Chapter 12 Managing Waiting Lines McGraw-Hill/Irwin Service Management: Operations, Strategy, and Information Technology, 6e Copyright © 2008 by The McGraw-Hill Companies, Inc. All Rights Reserved. Lines and Waiting “Every day I get in the queue, that waits for the bus that takes me to you …” Pete Townshend, Magic Bus 12-2 Learning Objectives        Describe the economies of waiting lines using examples. Describe how queues form. Apply Maister’s two “laws of service.” Describe the four psychology of waiting components and suggest strategies to deal with each. Describe the four principles of waiting line management. Describe the essential features of a queuing system. Describe the relationship between a negative exponential distribution of time between arrivals and a Poisson distribution of arrival rates. 12-3 Where the Time Goes In a life time, the average person will spend: SIX MONTHS Waiting at stoplights EIGHT MONTHS Opening junk mail ONE YEAR Looking for misplaced 0bjects TWO YEARS FOUR YEARS FIVE YEARS SIX YEARS Reading E-mail Doing housework Waiting in line Eating 12-4 Cultural Attitudes    “Americans hate to wait. So business is trying a trick or two to make lines seem shorter…” The New York Times, September 25, 1988 “An Englishman, even when he is by himself, will form an orderly queue of one…” George Mikes, “How to be an Alien” “In the Soviet Union, waiting lines were used as a rationing device…” Hedrick Smith, “The Russians” 12-5 Waiting Realities   Inevitability of Waiting: Waiting results from variations in arrival rates and service rates Economics of Waiting: High utilization purchased at the price of customer waiting. Make waiting productive (salad bar) or profitable (drinking bar). 12-6 Laws of Service     Maister’s First Law: Customers compare expectations with perceptions. Maister’s Second Law: Is hard to play catch-up ball. Skinner’s Law: The other line always moves faster. Jenkin’s Corollary: However, when you switch to another other line, the line you left moves faster. 12-7 Remember Me     I am the person who goes into a restaurant, sits down, and patiently waits while the wait-staff does everything but take my order. I am the person that waits in line for the clerk to finish chatting with his buddy. I am the one who never comes back and it amuses me to see money spent to get me back. I was there in the first place, all you had to do was show me some courtesy and service. The Customer 12-8 Psychology of Waiting      That Old Empty Feeling: Unoccupied time goes slowly A Foot in the Door: Pre-service waits seem longer that in-service waits The Light at the End of the Tunnel: Reduce anxiety with attention Excuse Me, But I Was First: Social justice with FCFS queue discipline They Also Serve, Who Sit and Wait: Avoids idle service capacity 12-9 Approaches to Controlling Customer Waiting     Animate: Disneyland distractions, elevator mirror, recorded music Discriminate: Avis frequent renter treatment (out of sight) Automate: Use computer scripts to address 75% of questions Obfuscate: Disneyland staged waits (e.g. House of Horrors) 12-10 Essential Features of Queuing Systems Renege Calling population Arrival process Balk Queue configuration Queue discipline Service process Departure No future need for service 12-11 Arrival Process Arrival process Static Dynamic Random arrivals with constant rate Random arrival rate varying with time Facilitycontrolled Accept/Reject Price Appointments Customerexercised control Reneging Balking 12-12 Relative frequency, % Distribution of Patient Interarrival Times 40 30 20 10 0 1 3 5 7 9 11 13 15 17 19 Patient interarrival time, minutes 12-13 3.5 3 2.5 2 1.5 1 0.5 0 1 3 5 7 9 11 13 15 17 19 21 23 Hour of day Percentage of average daily physician visits Average calls per hour Temporal Variation in Arrival Rates 140 130 120 110 100 90 80 70 60 1 2 3 4 5 Day of week 12-14 Poisson and Exponential Equivalence Poisson distribution for number of arrivals per hour (top view) 1 Arrival 2 Arrivals 0 Arrivals 1 Arrival One-hour interval 62 min. 40 min. 123 min. Exponential distribution of time between arrivals in minutes (bottom view) 12-15 Queue Configurations Multiple Queue Single queue Take a Number Enter 3 4 8 2 6 10 12 11 7 9 5 12-16 Queue Discipline Queue discipline Static (FCFS rule) Dynamic Selection based on individual customer attributes selection based on status of queue Number of customers waiting Round robin Priority Preemptive Processing time of customers (SPT or cµ rule) 12-17 Relative frequency, % Walk-in Service 15 10 5 0 1 11 21 31 Minutes 41 Relative frequency, % Relative frequency. % Outpatient Service Process Distributions Second Service Appointment Service 15 10 5 0 1 11 21 31 41 Minutes 15 10 5 0 1 11 21 31 41 Minutes 12-18 Service Facility Arrangements Service facility Server arrangement Parking lot Self-serve Cafeteria Servers in series Toll booths Servers in parallel Supermarket Self-serve, first stage; parallel servers, second stage Hospital Many service centers in parallel and series, not all used by each patient 12-19 Topics for Discussion      Suggest some strategies for controlling variability in service times. Suggest diversions that could make waiting less painful. Select a bad and good waiting experience, and contrast the situations with respect to the aesthetics of the surroundings, diversions, people waiting, and attitude of servers. Suggest ways that management can influence the arrival times of customers. What are the benefits of a fast-food employee taking your order while waiting in line? 12-20 Interactive Exercise The class breaks into small groups with at least one international student in each group, if possible. Based on overseas travel, each group reports on observations of waiting behavior from a cultural perspective. 12-21 Thrifty Car Rental Queue Features Customer Counter Garage Car Wash Calling Population Arrival Process Queue Configuration Queue Discipline Service Process 12-22 Eye’ll Be Seeing You      How are Maister’s First and Second Laws of Service illustrated? What good and bad features of a waiting process are evident? How should Dr. X respond to Mrs. F’s letter? How could Dr. X prevent future incidents? Should customers be rewarded for offering constructive criticism? 12-23 Sample Letter Dear Mrs. F.: I offer my deepest apologies for your recent bad experience on January 5, 1989. The treatment you were shown and the length of time you had to wait is completely inexcusable. You and the rest of your family are valued patients of mine and I hope this most unfortunate experience does not cause me to lose your patronage. I personally guarantee that this will not happen again. I hope you will make another appointment with us to have your problem taken care of. This service, of course, will be provided free of charge. Thank you for expressing your concerns. Please let me know immediately if you have any other problems. Sincerely yours, Dr. X, M.D. 12-24