diff --git a/src/notifications/schedulers/ETANotificationScheduler.ts b/src/notifications/schedulers/ETANotificationScheduler.ts
index 234b310..8789cdd 100644
--- a/src/notifications/schedulers/ETANotificationScheduler.ts
+++ b/src/notifications/schedulers/ETANotificationScheduler.ts
@@ -147,16 +147,17 @@ export class ETANotificationScheduler {
 
   /**
    * Check whether the notification is scheduled.
-   * @param deviceId
-   * @param shuttleId
-   * @param stopId
    */
-  public isNotificationScheduled({ deviceId, shuttleId, stopId }: NotificationLookupArguments): boolean {
+  public isNotificationScheduled(lookupArguments: NotificationLookupArguments): boolean {
+    return this.getSecondsThresholdForScheduledNotification(lookupArguments) != null;
+  }
+
+  public getSecondsThresholdForScheduledNotification({ deviceId, shuttleId, stopId }: NotificationLookupArguments): number | null {
     const tuple = new TupleKey(shuttleId, stopId);
     if (this.deviceIdsToDeliverTo[tuple.toString()] === undefined) {
-      return false;
+      return null;
     }
-    return deviceId in this.deviceIdsToDeliverTo[tuple.toString()];
+    return this.deviceIdsToDeliverTo[tuple.toString()][deviceId];
   }
 
   /**