A Queueing and Facility Design Case by
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 |
# of Workers |
Scheduled Shift |
| 10 a.m. - 1 p.m. |
| 10:30 a.m. - 1:30 p.m. |
| 11 a.m. - 2 p.m. |
| 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. |
|
10:30 - 11 a.m. |
|
11 - 11:30 a.m. |
|
11:30 - 12 noon |
|
12 - 12:30 p.m. |
|
12:30 - 1 p.m. |
|
1 - 1:30 p.m. |
|
1:30 - 2 p.m. |
|
2 - 2:30 p.m. |
|
2:30 - 3 p.m. |
|
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 ProblemThe 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. |
Period | Avg. Customer | Avg. Number of |
10 - 10:30 |
|
|
10:30 -11 |
|
|
11 - 11:30 |
|
|
11:30 - 12 |
|
|
12 - 12:30 |
|
|
12:30 - 1 |
|
|
1 - 1:30 |
|
|
1:30 - 2 |
|
|
2 - 2:30 |
|
|
2:30 - 3 |
|
|
* 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
Part Two: Additional Data and QuestionsSuppose 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. |
Activity Description | Time Spent (sec) |
Observe Customer Tray |
|
Receive Cash/Give Change |
|
Wait for Customer to Leave/ |
|
Observe Customer Tray |
|
Receive Cash/Give Change |
|
Wait for Customer to Leave/ |
|
Observe Customer Tray |
|
Scan Meal Card |
|
Wait for Customer to Leave/ |
|
Weigh Customer's Salad |
|
Observe Customer Tray |
|
Scan Meal Card |
|
Wait for Customer to Leave/ |
|
Observe Customer Tray |
|
Answer customer questions |
|
Receive Cash/Give Change |
|
Wait for Customer to Leave/ |
|
Observe Customer Tray |
|
Scan Meal Card |
|
Wait for Customer to Leave/ |
|
Find worker to refill soda machine |
|
Observe Customer Tray |
|
Receive Cash/Give Change |
|
Wait for Customer to Leave/ |
|
Discussion Questions
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Copyright 1997, John Wiley & Sons, Inc.