Contrary to intuition, PPPs generally do not provide additional resources for the public sector. Governments can finance their public infrastructure investments just as well as private firms. Only when governments are credit constrained and thus cannot borrow may private finance be superior. When governments do not have credit constraints, the primary effect of private finance in PPP arrangements is that the investment becomes more affordable within annual authority budgets and better matches user benefits, allowing governments to realize infrastructure investments earlier. PPPs mobilize private sector resources to cover the capital expenditure costs up front (or at least most of it) and make the public sector pay during delivery of the services, either through availability payments or usage payments (shadow toll) or a combination thereof (see figure below). Only if PPPs introduce fees for actual end users do they effectively increase total government revenues and funding. Hence the primary advantage PPPs may offer over traditional public procurement is potential efficiency gains that privately led construction and maintenance may bring, partly offset, however, by higher capital costs of the private investor. The assessment of public sector liabilities triggered by a PPP project is hence of utmost importance. These can amount to substantial direct liabilities, for example, up-front viability gap funding to make projects more commercially viable and the referred usage payment, or contingent liabilities, such as guarantees on particular risk variables, for example, to buffer the traffic demand risk for the private party, compensation payments for uninsurable force majeure, or termination payments.