Development of Delay Models for Roundabouts

Abstract

The purpose of this research is to develop an empirical model for total delay time prediction at roundabouts as a function of influence traffic and geometric features. Four roundabouts of fifteen approaches with different characteristics are selected in Karbala City. The traffic parameters are measured using video recording technique. Geometric elements are measured through field survey and satellite image. A statistical approach is used to develop three delay models (linear regression models with 95% and 50% confidence level, and polynomial regression model with 95% confidence level). The statistical analysis indicates that both geometric and traffic variables have a significant effect on delay time. The entry radius and circulating traffic have the greatest influence. These models have been compared with SIDRA delay model. It is found that although SIDRA delay overestimates delay time at high delay range, but it does not have a significant difference with the field delay at 95% confidence level.