This research presents the management of traffic impact study (TIS) through a case study for the Twin Tower Project (TTP), especially on the arterial urban street and the Sixth roundabout. The traffic impact is analyzed for the existing condition (2017), the short-term condition (2023) and the mid-term condition (2028) using Highway Capacity Manual (HCM 2010) and Highway Capacity Software (HCS 2010). The results of the analysis show a low level of service (LOS) for the Sixth roundabout and the two segments of the urban arterial street in all study periods, which represents a congestion in the network with a low quality of service. HCS 2010 and Synchro 10 are used to improve both traffic flow and network geometry, the results of the improvement show increment in the level of service (LOS) and the capacity of the network, and reduction in the control delay time. The study recommendations for the existing condition are to improve the network geometry by adding one lane for both directions of urban arterial street with exclusive right turn on the Sixth roundabout. For the short-term condition, it is recommended to redesign the roundabout to a signalized intersection. While for the mid-term condition, it is recommended to separate the high volume on the intersection by constructing an overpass. Keywords: Traffic Impact Study, Traffic Congestion, Traffic Control delay, Level of Service, Trip Generation, Trip Distribution, Active Traffic Management (ATM), Improvements, Capacity, Roundabout, Segment, Updating software (Synchro10, HCS 2010).