At the end of 2022, Brazil's National Land Transport Agency (ANTT) launched a public hearing on the proposal for a new risk allocation model in road infrastructure concession contracts. This study illustrates, using the real options methodology, how the proposed design modifies the concession's risk-return structures and influences the investment decision in the concession and the expected value of the upside risk sharing mechanism (cap) and downside (floor). Our analysis allows the granting authority to calculate the trade-off between the establishment of cap and floor bands, flexibility of Capex triggers (anticipation of the start of the risk sharing mechanism) and potential tariff discounts. The study shows that there is an optimal frontier of efficient portfolios (bands x triggers) that maintains the same risk-return structure and, consequently, discounts. In this sense, the granting power can allocate itself wherever it most desires depending on the concession object, which can be useful for analyzing regulatory impacts caused by this mechanism. This research contributes to the literature on the applications of real options in infrastructure projects, showing how the clauses governing managerial flexibilities in contracts must be carefully designed to achieve the objectives of the government and the private investor.