Extending the work of Koopman (1972), the
Mt/Ekt/k system was proposed by Kivestu (1976)
as a model that could be used to directly compute
approximate queueing statistics for airports—
rather than separately solving the M(t)/M(t)/k and
M(t)/D(t)/k models and then somehow interpolating
their results. (Note that negative exponential service
times (M and constant service times (D) are simply
special cases of the Erlang (Ek) family, with k = 1
and k=, respectively.) Kivestu (1976) noted that k
should be determined from the relationship ES
/S
√ =
k, where ES
and S denote the expected value
and the standard deviation of the service times and
can be estimated from field data. He also developed
a powerful numerical approximation scheme
that computes the (time varying) state probabilities
for the Mt/Ekt/k system efficiently. Malone (1995)
has demonstrated the accuracy and practicality of
Kivestu’s (1976) approach and developed additional
efficient approximation methods, well suited to the
analysis of dynamic airfield queues. Fan and Odoni
(2002) provide a description of the application of
Kivestu’s (1976) model to a study of the gridlock conditions
that prevailed at LaGuardia Airport in 2000
and early 2001.