Assessment of free flow bypass lanes at single-lane roundabouts

The paper aims to investigate the effect of the free-flow right-turn bypass lane at single-lane roundabouts in terms of overall delay improvements. In total, 47 different cases of various entry flows per approach were examined, utilizing 189 different distribution rates in left-turn, through and right-turn movements per case, resulting thus in 8883 discrete scenarios. The multiple linear regression analysis that followed revealed the most critical parameters that affect the overall roundabout’s operational performance in terms of delay when a free-flow right-turn bypass lane is introduced. The model extracted herein, which is statistically adequate to serve as a useful tool in roundabout design, at least during the planning stage, can identify whether the installation of a free-flow right-turn bypass lane can improve the total roundabout’s delay. Further analysis is required to investigate in more detail potential effects of additional parameters, such as multilane roundabouts, the existence of more than one bypass lanes and, more importantly, the presence of pedestrians, which may levy further constraints.