An Experimental Analysis on Capacity Estimation for Undisciplined Intersections/Junctions

This paper covers an experimental analysis on capacity estimation for undisciplined intersections/junctions. Rotary intersections are special form of at-grade intersections laid out for the movement of traffic in one direction around a central traffic island. Essentially all the major conflicts at an intersection namely the collision between through and right-turn movements are converted into milder conflicts namely merging and diverging. The vehicles entering the rotary are gently forced to move in a clockwise direction in orderly fashion. Rotary intersections are an effective intersection type which is also called as Roundabout which is provided for easier decision making than conventional intersections. These rotary intersections have a traffic calming effect by reducing vehicle speeds using geometric design. Rotaries require less maintenance than traffic signals. A well designed roundabout achieves a balance of safety and efficiency. Traffic rotaries reduce the complexity of crossing traffic by forcing them into weaving operations. The shape and size of the rotary are determined by the traffic volume and share of turning movements. Capacity assessment of a rotary is done by analyzing the section having the greatest proportion of weaving traffic. In the past years various models have been developed for analyzing the traffic flow on this intersection. These methods are classified in two groups. The first group consists of methods which are purely empirical and based on geometry of intersection. The second group consists of methods which are based on Gap acceptance process.