This report examines principles for determining the most appropriate models for investment in surface transport infrastructure. The primary focus is on network-based infrastructure – roads, rail and, to a lesser extent, inland waterways. The extent and quality of transport infrastructure is of profound importance for the functioning of society and the economy. All governments are faced with the challenge of maintaining vast transport infrastructure networks, and adding new capacity in strategic areas. This requires very large investments. In the context of intense competition for public resources from other policy priorities, governments are looking to a wider range of models for the delivery of surface transport infrastructure, many of which are characterised by increasing use of private sector resources, expertise and/or management practices. The full set of options considered in this report includes public ministries and agencies, fully or partially state-owned companies, private not-for-profit companies, public-private partnerships (PPPs), and outright privatisation.