The use of project finance in public infrastructure projects has been growing in the last decades. Governments around the world have been motivating private investments in infrastructure through public private partnerships (PPP) framework. In the transport sector, for example, project finance and PPP are largely used in toll road concessions. Some real options can be identified in these structures and it is necessary to use the correct methodology to analyze project economic feasibility and risk allocation. The PPP agreements may include subsidies, guarantees and other forms of support designed to reduce the risk to the private investor. Regarding the revenue risk in toll road concessions, different models of traffic guarantees have been offered by governments in many countries. This thesis intends to review these concessions, keeping in mind project finance, PPP features and real options that may exist in this context. A hypothetical toll road concession is proposed and three real options are identified and analyzed: a minimum traffic guarantee, a maximum traffic ceiling and a possible abandonment by the sponsors.