Evaluating the Impacts of Work Zone Traffic Control during the Construction of an Alternative and a Conventional Intersection

Alternative intersections and interchanges (AIIs) are increasingly being implemented across the United States due to their potential to improve traffic operations and safety. However, limited research has examined how work zone traffic control (WZTC) measures perform during the construction of these complex designs. This study investigated that gap by evaluating the construction-phase WZTC impacts of a diverging diamond interchange (DDI) relative to a conventional intersection (CI), using two projects in North Carolina as case studies. Effective WZTC is critical for managing construction activities and ensuring safety, yet it can disrupt traffic flow, increase travel time, and contribute to congestion and road user costs. To capture participant’s experience and real-world constraints not fully reflected in design manuals, the study integrates findings from 29 semistructured interviews and 68 survey responses with department of transportation personnel, contractors, and consultants experienced with AIIs. These qualitative insights were used to identify key WZTC cost drivers (staging complexity, detour strategies, temporary signals and signing, and site constraints) and to validate and refine a WZTC cost assessment framework. The framework quantifies WZTC impacts through travel time, congestion, and road user costs (delay and vehicle operating costs [VOCs]) for both DDI and CI projects. Results show that the DDI, while constructed without mainline lane reductions, generated substantially higher user delay and detour-related costs during ramp closures than the CI, reflecting greater staging and traffic control complexity. This framework establishes a foundation for broader research and introduces a novel way to assess WZTC impacts, enabling more effective, customized construction-phase planning and staging decisions for AII projects.