In this paper, we propose a route-based approach to improve the flow and density estimation methods for the case of urban traffic networks. For this proposal, a traffic assignment problem is solved at first, whose outputs are used to estimate the turning ratios for all intersections. Such information is not usually available at each node of the network. Second, the estimated turning ratios are used to better reconstruct the dynamic state of the network: the flow and density. To validate the proposed methods, we use real traffic data collected in the city of Grenoble in France, which include the measurement of Origin-Destination matrices, some turning ratios for validation, mean speeds of road sections and traffic flows at the boundaries of the network.