The article concerns the assessment of emmision of selected two-lane roundabout functioning in the city of Rzeszow and its alternate turbo version. In the work was considered four scenarios that represent two different in terms of traffic congestion time of day. The results of the emission of selected components of the exhaust gas (NOx and particulates PM10) were obtained on the basis of calculations of emission model VERSIT+ Enviver. While the input data for the calculations were taken from the modeled options of roundabouts in the Vissim program. The results from the Enviver program were compared to calculations from mesoscopic model COPERT 5. The results show that the overall reduction in average speed, as well as increased frequency of braking and sudden acceleration, directly contribute to the growth of harmful emissions. However, with respect to comparision of turbo roundabout in regard of currently running two-lane roundabout can be observed reduction of selected components of exhaust gases emission about approx. 1/3.