Innovative Work Zone Capacity Models from Nationwide Field and Archival Sources

Abstract

Freeway work zone capacity has been the focus of significant research, but most studies were limited to specific geographic regions or work zone configurations or both. To date, no work zone predictive capacity model exists for U.S. freeways that is based on a geographically representative data set or sensitive to key geometric and operational attributes of the work zone. This paper proposes a new capacity model for freeway work zones, developed from nationwide field data fused with data obtained from an in-depth review of archived literature of prior work zone capacity studies in the United States. The proposed model estimates work zone capacity as a function of the lane closure severity index, barrier type, area type, lateral clearances, and daytime or nighttime work conditions. The model was successfully validated with 25% of the combined data that were not used for the model development. In addition, findings from literature archives suggested a 13.4% difference between prebreakdown, uninterrupted capacity and the ensuing queue discharge rate. The developed capacity model is intended to be incorporated into the next release of the Highway Capacity Manual and provides important insights on the relative effects of work zone configuration and other variables on the expected capacity of freeway work zones.

Development of Breakdown Probability Models and Heavy Vehicle Passenger Car Equivalents for Rural Freeway Work Zones

“…Roess and Prassas synopsized nearly five decades of research on this topic, during which most researchers agreed the maximum throughput of a freeway facility drops after the transition from non-congested to congested conditions, but no consensus was drawn on how to define freeway capacity in the presence of bottlenecks such as work zones (10). Yeom et al noted how this has led to inconsistencies in practice and argued that if capacity is to be defined as a ''sustainable'' flow rate, the queue discharge rate (QDR) after breakdown may be a more appropriate measure than pre-breakdown capacity (PBC), since the latter is variable and more difficult to measure (11). The 6th edition of the HCM established formal freeway work zone capacity guidance based on this notion and developed a regression equation from the works associated with NCHRP Project 03-107, which utilized 90 archival literature sources and 12 field-collected datasets (12).…”

“…This section outlines the design of a Vissim experiment conducted to generate BPMs for rural freeway work zones. Based on findings from the literature, it was concluded that the following modelable factors may have a significant effect on the probability of breakdown and subsequent queueing at freeway work zones: traffic volume, upstream lane distributions, free flow speed, speed variance, truck percentage, and lane closure configuration (11,(37)(38)(39). Since field data was only available for a single site with a two-to-one lane closure, scenarios involving other lane closure configurations and traffic characteristics were not considered but may be a topic for future research.…”

Estimating Uncertainty of Work Zone Capacity using Neural Network Models

“…Their model estimates a deterministic capacity value based on work zone configuration features. Yeom et al proposed a capacity estimation model for freeway work zones, developed from nationwide field data fused with data obtained from prior work zone studies in the United States ( 12 ). In their model, they used average queue discharge rate as the definition of capacity.…”

Estimation of Saturation Headway in Work Zones on Urban Streets

“…Several studies have explored factors that affect work zone operations on urban streets. Work zone analysis of freeway segments and facilities is quite frequent in the literature (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14), but the coverage of arterial work zone analysis and associated methodologies is limited (15)(16)(17)(18)(19).…”