Work Zone Queue Length and Delay Methodology

Development of reliable strategies to overcome adverse mobility impacts of highway work zones requires accurate computation of delay and queues in work zones. This paper presents a methodology for quantifying the mobility impacts that considers the effects of roadway and traffic on speeds (and delays) of cars and heavy vehicles separately. Several factors such as roadway width, speed variation, and differences in speed of cars and heavy vehicles on delay and queue length are considered. The delay caused due to the differences in speeds of different vehicles can be significant when there is limited opportunity for passing or there are significant slow-moving vehicles. It is proposed to determine the impact of such factors on the operating speeds of the vehicles in work zones and use it to compute the capacity-at-operating-speed from the speed-flow curves developed for work zones. Then the speed and capacity are used to compute delay and queue length. Delay is divided into queue delay and moving delay. The moving delay is computed using delay-based passenger car equivalent (PCE) values for work zones. Queue delay is computed based on input-output analysis approach using the capacity as determined in this study. The methodology is illustrated by a step-by-step procedure for computing delay and queue length.