Abstract:
Intersection performance plays a significant role in network performance. Therefore, efficient
intersections have a positive impact on the overall performance of the network. The service
measure for all urban intersections irrespective of the type, including interchanges ramps, is
delay expressed as Seconds/vehicle, i.e., delay. Roundabouts are an inherently very safe type
of intersection, and mostly preference is given due to their safety feature. But there is no
guideline on selecting ICD of a roundabout concerning delay; only daily service volume and
design vehicle are given weightage for ICD selection. This study compares delays of different
roundabouts with inscribed circle diameters ranging from 35 m to 95 m. The results suggest
that no matter the lane configuration, there is a reduction in delay as the ICD increases. And
when we compare results of 35 m ICD to 95 m ICD, around 50 % reduction in the delay is
observed for 95 m ICD from 35 m ICD. It is also established that ICD does not affect the
saturation flow of a roundabout is dependent upon the number of entry lanes of the
Roundabout. Additional benefit of using larger ICD will be availability of ROW for planning
of grade separated facilities if required.
