| Freeways have only three percent of the total lane mileage in the U.S., but account for 33 percent of annual vehicle miles of travel according to the FHWA. As such, freeways are the backbone of the U.S. transportation infrastructure, contributing significantly to the nation's economy through enabling the work commute, freight connectivity, the tourism industry, etc. At the same time, much of the national interstate system was built in the 1960s and 70s, resulting in significant and ongoing needs for maintenance, repairs, and other construction activities. As such, freeway work zones are responsible for 24 percent of congestion and delay. To predict or analyze the congestion and delay resulting from these work zones, their capacity needs to be estimated accurately, as it represents a maximum capability of flow for each freeway. For this reason, agencies and researchers have tried for a long time to estimate and model the freeway work zone capacity, as well as understand and predict the impacts from freeway construction activities.;However, current available work zone capacity models were developed from limited local data, and have not been calibrated to a comprehensive national work zone performance data set. Additionally, most previous studies focused on capacity estimation only, and thus often fail to give guidance for estimating work zone free-flow speed (FFS), even if the FFS is a critical operating characteristic of a work zone.;This research provides both capacity and FFS models that were developed and validated using three sources: field, sensor, and literature archives. A total of 102 work zone sites from 12 States provided nationwide field and literature archives data for the development of the capacity model. The FFS model was developed using data collected from three sensor databases covering 14 work zones in several states.;The developed capacity model is intended to be incorporated into the next release of the HCM and provides important insights on the relative effects of work zone configuration and other variables on the expected capacity of freeway work zones. The research also presents guidance for estimating the difference between pre-breakdown capacity and queue discharge rate at work zones, and evaluates and validates different speed-flow models for work zone application through sensor data.;The research further provides a methodology for calibrating freeway work zone capacity in a microsimulation environment, and provides guidance for replicating field-observed work zone capacity through simulation. Guided by an in-depth literature review, key car following and lane changing parameters are proposed for the VISSIM simulation tool, as a result of the calibration effort and extensive sensitivity tests.;Finally, the study provides methodologies for modeling freeway work zones in proximity of interchanges in a microscopic simulation environment. Using calibrated modeling parameters, the research presents simulation results regarding the capacity available for mainline flow under various operating conditions. The result of the study indicates that the presence of a work zone with a lane closure considerably decreases the proportion of mainline flow.;As a result of the research, comprehensive and reliable freeway work zone lane closure capacity and FFS models are provided. They will assist other researchers as well as transportation engineers who seek to find and use freeway work zone capacity and free-flow speed in the multiple lane closure scenarios for their research, operation, maintenance, or analysis. In addition, extensive microsimulation guidance regarding work zones in proximity to interchanges will provide an opportunity for agencies and researchers to further apply and analyze work zone operational performance for their own purposes. |
