Abstract: Syftet med projekt är att kalibrera och validera samt ta fram råd för utformning av stora cirkulationsplatser, radie > 30 m, med hänsyn till trafiksäkerhet, miljö och tillgänglighet (kapacitet). Modellen är främst anpassad för semiurbana samt landbygdsförhållanden. Projektet bidrar till funktionsmålet Tillgänglighet och Hänsynsmålen Säkerherhet och Hälsa.Abstract: In the last major evaluation of roundabouts, an inventory made 1997, there were not many large roundabouts. This resulted in high variance in the statistical analysis. They were so large that it was impossible to draw some definite conclusions. The reason why larger roundabouts in certain environments are preferable is to keep down the number of stopping vehicles and delay costs for heavy vehicles on the major road. In many cases, there is a discussion between Trafikverket (Swedish Transport Administration) and municipalities about roundabouts on major arterials at so-called "Urban ports", as well as by-pass roads where an "entrance" must be organized to give the site identity. Since 1997, a large number of roundabout sites have been built, which means that there should be enough roundabouts with large radii today to be able to quantify accident risks and compare them with roundabouts with smaller radii. In order to make an optimization between different effects, capacity and environment in the form of emissions and particles are also important to study. A smaller study was made in 2015, where traffic safety impacts were studied regardless of size. The study resulted in a recomendation on the design of incoming roads in connection with high speed environment. The study was conducted without information on size or other detailed design parameters for the studied roundabouts. The aim of the project is to calibrate and validate, as well as to provide advice for designing large roundabouts, radius> 30 m, taking into account road safety, environment and accessibility (capacity). The model is mainly adapted for semiurbana and rural conditions.