Methodological Frontier in Operational Analysis for Roundabouts: A Review

Abstract

Several studies and researches have shown that modern roundabouts are safe and effective as engineering countermeasures for traffic calming, and they are now widely used worldwide. The increasing use of roundabouts and, more recently, turbo and flower roundabouts, has induced a great variety of experiences in the field of intersection design, traffic safety, and capacity modeling. As for unsignalized intersections, which represent the starting point to extend knowledge about the operational analysis to roundabouts, the general situation in capacity estimation is still characterized by the discussion between gap acceptance models and empirical regression models. However, capacity modeling must contain both the analytical construction and then solution of the model, and the implementation of driver behavior. Thus, issues on a realistic modeling of driver behavior by the parameters that are included into the models are always of interest for practitioners and analysts in transportation and road infrastructure engineering. Based on these considerations, this paper presents a literature review about the key methodological issues in the operational analysis of modern roundabouts. Focus is made on the aspects associated with the gap acceptance behavior, the derivation of the analytical-based models, and the calculation of parameters included into the capacity equations, as well as steady-state and non-steady-state conditions and uncertainty in entry capacity estimation. At last, insights on future developments of the research in this field of investigation will be also outlined.

Multi-lane Roundabout Capacity Evaluation

“…Empirical regression models are established on the basis of field data, employing which information that correlates capacity with delays and geometric features. Developing a reliable regression model requires a large set of data on saturated conditions (Giuffrè et al, 2016b). This task is often time consuming, and the resulting model represents traffic conditions only in the specific area where research is conducted.…”

“…An important issue for consideration, however, is that the critical gap and followup values depend on traffic conditions, the type and dimensions of intersections, and traffic flow structures. Thus, the assumptions are unrealistic: drivers do not behave in the same manner each time and often accept a smaller gap than expected (Giuffrè et al, 2016b). Nevertheless, simplifying the true nature of driving behavior has no significant influence on the final capacity results.…”

A Case Study on Roundabout under Congestion: Proposal to Improve Current Traffic Operation

“…The results indicated that SIDRA and VISSIM will, in general, think little of deferrals and line lengths for the multi-path roundabouts under the blockage, while RODEL results in higher postponement and line length estimations all things considered of the passage approaches [11]. Giuffrè et al (2016) displays an interesting writing audit about the key methodological issues in the operational investigation of the modern roundabouts. The concentrate is made on the angles related with the whole acknowledgment conduct, the inference of the investigative based models, and the computation of parameters included into the limit conditions, just as unfaltering state and nonconsistent state conditions and vulnerability in section limit estimation [12].…”

“…Giuffrè et al (2016) displays an interesting writing audit about the key methodological issues in the operational investigation of the modern roundabouts. The concentrate is made on the angles related with the whole acknowledgment conduct, the inference of the investigative based models, and the computation of parameters included into the limit conditions, just as unfaltering state and nonconsistent state conditions and vulnerability in section limit estimation [12]. Finally, bits of knowledge on future advancements of the exploration in this field of the examination will be additionally sketched out.…”

Estimation of Passenger Car Equivalents for Two-Lane and Turbo Roundabouts Using AIMSUN

“…Despite the advantage of this capacity formula, calibration of parameters to be included into the model was affected by local conditions and German driver behavior. Differently from turbo roundabouts for which a generalized capacity formula has not yet been proposed, methodological issues in the operational analysis and calculation of entry capacity at standard roundabouts were addressed by numerous studies on the topic; see e.g., Mauro (2010) for capacity calculation and issues of stochastic nature of the traffic phenomenon at roundabouts, Giuffrè et al (2016b) for a systematic review on derivation of the analytical-based models under steadystate entry conditions and gap-acceptance models, Šaric and FIGURE 1 | Summary of the main geometric features of the examined roundabout (roundabout 1).…”