First, two commonly suggested responses to traffic congestion—expansions of the road and public transit network—do not appear to have their desired effect: road and public transit expansions should not be expected to reduce congestion. Second, traffic levels do not help to predict which cities build roads. Therefore, new roads allocated to metropolitan areas on the basis of current rules are probably not built where they are most needed, which suggests that more careful reviews of highway expansion projects be required. Third, reductions in travel time caused by an average highway expansion are not sufficient to justify the expense of such an expansion. Whether or not other benefits of these expansions may justify their expense remains unresolved. In any case, expansions of the bus network are more likely to pass a cost–benefit test than expansions of the highway network
