Estimating minimum toll rates in Public Private Partnerships

Abstract

Public private partnership (PPP) is a project delivery method which is used in many countries. The main advantage of this method compared with traditional methods is in the allocation of private funds which are used for providing public services and delivery of projects such as hospitals, schools, roads, and bridges. Under road PPP projects, a commonly used mechanism for the repayment of the private investment is the user charge system, i.e., charging tolls to the facility users. Although the toll rate may be set by the government, there are certain constraints which the minimum toll rate has to meet. These constraints are mainly related to financial parameters such as project's financial internal rate of return (IRR) and debt service coverage ratio (DSCR) which private investors evaluate during the decision making process. In other words, there is a minimum toll rate required to attract private investments. In addition to the financial constraints, other project's parameters such as construction cost, concession life, or level of government subsidies also have an impact on toll rates. The objective of this paper is to investigate the relationship between the level of toll rates and several project technical and financial parameters. A financial model included in the Toolkit for PPP in Roads and Highways, developed by the World Bank and the Public-Private Infrastructure Advisory Facility (PPIAF), is used as a tool to calculate toll rates for various sets of input values. The approach which was chosen to test sensitivity of selected parameters to potential changes in input values (e.g., technical and financial parameters) is by estimation of elasticities.