Due to a lack of public funding in the last decade for infrastructure projects, private capital has been encouraged by government to participate in Public Private Partnerships (PPP). Transportation sector is a good example of opportunities to such association. The correct valuation of those types of projects is in the best interest of all society, but Traditional Methods, such as discounted cash flows, do not capture the value of the flexibilities embedded in those projects. This work proposes the use of Real Options Method as a complement to Traditional Analysis, by considering risks and uncertainties and flexibilities. The model was applied to the International Public Bid nº 42325212, which relates to the construction and operation of Line 4 of São Paulo City subway. By comparing both methods, traditional and real options, this work seeks to provide best way to measure this kind of project risks. The results suggest that Traditional Method does not considerate projects flexibilities, meanwhile, Real Optional Analysis does, and signalizing that is method is more suitable for this kind of project analysis.