Introduction
Despite the enormous sums of money being spent on transportation infrastructure,
surprisingly little systematic knowledge exists about the costs, benefits, and risks involved.
The literature lacks statistically valid answers to the central and self-evident question of
whether transportation infrastructure projects perform as forecasted. When a project
underperforms, this is often explained away as an isolated instance of unfortunate
circumstance; it is typically not seen as the particular expression of a general pattern of
under performance in transportation infrastructure projects. Because knowledge is wanting