We review international practice in concession-based public private partnerships (PPPs) for highways, in the light of the economic theory of incentives, procurement and regulation. In particular, we analyse alternative funding mechanisms to cover highway costs, and their impact on demand risk allocation, incentives, cost of capital, and likelihood of renegotiation. We note how real tolls must pursue a number of contrasting objectives, which may be best served by introducing tariff discrimination. We discuss alternative tariff regulations used in practice and warn against tariff mechanisms that transfer demand risk to users and depart from the principles of price cap regulation. We highlight that it is desirable to transfer some traffic risk to the concessionaire but the level of risk transfer should be lower at the beginning of the contract, especially for greenfield projects where little demand information is initially available. We discuss the procurement of highway PPPs, focusing on the choice of the bidding variables, and on the distortions that renegotiations introduce at bidding stage. We stress the importance of strong institutions and absence of political interference in regulatory matters, and we highlight the benefit of respecting and standardizing contract terms.