American International University Food Service
A Queueing and Facility Design Case

by
Joseph S. Martinich
University of Missouri - St. Louis

a case to supplement
Production and Operations Management: An Applied Modern Approach

This case is intended to be the basis for a business analysis and class discussion rather than to illustrate either effective or ineffective handling of a business situation. Companies and characters are fictitious and are not intended to represent actual companies or people.

Copyright 1997 by Joseph Martinich. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means without the permission of Joseph Martinich or the distributor, John Wiley & Sons, 605 Third Ave., New York, NY 10158. Printed in the U.S.A.

The Background

American International University (AIU) is a rapidly growing university that serves both a local and international student population. The University has grown from 5400 students and 1050 faculty and staff to almost 10,000 students and 1850 faculty and staff in the past ten years, and it is expected to continue to grow by approximately 400-500 students per year for the next 5-10 years. As with most growing universities, AIU is short on facilities, especially those related to student services. AIU has a single cafeteria on campus that serves the needs of both the residential student population of 1800 dormitory students, who have semester-long food contracts, and commuter students, faculty, and staff.

Current Operations

Lunchtime is the busiest period for the cafeteria, and in a typical day the cafeteria will serve 3500-5000 customers for lunch (ranging from purchase of a beverage to a complete meal). The lunch period runs from 11:00 a.m. to 2:00 p.m., with the heaviest volume occurring between 11:30 a.m. and 1 p.m.. (Table 1 gives the average customer volume for each half-hour period during a ten-day period, along with the average number of customers in line.) During most of this period the cafeteria uses all ten of its check-out stations. Each station is staffed by a cashier who has an electronic cash register, a scale (for weighing foods priced by the ounce, such as salads), a meal-card scanner (students who purchase a food contract are issued a card that can be scanned and the charges deducted from the account without having to use cash), and a long metal track upon which four or five food trays can be placed by waiting customers. Even with all ten check-out stations operating, during peak periods, there are often as many as 25 people in each check-out line and customers can wait more than 10 minutes in line. This waiting creates considerable complaining because hot food becomes cold, cold drinks become warm, and students and faculty have a limited amount of time between classes for lunch.

As with most restaurants, it is not cost-effective to use only full-time workers, because the customer demand varies so much during the course of a day. Therefore the cafeteria manager typically uses three full-time cashiers and several part-time cashiers during the course of the day. (There are usually 12-15 part-time cashiers (who are students) on the payroll. Typically seven part-time cashiers are scheduled during lunch and two during dinner. The extra part-time workers are available as replacements when other cashiers have vacations, days off, or are sick.) Two of the full-time cashiers work from 7:00 a.m. to 3:30 p.m. with a half-hour lunch break from 11:00-11:30 a.m., so they can return to their work stations during the peak of the lunch period. The third full-time cashier works from 10:30 a.m. until 7 p.m. with a half-hour lunch break from 2:30-3 p.m. The part-time cashiers all work three hour shifts. The manager establishes a weekly schedule for the part-time workers, taking into account the number of hours each one wants to work each week, their class schedules, requests for days off, and special circumstances that might suggest a larger or smaller number of customers on given days (e.g., during finals week demand patterns change). The manager tries to stagger the starting times for the part-time workers so that during the 11:30 a.m. - 1 p.m. period all ten cashiers are on duty, and during other times fewer than ten are scheduled to match the somewhat lower customer demand. For example, the following schedule for part-time cashiers is typical:

# of Workers

Scheduled Shift

1

10 a.m. - 1 p.m.

1

10:30 a.m. - 1:30 p.m.

3

11 a.m. - 2 p.m.

2

11:30 a.m. - 2:30 p.m.

With this schedule the number of cashiers working (not counting those on meal-break) during each half-hour period is

Period

# Working

10 - 10:30 a.m.

3

10:30 - 11 a.m.

5

11 - 11:30 a.m.

6

11:30 - 12 noon

10

12 - 12:30 p.m.

10

12:30 - 1 p.m.

10

1 - 1:30 p.m.

9

1:30 - 2 p.m.

8

2 - 2:30 p.m.

5

2:30 - 3 p.m.

2

This schedule allows there to be some extra cashiers available during the hour before and after the lunch period, when demand is too great for the full-time cashiers alone, but is not at a peak level.

The Problem

The manager of the cafeteria is concerned that as the University population continues to grow, the waiting lines and waiting times will get even longer and service will degrade further. The University has scheduled construction of a new Student Union Building that will have greater capacity, but because of the time required to secure funding and perform construction, the building will not be open for 3-4 years. Until then short-term solutions are needed. Several solutions have been recommended by the Student Government Association: (1) Knock down a wall and expand the food service and check-out area into the eating area (which is also in short supply), so as to add three more check-out stations; (2) require all purchases to be made using meal-cards because data that was collected indicated that the average meal-card purchase took 19 seconds while the average cash transaction took 27 seconds; (3) have an express beverage line, so that people who just want to buy a beverage don't have to wait in line so long.

The manager of the cafeteria was very receptive to these suggestions, and agreed to investigate the feasibility, benefits, and costs of each.

Customer Volume and Queue Lengths

Period

Avg. Customer
Volume*

Avg. Number of
Customers in Line**

10 - 10:30

203

4.7

10:30 -11

384

13.1

11 - 11:30

479

49.6

11:30 - 12

812

187.3

12 - 12:30

837

194.1

12:30 - 1

740

162.4

1 - 1:30

498

82.2

1:30 - 2

366

6.8

2 - 2:30

245

3.5

2:30 - 3

187

4.1

* Each cash register records the clock time at which a transaction is completed. The number of customers in each period is the number of customer transactions completed during that half hour. It is not the number of customers who entered the cafeteria or joined a check-out queue during that period.

** This is the total number of customers in all the check-out lines at the beginning of the half-hour period, including those being served by the cashiers. It is not the number in each check-out line.


Discussion Questions

1. Identify and explain the most important pros and cons of each of the three suggestions made by the Student Government Association. Consider queueing theory issues, as well as other economic and behavioral issues of importance.

2. Suppose you were asked to study this problem. Describe what data you would want to collect, how you would collect it, and how you would use it to develop recommendations to the cafeteria manager. Be very specific about the information you would seek and your method for collecting it. Describe any difficulties you would anticipate in gathering the data, and explain how you would overcome them.

3. Based on the information provided, what recommendations do you have for the cafeteria manager, or what possible actions should be investigated and evaluated?

4. The data in Table 1 indicate that the average number of customers processed each half hour varies. For example, during the peak time of 11:30-12 each cashier processes an averages 81.2 customers processed, while during the period 2:30 - 3, each cashier processes 93.5 customers, even though in the later period the servers are probably idle at times, as evidenced by the small average queue length. What might explain this difference? How should this be included in any analysis and recommendations?


Part Two: Additional Data and Questions

Suppose the cafeteria manager had some students study the check-out operation and collect data on the check-out process. The students studied the operation from 10 a.m. until 3 p.m. every day for 5 days. Table 2 is part of a time-study chart that describes the activities of one cashier for a typical period.

Cashier Time-Study Chart

Activity Description

Time Spent (sec)

Observe Customer Tray
Enter Purchase Data

12

Receive Cash/Give Change

9

Wait for Customer to Leave/
Next Customer to move up

4

Observe Customer Tray
Enter Purchase Data

8

Receive Cash/Give Change

5

Wait for Customer to Leave/
Next Customer to move up

1

Observe Customer Tray
Enter Purchase Data

11

Scan Meal Card

6

Wait for Customer to Leave/
Next Customer to move up

3

Weigh Customer's Salad

6

Observe Customer Tray
Enter Purchase Data

10

Scan Meal Card

6

Wait for Customer to Leave/
Next Customer to move up

6

Observe Customer Tray
Enter Purchase Data

13

Answer customer questions

11

Receive Cash/Give Change

17

Wait for Customer to Leave/
Next Customer to move up

8

Observe Customer Tray
Enter Purchase Data

8

Scan Meal Card

7

Wait for Customer to Leave/
Next Customer to move up

2

Find worker to refill soda machine

37

Observe Customer Tray
Enter Purchase Data

14

Receive Cash/Give Change

15

Wait for Customer to Leave/
Next Customer to move up

2

Discussion Questions

1. There is considerable variation in processing times. What may be causing the variations? Explain what impact this may have on customer service.

2. Assuming the data in Table 2 is typical, what suggestions do you have regarding the check-out operation?

 


Wiley's College Division

URL:http://www.umsl.edu/~jmartini/book/aiufs.html
Page Owner: Joseph Martinich (Joseph.Martinich@umsl.edu)
Last Updated: May 22, 1998

Copyright 1997, John Wiley & Sons, Inc.