Evaluation of Roundabout Capacity Models: An Empirical Case Study

Ren, Liang; Qu, Xiaobo; Guan, Hong; Easa, Said M.; Oh, Erwin

doi:10.1061/(asce)te.1943-5436.0000878

Cited by 17 publications

(7 citation statements)

References 33 publications

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“…Also, transportation agencies and local governments provide guidelines about the intersection design selection [16][17][18][19][20]. The operational performance of an existing or proposed roundabout can be assessed through capacity models [21][22][23][24][25][26][27][28][29]. However, it is well known that the capacity models vary depending on the driving behaviours [28].…”

Section: Literature Reviewmentioning

confidence: 99%

Mathematical Analysis for Roundabout Capacity

Suh

Kim

et al. 2018

Mathematical Problems in Engineering

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This paper investigates roundabout capacity analysis using mathematical modelling and microscopic simulation. The capacity in approach section in roundabout is calculated by estimating the number of vehicles that can enter a roundabout for a given approach given a certain circulating volume. Since roundabouts are working with only yield conditions, capacity is dependent on gap acceptance model. Priority rules are used to simulate the gap acceptance model and define the right-of-way for conflicting movements. In the case of roundabouts, priority rules can be utilized to establish right-of-way at each of the conflict points where the approach traffic merges with the circulating traffic of the roundabout. By altering the minimum acceptable gap and related parameters, it is possible to calibrate a simulation model to be that of a real-life roundabout or that of a theoretical roundabout that meets the operating characteristics defined in current capacity models. The proposed roundabout capacity analysis methodology is expected to assist modelling operational conditions for roundabouts. Results are presented that provide evidence to validate the proposed approach.

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Section: Literature Reviewmentioning

confidence: 99%

Mathematical Analysis for Roundabout Capacity

Suh

Kim

et al. 2018

Mathematical Problems in Engineering

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“…Roundabouts are often used in road design as an alternative to conventional intersections because of their abilities to accommodate high volumes of traffic and minimize delay (Bie et al, 2016;Ren et al, 2016). While numerous merits with regards to handling passenger vehicles, roundabouts become more debatable when considering heavy vehicles.…”

Section: Introductionmentioning

confidence: 99%

Estimating Passenger Car Equivalent of Heavy Vehicles at Roundabout Entry Using Micro-Traffic Simulation

Pajecki

Ahmed

et al. 2019

Front. Built Environ.

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Passenger Car Equivalent (PCE) is a unit used to represent the impact of a large vehicle on a road by expressing it as the number of equivalent passenger vehicles. This paper focuses on estimating the PCE of various sized heavy vehicles in roundabouts with respect to different entry flow rates. A single-lane roundabout was tested under predefined mixed traffic and demand scenarios in VISSIM micro-simulation environments. The individual and group behavior of four separate heavy-vehicle types were tested: single-unit trucks, buses, small semitrailers, and large semitrailers. The obtained PCE values were found to be on average lower than those suggested in the United States guidelines for roundabouts. The estimated PCE values for heavy vehicles in mixed traffic conditions are 1.30 for single unit trucks, 1.40 for small semitrailers, 1.60 for buses, and 1.70 for large semitrailers. Additional factors such as varying inflow (balanced, unbalanced, and congested traffic) show direct influences on the PCE values. The PCE value under these conditions ranged from 1.25 to 1.75 for smaller vehicles (single-unit trucks, buses, and small semitrailers) and 1.45-2.10 for larger heavy vehicles (large semitrailers). A general equation was developed based on the data to relate vehicle proportions and heavy-vehicle reduction factors that would be useful for professionals to analyze the operational performance of roundabouts with better accuracy.

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“…Ren et al calibrated five roundabout capacity models using the gap acceptance parameters measured at nine roundabouts in the Gold Coast, Australia ( 15 ). These calibrated models were then compared with the actual flow rates in the field.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the Roundabout Capacity Model in HCM6 Edition and HCM 2010 on a Multilane Roundabout

Chen

Hourdos

2018

Transportation Research Record: Journal of the Transportation R

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This study evaluated the performance of the new Highway Capacity Manual 6th Edition (HCM6) roundabout capacity model at a multilane roundabout in Richfield, Minnesota. Traffic flow rates and gap acceptance data were collected during 20 hours of afternoon peak period traffic over four days. The observed critical headways for the left and right lanes was equal to 4.43 and 3.99 s while the observed follow-up headways were 3.05 and 2.96 s, respectively. Roundabout capacity curves for both lanes were built through the collected flow information, as well as through the observed headways and the HCM formula. As compared with the field observed results, the default model in HCM6 overestimated the capacity of the study roundabout. The default model in HCM 2010 closely estimated the capacity for the right lane, but overestimated the capacity of the left lane when the circulating flow rate was high. The HCM6 model was calibrated with the observed critical and follow-up headways, as well as by calibrating the intercept of the model using only the follow-up headway. The fully calibrated model overestimated the capacity of the right lane by 7–10% as the circulating flow decreases and overestimated the capacity of the left lane by 7% and 31%. The partially calibrated model overestimated the capacity of the left lane by 6% and overestimated the capacity of the right lane by at most 10% under low circulating flow rate, but it underestimated the capacity by at most 21% under high circulating flow rate.

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Evaluation of Roundabout Capacity Models: An Empirical Case Study

Cited by 17 publications

References 33 publications

Mathematical Analysis for Roundabout Capacity

Mathematical Analysis for Roundabout Capacity

Estimating Passenger Car Equivalent of Heavy Vehicles at Roundabout Entry Using Micro-Traffic Simulation

Evaluation of the Roundabout Capacity Model in HCM6 Edition and HCM 2010 on a Multilane Roundabout

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