Entry and circulating flow relationship at a roundabout

Abstract

This study examined the two formulas stated in the Arahan Teknik (1) 11/87 of the Malaysian Public Work Department to estimate the capacity of small and conventional roundabouts. Field survey, which cover the roundabout inventories, and vehicle classification were carried out. Vehicle classification survey indicates lower entry flows at the single lane entries compared to the multilane entries for both morning and evening peak hours. Statistical analysis was used to identify the correlation between the circulating flows, entry flows and the entry width. Results showed that the capacity obtained from the weaving concept was generally higher than the regression equations for the single and multi entries. The difference between these results may be due to the regression equations that consider the interaction between the entry and circulating flow and the geometric parameters, while the Arahan Teknik (J) 11/87 only address the geometric parameter. The entry flows for both single and multilane entries were highly dependent on the circulating flows.