Analytical Methods for Work Zone Travel Time Reliability

Travel time reliability studies have garnered interest in recent years with researchers and practitioners recognizing reliability as a trait of significant importance to commuters. Presence of work zones can significantly impact the capacity and speeds at the location and consequently impact travel time reliability. This study built a framework for studying impacts of work zone on travel time reliability. The framework covers aspects of work zone selection, evaluation of work zones, derivation of travel time distributions for each work zone, and developing a predictive model for work zone impact on travel time reliability. Work zone and travel time data were collected from 19 freeway and highway work zones across the state of Wisconsin. Supporting hourly traffic counts were collected for the work zones where available. Average travel time trends through a day, travel time distribution, and reliability metrics were studied at each candidate location individually to observe the impacts of the work zone. Reliability measures from across all work zones were combined to study discernible relationships between the change in reliability measures caused due to the work zone and a variety of work zone properties, and predictive regression models were developed to estimate work zone impact on reliability. Due to limitations in the quality and quantity of data available, the regression modeling yielded moderate goodness of fits. A larger dataset and/or availability of detailed work zone information might result in better travel time reliability models. The report presents limitations and findings from the study and informs on quality of data that needs to be collected for future studies on work zone travel time reliability.