Vehicular traffic is a major problem in metropolitan areas and Mexico City is no exception. Located in a pollutant-trapping valley, Mexico City (one of the largest cities in the world) is famous for its size, its history, and the warmth of its people. Nevertheless, Mexico City is also famous for its mobility problems and air pollution. During the period September 2002 – July 2003 the former government of Mexico City built a bridge (known as the second floor of Periferico) to attempt to mitigate the vehicular traffic from one of the main avenues of the City. The government was the main proponent of the road but there were opponents for several reasons but in particular for the ecological impact this construction might have. Both, proponents and opponents, claimed the environmental impact studies they made were correct but they did not disclose them to the public in a clear way. This became a significant topic for the society. This report concisely summarizes the research conducted at the Center for Energy and Environmental Studies, IVEM, of the University of Groningen. The study uses a widely accepted environmental tool, Life Cycle Assessment (LCA), to explore the environmental impacts of this road in Mexico City. The structure of the LCA performed in this project follows the formal components of a LCA according to ISO standards. Here, it is important to indicate that for the life cycle inventory step specific unit processes, for the traffic situation in Mexico’s city main roads, were developed. Two systems were defined. System 1 considered the “present situation” whilst system 2 is related to a “future situation” where a bridge is built and used (all relative to the year 2002 when the bridge was proposed). First, the study compares both systems using the default settings. Next the impacts of the construction and use stages of system 2 are discussed. Then, a sensitivity analysis is performed. Different assumptions are made: for the lifespan of the bridge and for the distance between A and B in system 1. Finally, the influence of induced traffic was studied. The results show that, with the default settings, the construction of the bridge is preferable over the traditional road for all the environmental categories selected. The results also show that the traffic crossing the bridge has the highest environmental load of the system. The sensitivity analysis showed that the LCA results are not very sensitive to the lifespan of the bridge. Increasing or decreasing the lifespan with 50% (relative to the default value of 50 years) does not change the conclusion of the LCA. The LCA results are sensitive for the distance in system 1. Decreasing the distance with 25% distance inverts some of the conclusions of the LCA. It is therefore important to determine the actual distance between A and B in system 1 when performing the LCA. An induced traffic of 10% does not change the conclusions of the LCA. However, for the impact/damage categories the difference between system 1 and system 2 decreases. We found that with a 40% of induced traffic the conclusions of the LCA reverse. Then, system 2 causes a bigger damage than system 1. Therefore the attraction of extra traffic of the bridge should be modeled with care and can not be ignored. The choice of system 1 or system 2 involves besides environmental arguments, social and political aspects (weighting) and that is beyond the scope of this study. However, in our opinion the environmental arguments used to make the choice should be transparent, based on quantitative tools. Different stakeholders as the government, academy and society should contribute to the environmental arguments. Therefore, the information generated in this report can be used in similar projects in further studies in order to make informed decisions. The report will be of particular interest for the different stakeholders to be able to evaluate and compare the environmental effects. The results of the study may encourage and reinforce the LCA practice in Mexico.