Estimation of Entry Capacity for Single-Lane Modern Roundabouts: Case Study in Queensland, Australia

Abstract

Single-lane modern roundabouts are one of the most important intersection types in suburbs of Australia. It is therefore important to estimate their entry capacities. In this case study, we firstly propose an analytical model based on the gap acceptance theory by incorporating the effects of the exiting vehicles. It then proceeds to carry out a scenario analysis to assess the effects of the exiting indicators. This is followed by the discussions of the applicability of the proposed model. The results show that the transport authorities need to strictly enforce the use of indicators before exiting in order to achieve higher capacity.

Traffic Efficiency Evaluation of Elliptical Roundabout Compared with Modern and Turbo Roundabouts Considering Traffic Signal Control

“…Several studies have examined the capacity of roundabouts. Qu et al [9] estimated the entry capacity of single lane modern roundabout using a case study in Queensland. Sisiopiku and Oh [10] compared the performance of a roundabout with a four-leg intersection.…”

Investigation on Entry Capacities of Single-Lane Roundabouts

“…HCM 2000 model treat the exiting vehicles as non-existent, which are not counted as circulating traffic. Based on survey of 19 single-lane modern roundabouts in Queensland, Australia, Qu et al (2014) indicated that waiting vehicles will immediately (in an average of 1.4 seconds) enter the roundabout after exiting vehicles turn their indicators on (usually more than 1 second before the actual turning movements) [2]. In other words, a waiting vehicle might not necessarily wait for a critical gap if an exiting vehicle shows up.…”

“…A comparative study indicates that HCM 2000 model performs well under low to mid traffic conditions while it underestimates the capacities under high traffic conditions in combination with high proportions of exiting vehicles. [2]. In this paper, the two models are integrated using a scenario based approach to analyse the effects of not only exiting vehicles but also HGVs.…”

“…In other words, a waiting vehicle might not necessarily wait for a critical gap if an exiting vehicle shows up. Accordingly, by assuming that each exiting vehicle could provide one entry opportunity for waiting vehicles, a new roundabout capacity model (referred to as NRC model I hereafter) is proposed by Qu et al by considering influence of exiting vehicles [2], mathematically expressed by…”

“…However, their effects have not been taken into account in HCM 2000 model.Recently two studies have been carried out to address this issue: 1) Dahl and Lee (2012) proposed an expectation theory based approachto incorporate the effect of HGVs [1]; and2) deriveda new roundabout capacity model by assuming that each exiting vehicle could provide one entry opportunity for waiting vehicles [2]. In this paper, the two models are integrated using a scenario-based approachtoanalyse the effects of not only exiting vehicles but also HGVs.…”