diff --git a/src/repositories/InMemoryParkingRepository.ts b/src/repositories/InMemoryParkingRepository.ts
index f5c63df..e162dcb 100644
--- a/src/repositories/InMemoryParkingRepository.ts
+++ b/src/repositories/InMemoryParkingRepository.ts
@@ -3,7 +3,7 @@ import {
   IParkingStructure,
   IParkingStructureTimestampRecord
 } from "../entities/ParkingRepositoryEntities";
-import { HistoricalParkingAverageQueryResult } from "./ParkingGetterRepository";
+import { HistoricalParkingAverageQueryResult, ParkingStructureCountOptions } from "./ParkingGetterRepository";
 import { CircularQueue } from "../types/CircularQueue";
 
 export type ParkingStructureID = string;
@@ -74,7 +74,61 @@ export class InMemoryParkingRepository implements ParkingGetterSetterRepository
     return null;
   };
 
-  getHistoricalAveragesOfParkingStructureCounts = async (id: string): Promise<HistoricalParkingAverageQueryResult[]> => {
-    return [];
+  getHistoricalAveragesOfParkingStructureCounts = async (id: string, options: ParkingStructureCountOptions): Promise<HistoricalParkingAverageQueryResult[]> => {
+    const queue = this.historicalData.get(id);
+    if (!queue || queue.size() === 0) {
+      return [];
+    }
+
+    const results: HistoricalParkingAverageQueryResult[] = [];
+    const { startUnixEpochMs, endUnixEpochMs, intervalMs } = options;
+    
+    let currentIntervalStart = startUnixEpochMs;
+    
+    while (currentIntervalStart < endUnixEpochMs) {
+      const currentIntervalEnd = Math.min(currentIntervalStart + intervalMs, endUnixEpochMs);
+      const recordsInInterval = this.getRecordsInTimeRange(queue, currentIntervalStart, currentIntervalEnd);
+      
+      if (recordsInInterval.length > 0) {
+        const averageResult = this.calculateAverageForInterval(currentIntervalStart, currentIntervalEnd, recordsInInterval);
+        results.push(averageResult);
+      }
+      
+      currentIntervalStart = currentIntervalEnd;
+    }
+    
+    return results;
+  };
+
+  private getRecordsInTimeRange = (
+    queue: CircularQueue<IParkingStructureTimestampRecord>, 
+    startMs: number, 
+    endMs: number
+  ): IParkingStructureTimestampRecord[] => {
+    const recordsInInterval: IParkingStructureTimestampRecord[] = [];
+    
+    for (let i = 0; i < queue.size(); i++) {
+      const record = queue.get(i);
+      if (record && record.timestampMs >= startMs && record.timestampMs < endMs) {
+        recordsInInterval.push(record);
+      }
+    }
+    
+    return recordsInInterval;
+  };
+
+  private calculateAverageForInterval = (
+    fromMs: number,
+    toMs: number,
+    records: IParkingStructureTimestampRecord[]
+  ): HistoricalParkingAverageQueryResult => {
+    const totalSpotsAvailable = records.reduce((sum, record) => sum + record.spotsAvailable, 0);
+    const averageSpotsAvailable = totalSpotsAvailable / records.length;
+    
+    return {
+      fromUnixEpochMs: fromMs,
+      toUnixEpochMs: toMs,
+      averageSpotsAvailable
+    };
   };
 }
diff --git a/src/repositories/ParkingGetterRepository.ts b/src/repositories/ParkingGetterRepository.ts
index c098c0e..8ef13c9 100644
--- a/src/repositories/ParkingGetterRepository.ts
+++ b/src/repositories/ParkingGetterRepository.ts
@@ -9,7 +9,7 @@ export interface ParkingStructureCountOptions {
 export interface HistoricalParkingAverageQueryResult {
   fromUnixEpochMs: number;
   toUnixEpochMs: number;
-  averageSpotsTaken: number;
+  averageSpotsAvailable: number;
 }
 
 
diff --git a/test/repositories/InMemoryParkingRepositoryTests.test.ts b/test/repositories/InMemoryParkingRepositoryTests.test.ts
index 24c292f..ff74c68 100644
--- a/test/repositories/InMemoryParkingRepositoryTests.test.ts
+++ b/test/repositories/InMemoryParkingRepositoryTests.test.ts
@@ -5,6 +5,7 @@ import {
 } from "../../src/repositories/InMemoryParkingRepository";
 import { IParkingStructure, IParkingStructureTimestampRecord } from "../../src/entities/ParkingRepositoryEntities";
 import { CircularQueue } from "../../src/types/CircularQueue";
+import { ParkingStructureCountOptions } from "../../src/repositories/ParkingGetterRepository";
 
 describe("InMemoryParkingRepository", () => {
   let repository: InMemoryParkingRepository;
@@ -145,4 +146,112 @@ describe("InMemoryParkingRepository", () => {
       expect(result).toEqual(testStructure);
     });
   });
+
+  describe("getHistoricalAveragesOfParkingStructureCounts", () => {
+    const sortingCallback = (a: IParkingStructureTimestampRecord, b: IParkingStructureTimestampRecord) => a.timestampMs - b.timestampMs;
+    
+    const setupHistoricalData = (records: IParkingStructureTimestampRecord[]) => {
+      const queue = new CircularQueue<IParkingStructureTimestampRecord>(10);
+      records.forEach(record => queue.appendWithSorting(record, sortingCallback));
+      historicalData.set(testStructure.id, queue);
+    };
+
+    it("should return empty array for non-existent structure or no data", async () => {
+      const options: ParkingStructureCountOptions = {
+        startUnixEpochMs: 1000,
+        endUnixEpochMs: 2000,
+        intervalMs: 500
+      };
+      
+      // Non-existent structure
+      expect(await repository.getHistoricalAveragesOfParkingStructureCounts("non-existent", options)).toEqual([]);
+      
+      // Structure with no historical data
+      await repository.addOrUpdateParkingStructure(testStructure);
+      expect(await repository.getHistoricalAveragesOfParkingStructureCounts(testStructure.id, options)).toEqual([]);
+    });
+
+    it("should calculate averages for single and multiple intervals", async () => {
+      const records = [
+        { id: testStructure.id, spotsAvailable: 80, timestampMs: 1100 },
+        { id: testStructure.id, spotsAvailable: 70, timestampMs: 1200 },
+        { id: testStructure.id, spotsAvailable: 50, timestampMs: 1600 },
+        { id: testStructure.id, spotsAvailable: 40, timestampMs: 1700 }
+      ];
+      
+      setupHistoricalData(records);
+      await repository.addOrUpdateParkingStructure(testStructure);
+
+      // Single interval test
+      const singleIntervalOptions: ParkingStructureCountOptions = {
+        startUnixEpochMs: 1000,
+        endUnixEpochMs: 1500,
+        intervalMs: 500
+      };
+      
+      const singleResult = await repository.getHistoricalAveragesOfParkingStructureCounts(testStructure.id, singleIntervalOptions);
+      expect(singleResult).toHaveLength(1);
+      expect(singleResult[0]).toEqual({
+        fromUnixEpochMs: 1000,
+        toUnixEpochMs: 1500,
+        averageSpotsAvailable: 75 // (80 + 70) / 2
+      });
+
+      // Multiple intervals test
+      const multipleIntervalOptions: ParkingStructureCountOptions = {
+        startUnixEpochMs: 1000,
+        endUnixEpochMs: 2000,
+        intervalMs: 500
+      };
+      
+      const multipleResult = await repository.getHistoricalAveragesOfParkingStructureCounts(testStructure.id, multipleIntervalOptions);
+      expect(multipleResult).toHaveLength(2);
+      expect(multipleResult[0]).toEqual({
+        fromUnixEpochMs: 1000,
+        toUnixEpochMs: 1500,
+        averageSpotsAvailable: 75 // (80 + 70) / 2
+      });
+      expect(multipleResult[1]).toEqual({
+        fromUnixEpochMs: 1500,
+        toUnixEpochMs: 2000,
+        averageSpotsAvailable: 45 // (50 + 40) / 2
+      });
+    });
+
+    it("should handle edge cases: skipped intervals and boundaries", async () => {
+      const records = [
+        { id: testStructure.id, spotsAvailable: 90, timestampMs: 1000 }, // start boundary - included
+        { id: testStructure.id, spotsAvailable: 80, timestampMs: 1500 }, // interval boundary - included in second
+        { id: testStructure.id, spotsAvailable: 60, timestampMs: 2100 }  // skip interval, in third
+      ];
+      
+      setupHistoricalData(records);
+      await repository.addOrUpdateParkingStructure(testStructure);
+
+      const options: ParkingStructureCountOptions = {
+        startUnixEpochMs: 1000,
+        endUnixEpochMs: 2500,
+        intervalMs: 500
+      };
+      
+      const result = await repository.getHistoricalAveragesOfParkingStructureCounts(testStructure.id, options);
+      
+      expect(result).toHaveLength(3);
+      expect(result[0]).toEqual({
+        fromUnixEpochMs: 1000,
+        toUnixEpochMs: 1500,
+        averageSpotsAvailable: 90 // only record at 1000ms
+      });
+      expect(result[1]).toEqual({
+        fromUnixEpochMs: 1500,
+        toUnixEpochMs: 2000,
+        averageSpotsAvailable: 80 // only record at 1500ms
+      });
+      expect(result[2]).toEqual({
+        fromUnixEpochMs: 2000,
+        toUnixEpochMs: 2500,
+        averageSpotsAvailable: 60 // only record at 2100ms
+      });
+    });
+  });
 });