In the borderless world today, transportation have to provide a best performance, such as: safe, comfortable, and economical can be fulfilled. To find out how the assessment of road, survey of the road geometric and the traffic of the vehicle that passes through are needed to be done. By using Indonesian Highway Capacity Manual 1997 method, where the degree of saturation (DS) is the indicator of traffic activities on Roundabout of Jombor, Yogyakarta. From the results of processing survey data, the highest degree of saturation is 0.58 on road segment A. with a traffic flow 55.52 km/hour and traffic velocity 19.8 to 31.7 km/hour. Based on these results, the service performance of road is C. To improve the roadside barrier performance, installing the traffic sign like no stopping is a better idea. After installing the sign, the degree of saturation drops to 0.56 with service performance C where the road is stable, but the speed and movement of the vehicle is limited.