diff --git a/apps/server/src/lane-status.ts b/apps/server/src/lane-status.ts
index 82924d4..746ad3e 100644
--- a/apps/server/src/lane-status.ts
+++ b/apps/server/src/lane-status.ts
@@ -14,11 +14,13 @@ import { directionOf } from "./device-resolve.js";
 // flips free after BUSY_TTL_MS. A "both"-direction camera marks BOTH lanes.
 
 /** How long after the last vehicle detection a lane stays "busy" before clearing.
- *  Must exceed the camera's `active` re-fire interval (observed ~30-80s on the test
- *  unit) so a parked car keeps the lane busy. Override with LANE_BUSY_TTL_MS. */
+ *  Must exceed the camera's `active` re-fire interval so a still-present car keeps the
+ *  lane busy. Measured on the test unit: while a vehicle is in the zone the camera
+ *  re-fires `active` about every ~1s — so a few seconds of silence reliably means the
+ *  car has left. 5s gives fast clearing without flicker. Override with LANE_BUSY_TTL_MS. */
 export function busyTtlMs(): number {
-  const raw = Number(process.env.LANE_BUSY_TTL_MS ?? 90_000);
-  return Number.isFinite(raw) && raw > 0 ? raw : 90_000;
+  const raw = Number(process.env.LANE_BUSY_TTL_MS ?? 5_000);
+  return Number.isFinite(raw) && raw > 0 ? raw : 5_000;
 }
 
 export class LaneStatus {