The availability of Open Government Data (OGD) provides means for citizens to understand and follow governmental policies and decisions, showing evidence of how the latter have contributed to both the place they live in and their lives. In such a scenario, one of the proposals is the use of visualizations to support the process of data analysis and interpretation. Herein, we present the use of three different visualization tools, a commercial one and two academic ones, applied to two specific Brazilian cases: the implementation of the Drink Driving Law and the construction of a new overpass in an important city avenue. Our focus was on the analysis of how visualization could help in the identification of the effects of such traffic public policies. As our main contributions, we present details on the effects of the observed policies, as well as new cases showing how visualization tools can assist users to interpret OGD.