Chapter 12 Managing Waiting Lines

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
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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
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“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
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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
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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
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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
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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
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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
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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
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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