Evaluating Steady-State Assumption for Highway Queueing System

Stochastic queueing methods are often applied to highway systems to estimate performance characteristics such as delay and queue length. Inherent in stochastic queueing methods is the assumption that the system in question operates at steady state for the duration of the analysis period. The validity of this assumption with respect to traffic-flow facilities is, at times, in question. It is therefore somewhat surprising that the vast body of literature concerned with the application of stochastic queueing methods for the assessment of highway operation includes very little discussion on the relevance of the steady-state assumption. This paper presents a simulation-based methodology for evaluating the appropriateness of the steady-state assumption. The methodology is demonstrated using a particular type of highway facility—a two-lane highway work zone. Application of the methodology suggests that the assumption of steady-state operation may not always be reasonable and, as such, illustrates the potential need to investigate the steady-state tendencies of a facility type prior to exploiting stochastic queueing techniques.