Roundabout is a type of circular intersection in which road traffic flows in an anti-clockwise direction. They were developed as an alternative to classic intersection and have many adventages. From those stands out improvement of road safety because number of possible collision points compared to classic intersection is reduced by more than half. The two-lane roundabout have two circular lanes, but with that capacity doesn't duplicate but new possible collision points and conflicts areas are created. Today, two-lane roundabout are performed only exceptionally when a turbo roundabout can't be performed. A turbo roundabout is a roundabout with spiral course of circular lanes separated by a raised lane separator.
In this master thesis is discussed two-lane roundabout on the bypass road of Mengeš and a proposal of reconstruction into turbo roundabout. An analysis of the capacity parameters were performed with SIDRA INTERSECTION and analytically using Bovy model. In addition, a simulation model was developed for both solutions and simulations for the relevant morning traffic peak at the end of the planning period in 2038. As a result of the simulation, we also received vehicle trajectories that were used as inputs for the model analysis of conflict points. The traffic safety analysis of the two-lane and turbo roundabout shows that turbo roundabout has less possible collision points. On the basis of capacity analysis, traffic safety analysis and eligibility criteria, we can conclude that the turbo roundabout at this site is a more suitable solution than a conventional two-lane roundabout.