Latest edition of Croatian design guidelines for roundabouts was published in 2014, and its usage is mandatory for intersections on the state roads. This paper offers a review of aforementioned guidelines, with the emphasis on the roundabout geometric design, which are presented through several theoretical examples of suburban roundabouts with various external radii. On these roundabouts swept path analysis for tri-axle bus is conducted, and results of this analysis are commented on. This long passenger vehicle was chosen for the analysis even though it is not defined as a design vehicle in guidelines, due to the following facts: (1) Croatia is a popular tourist destination, with numerous guests arriving from distant locations, and tri-axle buses are a common mean of their transport; (2) swept path analyses have shown that the space needed by the vehicle body during the turning movements is larger for this type of vehicle, compared to design vehicles from the guidelines. Because of that, this paper presents the impact of aforementioned long passenger vehicles on the geometric design of roundabouts.

Croatian guidelines; roundabouts; design vehicle; three-axle buses