pump/fuel glyphs from one
+/// definition.
+extension FuelType {
+    var tintColor: Color {
+        switch self {
+        case .e10: return Color(red: 48/255.0, green: 209/255.0, blue: 88/255.0)      // #30D158
+        case .e5: return Color(red: 255/255.0, green: 214/255.0, blue: 10/255.0)      // #FFD60A
+        case .diesel: return Color(red: 100/255.0, green: 210/255.0, blue: 255/255.0) // #64D2FF
+        }
+    }
+}
+
 #if canImport(AppIntents)
 extension FuelType: AppEnum {}
 #endif
@@ -919,15 +934,75 @@ struct FuelStore {
     }
 
     // MARK: Onboarding — the app shows the intro screen on first launch only
-    // (a test button in the Alerts tab re-opens it). Stored in the app group
+    // (a test button in the Alerts tab re-opens it). Stored KEYCHAIN-FIRST
-    // so the widget can see it too if ever needed.
+    // (with an app-group mirror) for the same reason as favourites/distance
+    // unit: free SideStore accounts don't provision the app-group container,
+    // so an app-group-only flag silently fails to save AND reloads as false,
+    // making onboarding re-appear on every launch. Keychain survives reinstall
+    // and is shared with the extension.
 
     static func loadHasCompletedOnboarding() -> Bool {
-        UserDefaults(suiteName: appGroupSuite)?.bool(forKey: onboardingCompletedKey) ?? false
+        (loadString(service: onboardingCompletedKey) ?? "0") == "1"
     }
 
     static func saveHasCompletedOnboarding(_ completed: Bool) {
-        UserDefaults(suiteName: appGroupSuite)?.set(completed, forKey: onboardingCompletedKey)
+        saveString(completed ? "1" : "0", service: onboardingCompletedKey)
+    }
+
+    // MARK: Road distances (Apple-Maps-matched, computed by the app)
+
+    /// Cached road/routed distances (metres) keyed by station ID, computed by
+    /// the app via MapKit `MKDirections`. Stored in KEYCHAIN (survives on free
+    /// SideStore accounts where the app-group container isn't provisioned) so
+    /// the widget extension can read it too. Widget + Live Activity prefer
+    /// these over straight-line haversine for the displayed distance.
+    static let roadDistancesKey = "fuelboard.roadDistances"
+
+    /// How far (metres) the cache's source location may be from the current
+    /// user position before a cached road distance is treated as stale.
+    static let roadDistanceOriginToleranceMeters: Double = 600
+
+    static func saveRoadDistances(sourceLat: Double, sourceLng: Double, entries: [String: Double]) {
+        let cache = RoadDistanceCache(sourceLat: sourceLat, sourceLng: sourceLng,
+                                      updatedAt: Date().timeIntervalSince1970, entries: entries)
+        if let data = try? JSONEncoder().encode(cache) {
+            saveString(data.base64EncodedString(), service: roadDistancesKey)
+        }
+    }
+
+    static func loadRoadDistances() -> RoadDistanceCache? {
+        guard let raw = loadString(service: roadDistancesKey),
+              let data = Data(base64Encoded: raw),
+              let cache = try? JSONDecoder().decode(RoadDistanceCache.self, from: data)
+        else { return nil }
+        return cache
+    }
+
+    /// Cached road distance (metres) to a station from the user's location, or
+    /// nil when not cached / the cache was built too far from where the user
+    /// is now.
+    static func roadDistanceMeters(for stationID: String, userLat: Double, userLng: Double) -> Double? {
+        guard let cache = loadRoadDistances(),
+              let meters = cache.entries[stationID] else { return nil }
+        // The cache is only valid near the location it was built from.
+        let dLat = (userLat - cache.sourceLat) * .pi / 180
+        let dLng = (userLng - cache.sourceLng) * .pi / 180
+        let r = 6371000.0
+        let a = sin(dLat / 2) * sin(dLat / 2) +
+                cos(cache.sourceLat * .pi / 180) * cos(userLat * .pi / 180) *
+                sin(dLng / 2) * sin(dLng / 2)
+        let originDistanceMeters = r * 2 * atan2(sqrt(a), sqrt(1 - a))
+        guard originDistanceMeters <= roadDistanceOriginToleranceMeters else { return nil }
+        return meters
+    }
+
+    /// Distance (km) to display for a station: cached ROAD distance when
+    /// available (matches Apple Maps), else straight-line haversine.
+    static func displayDistanceKM(station: FuelStation, userLat: Double, userLng: Double) -> Double {
+        if let meters = roadDistanceMeters(for: station.id, userLat: userLat, userLng: userLng) {
+            return meters / 1000.0
+        }
+        return station.distanceKM(to: userLat, lng2: userLng)
     }
 
     // MARK: Low-level keychain helpers
@@ -989,3 +1064,12 @@ struct FuelStore {
         loadString(service: "widget.diag.\(intentType)")
     }
 }
+
+/// Cached Apple-Maps road distances for nearby stations (see
+/// `FuelStore.roadDistancesKey`). `entries` maps stationID → road metres.
+struct RoadDistanceCache: Codable {
+    let sourceLat: Double
+    let sourceLng: Double
+    let updatedAt: TimeInterval
+    let entries: [String: Double]
+}