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Develop Traffic Capacity Models for Mini-Roundabouts from Simulation

Project Information

Project ID: 
Project Status: 
Start Date: 
Monday, May 30, 2011
End Date: 
Friday, March 30, 2012
FHWA Program: 
FHWA Topics: 
Research/Technologies--Turner-Fairbank Highway Research Center (TFHRC)
TRT Terms: 
Simulation; Roundabouts; Capacity; Operations; Research; Highway Traffic Control
FHWA Discipline: 
Safety, Operations, Design, Planning
TRB Subject Area: 
Research, Operations and Traffic Management, Design, Highways, Pedestrians and Bicyclists

Contact Information

First Name: 
Last Name: 
(202) 493-3293
Email Address: 

Project Details

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No capacity models for mini-roundabouts exist, other than from ARCADI, a UK model whose equations are unpublished.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.


Develop capacity equations for a 50' and 75' inscribed circle diameter (ICD) mini-roundabout from driver performance in the United States.

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.

For more information, see Determination of Mini-Roundabout Capacity in the United States.


Deliverable Name: 
Paper on the capacity model based on simulation
Deliverable Type: 
Deliverable 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).