This paper demonstrates a simple and elegant lattice path combinatoric tech
nique for computing transient probabilities concerning M/M/1 queueing model
s. Through this lattice path approach time dependent analysis of T-policy M
/M/1 queue is presented. The transient probabilities computed herein are fr
ee from modified Bessel function and are amenable to pragmatic probabilisti
c interpretations. As a special case the results for ordinary M/M/1 queues
are checked.