Government has encouraged to install the roundabout which is a major project of ‘Policies for the Advanced Traffic Control & Operation Systems(2009)’. However, the roundabout is unfamiliar to drivers because it is introduced quickly in Korea and drivers can`t distinguish from rotary. The most notable point is that the existing roundabouts are constructed and operated without standard design guidelines. This is because the guidelines of Korean version is published in December, 2010.

In order to introduce the roundabout, the improvement from rotary rather than signalized intersection is evaluated to be better. Therefore, this study investigates the geometric structure, operational conditions and others, analyzes the problems and suggests improvements, and evaluates the effects using the above collected data, VISSIM and NLOGIT 4.0. The main results are as follows.

First, as a result of field survey, the domestic rotaries were analyzed to need many improvements of both geometric structure and operational method.

Second, as an operational analysis related to before and after improvements, the operational effectiveness was evaluated to be rapidly increasing according to the growth of traffic volume in the most rotaries except 3-legged.

Third, as an economic analysis of before and after improvements, the travel costs were analyzed to be rapidly decreasing according to the growth of traffic volume in the 4-legged and multi-legged rotaries.

Finally, 3 Poisson regression models that dependent variables were the number of accidents, property damage and personal damage EPDO were developed. The models were all analyzed to be statistically significant. The forecasting results of after improvement showed that the number of accidents and accident costs were analyzed to be decreased, and the 3-legged rotaries were analyzed to have the highest decreasing effects.

This study gave particular attentions to analyzing the effects using both real and simulation data unlike the existing studies. Also, this study suggested to compare and evaluate the relations between real data from conversion and simulation outputs.