Comparative analysis of four new alternative types of roundabouts: \u201cTurbo\u201d, \u201cflower\u201d, \u201ctarget\u201d and \u201cfour-flyover\u201d roundabout

Analysis of literature shows that \u201cmodern roundabouts\u201d nowadays exist in all European countries, as well as in more than 60 countries elsewhere in the world. Nowadays, a growing number of studies, presented in scientific and professional literature, point out a poor traffic safety characteristics of \u201cstandard\u201d two-lane roundabouts and lower capacity then was expected. These problems are resolved in more ways in different countries; however the solution, whereby the number of conflict spots is diminished has proven to be the most successful. Lower number of conflict spots is one of characteristics of the alternative types of roundabouts. The alternative types of roundabouts are usually more recent and implemented only in certain countries. It is typical for them that they differ from \u201cstandard\u201d one- and two-lane roundabouts in one or more design elements, while the purpose of their implementation is also specific. This paper illustrate four relative new alternative types of roundabouts - \u201cturbo\u201d, \u201cflower\u201d, \u201ctarget\u201d and \u201cfour flyover\u201d roundabouts and their comparison from designing, capacity and traffic - safety point of view

Surrogate Measures of Safety at Roundabouts in AIMSUN and VISSIM Environment

This paper addresses issues on road safety analysis through microscopic traffic simulation models. The Surrogate Safety Assessment Model (SSAM) was applied to read vehicle trajectory files generated by two microsimulators and then calculate surrogate measures of safety. Since safety assessment of any road entity can provide different results based on the microsimulator which is used, the main objective of this research was to estimate the safety performance of three roundabout layouts and compare the conflict events simulated by AIMSUN and VISSIM. The two micro-simulators were used to build the calibrated models of the roundabouts, each fitting the corresponding empirical capacity function. The results provided insights on how to set the SSAM filters in order to have a comparable frequency of conflicts by simulation and examine conditions under which a safety analysis could be independent of the software used