engleski

Offtracking control reqirements for quality roundabout design

In the last 10 years numerous roundabouts have been built in urban and interurban areas in Croatia. As a rule, these roundabouts replaced the existing three-leg and four-leg intersections in order to increase intersection safety and capacity. Replacement of four and three-leg intersections with roundabouts was often carried out without taking into account the ranking of intersecting roads and space requirements. Because of that the capacity and safety levels on these roundabouts were often lower than those on previous four or three-leg intersections. In some cases, poor roundabout design decisions resulted in insufficient lane width on entrance and exit (offtracking control problem) and tangential entrances. These problems are particularly pronounced when the road axes do not intersect at right angles. Unfortunately, lessons learned from these bad examples were not adopted and designers are continuing with poorly designed roundabouts. The main reason for this stems from the fact that there are no official guidelines or regulations for the roundabout design in Croatia. Designers are trying to cope with this situation in different ways ; often they partially study foreign guidelines and seek for the solution that fits their problem. In this paper key elements for successful roundabout design will be shown, based on the example of a recently constructed roundabout in Croatia, findings from other researchers and international guidelines. Proposed instructions could be used for the development of quality national guidelines for roundabout design.

design ; roundabout ; guidelines ; offtracking control ; design vehicle

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