We identify four main features (see also Martimort and Iossa2009):
• Bundled projects-typically including design, building, financing, and operating-are contracted out to a consortium of private firms, which takes the responsibility for the entire project development.
• A significant part of the risks involved in the project is transferred to the private partner, but are dependent on tolls.
• The use of private capital is a crucial aspect of the partnership. User charges are often set to reward the private investors. For instance, highway users pay a toll in countries such as Italy and France;23 airlines and lessees pay a landing fee and a rental charge to airport contractors; train operating companies, which obtain revenues from passengers, pay railway contractors for the right to access the rail infrastructure.
• The contractual relationship typically ranges from 20 to 35 years.