Restricted and unrestricted express lane queuing in the critical utilization of M/G/N queues

Abstract

We present an agent-based study on the effect of restricted and unrestricted express lane queuing in the critical utilization of an N-server queuing system with Gaussian-distributed service times T_S. Introduction of express lanes at critical utilization of a queue is assumed to make a significant difference in the average T_C of agents. We find that this is not always the case. With restricted express lane queuing, there is an optimal restriction on the T_S for agents taking the express lane. Unoptimal T_S restriction overutilizes either the express lane or the regular lanes. With unrestricted express lane queuing on the other hand, a threshold restriction exists. T_S restriction less than the threshold overutilizes the regular lanes. Express lane are able to redistribute loads over different service counters, however, on the average, it gives no significant improvement to the overall performance of the system.