As matters now stand, the planned investment in transport infrastructure cannot accomodate the growth in demand that will result from increased flows of traffic. Moreover, such investment has a whole range of effects on regional development, wealth distribution, and public well-being. The need to protect the environment also suggests that the construction of more infrastructure will be curbed and that any increases in capacity will be optimized. These factors have led to an appraisal of the reliability of methods of evaluating the relevant investment choices. This publication describes the techniques used for evaluation in a number of ECMT countries and the effectiveness of such methods, and examines conditions governing their use.