Comparison between Simulated and Experimental Crossing Speed Profiles on Roundabout with Different Geometric Features

Many researchers have shown in recent studies how roundabouts speed distribution, together with other features (entering flow, circulating flow, entry curvature, entry path radius, entry width, approach width, ratio of inscribed circle diameter/central island diameter, angle to next leg, etc.), can be used as a measure of safety level for these intersections. The wide use of different micro-simulation models for a preventive analysis of roundabouts performance (capacity, delays, levels of service, etc.) highlights the need for a deeper study of the most sensitive parameters for a better fitting between simulated and observed traffic conditions.This work is based on an experimental analysis of the crossing movement in two roundabouts characterized by different values of the inscribed circle diameter (D1≈½
• D2) and located close together on the same road in the University Campus of Arcavacata, Italy. The main aim of the research is the suggestion of a methodological approach to the simulation process of the through movement by the use of VISSIM® micro-simulation software.Resultsconcern the following issues: (i) coherence validation of experimental data regarding speed distributions along the crossing movement as a function of roundabout radius; (ii) methodological and procedural issues related to the implementation of simulation parameters in VISSIM, particularly referring to speed distributions along the crossing movement, in order to better understand the effects of the change of roundabouts geometric features on simulation results.