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Project Information
Project ID:   FHWA-PROJ-11-0045
Project Name:   Develop Traffic Capacity Models for Mini-Roundabouts from Simulation
Project Status:   Completed
Start Date:  May 30, 2011
End Date:  March 30, 2012
Contact Information
Last Name:  Lochrane
First Name:  Taylor
Telephone:  202-493-3293
E-mail:  taylor.lochrane@dot.gov
Office:   Office of Operations Research and Development
Team:   Trans Ops Concepts and Analysis Team [HRDO-20]
Laboratory:   Saxton Transportation Operations Laboratory
Project detail
Project Description:   No capacity models for mini-roundabouts exist, other than from ARCADI, a UK model whose equations are unpublished. Based on VisSim and using typical sizes of small size roundabouts, layouts and models will be developed to simulate at least two typical designs. The models will include effects of large vehicles and assumptions about driving behaviors. The objective is to simulate numerous traffic scenarios representative of all possible traffic volume conditions and estimate maximum throughput at one of the approaches. The maximum throughput data will be fitted in an exponential function as a function of circulating or conflicting volume, and percent of large vehicles.
Goals:   Develop capacity equations for a 50' and 75' inscribed circle diameter (ICD) mini-roundabout from driver performance in the United States.
Field Test:   Gap and headway was collected to calibrate the model from a similar design in Stevensville, MD.
Product Type:   Article
Conference displays
Test Methodology:   Modeling and Simulation
Expected Benefits:   Development of capacity model for mini-roundabouts.
Deliverables: Name: Paper on the capacity model based on simulation.
Product Type(s): Other, Article, Conference displays
Description: Based on VisSim, field data, and using typical sizes of small-size roundabouts, layouts and models will be developed to determine the capacity of the mini-roundabout. A paper will be submitted to ITE Journal [Institute of Transportation Engineers] and the Transportation Research Board (TRB).
Project Findings:   This research has presented a methodology to estimate parameters of an analytical capacity model for the 50' and 75' inscribed circle diameter (ICD) mini-roundabouts. The linear models presented are based on VisSim simulation results where VisSim has been calibrated from field data. The models presented include parameters for the 50' and 75' inscribed circle diameter (ICD) mini-roundabout designs. The simulation results suggest that linear models provide useful estimates of capacity for the two selected prototype designs. Estimated capacity for the 50' ICD mini-roundabout is smaller than the 75' ICD where heavy vehicles are shown to affect the capacity at high heavy vehicle presence. When comparing the land required to construct or convert from an all-way stop-control (AWSC) to a mini-roundabout or single-lane roundabout, the mini-roundabout has higher entering capacity per square foot. This would be a useful design when optimizing existing land in urban areas to increase capacity at lower cost.
FHWA Topics:   Research/Technologies--Turner-Fairbank Highway Research Center (TFHRC)
TRT Terms:   Simulation
Highway Traffic Control
FHWA Disciplines:   Safety
Subject Areas:   Research
Operations and Traffic Management
Pedestrians and Bicyclists


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