Waiting Time Management_2016

8/19/2019 Waiting Time Management_2016

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Waiting TimeManagement

A Key Service Marketing-Operations Interface Question


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Queues: Everywhere!!

Examples

System Queue Service

Bank Account holders Transactions

Telephone Callers Tech support

Fast food Customers Food

Airport Airplanes Runways


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Waiting Time Management

Importance of waiting time management

Operations- based initiatives to manage customers’ waiting time

Perceptions-based initiatives to manage waiting experiences


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The Operations Approach

Objective:

Capacity planning, capacity utilization, scheduling, minimizing

waiting time

Actions:

Facilities design, designing queues

Selected Performance Criteria: Average utilization, average queue

length, average waiting time


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The Perceptions Approach

Objective:

Control perception of time, anxiety, boredom, and anger

Actions:

Activity planning, information sharing

Performance Criterion: Customer satisfaction


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The Base Case

If you have customers arriving at your facility a uniform rate of 2 per

hour, and one server takes exactly 30 minutes to serve one

customer, how many servers will you employ?

What will be the utilization of your facility?

What will be the average waiting time for your customers?


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A simple waiting line model: single server, Poisson arrival, exponentialservice time

Assumptions

Customer population is infinite

Waiting line has a single server

The arrival rate of customers is well approximated by a Poisson distributionService times follow an exponential distribution

Customers are served on a first-come-first-serve basis

Characteristics

= mean arrival rate, i.e., average number of arrivals per unit time

= mean service rate, i.e., average number of customers served per unit time

> 1; service rate > arrival rate.

Real Systems


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TradeoffsNumber of serversWaiting time

Components of a waiting line system

Arrival process

Distribution of service times

Queue discipline: priority ruleNumber of servers

Operating characteristics of a Waiting Line Model

Average number of customers in the system

Average time a customer spends in the system

Service facility utilization


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Utilization factor

=

Idle time = 1-


L =

Average time a customer spends in the

system

W = 1


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Mean

number

in queue

Utilization factor 0 1

0

2

0

Relationship between queue length

and utilization


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A Waiting Time Model with multiple servers

Assumptions

Waiting line has two or more servers (s servers)

Arrival rate follows a Poisson process

Arrivals wait in a single queue and move to the first available server

Service times are exponentialMean service rate is for each server

Characteristics

Utilization factor

s


L = W


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Increasing service levels at a facility

If we want customers’ waiting times to reduce we can do one of three things:

increase the speed of the server,

adding another server at the same location that draws on the same waiting line

adding another server at a different physical location


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Would these three actions result in similar gains?

Consider, for example, a case when = 8, = 10, i.e., / = 0.8.

Now let us double capacity using each of the three strategies mentioned above.

A summary of what happens to the system performance is given below.


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Doubling Capacity

Parameter Base Double Add Add

Case Speed Server Facility

Queue

length 3.2 0.267 0.153 0.267

Waiting

time (hr) 0.40 0.033 0.019 0.067

Total

time (hr) 0.50 0.083 0.119 0.167

(min) 30 5.0 7.15 10.0


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Maister’s eight propositions*

1)Unoccupied time feels longer than occupied time

2)Preprocess waits feel longer than in-process waits

3)Anxiety makes waits seem longer

4)Uncertain waits seem longer than known waits5)Unexplained waits are longer than explained waits

6)Unfair waits are longer than equitable waits

7)The more valuable the service, the longer people will

wait

8)Solo wait feels longer than group waits

David H. Maister, “The Psychology of Waiting in Lines,” HBS note 9-684-064

The Psychology of Waiting


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Multiple channel, single phase

Single channel, multiple phase

Multiple channel, multiple phase

Single Channel, Single

phase

Service Lines


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Selecting Service Line

Formats

Sojourn time is minimized with single-line-single-stage format. When sojourn times are short, customers prefer single lines. When

sojourn times are longer, customers prefer multiple parallel lines.

Customers are averse to multi-staging. If multi-staging is essential, its adverse effect can be reduced by

using open layouts or stage integrators.

Piyush Kumar and Maqbool Dada (2005), “Incorporating the service perspective in service line

design.”


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Customer Satisfaction Model

Sat (T | T0) = -A(T0)exp[c(T0 - T) + c2(S2)],

T = Customer’s estimate of the waiting time

T0 = Customer’s prior expectation of the waiting time

S2= Variance in customer’s estimate of the waiting time

c = customer’s risk aversion parameter

*Piyush Kumar, Manohar U. Kalwani, and Maqbool Dada, “The Impact of Waiting Time

Guarantees on Customers’ Waiting Experiences

Waiting Time Guarantees


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Waiting Time Guarantees

Guarantees enhance satisfaction at the beginning of a wait

During a wait, satisfaction is generally higher in guaranteed waiting

environments

At the end of a wait guarantees have a favorable impact on

satisfaction if they are met and an unfavorable impact if they areviolated.


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Managing Waiting Experiences

Never overlook the impact of managing customers’ perceptions

Determine what is an acceptable waiting time for your customers

Install distractions to entertain and physically involve your customers

Get customers out of line

Make people conscious of time only if they grossly overestimate it

Modify customer arrival behavior

Keep resources not serving customers out of sight

Segment customers by personality type

Karen L. Katz, Blaire M. Larson, and Richard C. Larson, “Prescription for waiting in Line Blues:Entertain, Enlighten, and Engage,” Sloan Management Review,Winter, 1991.


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Waiting Time Management

Decision Domains

Capacity: Overall and variability

Visibility: Observable or unobservable queues

Service Line Format: Default and flexibility

Threshold Enhancing Tools: Psychological

Assurance: Guarantees

Documents

Waiting Time Management_2016