CALL CENTERS (CENTRES) - Faculty of Industrial Engineering and ...

The major result which has come from this effort is that the average daily retrial percentage
taken across location and time of year seems to be moderately stable about a mean value of 69%,
somewhat dependent on both location and (particularly) time of year. The value is consistently
higher during periods close to important filing milestones and lower otherwise. We show this
to mean that, whenever a rate of 69% is used, the actual demand would be estimated by augmenting
completed loads by 31% of the number of blocked and abandoned calls for the period
of concern.
Keywords: Communications, Queues, Stochastic processes, Operations research, Statistics, Telephone
systems, Caller retrial rate, Taxpayer service telephone network, US Internal Revenue
Service, Statistical method
17. Harris, C.M., K.L. Hoffman and P.B. Saunders. Modeling the IRS telephone taxpayer information
system, Operations-Research, 35 (4), 1987, 504–523.
Abstract. The Internal Revenue Service (IRS) toll-free, nationwide telephone system provides
prompt tax-information assistance. In 1986, the IRS processed 37.8 million calls from taxpayers
at 32 answering sites. This paper documents a critical review of the IRS approach to allocating
its staff and equipment. The authors built a simulation-based model to test various allocation
policies for deploying IRS resources. The simulation study included detailed sensitivity analysis
of key network variables, and showed the feasibility of modeling a typical IRS location as a
multiserver loss/delay queue with retrial and reneging. The second phase of this effort therefore
centered around developing a prototype probabilistic model for determining the most effective
way of providing service at reasonable levels and at minimum cost. The resulting model allows
the IRS to determine from tables the best configuration of people and telephone lines for any
expected levels of incoming traffic. In addition, the authors provided flow balance analyses of
the underlying feedback queues that permit the IRS to separate their caller streams into fresh
and repeat callers, and thus to estimate actual demand for service.
Keywords: Queueing theory, Telephone traffic, Telephone taxpayer information system, Internal
Revenue Service, Simulation-based model, Allocation policies, Probabilistic model, Flow balance
analyses, Feedback queues, Caller streams
18. Kuhn, Patricia and Thomas P. Hoey. Improving police 911 operations in Washington, D.C.
National Productivity Review, New York, 6 (2), 1987, 125–134.
Abstract. The 911 operation in Washington, DC, has generated an increasing number of complaints
from city officials and residents in recent years. Call handling performance was not
satisfactory, with 33% of the calls in 1985 kept waiting and 17% abandoned for lack of response.
In 1986, two initiatives were begun to improve 911 operations. New technology, Enhanced 911,
was introduced to replace antiquated telephone and call distribution equipment. The 2 foremost
features of Enhanced 911 are automatic number identification and automatic location identification.
An operations improvement project also was initiated, emphasizing: 1. matching staff
deployment with call demand, 2. improving call-handling performance, and 3. improving civilian
pay equity. Call-handling performance gains were brought about by: 1. modifying call distributor
software to increase call processing efficiency, 2. starting revised employee and supervisor
work schedules, and 3. beginning a workstation coverage policy to guarantee constant manning
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