Guidance 50

A New Approach to Private Roads
Eduardo Engel, Ronald Fischer and Alexander Galetovic,
Regulation (2002)

Pages 18-22 describe the "Least-Present-Value-of-Revenue" criterion used to award concessions pioneered in Chile’s toll road PPP programme.

http://www.cato.org/pubs/regulation/regv25n3/v25n3-6.pdf