The high traffic volume is the main source of the congestion in cities, which is a big problem on transportation systems. This congestion is the main cause of the increase in the level of noise and air pollution in urban centers what directly affects the quality of life of the population. Also, contributing to the big number of vehicle conflicts that affects the performance of the transportation systems and the quality of life of the population. These problems are the result of the high volumes of the through traffic. Therefore, to reduce the traffic volume in urban center of Guimarães, Portugal we studied a possible conclusion of the ring road, on the slope of the Penha hill for the morning peak hour. To carry out our study, the Origin – Destination Matrix for peak hour was estimated from the data of traffic counts. Concluding that there was a reduction of the traffic volume in the section of the ring road that was already built. However, in the city center there were no major variations of the traffic volume and accessibilities.