OFFTRACKING CONTROL REQUIREMENTS FOR QUALITY ROUNDABOUT DESIGN
Last modified: 2017-02-28
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), inadequate intertwining lengths (on two-lane roundabouts), tangential entrances, and travel speed. These problems are particularly pronounced when the road axis do not intersect at right angle.
Unfortunately, lessons learned from these bad examples weren’t 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 are partially studying foreign guidelines and seeking for the solution that fits their problem.
In this paper key elements for successful roundabout design will be shown, based on several examples of Croatian roundabouts, findings from other researchers and international guidelines. Proposed instructions could be used for the development of quality guidelines for roundabout design in Croatia.