engleski

Approach Alignment Impact on the Geometric Design of Urban Roundabouts

Nowadays existing three and four-leg intersections are frequently replaced by roundabouts. Compared to conventional intersections, the implementation of roundabouts on a road network offers several advantages, such as increased safety and intersection capacity, reduced maintenance costs and air pollution. However, in some cases, these are not realized because of the poor geometric design. One of the main prerequisites for the optimal roundabout design is that all the approach axes must intersect at the centre of a roundabout. The alignment of the approach axis relative to the centre of a roundabout plays an important role in the roundabout design. It affects the amount of deflection (the ability to control driving speed through roundabout), the swept path of a design vehicle and the sight distance. In practice, due to spatial constraints and increasing property development along the road, this precondition cannot always be satisfied. This comes to the fore particularly in urban environments, where the reconstruction of the approach axis is usually not possible. Considering the above, this paper will investigate the impact of the radial offset of the approach axis (the axis does not pass through the roundabout centre) on the geometric design of urban roundabouts. The research is carried out through several theoretical examples of the small and medium- sized urban roundabouts with various external radii and for the design vehicle 12.0 m long bus.

urban roundabouts ; geometric design ; approach centreline offset ; swept path analysis ; fastest path analysis

nije evidentirano